A Comparison of Metal Enrichment Histories in Rich Clusters and Individual Luminous Ellipti

The study of the properties of metalcomplexesMetal complexes are compounds formed by metal ions and ligands. They have unique properties that make them important in various fields like medicine, material science, nanotechnology, and environmental studies. Understanding the properties of metal complexes is crucial for designing new compounds with specific functions. In this article, we will discuss the important properties of metal complexes and their applications.Ligand Exchange ReactionsLigand exchange reactions are the most important properties of metal complexes. In these reactions, a ligand replaces another ligand from the metal ion, which results in the formation of a new complex. The rate of the ligand exchange reaction depends on the steric and electronic factors. Steric factors such as the size of the ligand and the geometry of the metal complex affect the rate of the reaction. Electronic factors such as the charge and the electronegativity of the ligand also play a crucial role.Applications: Ligand exchange reactions are important in catalysis and bioinorganic chemistry. Many catalysts use metal complexes because of their ability to undergo ligand exchange reactions. In bioinorganic chemistry, metal complexes play a crucial role in the transport and storage of metals in the body.Redox PropertiesRedox properties refer to the ability of a metal complex to undergo oxidation-reduction reactions. In these reactions, the metal ion changes its oxidation state, resulting in the formation of a new complex. The redox potential of a metal complex depends on the ligands and the metal ion. The presence of strong field ligands like cyanide and carbon monoxide increases the redox potential of the metal complex.Applications: Redox properties of metal complexes are important in electrochemistry and catalysis. In electrochemistry, metal complexes are used as mediators in the redoxreactions. In catalysis, many reactions are driven by the redox properties of metal complexes.Optical PropertiesOptical properties refer to the ability of a metal complex to exhibit color and luminescence. The color of a metal complex depends on the nature of the ligands and the metal ion. The presence of d-orbitals in the metal ion gives rise to the color of the complex. The luminescence of a metal complex depends on the energy gap between the ground and excited states.Applications: Optical properties of metal complexes are important in materials science, biology, and medicine. In materials science, metal complexes are used as dyes, pigments, and sensors. In biology, metal complexes are used as probes to study biological processes. In medicine, metal complexes are used as imaging agents and anticancer drugs.Structural PropertiesStructural properties refer to the geometry and bonding of a metal complex. The geometry of a metal complex is determined by the coordination number, the ligands, and the metal ion. The bonding in a metal complex can be classified as covalent, ionic, and dative.Applications: Structural properties of metal complexes are important in catalysis, material science, and environmental studies. In catalysis, the geometry and bonding of metal complexes determine their catalytic activity. In material science, the structure of metal complexes determines their thermal stability and mechanical properties. In environmental studies, the structure of metal complexes plays a crucial role in their toxicology and biodegradation.In conclusion, the study of the properties of metal complexes is crucial for their understanding and applications. The properties of metal complexes like ligand exchange reactions, redox properties, optical properties, and structural properties make them important in various fields like medicine, material science, nanotechnology, andenvironmental studies. Further research in this field will lead to the development of new compounds with specific functions.。

DOI: 10.19289/j.1004-227x.2020.24.006 金属沉积技术在手印显现领域中应用的研究进展张晓顺（中国刑事警察学院，辽宁沈阳110035）摘要：结合潜手印的形成与显现原理，综述了潜手印显现技术的发展过程和常见技术方法。

论述了金属沉积技术在油潜手印显现中的作用，探析了电化学沉积技术和化学镀技术显现油潜手印的原理，分析了金属沉积方法显现潜手印所需要解决的关键技术，展望了金属沉积技术在法庭科学领域中的发展方向。

关键词：潜手印；显现；法庭科学；电化学沉积；化学镀；综述中图分类号：O69; TQ153 文献标志码：A 文章编号：1004 – 227X (2020) 24 – 1723 – 05Research progress of application of metal plating technology to fingerprint visualization // ZHANG Xiaoshun Abstract: The development history and common technologies for visualization of latent fingerprint were summarized based on the formation and visualization mechanisms of latent fingerprint. The role of metal plating technology in fingerprint visualization was introduced. The visualization mechanism of latent greasy fingerprint when using electrochemical deposition and electroless plating technologies was discussed. The key technologies for the application of metal plating to visualization of latent fingerprint were analyzed. The research directions of metal plating technologies in forensic science were prospected.Keywords:latent fingerprint; visualization; forensic science; electrochemical deposition; electroless plating; review Author’s address: Criminal Investigation Police University of China, Shenyang 110035, China手印是各类案件现场中最为常见的痕迹物证，犯罪分子在实施犯罪行为的过程中，由于手部不可避免地会与被害人、现场客体、作案工具等发生接触，极有可能遗留下指头、指节和手掌部位的乳突花纹印痕，这些遗留在现场的痕迹在司法实践中具有重要作用。

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a rXiv:as tr o-ph/31292v11Oct23Recycling intergalactic and interstellar matter IAU Symposium Series,Vol.217,2004Pierre-Alain Duc,Jonathan Braine and Elias Brinks,eds.Metal Abundances and Kinematics of the Ly-αabsorbers Sergei A.Levshakov Department of Theoretical Astrophysics,Ioffe Physico-Technical Institute,Politekhnicheskaya Str.26,194051St.Petersburg,Russia Abstract.Both high resolution spectra of QSOs observed at the 8-10m telescopes and advanced methods of data analysis are crucial for accu-rate measurements of the chemical composition and physical parameters of the intervening clouds.An overview of our recent results obtained with the Monte Carlo inversion (MCI)procedure is presented.This includes:(1)variations of the shape of the local background ionizing continuum in the 1–5Ryd range at redshift z ∼2.8−3.0;(2)an inverse correlation between the measured metallicity,[C/H],and the absorber line-of-sight linear size,L ;(3)a functional dependence between the line-of-sight ve-locity dispersion,σv ,and L .1.Introduction A study of quasar (QSO)absorption-line spectra is generally recognized as the most reliable technique for inferring the physical and dynamical state of gas in the intervening absorption clouds at high redshifts,z ∼>2.Of particular interest are the measurements of metallic absorptions in the optically thin diffuse clouds with neutral hydrogen column densities N (H i )∼<3×1017cm −2.These systems will be called as ‘Ly-αabsorbers’(LAA)to distinguish from the damped Ly-αabsorption systems (DLA)which show much higher column densities,N (H i )∼>2×1020cm −2.The latter are believed to arise in the galactic disks (e.g.,Wolfe et al.1995),whereas the former may be physically related to the external (∼10-100kpc-scale)regions of galaxies (e.g.,Chen et al.2001).Thus the measurements of the LAAs can provide fundamental insights into conditions prevailing in the galactic environments (external halos)in the early universe.Since these regions are mainly photoionized by the local metagalactic UV radiation,the ionization states of the LAAs are sensitive to the spectral shape of the background radiation in the 1-5Ryd range.The spectral energy distribution in the metagalactic ionizing background is defined in turn by the QSO continua filtered through the quasar environments and the IGM.Two implications of the LAA analysis –the metal content of the external halos and the spectral shape of the local UV background –are,therefore,tightly coupled.To clarify the mechanism of the metal enrichment,accurate measurements of the metal abundances in the LAAs are required.The main problem here is how to account for the ionization correction.In general,the contribution to the line intensity Iλwithin the profile comes from all volume elements distributedalong the line of sight and having the same radial velocity.If the gas number12S.A.Levshakovdensity,n H,varies from point to point,then the intensity Iλis caused by a superposition of different ionization states.Recently,we have developed a method called‘Monte Carlo inversion’(MCI) to recover the physical parameters of the LAAs assuming that the absorb-ing cloud is a continuous region withfluctuating density and velocityfields (Levshakov et al.2000,hereafter LAK).The MCI was applied to high qual-ity QSO spectra obtained with the VLT/UVES,Keck/HIRES,and HST/STIS (Levshakov et al.2002;Levshakov et al.2003a,b,c,d,e).The results of these studies are briefly reviewed in this contribution.2.The MCI procedureThe layout of the MCI procedure is the following.We assume that the metal abundances within the absorber are constant,the gas is optically thin for the ionizing UV radiation,and the gas is in thermal and ionization equilibrium. The radial velocity v(x)and the total hydrogen density n H(x)along the line of sight are considered as two randomfields which are represented by their sampled values at equally spaced intervals∆x,i.e.by the vectors{v1,...,v k} and{n1,...,n k}with k large enough(∼150−200)to describe the narrowest components of the complex spectral lines.The radial velocity is assumed to be normal distributed with the dispersionσv,whereas the gas density is log-normal distributed with the mean n0and the dispersionσy(y=n H/n0).The stochasticfields are approximated by the Markovian processes.The accuracy of the restoring procedure depends on the number of different ions in different ionization stages involved in the analysis of a given LAA.A set of thefitting parameters in the least-squares minimization of the objective function(Eqs.[29]and[30]in LAK)includesσv andσy along with the total hydrogen column density N H,the mean ionization parameter U0,and the metal abundances Z a for a elements observed in the LAA.With these parameters we can further calculate the mean gas number density n0,the column densities for different species N a,the mean kinetic temperature T kin,and the line-of-sight size L=N H/n0of the absorber(note that n0and,correspondingly,L scales with the intensity of the local background radiationfield).We start calculations assuming some standard ionizing spectrum[e.g.,power law,Mathews&Ferland(1987),or Haardt&Madau(1996,hereafter HM)]and compute the fractional ionizations and the kinetic temperatures at each point x along the sightline with the photoionization code CLOUDY(Ferland1997). To optimize the patterns of{v i}and{n i}and to estimate simultaneously the fitting parameters,the simulated annealing algorithm with Tsallis acceptance rule and an adaptive annealing temperature choice are used.If thefitting with the standard spectrum is impossible,its shape is adjusted using the procedure based on the experimental design technique(Levshakov et al.2003e).3.The spectral shape of the ionizing continuumIn practice,the shape of the ionizing spectrum can be estimated in cases when the value of N(H i)is measured accurately and the absorption system containsAbundances and Kinematics of the Ly-αabsorbers3Figure1.A typical metagalactic ionizing spectrum at redshift z∼3(the dotted curve)modeled by Haardt&Madau(1996),and its modifi-cation(the solid curve)required to match the absorption lines observedin a LAA at z=2.82toward HE0940–1050(Levshakov et al.2003e).The spectrum is normalized so that Jν(hν=1Ryd)=1.The emissionbump at3Ryd is caused by reemission of He ii Lyαand two-photoncontinuum emission from intergalactic clouds.unsaturated lines of at least C ii–C iv and Si ii–Si iv,otherwise the system is not sensitive to thefine tuning of the continuum shape.We estimated the spectral shape for the LAAs at z=2.82(H i,C ii,C iii, Si iii,C iv,Si iv)toward HE0940–1050;z=2.7711(H i,C ii,Si ii,C iii,N iii, Si iii,C iv,Si iv,O vi),and z=2.94(H i,C ii,Si ii,C iii,Si iii,C iv,Si iv) toward Q1157+3143(Levshakov et al.2003e).All three recovered spectra of ionizing radiation show common features:a bump at E=3Ryd,which is more pronounced comparing to the model mean intergalactic UV spectra at z=3like that of Haardt&Madau(1996),and a sharp break just after the bump–also at variance with the model predicting a smeared out break at E=4Ryd due to ionization of He ii.An example of ionizing background estimated for the z=2.82absorption system toward HE0940–1050is shown in Fig.1.This spectral shape rules out a considerable galactic contribution to the QSO dominated UV ionizing background at z∼3. The recovered UV spectrum can be well explained in the scenario of the delayed re-ionization of He ii(Reimers et al.1997).In this case the sharp break at E=3Ryd occurs due to strong resonant scattering of QSO radiation in metal4S.A.LevshakovFigure2.Carbon abundances[C/H]plotted against the logarithmiclinear size L of the absorber estimated by the MCI procedure(Lev-shakov et al.2002;2003a,b,c,e).[C/H]decreases with increasing Lreflecting,probably,the dilution of metals within galactic halos causedby the mass transport processes.and He ii Lyman series lines whereas a part of the absorbed photons re-emitted by the intergalactic gas in the He ii Lyαand two-photon continuum emission increases the amplitude of the bump at3Ryd.Our results also indicate that the re-ionization of He ii has not been yet completed by z=2.77.This results is in line with recent observations of the He ii Ly-αforest by Shull et al.(2003) who claim that‘the ionizing background is highly variable throughout the IGM’at z∼2.8.4.‘[C/H]−L’and‘σv−N H L’relationsThe analyzed LAAs show that they are a heterogeneous population that is formed by at least three groups of absorbers:(1)extended metal-poor(Z<0.1Z⊙)gas halos of distant galaxies;(2)gas in dwarf galaxies(0.1Z⊙<Z∼<0.3Z⊙);and (3)metal-enriched gas(Z∼>0.5Z⊙)arising from the inner galactic regions and condensing into the clouds within the hot galactic halo(high redshift analogs to the Galactic high velocity clouds,HVC).Abundances and Kinematics of the Ly-αabsorbers5Figure3.Plot of the line of sight velocity dispersion log(σv)vs.log(N H L)for the same sample of the LAAs shown in Fig.2.Thedashed line corresponds to the relation log(σv)∝0.5log(N H L)ex-pected for the virialized systems.Open squares represent HVC-likeclouds with L∼<1kpc.Figure2shows a plot of the measured carbon abundances[C/H]1versus logarithmic sizes of the studied systems.Systematically higher abundances are seen in compact systems.This tendency reflects,probably,the dilution of met-als within galactic halos caused by the mass transport processes(like diffu-sion,turbulent mixing,galactic rotation,shear,and etc.).Metals are,probably, transported into the halo in form of small dense clouds carried out by wind or jets.In some cases we directly observe such blobs.For instance,the LAAs at z=1.385([C/H]≃−0.3,L≃1.7−2.5kpc)and at z=1.667([C/H]≃−0.5, L≃1kpc)toward HE0515–4414as well as that at z=2.966([C/H]≃−0.4, L≃100pc)toward Q0347–3819are embedded in extremely metal-poor halos with[C/H]<−2(Levshakov et al.2003b,c).If LAAs are formed in gas clouds gravitationally bound with intervening galaxies,their internal kinematics should be closely related to the total masses of the host galaxies.Wefind a correlation between the absorber’s linear size L and its line-of-sight velocity dispersionσv.The virial theorem states:σ2v∝M/L∝n0L2=N H L.Assuming that the gas systems are in quasi-equilibrium,6S.A.Levshakovone can expectσv∝(N H L)1/2.In Fig.3we plot the measured values ofσv versus the product of L and the total gas column density N H.It is seen that most systems with linear sizes L>1kpc lie along the line with the slope0.5. Taking into account that we know neither the impact parameters nor the halo density distributions,this result can be considered as a quite goodfit to the expected relation for the virialized systems.Hence we may conclude that most absorbers with L>1kpc are gravitationally bound with systems that appear to be in virial equilibrium at the cosmic time when the corresponding LAAs were formed.Acknowledgments.This work would not have been possible without the contribution of many individuals,including Irina Agafonova,Wilhelm Kegel, Miriam Centuri´o n,Paolo Molaro,Igor Mazets,Miroslava Dessauges-Zavadsky, Sandro D’Odorico,Dieter Reimers,Robert Baade,David Tytler,and Art Wolfe.I also appreciate support from the RFBR grant No.03-02-17522,and I am very grateful to the IAU for a travel grant.ReferencesChen,H.-W.,Lanzetta,K.M.,&Webb,J.K.2001,ApJ,556,158Ferland,G.J.1997,A Brief Introduction to Cloudy(Internal Rep.,;Lexington: Univ.Kentucky)Haardt,F.,&Madau,P.1996,ApJ,461,20[HM]Holweger,H.2001,in Solar and Galactic Composition,ed.R.F.Wimmer-Schweingruber,AIP Conf.Proceed..598,23Levshakov,S.A.,Agafonova,I.I.,&Kegel,W.H.2000,A&A,360,833[LAK] Levshakov,S.A.,Agafonova,I.I.,Centuri´o n,M.,&Mazets,I.E.2002,A&A, 383,813Levshakov,S.A.,Agafonova,I.I.,Centuri´o n,M.,&Molaro,P.2003a,A&A, 397,851Levshakov,S.A.,Agafonova,I.I.,D’Odorico,S.,Wolfe,A.M.,&Dessauges-Zavadsky,M.2003b,ApJ,582,596Levshakov,S.A.,Agafonova,I.I.,Reimers,D.,&Baade,R.2003c,A&A,404, 449Levshakov,S.A.,D’Odorico,S.,Agafonova,I.I.,&Dessauges-Zavadsky,M.2003d,A&A,in press,astro-ph/0310141Levshakov,S.A.,Agafonova,I.I.,Molaro,P.,Centuri´o n,M.,&Tytler,D.2003e,A&A,submittedMathews,W.G.,&Ferland,G.J.1987,ApJ,323,456Reimers,D.,K¨o hler,S.,Wisotzki,L.,Groote,D.,Rodriguez-Pascual,P.,& Wamsteker,W.1997,A&A,327,890Shull,J.M.,Tumlinson,J.,Giroux,M.L.,Kriss,G.A.,&Reimers,D.2003, ApJ,in press,astro-ph/0309625Wolfe,A.M.,Lanzetta,K.M.,Foltz,C.B.,&Chaffee,F.H.1995,ApJ,454, 698。

REVIEW PAPEREnvironmental epigenetics:prospects for studying epigenetic mediation of exposure–response relationshipsVictoria K.Cortessis •Duncan C.Thomas •A.Joan Levine •Carrie V.Breton •Thomas M.Mack •Kimberly D.Siegmund •Robert W.Haile •Peter irdReceived:21February 2012/Accepted:7June 2012/Published online:28June 2012ÓThe Author(s)2012.This article is published with open access at Abstract Changes in epigenetic marks such as DNA methylation and histone acetylation are associated with a broad range of disease traits,including cancer,asthma,metabolic disorders,and various reproductive conditions.It seems plausible that changes in epigenetic state may be induced by environmental exposures such as malnutrition,tobacco smoke,air pollutants,metals,organic chemicals,other sources of oxidative stress,and the microbiome,particularly if the exposure occurs during key periods of development.Thus,epigenetic changes could represent an important pathway by which environmental factors influ-ence disease risks,both within individuals and across generations.We discuss some of the challenges in studyingepigenetic mediation of pathogenesis and describe some unique opportunities for exploring these phenomena.Abbreviations ART Assisted reproductive technologies ASM Allele-specific DNA methylation ChIP Chromatin immunoprecipitation CIMP CpG island methylator phenotype CpG Cytosine-phosphate-guanine dinucleotide CRC Colorectal cancer DES Diethylstilbestrol feNO Fractional exhaled nitric oxide FFPE Formalin-fixed paraffin-embedded HDAC Histone deacetylases iNOS Inducible nitric oxide synthase IUGR Intra-uterine growth restriction IVF In vitro fertilizationPBMCs Peripheral blood mononuclear cells PTS Maternal smoking during pregnancy SNP Single nucleotide polymorphismBackgroundThe field of epigenetics grew from attempts,beginning over 70years ago,to understand mechanisms whereby multiple cellular phenotypes arise from a single genotype during the complex process of developmental morpho-genesis termed epigenesis.The term ‘‘epigenetics’’was initially reserved for mechanisms by which phenotypic state,as determined by differential gene expression,could be stably retained through cell division by non-genetic factors.Various mechanisms have been proposed to have the potential to encode this phenotypic information;these include enzymatic methylation of cytosine bases (DNAV.K.Cortessis and D.C.Thomas contributed equally to this work.V.K.Cortessis ÁA.J.Levine ÁT.M.Mack ÁR.W.HaileDepartment of Preventive Medicine,Keck School of Medicine,University of Southern California,USC Norris Comprehensive Cancer Center,1441Eastlake Avenue,Los Angeles,CA 90089,USA D.C.Thomas (&)Department of Preventive Medicine,Keck School of Medicine,University of Southern California,2001N.Soto St.,SSB-202F,Los Angeles,CA 90089-9234,USA e-mail:dthomas@C.V.Breton ÁK.D.SiegmundDepartment of Preventive Medicine,Keck School of Medicine,University of Southern California,2001N.Soto St.,Los Angeles,CA 90089-9234,USAirdDepartments of Surgery,Biochemistry and Molecular Biology,Keck School of Medicine,University of Southern California,USC Norris Comprehensive Cancer Center,Epigenome Center,1441Eastlake Avenue,Los Angeles,CA 90089-9601,USAHum Genet (2012)131:1565–1589DOI 10.1007/s00439-012-1189-8methylation),post-translational modification of tail domains of histone proteins(histone modifications)and associated nucleosome positioning or chromatin remodel-ing,non-coding RNAs,and transcription factor regulatory networks(Ptashne2007).Epigenetic marks established by each of these processes are often shared within a cell lineage; however,whether all persisting epigenetic marks satisfy requirements for stable transmission through cell division or some are merely reestablished from other information fol-lowing mitosis remains a vigorously debated question.The term epigenetics has more recently been used in the scientific literature to describe various unspecified non-genetic mechanisms influencing phenotype.This broader usage emerged from mouse studies addressing transgen-erational nutritional effects on phenotype,as well as human studies of phenotypic differences between monozygotic twins.In the popular press‘‘epigenetics’’has become almost synonymous with nutritional and environmental influences on gene expression.Thus,while‘‘epigenetics’’initially referred to largely self-contained developmental processes,it has come to describe environmental influences on phenotypic readout of genotypes.This semantic evo-lution has caused confusion and controversy regarding the meaning of‘‘epigenetics’’at a time of intensified interest in the possible role of epigenetic mechanisms in disease.In this review we define as epigenetic processes those that stably affect gene expression through mechanisms not involving the primary nucleotide sequence,and epigenetic state as the configuration of chromatin and DNA marks utilized by these processes.By contrast,genetic state is widely understood to refer to the primary nucleotide sequence itself,while genetic processes maintain or change nucleotide sequence.Epidemiologic research addressing epigenetic mecha-nisms as mediators of environmental exposures on disease risk is constrained by important ethical considerations. These often preclude both experimental exposure to candi-date environmental causes,and invasive collection of cell types of greatest developmental and functional relevance to disease processes.Inquiry has therefore progressed largely by integrating information about biological mechanisms obtained in model systems with observational data provided by humans.To address the current state and future promise of this research,we undertook this review with two goals:to illustrate the potential of epigenetic processes to mediate exposure–phenotype relationships and to discuss study design and statistical analysis methods needed to investigate such mechanisms in relation to origins of human disease.We begin by discussing genetic,developmental,and environ-mental determinants of epigenetic state in human and model systems,then describe some of the diverse data implicating epigenetic mechanisms in various human diseases,both within individuals and across generations.We conclude by discussing technical challenges,suggesting promising opportunities for epidemiologic research in environmental epigenetics,and offering some thoughts about translational significance and future directions of thisfield. Determinants of epigenetic stateEpigenetic mechanisms work in concert to influence the potential for gene expression at myriad locations through-out the genome.The resulting epigenetic state of the gen-ome,termed epigenome,varies by cell type.Considering the tremendous diversity of epigenetic marks,which include dozens of different post-translational histone modifications and more than50million sites of potential DNA methylation in a diploid human genome(and thus [250M possible epigenotypes!),it seems that no two human cells would have identical epigenomes.Indeed,within each individual there are many epigenomes,and these change over time as a consequence of both normal developmental and pathological processes,as well as environmental exposures and random drift.Despite this potential for considerable variability of epigenetic patterns within and between individuals,there can also be remarkable consis-tency.In a study of11tissues in6autopsies,DNA meth-ylation patterns in a highly selected set of loci were found to be highly conserved,with intraclass correlations of0.85 across tissues within individuals and0.83across individ-uals within tissues(Byun et al.2009).The authors inter-preted these patterns as revealing different sets of person-specific and tissue-specific differentially methylated genes, anticipating subsequently observed differential genetic and acquired determination(Waterland et al.2010).DNA methylation has been the epigenetic mark most extensively measured in epidemiologic research for numerous reasons.It is of fundamental biological interest owing to its unambiguously stable transmission during cell division.It also has practical advantages:as a chemically stable covalent change to the DNA itself,DNA methylation is the only epi-genetic mark that survives the DNA extraction and purifica-tion that is routine in molecular sample processing,and it can endure decades of archival sample storage(Kristensen et al. 2009).Genetic influencesNucleotide sequence is a primary determinant of epigenetic state,clearly evident from the distribution of epigenetic marks across the genome,determined in part by direct effects of G:C content and CpG(cytosine-phosphate-guanine dinucleotide) density(Tanay et al.2007;Thomson et al.2010).Additional genetic influences include proximity to repetitive elements such as Alu and LINE1(Estecio et al.2010),nucleararchitecture(Berman et al.2011),and binding sequences for transacting proteins(Bell et al.2011b;Weth and Renkawitz 2011).Motif searches and screening strategies have identified sequence elements that predispose to particular epigenetic states(Feltus et al.2006;Ideraabdullah et al.2011;Keshet et al.2006;Lienert et al.2011).Several lines of evidence indicate that genetic poly-morphisms can affect epigenetic state.Greater differences were observed between dizygotic co-twins than between monozygotic co-twins in two forms of epigenetic state: skewed patterns of X-inactivation,and DNA methylation at differentially methylated regions of the imprinted IGF2/ AH19locus(Wong et al.2011;Heijmans et al.2007; Ollikainen et al.2010).Extensive DNA methylation anal-yses in a multigenerational family revealed that epiallelic similarity was greater amongfirst-degree relatives than among more distantly related family members.In the same study,analyses addressing both genetic variation and DNA methylation identified widespread occurrence of allele-specific DNA methylation(ASM)that was associated with polymorphic nucleotides located near the DNA methyla-tion site,but not parent of origin.Authors of this report concluded that the majority of such ASM events depend on cis-acting DNA sequence(Gertz et al.2011).Such ASM events have yet to be characterized in large population-based studies,but more modest studies addressing hetero-zygous non-imprinted loci have identified widespread ASMs associated with nearby genotypic polymorphisms in DNA from multiple tissue types(Kerkel et al.2008;Tycko 2010;Schalkwyk et al.2010),as well as allele-specific chromatin structure and transcription factor binding in lymphoblastoid cell DNA(McDaniell et al.2010,reviewed in Birney et al.2010).Presumed transgenerational inheri-tance of epigenetic changes(‘‘epimutations’’)in the MLH1 (Suter et al.2004)and MSH2(Chan et al.2006)mismatch repair genes,both associated with colorectal cancer,were also traced to germline genetic variation.In the case of the MSH2 epimutation,deletion of a gene immediately upstream of the MSH2gene causes transcription to run through the MSH2 promoter,causing somatic hypermethylation and gene silencing(Ligtenberg et al.2009).The MLH1epimutation was found to be caused by a polymorphism in the50UTR of the MLH1gene,reducing transcriptional activity,and pre-disposing to aberrant somatic DNA methylation in each generation(Hitchins et al.2011).Developmental programming of the epigenomeIn successful mammalian reproduction,the single-cell zygote gives rise to an organism with hundreds of cell types.These diverse cellular phenotypes arise from the same shared genomic sequence by control of the subset of genes expressed in each cell type.Cellular differentiation is tightly linked to extensive erasure and establishment of lineage-specific epi-genetic marks,a process termed epigenetic reprogramming. Relatively detailed descriptions of DNA methylation in developing tissues have been carried out in the mouse,which serves as a model of epigenetic reprogramming in mammalian development(Trasler2009).At fertilization,reprogramming begins with extensive erasure of methyl marks in DNA of the paternal(sperm-derived)DNA,followed by more general loss of methyl marks in the zygote and embryo during cleavage divisions,while sparing parent-of-origin specific imprints.By the blastocyst stage,de novo DNA methylation distinguishes inner cell mass cells(from which embryonic lineages arise to create fetal structures)from relatively hypomethylated trophectoderm cells(from which extra-embryonic lineages arise to create transient structures,including placenta)(Fig.1).Germ cell lineage specification begins in cells of the proximal epiblast,and involves a second extensive erasure of DNA methylation that removes parental imprint marks (Fig.1).Thereafter,the germ line develops in a sexually dimorphic fashion.New DNA methyl marks are established over many stages,extending through sexual maturity in accordance with the sex of the developing individual.At this time,the sex-specific imprint marks that govern parent-of-origin specific expression of imprinted genes in the sub-sequent generation are established(Faulk and Dolinoy2011).Developmental reprogramming can result in dramatic epigenetic differences between the two alleles.The asso-ciation between mono-allelic gene expression and DNA methylation has long been recognized,both in the context of X-inactivation in females(Boggs et al.2002;Sharp et al. 2011)and in parent-of-origin determined genomic imprinting(Ferguson-Smith2011),but now also in the mono-allelic expression of non-imprinted autosomal loci (Harris et al.2010;Tarutani and Takayama2011).Further resetting of epigenetic marks accompanies differ-entiation of many specialized cell types of the body as well as placenta and other transient structures during pregnancy,and subsequent development of body structures during various postnatal stages of development.Chromatin states that arise during development can affect the propensity to subsequent epigenetic change.An example of this is the predisposition of polycomb-repressive complex occupied genes in stem cells to the acquisition of DNA methylation abnormalities in aging and cancer(Ohm et al.2007;Schlesinger et al.2007; Teschendorff et al.2010;Widschwendter et al.2007).Environmental influencesMultiple differences in gene expression,presumably reflecting intrauterine epigenetic differences,have been identified in several tissues from newborn identical twins (Gordon et al.2011).The global methylation pattern ofindividuals changes with increasing age (Bjornsson et al.2008),as does the difference in global methylation between MZ twin pairs (Fraga et al.2005).Genetically identical MZ twins show some epigenetic discordance at birth,as indi-cated by gene expression discordance (Gordon et al.2011).Even over the first decade of life (Wong et al.2010),and as aging adults (Talens et al.2010),MZ twins acquire addi-tional differences in epigenetic state,which may partly reflect different exposure histories,as would be expected if environmental exposures influence epigenetic state.How-ever,stochastic drift in epigenetic state and related con-sequences such as mono-allelic expression described in the previous section is likely responsible for much of the observed divergence.Therefore,other forms of data (dis-cussed below)are needed to determine what type of exposures may influence epigenetic state and the extent of resulting changes.Experimental studiesThe most direct evidence suggesting that ambient exposures may influence epigenetic state is experimental.In vitro studies have demonstrated associations of DNA methylation with various metals (Dolinoy et al.2007b ;Wright and Baccarelli 2007).In the in vivo setting,prenatal protein restriction is associated with hypomethylation of the gluco-corticoid receptor (GR )and PPAR a gene promoter regions inrat liver (Lillycrop et al.2005),changes that were prevented by folic acid supplementation (Lillycrop et al.2005)and which were transmitted to the F2generation (Burdge et al.2007).Plagemann et al.(2009)found hypermethylation in the promoter of the anorexigenic gene for proopiomelano-cortin in rats overfed as neonates.Whether this change could be transmitted to offspring was not assessed.DNA from sperm of mice exposed to steel plant air was found to be persistently hypermethylated long after exposure ended (Yauk et al.2008).Additionally,maternal nurturing behav-ior has been shown to modify methylation at individual CpG sites in the ngf1a binding region of the GR gene in the hip-pocampus of the offspring (Weaver et al.2004),an epige-netic modification that persisted both into adulthood to modify response to stress,and into the F2generation.Human studiesChristensen and Marsit (2011)and Terry et al.(2011)have provided comprehensive reviews of environmental influ-ences on epigenetic state in humans.Here we note expo-sure periods of particular interest and several examples of environmental exposures reportedly associated with epi-genetic state of specific human cell types.The epigenome may be most vulnerable to environ-mental insults during periods of extensive epigenetic reprogramming,which may in theory be disruptedbyFig.1Reprogramming ofDNA methylation in the zygote,early embryo,and primordial germ cells.Thickness of the outer arrows indicates levels of DNA methylation.Red maternal genome,blue paternal genome,black diploid genome.Embryonic lineages arise from cells of the inner cell mass (ICM),the placenta and extraembryonic membranes from trophectoderm cells,and the germ cell lineage fromprimordial germ cells following their determination fromproximal epiblast.Inner circles indicate developmental stages when key elements ofepigenetic programming are thought to occur (Adapted from Feng et al.2010)exposures that interfere with any process that governs reprogramming.Periods of particular vulnerability may therefore include the early stages of embryonic develop-ment mentioned above.Childhood is also proposed as a period of vulnerability,especially in the germline of females,since oocytes remain in a haploid de-methylated state until puberty,so environmental insults may poten-tially disturb the epigenetic state of the oocyte for many years(Faulk and Dolinoy2011),with potential implica-tions for both fertility and initial epigenetic state of off-spring of an exposed female.Somatic changes to DNA methylation may also result from environmental exposures in adults,as have been observed in aging and disease processes such as cancer described in the next section. Energy and nutrient intakeSignificant epigenetic changes in the IGF2gene have been documented in those prenatally exposed to severe caloric restriction during the Dutch hunger winter of World War II (Heijmans et al.2008).Hughes et al.(2009)additionally found that those most likely to be exposed to this famine during adolescence or young adulthood had a significantly decreased risk of developing colorectal cancers(CRC) characterized by the CpG island methylator phenotype (CIMP),suggesting a role for early life exposures in CIMP-specific CRC pathogenesis.Folates are the major source of the methyl groups used for DNA and histone methylation.One study of folates and other one-carbon nutrients reported a differential effect of folate on the risk of the CIMP CRC subset compared to the non-CIMP subset(Van Guelpen et al.2010),while two other studies did not(Slattery et al.2006;van den Donk et al.2007).Most studies of the microsatellite instability high subset,characterized by hypermethylation of the MLH1gene promoter region and CIMP(Weisenberger et al.2006),have yielded similarly negative results(Eaton et al.2005;Schernhammer et al.2008;Slattery et al.2001; Wark et al.2005).On the other hand,in some studies the association between intake of alcohol(which degrades folates)and CRC risk has been reported to be greater in MSI-H and CIMP tumors(Diergaarde et al.2003;Eaton et al.2005;Slattery et al.2001).Micro-RNAs(miRNAs)are very short non-coding RNA molecules that can downregulate protein-coding genes by destabilizing mRNAs or blocking translation.The possi-bility that exogenous microRNA consumed in food may epigenetically regulate gene expression has emerged from recent studies demonstrating the presence of plant-derived miRNAs in sera of humans and other mammals(Zhang et al.2012).One of these plant microRNAs,MIR168a, which was demonstrated to be only of plant origin in control mice,binds coding sequence of the mammalian LDLRAP1 gene in vitro.Functional consequences in mammalian sys-tems were demonstrated experimentally,as MIR168a administered in vitro and during in vivo feeding studies decreased expression of the protein product of LDLRAP1. This line of research suggests novel epigenetic mechanisms whereby diet may modify risk of human disease.Air pollutionEmerging evidence suggests that air pollutants can influ-ence epigenetic changes,including DNA methylation as well as up-or down-regulation of miRNAs(Jardim2011). In human epidemiologic studies,PM2.5and PM10expo-sures are associated with hypomethylation of Alu and/or LINE1elements in leukocytes and buccal cells(Baccarelli et al.2009;Bollati and Baccarelli2010;Madrigano et al. 2011;Salam et al.2012;Tarantini et al.2009),as well as altered DNA methylation in NOS2A,a gene involved in production of nitric oxide(Salam et al.2012;Tarantini et al.2009).Living in highly polluted cities(high PM and ozone)is also associated with hypermethylation of FOXP3 in regulatory T cells(Nadeau et al.2010),while neonates who were prenatally exposed to polyaromatic hydrocarbon (PAH)had hypermethylated ACSL3in DNA of umbilical cord white blood cells(Perera et al.2009);notably,both of these genes are involved in asthma pathogenesis.PAHs are also associated with hypermethylation of LINE1and Alu (Pavanello et al.2009;Perera et al.2009).More limited evidence is emerging to suggest that air pollution is asso-ciated with changes in miRNA expression(Bollati et al. 2010;Jardim2011),and adverse effects of air pollution constituents may be modified by variant alleles of genes involved in miRNA processing(Wilker et al.2010). Tobacco smokeFetal exposure to maternal smoking during pregnancy (PTS)is associated with reduced methylation of several repeated sequences,including Sat2(Flom et al.2011),Alu, and LINE1among children with the GSTM1null genotype (Breton et al.2009).PTS exposure is also associated with increased DNA methylation in specific genes,such as AXL and PTPRO(Breton et al.2009,2011b)and IGF2(Murphy et al.2011).In adult lung cancer patients,quantity and duration of active smoking as well as second-hand smoke is associated with increased DNA methylation of p16(Kim et al.2001;Scesnaite et al.2012),MGMT,and DAPK (Russo et al.2005).Tobacco smoke is also associated with tumor cell DNA methylation changes in esophageal squa-mous cell carcinoma(Huang et al.2011),significantly higher frequencies of abnormal DNA hypermethylation inprostate(Enokida et al.2006)and gastric cancers tumor cells(Nan et al.2005)and with a higher risk of CIMP?colorectal tumors(Limsui et al.2010;Samowitz et al.2006).Lastly,the F2RL3gene is hypomethylated in smokers and may mediate the detrimental impact of smoking on cardiovascular mortality,since hypomethylat-ed F2RL3was found to be strongly associated with car-diovascular mortality among patients with stable coronary heart disease(Breitling et al.2012).Oxidative stressReactive oxygen species(ROS)are involved in numerous cellular processes including cellular redox alterations, immune response,signaling pathways,chromatin remod-eling and gene expression(Sundar et al.2010).ROS have the potential to influence epigenetic mechanisms(Baccar-elli and Bollati2009),and have been shown to inhibit binding of methyl-CpG binding protein2,a critical epi-genetic regulator that recruits cytosine methyl transferases and histone deacetylases to DNA(Valinluck et al.2004). Numerous environmental exposures,including constituents of air pollution and tobacco smoke,can generate ROS and thus may potentially alter epigenetic processes through oxidative stress mechanisms.MetalsPrenatal lead exposure is associated with decreased meth-ylation of LINE1and Alu in cord blood(Pilsner et al. 2009),and a similar pattern of LINE1methylation was reported in an elderly cohort(Wright et al.2010).Studies in humans have shown that arsenic exposure is associated with either global hypermethylation or hypomethylation in peripheral blood mononuclear cells(PBMCs)depending on dose(Majumdar et al.2010),as well as DNA hyperme-thylation of several genes,including CDKN2A(Chanda et al.2006),RASSF1A and PRSS3(Marsit et al.2006). Exposure to airborne particulates rich in lead,cadmium and chromium are associated with miRNA expression in peripheral blood(Bollati et al.2010)and airborne levels of nickel and arsenic are positively correlated with both his-tone3-lysine4trimethylation(H3K4me3)and histone 3-lysine9acetylation(H3K9ac)in blood leukocytes (Cantone et al.2011).Occupational exposure to nickel is associated with increased H3K4me3and decreased H3K9me2in PBMCs(Arita et al.2011).Lastly,cadmium can induce overexpression of the DNA methyltransferase genes DNMT1and DNMT3a in human embryo lung fibroblasts,and is associated with hypermethylation and silencing of the MSH2,ERCC1,XRCC1and OGG1genes in human bronchial epithelial cells(Jiang et al.2008;Zhou et al.2011).Organic chemicalsGas-station attendants and police officers occupationally exposed to low levels of benzene were found to have significantly lower LINE1and Alu methylation,hyper-methylation of p15,and hypomethylation of MAGE-1in blood(Bollati and Baccarelli2010;Bollati et al.2007).Genetic9epigenetic9environmental interactionsMost work investigating effects of environmental factors on epigenetic state has not considered the potential for genetic susceptibility to modify these associations.However,Salam et al.(2012)recently investigated contributions of both genetic and epigenetic variation in air pollution-mediated levels of fractional exhaled nitric oxide(feNO).Measure-ment of feNO provides an in vivo summary assessment of inducible nitric oxide synthase(iNOS)activity as well as airway inflammation.These investigators found interrelated effects of exposure to the air pollution constituents PM2.5, NOS2A promoter haplotypes,and methylation of the iNOS encoding gene NOS2A and NOS2promotor haplotypes on feNO level.These observations illustrate not only the feasi-bility of assessing interactions between epigenetic,genetic, and environmental factors,but also the importance of doing so in order to delineate complex biological relationships and identify susceptible subpopulations.Epigenetic effects in human diseaseConditions associated with improper parental contributions of imprinted genes are currently the clearest examples of human diseases related to epigenetic state.Even before genomic imprinting was described,experiments in which pronuclei were transplanted into enucleated eggs demon-strated that both maternal and paternal chromosomal con-tributions are required for normal development.Control conceptuses receiving one set(haploid genome)of mater-nal(egg-derived)and one set of paternal(sperm-derived) chromosomes could develop normally.However,abnormal development and early demise occurred in all conceptuses receiving either two maternal sets or two paternal sets of chromosomes(McGrath and Solter1984),which devel-oped into tissues with histologic features of dermoid cysts and hydatiform moles,respectively.Model imprinting disorders such as Beckwith–Wiede-mann,Angelman,Russell–Silver,and Prader–Willi syn-dromes are human conditions that can be caused by aberrant epigenetic state(Ferguson-Smith2011).The specific features,early onset,and rarity of these disorders facilitated recognition of their relation to improper parental contributions of imprinted loci(e.g.two maternal or two。

Pore size and interactions effect on removal of dyes with two lead(II)metal-organic frameworksMao-Lin Hu a,n,Lida Hashemi b,Ali Morsali b,nna College of Chemistry and Materials Engineering,Wenzhou University,Wenzhou325035,Chinab Department of Chemistry,Faculty of Sciences,Tarbiat Modares University,P.O.Box14115-175,Tehran,Islamic Republic of Irana r t i c l e i n f oArticle history:Received30November2015Received in revised form23February2016Accepted19March2016Available online19March2016Keywords:Porous materialDye eliminationAnionic dyeCationic dyeSpectroscopya b s t r a c tTwo typical highly porous metal-organic framework(MOF)materials based on lead(II),[Pb(4-bpdh)(NO3)2(H2O)]n(TMU-1)and[Pb(4-bpdh)(NO3)2]n(TMU-2)have been used for the removal ofharmful dyes(anionic dye methyl orange(MO)and cationic dye methylene blue(MB))from con-taminated water via adsorption.The adsorption capacities of TMU-1and TMU-2are much higher thanthose of an activated carbon.Our results show that the difference between MO and MB adsorption inTMU-1and TMU-2could be relate to pore size and coordinated H2O interactions.Dye elimination hasalso been studied by the use of adsorption/desorption process.The delivery of dyes from compounds inmethanol at room temperature was determined by UV/vis spectroscopy.&2016Elsevier B.V.All rights reserved.1.IntroductionMetal–organic frameworks(MOFs),hybrid materials built upfrom metal clusters and organic linkers,have shown a huge po-tential for a wide range of applications[1].In recent years,MOFshave set new records in terms of specific surface areas and porevolumes[2,3]and therefore are highly suitable as storage mate-rials for small and large molecules.In the textile and food in-dustries,the uses of organic dyes are the important sources ofenvironmental contaminations due to their high toxicity to aquaticcreatures and carcinogenic effects on humans[4,5].There are anumber of technologies available for the removal of dyestuffs,suchas physical,chemical and biological methods[6–8].Adsorptiontechnology is regarded as one of the most competitive methodsbecause it does not need a high operation temperature and severalcoloring materials can be removed simultaneously[9].Physicaladsorption,because of its low cost,high efficiency,easy handling,wide variety of adsorbents,and high stabilities toward the ad-sorbents,has become the mostly widely used method for elim-inating dyes from wastewaters.Meanwhile,other methods,suchas solvent extraction[10],sonochemistry[11],and biodegradation[12],have also demonstrated high potential for applications.Methyl orange(MO)is one of the well-known acidic/anionic dyes,and has been widely used in textile,printing,paper,food andpharmaceutical industries and research laboratories.Methyleneblue(MB)is one of the most common dying materials for wood,silk and cotton.The structures of MO and MB are shown in TableS1and the removal of MO and MB from water is very importantdue to their toxicity[13–15].In this work,we report the results ofthe adsorption of not only an anionic dye(MO)but also a cationicdye(MB)over two our reported MOFs,[Pb(4-bpdh)(NO3)2(H2O)]n(TMU-1)[16]and[Pb(4-bpdh)(NO3)2]n(TMU-2)[17],because re-moval of both cationic and anionic dyes are not readily achievedsimultaneously and the adsorption can be understood with acomparison of the two adsorbents.2.Results and discussionTMU-1and TMU-2were obtained by the branched tubemethod with a thermal gradient method[16,17].Compound TMU-1is a porous3D coordination polymer with nano-size pores(1.8Â2.1nm).Absence of H2O molecules in compound TMU-2lead to smaller pore size only(0.4Â1.8nm)(Fig.S1).Porousstructure in TMU-1and TMU-2are suitable for adsorption of somemolecules with special directional physical properties and a fewexamples of dye inclusion into MOFs[18,19]are known.For ar-gument of porosity in the compounds TMU-1and TMU-2wesuccessfully tested their porosity with MO and MB by suspendingContents lists available at ScienceDirectjournal homepage:/locate/matletMaterials Letters/10.1016/j.matlet.2016.03.1000167-577X/&2016Elsevier B.V.All rightsreserved.n Corresponding author.nn Corresponding author.E-mail addresses:Maolin_hu@(M.-L.Hu),morsali_a@modares.ac.ir(A.Morsali).Materials Letters175(2016)1–4them in a water solution of MO and MB.The IR spectra of TMU-1,TMU-2,MO,and MB@TMU-1as well as TMU-2are shown in Fig.S2.The IR spectrum of the compound TMU-1shows more simi-larity with the IR spectra of MO@TMU-1and MB@TMU-1material,so the MO@TMU-1,MB@TMU-1and TMU-1have the same structures.The IR spectrums of TMU-2and MO@TMU-2and MB @TMU-2are shown in Fig.S2,too.The IR spectrum of the these compounds also shows more similarity with the IR spectra of MO@TMU-2and MB@TMU-2material,so the MO@TMU-2and MB@TMU-2and TMU-2have the same structures.Fig.S3makes a comparison between the XRD pattern of single crystal X-ray data of compound TMU-1and TMU-2with the XRD pattern of a typical sample of MO@TMU-1,MB@TMU-1and MO@TMU-2as well as MB@TMU-2.An acceptable match,with slight differences in 2θ,was observed between TMU-1and MO@TMU-1and MB@TMU-1,but several re flections are shifted up to 3°in 2θ.The comparison between TMU-2and MO and MB@TMU-2also has been shown an acceptable match,with slight differences in 2θ.The slight differ-ences in the IR spectra and PXRD patterns of MO@TMU-n and MB@TMU-n with related TMU-n materials may suggest the load-ing of MO and MB into the TMU-1and TMU-2and also presence of some interactions between the TMU-n and dyes.2.1.Dye adsorptionA few samples (100mg of TMU-1and TMU-2)in a suf ficient amount of water solution of MO and MB (200ppm)have been immersed in a small sealed flask at room temperature,and ob-served that the dark solutions of MO and MB fade slowly to very pale yellow and blue (Figs.1and 2)respectively.Our observation shows that compound TMU-2adsorbed MO and MB molecules in a longer time (about 72h)whereas compound TMU-1becometransparent in about 48h and adsorb 100%of dye (Fig.1).Our observation shows that this result for MB adsorption is same (Fig.2).MO and MB adsorption in TMU-1occurs in shorter time in comparison with TMU-2that must be because of larger pore size in TMU-1.This phenomenon can justi fied with attendance of H 2O molecules in TMU-1pores too,so interactions between H 2O and MO and MB molecules led to higher amount of adsorption and faster adsorb rate.2.2.Dye eliminationThe delivery of dyes from TMU-1and TMU-2performed in methanol,a nonaromatic solvent,at room temperature that was determined by UV/vis spectroscopy.The temporal evolution UV/vis spectrum for dyes in methanol solution,which shows λmax at different regions,becomes stronger by increasing the dye content (Fig.3).Presence of H 2O molecules prevented the release of MO and MB molecules and so we expect that desorbed rate in TMU-2will be faster than TMU-1that has been shown in Fig.S4.Fig.S4shows progress of the MO and MB release from TMU-1and TMU-2when the MOFs containing of MO and MB crystals were immersed in methanol.It seems that in TMU-2the pores become smaller and the MO and MB molecules are more accessible than TMU-1,so the delivery of MO and MB from TMU-2can be faster than TMU-1but the amount of absorbance is parison of MO and MB desorbed rate from TMU-1and TMU-2have been shown in Fig.4.Fig.4shows that the regularity of dye elimination rate conforms from this relation:MO@TMU-24MB@TMU-24MB@TMU-14MO@TMU-1.parison of MO enrichment progress between TMU-1and TMU-2;(a)blank,(b)MO@TMU-1and (c)MO@TMU-2.(For interpretation of the references to color in this figure,the reader is referred to the web version of this article.)M.-L.Hu et al./Materials Letters 175(2016)1–42parison of MB enrichment progress between TMU-1and TMU-2;(a)blank,(b)MB@TMU-1and (c)MB@TMU-2.(For interpretation of the references to color in this figure,the reader is referred to the web version of thisarticle.)Fig.3.Temporal evolution of UV/vis absorption spectra for the delivery of MO,MB from TMU-1and TMU-2in the first 2h.M.-L.Hu et al./Materials Letters 175(2016)1–433.ConclusionsIn summary two lead(II)metal-organic frameworks,(TMU-1)and (TMU-2)with rigid empty pores have been constructed for adsorption of dyes.The empty phases of these MOFs have ex-cellent and promising dye af finity,and it can be slowly delivered to methanol controllably.The comparison of adsorption and deso-rption of (MO)and (MB)between TMU-1and TMU-2shows that the coordinated water molecules in TMU-1can increase both af-finity and amount of MO and MB adsorption.The results support further the idea that assembling MOFs can be more applicable in encapsulation of functional substances to achieve novel oriented properties.AcknowledgementsThe authors thank Tarbiat Modares University for all thesupports.The work was supported by the National Natural Science Foundation of China (Nos.21371137and 21571143).Appendix A.Supplementary materialSupplementary data associated with this article can be found in the online version at doi:/10.1016/j.matlet.2016.03.100.References[1]D.Farrusseng,S.Aguado,C.Pinel,Angew.Chem.Int.Ed.48(2009)7502–7513.[2]L.J.Murray,M.Dinca,J.R.Long,Chem.Soc.Rev.38(2009)1294–1314.[3]H.Furukawa,N.Ko,Y.B.Go,N.Aratani,S.B.Choi,E.Choi,et al.,Science 329(2010)424–428.[4]M.A.Brown,S.C.De Vito,Crit.Rev.Environ.Sci.Technol.23(1993)249–324.[5]G.L.Baughman,E.J.Weber,Environ.Sci.Technol.28(1994)267–276.[6]E.Haque,J.E.Lee,I.T.Jang,Y.K.Hwang,J.S.Chang,J.Jegal,S.H.Jhung,J.Hazard.Mater.181(2010)535–542.[7]L.G.da Silva,R.Ruggiero,P.D.Gontijo,et al.,Chem.Eng.J.168(2011)620–628.[8]banda,J.Sabate,J.Llorens,Chem.Eng.J.166(2011)536–543.[9]S.H.Chen,J.Zhang,C.L.Zhang,Q.Y.Yue,Y.Li,C.Li,Desalination 252(2010)149–156.[10]P.Pandit,S.Basu,Environ.Sci.Technol.38(2004)2435–2442.[11]M.Karkmaz,E.Puzenat,C.Guillard,Appl.Catal.B:Environ.51(2004)183–194.[12]H.An,Y.Qian,X.Gu,W.Z.Tang,Chemosphere 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Journal of Colloid and Interface Science318(2008)160–166/locate/jcisAdsorption of Pb2+,Zn2+,and Cd2+from watersby amorphous titanium phosphateKun Jia,Bingcai Pan∗,Qingrui Zhang,Weiming Zhang,Peijuan Jiang,Changhong Hong,Bingjun Pan,Quanxing ZhangState Key Laboratory of Pollution Control and Resource Reuse,School of the Environment,Nanjing University,Nanjing210093,People’s Republic of ChinaReceived24August2007;accepted16October2007Available online26November2007AbstractIn the current study,amorphous titanium phosphate(TiP)was prepared as an adsorbent for heavy metals from waters.Uptake of Pb2+,Zn2+, and Cd2+onto TiP was assayed by batch tests;a polystyrene–sulfonic acid exchanger D-001was selected for comparison and Ca2+was chosen as a competing cation due to its ubiquitous occurrence in waters.The pH-titration curve of TiP implied that uptake of heavy metals onto TiP is essentially an ion-exchange pared to D-001,TiP exhibits more preferable adsorption toward Pb2+over Zn2+and Cd2+even in the presence of Ca2+at different levels.FT-IR analysis of the TiP samples laden with heavy metals indicated that the uptake of Zn2+and Cd2+ions onto TiP is mainly driven by electrostatic interaction,while that of Pb2+ions is possibly dependent upon inner-sphere complex formation,except for the electrostatic interaction.Moreover,uptake of heavy metals onto TiP approaches equilibrium quickly and the exhausted TiP particles could be readily regenerated by HCl solution.©2007Elsevier Inc.All rights reserved.Keywords:Titanium phosphate;Heavy metals;Adsorption;Mechanism1.IntroductionWater pollution by heavy metals remains an important envi-ronmental issue associated negatively with health and the econ-omy[1],and more stringent regulations have been established to restrict their random discharge.Accordingly,various tech-nologies,including chemical precipitation[2],adsorption[3], membrane processes[4],electrolytic methods[5],and ion ex-change[6–9],have been proposed for their remediation from waste streams.Ion exchange is one of the most frequently studied and widely applied techniques for the treatment of metal-contaminated wastewater[6,7],and polymeric cation or anion exchangers are always employed for this specific pur-pose[6,7].*Corresponding author.E-mail address:bcpan@(B.Pan).As a family of inorganic cation exchangers,zeolite or zeolite-based adsorbents have been studied extensively for se-lective removal of heavy metals from industrial and natural waters[10,11].Unfortunately,we have less knowledge of stud-ies involving adsorption of heavy metals onto another important group of inorganic cation exchangers,M(HPO4)2(M=Zr,Ti, Sn).M(HPO4)2compounds are good ion-exchange materials and exhibit remarkable thermal and radiolytic stability[12,13]. There are numerous reports on ion-exchange properties of dif-ferent M(HPO4)2with alkali or alkaline earth metal ions in aqueous solution[13,14].However,little is known about their ion-exchange properties in the presence of aqueous heavy metal ions[15,16].In our previous study we demonstrated the applicability of Zr(HPO4)2as an adsorbent for heavy metals[17,18].Here we attempt to explore the adsorption behavior and mechanism of heavy metals onto another important M(HPO4)2,Ti(HPO4)2. D-001,a widely used polystyrenesulfone cation exchanger,was chosen for comparison.0021-9797/$–see front matter©2007Elsevier Inc.All rights reserved. doi:10.1016/j.jcis.2007.10.043K.Jia et al./Journal of Colloid and Interface Science318(2008)160–1661612.Materials and methods2.1.MaterialsLead nitrate,zinc nitrate,and cadmium nitrate were used as heavy metal sources in this study by dissolving them in the double-deionized water.All chemicals,including titanium chlo-ride(liquid,purity>98%),are of analytical grade and were purchased from Shanghai Reagent Station(Shanghai,China). D-001,a macroreticular polystyrenesulfone exchanger(of H-type)with total capacity of4.30meq/g and cross-linking den-sity of8%,was kindly provided by Langfang Electrical Resin Co.,Ltd.(Hebei Province,China).It was obtained in spheri-cal bead form with sizes ranging from0.6to1.0mm.Prior to use,D-001was subjected toflushing with deionized water to remove residual impurities until neutral pH(6.8–7.2)and then vacuum-desiccated at348K for24h until it reached a constant weight.2.2.Preparation and characterization of titanium phosphateFor preparation of TiP(titanium phosphate)particles,40ml of titanium chloride wasfirst dissolved into60ml of4M HCl solution.At the ambient temperature,the above solution was gradually added into aflask containing250ml of5M H3PO4and shaken at120rpm overnight.Then the mixture was subjected tofiltration,and the resulting solid particles(TiP) were rinsed with double-deionized water till neutral pH.Sub-sequently,the TiP particles were vacuum-desiccated at323K for24h for further study.X-ray diffraction(XRD)spectra of the TiP particles were recorded by an XTRA X-ray diffrac-tometer(Switzerland).XPS analysis of the TiP samples was performed with a spectrometer(ESCALAB-2,Great British) equipped with an Mg KαX-ray source(1253.6-eV protons). The software package Scalab was used tofit the spectra peaks. FT-IR spectra of TiP particles before and after metal adsorp-tion were taken from a Nexus870FT-IR spectrometer(USA) with a pellet of powered potassium bromide and adsorbent in the range of500–4000cm−1.2.3.pH titrationpH titration of TiP particles was performed according to the reference[13,19].Portions(500mg)of each exchanger were mixed with100ml of0.1M NaCl.This mixture was kept for 6h and titrated against0.15M NaOH solution.The pH of the solution was recorded after each addition of1.0ml of the titrant till the pH became constant.From the solution pH values before and after the exchange process,the milliequivalents of OH−ion consumed were liequivalents of OH−ions consumed by the exchanger were then plotted against the cor-responding pH values to get the pH-titration curves.2.4.Batch adsorption and regeneration experimentsBatch adsorption tests were determined by contacting TiP particles or D-001beads with a range of different concentra-tions of heavy metal solution in250-ml glassflasks,maintainedFig.1.XRD spectra of the TiP particles prepared in the current study.at desired pH and temperature.To start the experiment,known amounts of the individual adsorbents(TiP or D-001)were intro-duced into a100-ml solution containing each individual metal (50–500mg/l).Theflasks were then transferred to a G25 model incubator shaker with thermostat(New Brunswick Sci-entific Co.,Inc.)and shaken at200rpm for24h at303K to ensure that the adsorption process reaches equilibrium.HNO3 solution(0.5M)was used to adjust the solution pH throughout the experiment when necessary.A quantity of0.5ml of solution at various time intervals was sampled from theflasks to deter-mine adsorption kinetics.The amount of each metal loaded onto the adsorbent is calculated by conducting a mass balance before and after the test.The TiP samples from adsorption runs were transferred to anotherflask afterfiltering and10.0ml of0.5M HCl solution was used for extraction of the loaded metals.2.5.AnalysesConcentrations of all the heavy metals were determined by atomic absorption spectroscope(Z-8100,Hitachi,Japan)ex-cept for those less than1mg/l,which were determined by an atomicfluorescence spectrophotometer with an online reducing unit(AF-610A,China)with NaBH4and HCl solution[20].3.Results and discussion3.1.Characterization of TiP particlesTiP particles with sizes ranging from1to100µm generally were prepared according to the following equation:TiCl4+2H3PO4→Ti(HPO4)2↓+4HCl.(1) The Ti/P ratio in the TiP phase,determined as1:2by XPS analysis,further ensured its structure of Ti(HPO4)2.As indi-cated by XRD spectra(Fig.1),the TiP particles are amorphous in nature[21,22].To elucidate the nature and numbers of ex-changeable sites in TiP,pH titration of the TiP sample was carried out by comparison with D-001.The total number of hy-drogen ions in TiP deduced from Fig.2is about8.25mmol/g,162K.Jia et al./Journal of Colloid and Interface Science318(2008)160–166Fig.2.pH-titration curves of D-001and TiP using0.15M NaOH solution at 303K(0.50g of each adsorbent was used for titration test).which is consistent with the value calculated from its molecu-lar formula(8.34mmol/g).Similarly to ZrP[17],the hydrogen ion within TiP is also released in a stepwise manner because the acid groups within TiP are weakly dissociated and it is reluc-tant to exchange its H+ion for Na+,so that the ion exchange remains incomplete.Only about4.11meq/g of hydrogen ion (about half of the total amount)can be released to solution for ion exchange below the neutral pH.In contrast,as a strong acid cation exchanger,all the hydrogen ions in D-001parti-cles are readily released for ion exchange with Na+and then neutralization by the added OH−.Hence,the pH of the super-natant aqueous solution remains essentially unchanged.Note that heavy metals can always be effectively trapped by ion ex-change in weakly acidic solution because most of the heavy metal ions are precipitated in alkaline solution.Thus,it can be assumed that the conceptual mechanism of heavy metal adsorp-tion by TiP may be presented asTi(HPO4)2+(1/2)M2+ TiM1/2H(PO4)2+H+,(2) where M represents the corresponding heavy metal element. 3.2.Effect of solution pH on adsorptionThe effect of solution pH on metal extraction by TiP was examined and the results are presented in Fig.3.The uptake capacity of each metal was increased with the increasing so-lution pH,and the optimum solution pH for lead,zinc,and cadmium is about3,4.5,and5,respectively.According to the pH-titration curve and our previous study of heavy metal re-moval onto zirconium phosphate(ZrP)particles[17,18],the pH-dependent trend is assumed to result from ion exchange between metal ions and TiP.In addition,negligible uptake at pH less than0.5suggested that the metal-laden TiP particles might be regenerated by strong acid solutions,which was fur-ther demonstrated in the desorption experimentsbelow.Fig.3.Effect of solution pH on heavy metal adsorption onto TiP at303K (0.050g TiP particles were added into100ml solution containing1.10mmol/l of each metal,respectively).3.3.Adsorption isotherms and kineticsAdsorption isotherm experiments on heavy metals onto TiP were performed at303K and the results are illustrated in Fig.4 and correlated by the traditional Langmuir and Freundlich mod-els[15],(3)C eq e=1K L q m+C eq m,(4) q e=K F C1/n e,where C e is the concentration of each target species in equilib-rium,q e is adsorption capacity in equilibrium,q m is the max-imum amount of solute exchanged per gram of the exchanger, and K L is a constant that can indicate the capability of adsorp-tion.K F and n are constants to be determined.All the constants are listed in Table1.Results indicated that lead removal by TiP can be represented by the Langmuir model more reasonably, while zinc and cadmium adsorption can be well correlated by both models.Adsorption kinetic experiments of three metals on TiP were also performed and the results are presented in Fig.5.It can be seen that initial adsorption of heavy metals is very quick,fol-lowed by a gradual adsorption approaching equilibrium within 1h.The kinetic data are not correlated by any mathematic mod-els,mainly because we cannot define the size ranges of TiP particles due to their ultrafine nature,which is necessary before properly modeling the kinetic performance of a given sorbent.3.4.Effect of Ca2+on removal of heavy metalsTaking into account the fact that a relatively high level of common cations such as Na+,Ca2+,and Mg2+is ubiquitous in waste streams laden with heavy metals,adsorption selectivity of a specific exchanger toward heavy metals is a key factor in ensuring its technical applicability.In the current study,Ca2+ was selected as a model competing cation and its effect on theK.Jia et al./Journal of Colloid and Interface Science318(2008)160–166163Fig.4.Adsorption isotherms of(a)Pb2+(pH3.0–3.2);(b)Cd2+(pH4.5–5.0);(c)Zn2+(pH4.5–5.0)onto TiP particles at303K.Table1Isotherm constants for heavy metals adsorption onto TiP at303KHeavy metals Langmuir model Freundlich modelK L q m(mmol/g)R2K f n R2Pb2+0.0946 1.890.9600.0809 2.000.859 Cd2+0.02820.5580.9930.0704 2.620.961 Zn2+0.01870.7190.9920.0606 2.320.986Fig.5.Adsorption kinetics of heavy metals onto TiP at303K(0.40g TiP and 1000ml solution containing0.5mmol/l of each metal were selected for the study).removal of heavy metals was examined as compared to D-001 of sulfonic acid functionality.As seen in Fig.6,increasing Ca2+/M2+ratio inevitably results in decreasing uptake capacity of target species of both D-001and TiP due to the competi-tive effect.However,compared to D-001,TiP displays a high preference toward lead over other two metals.To compare the selectivity of the two adsorbents,the distribution ratio K d was quantified by the equation[23](5) K d=(C0−C e)/C0V/m,where C0is the initial concentration of the solute,V is the vol-ume of the solution,and m is the mass of the solute.The K d values listed in Table2further elucidate the preferable sequence toward different heavy metals,and the competitive effect of Ca2+was also demonstrated by the variation of K d values with the Ca/M ratios.In general,ion-exchange preference of a given exchanger for target ions follows the principle of hard and soft acids and bases(HSAB)[24,25].Therefore,TiP and similar compounds with hard Lewis basic oxygen-rich functional groups would be more likely to undergo ion exchange with hard Lewis acids. Therefore,Pb2+,grouped as a harder Lewis acid than Cd2+ and Zn2+[25],can be trapped by TiP particles more effectively than the other two metals.However,as a harder Lewis acid, Ca2+does not display an adverse effect on Pb2+removal by TiP as compared to the other two metals,which seems incon-sistent with the HASB principles.The underlying mechanism will be further elucidated in the following section.On the other hand,stronger adsorption affinity always oc-curs when thefixed ionic groups are similar in structure to precipitating or complexing agents that react with the counte-rions[13].Table3lists the log K sp values of some metal phos-phates or sulfates.Apparently,the absolute log K sp values of metal phosphates also follow the same sequence as their selec-tivity behavior,i.e.,Pb2+>Zn2+≈Cd2+>Ca2+.In contrast, calcium ions are preferred by sulfate ions,which are hard bases, over other cations and result in a great decrease in selectivity of heavy metals onto D-001accordingly.164K.Jia et al./Journal of Colloid and Interface Science318(2008)160–166Fig.6.Effect of Ca2+on(a)Pb2+(pH3.0–3.2);(b)Cd2+(pH4.5–5.0);(c) Zn2+(pH4.5–5.0)removal by TiP and D-001at303K(0.025g TiP particles or D-001beads were introduced in solution with each metal at initial concentration of0.25mmol/l,respectively).3.5.FT-IR analysisTo gain insight into the adsorption mechanism of different heavy metals onto TiP,FT-IR analysis of TiP samples laden with different metals was performed by comparison with the fresh ones.As seen from the IR spectra(Fig.7),the pres-Table2Effect of Ca2+on the distribution coefficients(K d)of heavy metals(M)ad-sorption onto TiP and D-001at303KHeavymetals(M2+)Adsorbent K d(l/g)at different initial Ca2+/M2+ratiosin solution2481632 Pb2+TiP12411610486.364.9 D-00116.87.05 3.30 1.680.84 Zn2+TiP 1.45 1.000.410.550.29 D-001 3.25 1.170.610.270.21 Cd2+TiP 1.75 1.400.780.700 D-001 3.64 1.310.2800Table3log K sp values of some metal phosphates and sulfates aMetal phosphates Ca3(PO4)2Cd3(PO4)2Zn3(PO4)2Pb3(PO4)2 log K sp−27.70−31.44−32.04−42.09 Metal sulfates CaSO4CdSO4ZnSO4PbSO4 log K sp−7.80NA NA−6.50a The corresponding values of CdSO4and ZnSO4are not available(NA) because they are soluble in water.ence of external water within the TiP particles in addition to the strongly hydrogen-bonded OH or extremely strongly co-ordinated H2O is confirmed by the sharp peaks at3500and 1650cm−1[19,26].The band from1000to1020cm−1repre-sents asymmetric stretching vibration of Ti–P–OH[27,28],and the weak band at605–615cm−1is assigned to the deforma-tion vibration for the Ti–O bond[29].Detailed band variation data of TiP samples before and after uptake of metals are listed in Table4.The bands of Ti–P–OH in all the TiP samples were shifted to higher frequency in the sequence Pb Zn≈Cd, which is consistent with their selectivity sequence.Note that negligible variation for Ca2+-laden TiP was observed in the band.This shift of the P–OH band reflects different electrostatic interactions between the orthophosphate group and metals af-ter replacement of hydrogen ion.Meanwhile,the obvious shift of the Ti–O band after uptake of Pb2+and Ca2+implies the presence of Pb–O or Ca–O interaction,which may result from inner-sphere complex formation of both metals with TiP.This is not the case for Zn2+and Cd2+,and the corresponding shifts are negligible.Therefore,adverse effects of Ca2+on Cd2+and Zn2+adsorption by TiP mainly result from the possible forma-tion of inner-sphere complexes between Ca2+and TiP,and TiP prefers Pb2+adsorption over the other three metals,mainly be-cause of the synergistic effect of the electrostatic interaction and possible inner-sphere complex formation[17].Further study should be performed to elucidate the mechanism of adsorption of heavy metals onto titanium phosphate.3.6.Environmental implicationsOther preliminary results also indicated that other common cations,including Na+and Mg2+ions,play a less significant role than Ca2+ions in uptake of heavy metals onto TiP,which also follows the HSAB principles.Following several trials,HClK.Jia et al./Journal of Colloid and Interface Science318(2008)160–166165Fig.7.FT-IR spectra of TiP samples loaded with different metal ions(the capacity of each metal ranges from0.7to0.8mmol/g).Table4Absorption peaks of TiP samples loaded with different heavy metals in FT-IR spectra aTiP TiP/Pb TiP/Zn TiP/Cd TiP/Ca A(cm)1019.91002.71016.91017.51020.3 B(cm−1)615.3607.1613.7614.4610.3 a A and B refer to Fig.7.solution was proved to be an efficient regenerant for TiP loaded with heavy metals.Batch desorption runs indicated that more than92%of Pb2+,95%of Zn2+,and80%of Cd2+preloaded on the TiP particles can be trapped by10ml0.5M HCl solution at303K.All the above results indicated that TiP is a potential candidate for removal of heavy metals,particularly for Pb2+. However,like other functional inorganic compounds,such as hydrated ferric oxide and ZrP,TiP as ultrafine particles in nature cannot be directly used for removal of heavy metals,due to the excessive pressure drop in anyflow-through systems[30,31]. An effective approach is to immobilize TiP particles on porous materials to obtain hybrid adsorbents,and the relevant study is under the way in our laboratory.4.ConclusionsAmorphous titanium phosphate(TiP)was proved to be an ef-fective adsorbent for Pb2+,Cd2+,and Zn2+from water through an ion-exchange mechanism.High preference of TiP for Pb2+ over Cd2+and Zn2+was observed even in the presence of Ca2+at relatively high levels,which can be explained by hard and soft acids and bases(HASB)principles.FT-IR analysis in-dicated that Cd2+and Zn2+adsorption onto TiP was mainly driven through electrostatic interaction,while Pb2+extraction by TiP was enhanced due to the synergetic effect of electrostatic interaction and inner-sphere complex formation.Additionally, the metal-laden TiP can be effectively regenerated by HCl so-lution.AcknowledgmentsThis study was partially supported by the NSFC of China (20504012)and Jiangsu NSF(BK2007717/2006129). 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文章编号：1672-2019（2009）01-0019-05·综述·生物质材料对水体中染料和其他有机污染物的吸附顾迎春1，郑静2，石碧1（1.四川大学制革清洁技术国家工程实验室，四川成都610065；2.成都信息工程学院图书馆，四川成都610225）摘要：大量研究表明：纤维素基生物质、甲壳素和微生物对水体中染料的吸附容量低于商品活性碳对染料的吸附容量；虽然壳聚糖对一些阴离子型染料有相当大的吸附容量，但由于其性能不稳定，因此难以获得大规模工业应用。

关于生物质对其他有机污染物吸附性能的研究报道相对较少，说明这方面的研究有待于进一步深入和拓展。

废弃皮胶原是一类来源极其丰富的生物质，近年来的研究发现：基于皮胶原研制的新型吸附剂对水体中的阴离子型染料和有机酸能有效去除，有可能在染料和有机废水处理方面得到应用。

关键词：生物质，吸附，染料，有机污染物，皮胶原中图分类号：TQ028文献标识码：Adsorption of dyes and other organic pollutants on biomassmaterials from aqueous solutionsGU Ying-chun 1,ZHENG Jing 2,SHI Bi 1(1.National Engineering Laboratory for Clean Technology of Leather Manufacture,Sichuan University,Chengdu 610065,China;2.Library of Chengdu University of Information andTechnology,Chengdu,610225,China)Abstract ：A large number of researches have indicated that the adsorption capacities of dyes on cellulose-based biomass,chitin and microbe were lower than those on commercial activated carbons from aqueous solutions.Al －though the adsorption capacities of some anionic dyes on chitosan were great considerably,the properties of chitosan were not stable enough to acquire the industrial application on large scale.The relatively fewer reports illustrate that there should be more profound and extended research concerned with the adsorption characteristics of other organic pollutants on biomass.Waste hide collagen is a type of very abundant biomass.The recent investigation has found that a novel adsorbent based on hide collagen had the effective removal of anionic dyes and organic acids from aqueous solutions and might have the potential usefulness on the treatment of dye and organic wastewater.Key words ：biomass,adsorption,dyes,organic pollutions,hide collagen收稿日期：2008-12-07*基金项目:国家科技支撑计划课题（No.2006BAC02A09）；四川省重点科学与技术研究项目(04SG012-009)；四川大学青年科学基金(200452)[通讯作者]石碧，E-mail:shibi@ or sibitannin@ ，Tel:(028)85405508第17卷第1期中国医学工程Vol.17No.12009年3月China Medical EngineeringMar.2009对水体中染料和其他有机污染物吸附性能的研究的主要目的是对染料和有机废水进行脱色和净化处理。

AFM-microRaman and nanoRaman TMIntroductionThe use of Raman microscopy has become animportant tool for the analysis of materials on themicron scale. The unique confocal and spatialresolution of the LabRAM series has enabled opticalfar field resolution to be pushed to its limits withoften sub-micron resolution achievable.The next step to material analysis on a smallerscale has been the combination of Ramanspectroscopic analysis with near field optics and anAtomic force microscope (AFM). The hybridRaman/AFM combination enables nanometrictopographical information to be coupled to chemical(spectroscopic) information. The unique designsdeveloped by HORIBA Jobin Yvon enable in-situRaman measurements to be made upon variousdifferent AFM units, and for the exploration of newand evolving techniques such as nanoRamanspectroscopy based on the TERS (tip enhancedRaman spectroscopy) effect.AFM image of nano-structures on a SiN sampleHORIBA Jobin Yvon offers both off-axis and on-axisAFM/Raman coupling to better match your sampleand analysis requirements.Off-axis and inverted on-axis configurations forAFM/Raman coupling showing the laser (blue) andRaman (pink) optical pathThe LabRAM-Nano Series is based on the provenLabRAM HR system providing unsurpassedperformance for classical Raman analysis. With theAFM coupling option, it becomes the platform ofchoice for AFM/Raman experiments. The off-axisgeometry offers large sample handling capabilitiesand is ideally suited for the analysis ofsemiconductor materials, wafers and more generallyopaque samples.For biological and life science applications, theLabRAM-Nano operates in inverted on-axisconfiguration with a confocal inverted Ramanmicroscope on top of which the AFM unit is directlymounted. This system is ideally suited for the studyof transparent biological samples such as singlecells, tissue samples and bio-polymers.In both systems, AFM and SNOM fluorescencemeasurements can be combined with Ramananalysis to provide a more completecharacterisation of sample chemistry andmorphology on the same area. Several AFMsystems from leading AFM manufacturers can beadapted on these two instruments. Please contactus to find out which one is best for you!AFM- microRaman dual analysisThe seamless integration of hardware and software of both systems onto the same platform enables fast and user-friendly operation of both systems at the same time. Furthermore, the AFM/Raman coupling does not compromise the individual capabilities of either system and the imaging modes of the AFM remain available (EFM, MFM, Tapping Mode, etc.)The operator has direct access to both the nanometric topography of a sample given by the AFM, and the chemical information from the micro-Raman measurement. An AFM image can berecorded as an initial survey map, in which regions of interest can be defined for further Raman analysis, using the same software.An example of such analysis is illustrated below by an AFM image of Carbon Nanotubes (CNTs) giving information on the CNTs’ length, diameters and aggregation state. A more detailed AFM image is then obtained in which Raman analysis can be performed.Carbon nanotubes AFM images with a gold-coated tip in contact mode. The diameter of the bundles of nanotubes is between 10 and 30 nm.NanoRaman for TERS experimentsSurface Enhance Raman Scattering (SERS) has long been used to enhance weak Raman signals by means of surface plasmon resonance using nanoparticle colloids or rough metallic substrates, allowing to detect chemical species at ppm levels.The TERS effect is based on the same principle, but uses a metal-coated AFM tip (instead of nanoparticles) as an antenna that enhances the Raman signal coming from the sample area which is in contact (near-field). Although not yet fully understood, the TERS effect has attracted a lot of interest, as it holds the promise of producing chemical images with nanometric resolution.The LabRAM-Nano offers an ideal platform,combining state-of-the-art AFMs with our Raman expertise to perform exploratory TERS experiments with confidence.Raman signal TERS enhancement on a Silicon sample with far field suppression thanks to adequate polarization configuration. Red : Far field + Near Field (tip in contact)– Blue : Far field only (tip withdrawn)Technical specificationsFlexure guided scanner is used to maintain zero background curvature below 2 nm out-of-planeFor non-TERS measurements, classical Raman measurements can be made on the same spot as AFM images by translating the sample with a high-accuracy positioning stage from the AFM setup to the Raman setup (and vice et versa). The AFM map can be used to define a region of interest for the Raman analysisusing a common software.LabRAM-Nano coupled with Veeco’s Dimension 3100 AFMThe on-axis coupling configuration enables both AFM-microRaman dual analysis and TERS measurementson transparent and biological samples. The AFM is directly coupled onto the inverted microscope and directlyinterfaced to the LabRAM HR microprobe. It can also be taken off the optical microscope to obtain AFMimages in a different location. Seamless software integration is realized to provide a common platform to bothsystems for both AFM and Raman analysis of the same area and TERS investigation.Bioscope II from VeecoLabRAM-Nano coupled with Park Systems(formerly PSIA) XE-120Off-axis coupling for AFM-microRaman and nanoRaman (TERS)For both dual AFM-microRaman dual analysis and TERS measurements, the off-axis coupling is ideally suited for opaque and large samples. For opaque samples, the inverted on-axis coupling is not possible as the sample will not transmit the laser beam. This can be solved by setting the microscope objective at some angle to avoid “shadowing” effects from the AFM cantilever. Here also, seamless software integration is realized to provide a common platform to both systems. The AFM can be controlled by the Raman software (LabSpec), and mapping areas can be defined on AFM images for further Raman analysis.France : HORIBA Jobin Yvon S.A.S., 231 rue de Lille, 59650 Villeneuve d’Ascq. Tel : +33 (0)3 20 59 18 00, Fax : +33 (0)3 20 59 18 08. Email : raman@jobinyvon.fr www.jobinyvon.frUSA : HORIBA Jobin Yvon Inc., 3880 Park Avenue, Edison, NJ 08820-3012. Tel : +1-732-494-8660, Fax : +1-732-549-2571. Email : raman@ Japan : HORIBA Ltd., JY Optical Sales Dept., 1-7-8 Higashi-kanda, Chiyoda-ku, Tokyo 101-0031. Tel: +81 (0)3 3861 8231, Fax: +81 (0)3 3861 8259. Email: raman@ LabRAM-Nano coupled with Park Systems (formerly PSIA) XE-100Combined polarized Raman and atomic force microscopy:In situ study of point defects and mechanical properties in individual ZnO nanobelts Marcel Lucas,1Zhong Lin Wang,2and Elisa Riedo1,a͒1School of Physics,Georgia Institute of Technology,Atlanta,Georgia30332-0430,USA2School of Materials Science and Engineering,Georgia Institute of Technology,Atlanta,Georgia30332-0245,USA͑Received8June2009;accepted23June2009;published online4August2009͒We present a method,polarized Raman͑PR͒spectroscopy combined with atomic force microscopy͑AFM͒,to characterize in situ and nondestructively the structure and the physical properties ofindividual nanostructures.PR-AFM applied to individual ZnO nanobelts reveals the interplaybetween growth direction,point defects,morphology,and mechanical properties of thesenanostructures.In particular,wefind that the presence of point defects can decrease the elasticmodulus of the nanobelts by one order of magnitude.More generally,PR-AFM can be extended todifferent types of nanostructures,which can be in as-fabricated devices.©2009American Instituteof Physics.͓DOI:10.1063/1.3177065͔Nanostructured materials,such as nanotubes,nanobelts ͑NBs͒,and thinfilms,have potential applications as elec-tronic components,catalysts,sensors,biomarkers,and en-ergy harvesters.1–5The growth direction of single-crystal nanostructures affects their mechanical,6–8optoelectronic,9 transport,4catalytic,5and tribological properties.10Recently, ZnO nanostructures have attracted a considerable interest for their unique piezoelectric,optoelectronic,andfield emission properties.1,2,11,12Numerous experimental and theoretical studies have been undertaken to understand the properties of ZnO nanowires and NBs,11,12but several questions remain open.For example,it is often assumed that oxygen vacancies are present in bulk ZnO,and that their presence reduces the mechanical performance of ZnO materials.13However,no direct observation has supported the idea that point defects affect the mechanical properties of individual nanostructures.Only a few combinations of experimental techniques en-able the investigation of the mechanical properties,morphol-ogy,crystallographic structure/orientation and presence of defects in the same individual nanostructure,and they are rarely implemented due to technical challenges.Transmis-sion electron microscopy͑TEM͒can determine the crystal-lographic structure and morphology of nanomaterials that are thin enough for electrons to transmit through,4,14–17but suf-fers from some limitations.For example,characterization of point defects is rather challenging.14–17Also,the in situ TEM characterization of the mechanical and electronic properties of nanostructures is very challenging or impossible.15–17 Alternatively,atomic force microscopy͑AFM͒is well suited for probing the morphology,mechanical,magnetic, and electronic properties of nanostructures from the micron scale down to the atomic scale.3,6,7,10In parallel, Raman spectroscopy is effective in the characterization of the structure,mechanical deformation,and thermal proper-ties of nanostructures,18,19as well as the identification of impurities.20Furthermore,polarized Raman͑PR͒spectros-copy was recently used to characterize the crystal structure and growth direction of individual single-crystal nanowires.21Here,an AFM is combined to a Raman microscope through an inverted optical microscope.The morphology and the mechanical properties of individual ZnO NBs are deter-mined by AFM,while polarized Raman spectroscopy is used to characterize in situ and nondestructively the growth direc-tion and randomly distributed defects in the same individual NBs.Wefind that the presence of point defects can decrease the elastic modulus of the NBs by almost one order of mag-nitude.The ZnO NBs were prepared by physical vapor deposi-tion͑PVD͒without catalysts14and deposited on a glass cover slip.For the PR studies,the cover slip was glued to the bottom of a Petri dish,in which a hole was drilled to allow the laser beam to go through it.The round Petri dish was then placed on a sample plate below the AFM scanner,where it can be rotated by an angle␸,or clamped͑see Fig.1͒.The morphology and mechanical properties of the ZnO NBs were characterized with an Agilent PicoPlus AFM.The AFM was placed on top of an Olympus IX71inverted optical micro-scope using a quickslide stage͑Agilent͒.A silicon AFM probe͑PointProbe NCHR from Nanoworld͒,with a normal cantilever spring constant of26N/m and a radius of about 60nm,was used to collect the AFM topography and modulated nanoindentation data.The elastic modulus of the NBs was measured using the modulated nanoindentation method22by applying normal displacement oscillations at the frequency of994.8Hz,at the amplitude of1.2Å,and by varying the normal load.PR spectra were recorded in the backscattering geometry using a laser spot small enough ͑diameter of1–2␮m͒to probe one single NB at a time.The incident polarization direction can be rotated continuouslywith a half-wave plate and the scattered light is analyzedalong one of two perpendicular directions by a polarizer atthe entrance of the spectrometer͑Fig.1͒.Series of PR spec-tra from the bulk ZnO crystals and the individual ZnO NBswere collected with varying sample orientation␸͑the NBs are parallel to the incident polarization at␸=0͒,in the co-͑parallel incident and scattered analyzed polarizations͒and cross-polarized͑perpendicular incident and scattered ana-lyzed polarizations͒configurations.For the ZnO NBs,addi-tional series of PR spectra were collected where the incidenta͒Electronic mail:elisa.riedo@.APPLIED PHYSICS LETTERS95,051904͑2009͒0003-6951/2009/95͑5͒/051904/3/$25.00©2009American Institute of Physics95,051904-1polarization is rotated and the ZnO NB axis remained paral-lel or perpendicular to the analyzed scattered polarization ͑see supplementary information 25͒.The exposure time for each Raman spectrum was 10s for the bulk crystals and 20min for NBs.After each rotation of the NBs,the laser spot is recentered on the same NB and at the same location along the NB.Prior to the PR characterization of ZnO NBs,PR data were collected on the c -plane and m -plane of bulk ZnO crystals ͓Fig.2͑a ͔͒.In ambient conditions,ZnO has a wurtzite structure ͑space group C 6v 4͒.Group theory predicts four Raman-active modes:one A 1,one E 1,and two E 2modes.11,20,23The polar A 1and E 1modes split into transverse ͑TO ͒and longitudinal optical branches.On the c -plane ͑0001͒-oriented sample,only the E 2modes,at 99͑not shown ͒and 438cm −1,are observed,and their intensity is independent of the sample orientation ␸͓Fig.2͑a ͔͒.On them -plane ͑101¯0͒-oriented sample,the E 2,E 1͑TO ͒,and A 1͑TO ͒modes are observed at 99,438,409,and 377cm −1,respectively ͓Fig.2͑a ͔͒,and their intensity depends on ␸.Peaks at 203and 331cm −1in both crystals are assigned to multiple phonon scattering processes.The intensity,center,and width of the peaks at 438,409,and 377cm −1were obtained by fitting the experimental PR spectra with Lorent-zian lines ͑see supplementary information 25͒.The successful fits of the angular dependencies by using the group theory and crystal symmetry 23indicate that PR data can be used to characterize the growth direction of ZnO NBs.It is noted that the ZnO NBs studied here have dimensions over 300nm,so the determination of the growth direction is not ex-pected to be affected by any enhancement of the polarized Raman signal due to their high aspect ratio.24AFM images and PR data of three individual ZnO NBs are presented in Figs.2͑b ͒–2͑d ͒.These NBs,labeled NB1,NB2,and NB3,have different dimensions and properties assummarized in Table I .A comparison of the PR spectra in Figs.2͑a ͒–2͑d ͒reveals differences between bulk ZnO and individual NBs.First,the glass cover slip gives rise to a weak broadband centered around 350cm −1on the Raman spectra of the NBs ͓see bottom of Fig.2͑d ͔͒.Second,there are additional Raman bands around 224and 275cm −1for NB2and NB3.These bands are observed in doped or ion-implanted ZnO crystals.11,20Their appearance is explained by the disorder in the crystal lattice due to randomly distrib-uted point defects,such as oxygen vacancies or impurities.The defect peaks area increases in the order NB1ϽNB2ϽNB3.Since the laser spot diameter is larger than the width of all three NBs,but smaller than their length,L ,the NB volume probed by the laser beam is approximated by the product of the width,w ,with the thickness,t .ThevolumeFIG.1.͑Color online ͒Schematic of the experimental setup,showing the path of the laser beam.The ZnO NBs are deposited on a glass slide,which is placed inside a rotating Petridish.FIG.2.͑Color online ͒͑a ͒PR spectra from the c and m planes of a ZnO crystal,shown in blue and green,respectively.The wurtzite structure ͑Zn atoms are brown,O atoms red ͒is also shown,where a ء,b ء,and c ءare the reciprocal lattice vectors.͓͑b ͒–͑d ͔͒AFM images ͑3ϫ3␮m ͒of three NBs labeled NB1,NB2,and NB3and corresponding PR spectra.In ͑d ͒a PR spectrum of the glass substrate is shown at the bottom.All the PR spectra in ͑a ͒–͑d ͒are collected in the copolarized configuration for ␸=0and 90°.The spectra are offset vertically for clarity.TABLE I.Summary of the PR-AFM results for NB1,NB2,and NB3.w ͑nm ͒t ͑nm ͒w /t L ͑␮m ͒␪͑°͒E ͑GPa ͒Defects NB11080875 1.24028Ϯ1562Ϯ5No NB21150710 1.64972Ϯ1538Ϯ5Yes NB315104553.35966Ϯ1517Ϯ5Yesprobed decreases in the order NB1͑wϫt=9.45ϫ103nm2͒ϾNB2͑8.17ϫ103nm2͒ϾNB3͑6.87ϫ103nm2͒.This indi-cates that the density of point defects is highest in NB3,and increases with the width to thickness ratio,w/t,in the order NB1ϽNB2ϽNB3.The PR intensity variations of the438cm−1peak as a function of␸in the various polarization configurations were fitted by using group theory and crystal symmetry to deter-mine the angle␪between the NB long axis͑or growth di-rection͒and the c-axis͓͑0001͔axis͒of the constituting ZnO wurtzite structure21,23͑see supplementary information25͒.In-tensity variations of the377cm−1peak,when present,are used to confirm the obtained values of␪.The results are shown in Table I and indicate that growth directions other than the most commonly observed c-axis are possible,par-ticularly when point defects are present.Finally,the elastic properties of NB1,NB2,and NB3are characterized by AFM using the modulated nanoindentation method.6,7,22In a previous study,the elastic modulus of ZnO NBs was found to decrease with increasing w/t and this w/t dependence was attributed to the presence of planar defects in NBs with high w/t.6,7By using PR-AFM,we can study the role of randomly distributed defects,morphology,and growth direction on the elastic properties in the same indi-vidual ZnO NB.The measured elastic moduli,E,are62GPa for NB1,38GPa for NB2,and17GPa for NB3.These PR-AFM results confirm the w/t dependence of the elastic modulus in ZnO NBs,but more importantly they reveal that the elastic modulus of ZnO NBs can significantly decrease, down by almost one order of magnitude,with the presence of randomly distributed point defects.In summary,a new approach combining polarized Raman spectroscopy and AFM reveals the strong influence of point defects on the elastic properties of ZnO NBs and their morphology.Based on a scanning probe,PR-AFM pro-vides an in situ and nondestructive tool for the complete characterization of the crystal structure and the physical properties of individual nanostructures that can be in as-fabricated nanodevices.The authors acknowledge thefinancial support from the Department of Energy under Grant No.DE-FG02-06ER46293.1Y.Qin,X.Wang,and Z.L.Wang,Nature͑London͒451,809͑2008͒.2X.Wang,J.Song,J.Liu,and Z.L.Wang,Science316,102͑2007͒.3D.J.Müller and Y.F.Dufrêne,Nat.Nanotechnol.3,261͑2008͒.4H.Peng,C.Xie,D.T.Schoen,and Y.Cui,Nano Lett.8,1511͑2008͒. 5U.Diebold,Surf.Sci.Rep.48,53͑2003͒.6M.Lucas,W.J.Mai,R.Yang,Z.L.Wang,and E.Riedo,Nano 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Rev.Lett.94,175502͑2005͒.23C.A.Arguello,D.L.Rousseau,and S.P.S.Porto,Phys.Rev.181,1351͑1969͒.24H.M.Fan,X.F.Fan,Z.H.Ni,Z.X.Shen,Y.P.Feng,and B.S.Zou, J.Phys.Chem.C112,1865͑2008͒.25See EPAPS supplementary material at /10.1063/ 1.3177065for more information on the PR spectra.Growth direction and morphology of ZnO nanobelts revealed by combining in situ atomic forcemicroscopy and polarized Raman spectroscopyMarcel Lucas,1,*Zhong Lin Wang,2and Elisa Riedo1,†1School of Physics,Georgia Institute of Technology,Atlanta,Georgia30332-0430,USA 2School of Materials Science and Engineering,Georgia Institute of Technology,Atlanta,Georgia30332-0245,USA ͑Received26June2009;revised manuscript received28September2009;published14January2010͒Control over the morphology and structure of nanostructures is essential for their technological applications,since their physical properties depend significantly on their dimensions,crystallographic structure,and growthdirection.A combination of polarized Raman͑PR͒spectroscopy and atomic force microscopy͑AFM͒is usedto characterize the growth direction,the presence of point defects and the morphology of individual ZnOnanobelts.PR-AFM data reveal two growth modes during the synthesis of ZnO nanobelts by physical vapordeposition.In the thermodynamics-controlled growth mode,nanobelts grow along a direction close to͓0001͔,their morphology is growth-direction dependent,and they exhibit no point defects.In the kinetics-controlledgrowth mode,nanobelts grow along directions almost perpendicular to͓0001͔,and they exhibit point defects.DOI:10.1103/PhysRevB.81.045415PACS number͑s͒:61.46.Ϫw,61.72.Dd,78.30.Ly,81.10.ϪhI.INTRODUCTIONControl over the morphology and structure of nanostruc-tured materials is essential for the development of future de-vices,since their physical properties depend on their dimen-sions and crystallographic structure.1–15In particular,the growth direction of single-crystal nanostructures affects their piezoelectric,1,2transport,3catalytic,4mechanical,5–9 optoelectronic,10and tribological properties.11ZnO nano-structures with various morphologies͑wires,belts,helices, rings,tubes,…͒have been successfully synthesized in solu-tion and in the vapor phase,14–19but little is known about their growth mechanism,particularly in a process not involv-ing catalyst particles.17Understanding the growth mecha-nism and determining the decisive parameters directing the growth of nanostructures and tailoring their morphology is essential for the use of ZnO nanobelts as power generators or electromechanical systems.1,2,5,6From a theoretical stand-point,a shape-dependent thermodynamic model showed that the morphology of ZnO nanobelts grown in equilibrium con-ditions depends on their growth direction,but the role of defects was not considered.20Experimentally,it was shown that the growth direction of ZnO nanostructures can be di-rected by the synthesis conditions,such as the oxygen con-tent in the furnace.19A previous study combining scanning electron microscopy and x-ray diffraction suggested a growth-direction-dependent morphology.20An atomic force microscopy͑AFM͒combined with transmission electron mi-croscopy also suggested that the morphology of ZnO nano-belts is correlated with their growth direction and highlighted the potentially important role of planar defects.5 Growth modes out of thermodynamic equilibrium and the role of point defects5,17are particularly challenging to inves-tigate experimentally,21due to the lack of appropriate experi-mental techniques.Electron microscopy can determine the crystallographic structure and morphology of conductive nanomaterials,3,17,22–24but is not suitable for the character-ization of point defects,especially when their distribution is disordered.17,22–24Raman spectroscopy has been used for the characterization of the structure of carbon nanotubes,25,26the identification of impurities,27and the determination of the crystal structure28and growth direction of individual single-crystal nanowires.29Recently,polarized Raman͑PR͒spec-troscopy has been coupled to AFM to study in situ the inter-play between point defects and mechanical properties of ZnO nanobelts.30Here,PR-AFM is used to study the growth mechanism and the relationship between growth direction,point defects, and morphology of individual ZnO nanobelts.The morphol-ogy of an individual ZnO nanobelt is determined by AFM, while the growth direction and randomly distributed defects in the same individual nanobelt are characterized by polar-ized Raman spectroscopy.II.EXPERIMENTALThe ZnO nanobelts were prepared by physical vapor deposition͑PVD͒without catalysts following the method de-scribed in Ref.17.The ZnO nanobelts were deposited on a glass cover slip,which was glued to a Petri dish.The rotat-able Petri dish was then placed on a sample plate under an Agilent PicoPlus AFM equipped with a scanner of100ϫ100␮m2range.Topography images of the ZnO nanobelts were collected in the contact mode with CONTR probes͑NanoWorld AG,Neuchâtel,Switzerland͒of normal spring constant0.21N/m at a set point of2nN.The AFM was placed on top of an Olympus IX71inverted optical micro-scope that is coupled to a Horiba Jobin-Yvon LabRam HR800.PR spectra were recorded in the backscattering ge-ometry using a40ϫ͑0.6NA͒objective focusing a laser beam of wavelength785nm on the sample to a power den-sity of about105W/cm2and a spot size of about2␮m. The incident polarization direction can be rotated continu-ously with a half-wave plate.The scattered light was ana-lyzed along one of two perpendicular directions by a polar-izer at the entrance of the spectrometer.The intensity,center, and width of the Raman bands were obtained byfitting the spectra with Lorentzian lines.The polarization dependence of the quantum efficiency of the Raman spectrometer was tested by measuring the intensity variations of the377,409,PHYSICAL REVIEW B81,045415͑2010͒1098-0121/2010/81͑4͒/045415͑5͒©2010The American Physical Society045415-1and 438cm −1bands from two bulk ZnO crystals ͑c -plane and m -plane ZnO crystals,MTI Corporation ͒.The PR data from bulk crystals were successfully fitted using group theory and crystal symmetry 28without further calibration of the spectrometer or data correction.III.RESULTS AND DISCUSSIONAFM images and PR data of two individual ZnO nano-belts are presented in Fig.1.These nanobelts have different cross-sections,1320ϫ1080nm 2͑nanobelt labeled NB A͒FIG.1.͑Color online ͒PR-AFM results on individual ZnO nanobelts.͑a ͒AFM topography image,͑b ͒typical PR spectra for different sample orientations ␸and polarization configurations,and ͑c ͒–͑f ͒polar plots of the angular dependence of the Raman intensities for the nanobelt NB A.͑g ͒AFM topography image,͑h ͒typical PR spectra,and ͑i ͒–͑l ͒polar plots of the angular dependence of the Raman intensities for the nanobelt NB B.The Raman spectra in ͑h ͒exhibit peaks centered at 224and 275cm −1͑triangles ͒that are characteristic of defects in the nanobelt NB B.The Raman spectra are offset vertically for clarity.In ͑c ͒,͑d ͒,͑i ͒,and ͑j ͒,the nanobelt axis is rotated in a fixed polarization configuration ͑solid squares:copolarized;open squares:cross polarized ͒and is parallel to the incident polarization for ␸=0°.In ͑e ͒,͑f ͒,͑k ͒,and ͑l ͒,the incident polarization is rotated,while the analyzed polarization and the nanobelt axis are fixed.In ͑e ͒,͑f ͒,͑k ͒,and ͑l ͒,at the angle 0°,the nanobelt is perpendicular to the incident polarization and the incident and analyzed polarizations are parallel ͑solid squares ͒or perpendicular ͑open squares ͒.Typical Raman spectra of the glass cover slip in the copolarized and cross-polarized configurations are shown as a reference in ͑b ͒and ͑h ͒,respectively.LUCAS,WANG,AND RIEDO PHYSICAL REVIEW B 81,045415͑2010͒045415-2。

a r X i v :a s t r o -p h /0504008v 2 2 N o v 2005Accepted for publication in the Astrophysical JournalPreprint typeset using L A T E X style emulateapj v.6/22/04A CHANDRA SURVEY OF EARLY-TYPE GALAXIES,I:METAL ENRICHMENT IN THE ISM.Philip J.Humphrey 1and David A.Buote 1Accepted for publication in the Astrophysical JournalABSTRACTWe present the first in a series of papers studying with Chandra the X-ray properties of a sam-ple of 28early-type galaxies which span ∼3orders of magnitude in X-ray luminosity (L X ).We report emission-weighted Fe abundance (Z Fe )constraints and,for many of the galaxies,abundance constraints for key elements such as O,Ne,Mg,Si,S and Ni.We find no evidence of the very sub-solar Z Fe historically reported,confirming a trend in recent X-ray observations of bright galaxies and groups,nor do we find any correlation between Z Fe and luminosity.Except in one case we do not find evidence for a multi-phase interstellar medium (ISM),indicating that multi-temperature fits required in previous ASCA analysis arose due to the strong temperature gradients which we are able to resolve with Chandra .We compare the stellar Z Fe ,estimated from simple stellar population model fits,to that of the hot gas.Excepting one possible outlier we find no evidence that the gas is substantially more metal-poor than the stars and,in a few systems,Z Fe is higher in the ISM.In general,however,the two components exhibit similar metallicities,which is inconsistent with both galactic wind models and recent hierarchical chemical enrichment simulations.Adopting standard SNIa and SNII metal yields our abundance ratio constraints imply 66±11%of the Fe within the ISM was produced in SNIa,which is remarkably similar to the Solar neighbourhood,and implies similar enrichment histories for the cold ISM in a spiral and the hot ISM in elliptical galaxies.Although these values are sensitive to the considerable systematic uncertainty in the supernova yields,they are also in very good agreement with observations of more massive systems.These results indicate a remarkable degree of homology in the enrichment process operating from cluster scales to low-to-intermediate L X galaxies.In addi-tion the data uniformly exhibit the low Z O /Z Mg abundance ratios which have been reported in the centres of clusters,groups and some galaxies.This is inconsistent with the standard calculations of metal production in SNII and may indicate an additional source of α-element enrichment,such as Population III hypernovae.Subject headings:Xrays:galaxies—galaxies:elliptical and lenticular,cD—galaxies:abundances—galaxies:halos—galaxies:ISM1.INTRODUCTIONThe entire history of star-formation and evolution leaves its chemical signature in the hot gas of early-type galaxies.X-ray observations therefore provide a natural and powerful diagnostic tool to unlock this in-formation (e.g.Loewenstein &Mathews 1991;Mathews &Brighenti 2003).However,historically X-ray mea-surements of interstellar medium (ISM)abundances have been problematical,as typified by the so-called “Fe dis-crepancy”(Arimoto et al.1997).Early Rosat and ASCA observations of these galaxies tended to imply extremely sub-solar metal abundances (generally expressed as Z Fe ,the Fe abundance with respect to the adopted solar stan-dard,since Fe has the strongest diagnostic lines in the soft X-ray band)(e.g.Loewenstein &Mushotzky 1998),in stark contrast to ∼solar abundances in the stellar pop-ulation.Since individual galaxies are not “closed boxes”,the ISM is believed to be built up primarily through stellar mass-loss and Type Ia supernovae (SNe)ejecta.These two crucial ingredients lead classical “wind mod-els”of gas enrichment to predict highly super-solar Z Fe in these galaxies (e.g.Ciotti et al.1991;Loewenstein &Mathews 1991).The problems caused by this discrep-ancy are exacerbated further when attempting to under-stand gas enrichment in clusters of galaxies,for which X-1Department of Physics and Astronomy,University of California at Irvine,4129Frederick Reines Hall,Irvine,CA 92697-4575ray observations typically find Z Fe ∼0.3–0.5.The metal content of the intra-cluster medium (ICM)is primarily attributed to the stellar ejecta from giant elliptical galax-ies,and so it is difficult to envisage there being lower metal abundances in individual galaxies than in the ICM (Renzini 1997).Attempts to reproduce the low Z Fe in early-type galax-ies from a modelling standpoint by,for example,incorpo-rating ongoing accretion of unenriched gas (e.g.Brighenti &Mathews 1999)or allowing complex star-formation his-tories (e.g.Kawata &Gibson 2003)have not been en-tirely successful,leading some to point a finger at the spectral-modelling.Arimoto et al.(1997),for instance,called into question the plasma codes being fitted to the data,particularly in light of uncertainties associated with the Fe L-shell transitions in X-ray emission plasma codes.This point was investigated further by Matsushita et al.(2000),who argued that,having degraded the data qual-ity in the vicinity of the Fe L-shell,Z Fe ∼>0.5can be found in the highest X-ray luminosity (L X )galaxies.Consistent results from spectral-fitting with plasma codes that treat the Fe L-shell transitions differently would seem,how-ever,to conflict with this explanation (e.g.Buote et al.2003b).Although remaining errors in the treatment of the Fe L-shell in the plasma codes can be important for high-resolution spectroscopy (e.g.Behar et al.2001),at CCD resolution the effects are substantially washed out2Humphrey&Buote.so that they contribute only a∼10–20%systematic un-certainty to the abundance measurement(Buote et al. 2003b).Perhaps a more natural alternative was suggested by Buote&Fabian(1998),who demonstrated thatfitting a single temperature model to the emission spectrum of intrinsically non-isothermal hot gas gives rise to a sub-stantially under-estimated abundance(not to mention a significantly poorerfit),an effect dubbed the“Fe bias”(see also Buote2000b).This effect had previously been recognized by Buote&Canizares(1994),and Trinchieri et al.(1994)found thatfitting a two-temperature model to the Rosat spectrum of the bright elliptical NGC4636 resulted in poorly-constrained abundances which could be consistent with solar values,in contrast to low Z Fe required for single-temperaturefits.A spectrally hard (kT∼>5keV)component had long been recognized in the ASCA spectra of the many early-type galaxies,which was attributed to emission from undetected X-ray bina-ries(Matsushita et al.1994).The composite spectrum from these sources,which dominate the emission of low-L X galaxies,can typically be approximated as a pure bremsstrahlung model.Therefore,fitting only a single-temperature hot gas model to the spectra of such galax-ies also tends to give rise to unphysically low abundances (e.g.Fabbiano et al.1994;Kim et al.1996,who found es-sentially unconstrained abundances when incorporating a term to account for this effect in their Rosat analy-sis).This effect is clearly distinct from,albeit related to, the Fe bias(see discussion in Buote2000b).Although the spectral-shape of the unresolved source component is sufficiently hard that it cannot move to mitigate,even in part,the Fe bias arising from multi-temperature hot gas components,Buote&Fabian(1998)still found Z Fe consistent with solar in the lower-L X systems,in which thefit implied only a single hot gas component,plus un-detected sources.However,the poor signal-to-noise ra-tio(S/N)characteristic of the lower-L X galaxies tended to produce poorly-constrained abundances,so that very sub-solar abundances could not be ruled out.Recent Chandra and XMM measurements of abun-dances in X-ray bright galaxies and the centres of groups have tended to support∼solar or even slightly super-solar abundances for the ISM(e.g.Buote et al.2003b; Tamura et al.2003;Gastaldello&Molendi2002;Buote 2002;Xu et al.2002;O’Sullivan et al.2003;Kim&Fab-biano2004b).In contrast,very sub-solar Z Fe are still being reported in the lowest L X/L B systems(e.g.Irwin et al.2002;Sarazin et al.2001).Perhaps the most dra-matic examples of this latter effect are the three very low-L X galaxies for which O’Sullivan&Ponman(2004) reported Z Fe∼<0.1.This apparent lack of consistency in the enrichment processes operating on different scales is intriguing,and it remains to be assessed whether it is an artefact of the poorer S/N or a real effect in low-L X sys-tems.Although a major problem for our understanding of galaxy evolution,a full understanding of this effect is inhibited by the lack of interesting abundance con-straints in galaxies with L X intermediate between these two extremes.In a recent paper,Humphrey et al.(2004), we made some initial progress in this area by report-ing constraints for the normal,moderate-L X S0galaxy NGC1332and the elliptical NGC720,in both cases strongly excluding the extremely sub-solar(Z Fe∼<0.4)abundances historically reported for these systems.Cou-pled with similar constraints on the abundances in the moderate L X/L B radio galaxy NGC1316(Kim&Fab-biano2003),this would hint at a consistent picture of enrichment from cluster to moderate-L X galaxy scales. In addition to the insight into enrichment afforded from global Z Fe measurements,theα-element abundance ra-tios,with respect to Fe,provide an additional power-ful diagnostic.Different types of SNe inject material imprinted with characteristic chemical“fingerprints”,so that the measured abundance pattern can be used to as-sess the relative contribution of SNIa and SNII to ISM enrichment.Early attempts to extract this information (e.g.Matsushita et al.2000;Finoguenov&Jones2000) were largely affected by a failure to treat the Fe bias, although a significant contribution of SNIa to the en-richment process was indicated.More recently,studies with high-quality XMM and Chandra data have revealed typically∼70–90%of the ISM enrichment in the cen-tres of groups and clusters seems to have its origin in SNIa,which is close to the∼75%value in the Solar neigh-bourhood(e.g.Gastaldello&Molendi2002;Buote et al. 2003b).For NGC1332and NGC720,we were able to obtain interesting constraints on theα-to-Fe ratios in some of the lowest-L X systems to date,again inferring ∼70–80%of the Fe to have been produced in SNIa.This also supports the suggestion of homology in the enrich-ment process over different mass-scales,at least down to moderate-L X galaxies.Although these results are intriguing,it is by no means clear that the two galaxies we considered are representa-tive,nor is it clear that all X-ray bright galaxies follow the trend of∼solar abundances(e.g.Sambruna et al. 2004).Furthermore,these studies have not elucidated the processes which may be giving rise to very low-Z Fe measurements in the faintest systems.In light of these results,therefore,the next logical step is to consider a uniformly-analyzed sample of galaxies spanning a large range of L X,and particularly expanding the number of moderate-L X galaxies studied.In this paper,we present the results of a study of metal enrichment in a sample of 28early-type galaxies drawn from the Chandra archive. In subsequent papers we will discuss the gravitating mass and point-source populations of these objects as a whole. The galaxies have been carefully selected to span the available X-ray luminosity range,from group-dominant to low-L X galaxies.In many respects,Chandra ACIS is the natural instru-ment with which to undertake such a study.Although XMM has a significantly higher collecting area,the anal-ysis of faint,diffuse sources is complicated by difficulties in treating the background.Chandra also has an intrin-sic advantage in being able to resolve out a substantial fraction of the X-ray binary contribution into individual sources,which must otherwise be disentangled spectrally. The excellent spatial resolution of Chandra also provides an unprecedented opportunity to investigate any spatial temperature variation,which would provide the natural source of the Fe bias.Imaging spectroscopy at CCD reso-lution is well-suited to determine reliable abundances in a galaxy.In fact there are a number of drawbacks to using the Chandra and XMM gratings instead for such a study. The extended nature of the sources makes grating spec-troscopy extremely challenging.The significantly lowerISM abundances in early-type galaxies.3effective area of the grating spectrographs in comparison to the ACIS CCDs and,especially for the XMM RGS in-strument,the more limited bandwidth both exacerbate this problem.Although one of the key issues of inter-est is the determination of multiple temperature compo-nents in the extraction aperture,this tends to produce features broad enough to be evident in CCD spectra.In fact,based on high S/N data of the group NGC5044 there was excellent agreement in the abundances deter-mined with the XMM gratings and the XMM and Chan-dra CCDS(Buote et al.2003b;Tamura et al.2003),con-firming that CCD resolution is sufficient to obtain reli-able abundances.Throughout this paper we adopt the latest solar abun-dances standard of Asplund et al.(2004,see§4.1),which resolve several previously-noted discrepancies between “photospheric”and“meteoritic”values.All error-bars quoted refer to the90%confidence region,unless other-wise stated.2.TARGET SELECTIONBy its nature,the Chandra archive contains a nonuni-form sample of galaxies.Although this prevents our choosing a statistically complete sample,we selected28 galaxies approximately spanning the range of measured L X,from∼8×1039–1043erg s−1.We only considered relatively nearby galaxies which had been observed for a total of at least10ks with the ACIS-S or ACIS-I, and without any grating employed.For selection pur-poses X-ray luminosities were taken from the catalogue of O’Sullivan et al.(2001),although all luminosities have subsequently been recomputed in the present work (§3.2).To an initial sample of26galaxies chosen in this way,we also added two further interesting objects not in the O’Sullivan catalogue—NGC1132,one of the clos-est examples of a“fossil group”(Mulchaey&Zabludoff1999,F.Gastaldello et al,2005,in prep.)and the rela-tively isolated,moderate-L X galaxy NGC1700which has an unusually high X-ray ellipticity,which Statler&Mc-Namara(2002)argued may indicate rotational support. Two of our sample,NGC1332and NGC720,have al-ready been discussed in Humphrey et al.(2004),and we adopt the results from that work here.The sample con-tains10high-L X(log10L X∼>41.5)galaxies,12moderate-L X(log10L X≃40.5–41.5)and6low-L X(log10L X∼<40.5) galaxies.Most of the sample was observed with ACIS-S, although in a few cases ACIS-I was employed.To give ex-tra coverage at large radii both ACIS-S and ACIS-I data for the two bright galaxies NGC1399and NGC4472, were analysed together.A summary of the properties of the galaxies and details of the Chandra exposures are given in Table1.In order to provide accurate luminosity estimates,we searched the literature for reliable distance estimates.Where pos-sible,we adopted those determined from surface bright-nessfluctuations(SBF)by Tonry et al.(2001,correcting for an improved Cepheid zero-point:Jensen et al.2003) or Jensen et al.(2003).Alternatively,we used distances determined from the D n−σrelation(Faber et al.1989), or the redshift,corrected for Virgo-centricflow,as given in LEDA.We assumed H0=70km s−1Mpc−1.Of this sample,6systems(IC4296,NGC507, NGC741,NGC1399,NGC4472,NGC7619)appear to be the central galaxies in substantial,optically-identified groups so their X-ray emission may be to some extent in-tertwined with that of a surrounding intra-group medium (IGM).In the present context,it suffices to consider that all the systems comprise a continuum over a range of mass-scales.In a subsequent paper,we will discuss the is-sue of group membership,and the total gravitating mass, in detail.3.DATA REDUCTIONFor data reduction we used the CIAO3.1and Hea-soft5.3software suites,in conjunction with Chandra Caldb calibration database2.28.For spectral-fitting we used Xspec11.3.1.In order to ensure the most up-to-date calibration,all data were reprocessed from the“level 1”eventsfiles,following the standard Chandra data-reduction threads2.We applied corrections to take ac-count of a time-dependent drift in the satellite gain and, for ACIS-I observations,the effects of“charge transfer in-efficiency”,as implemented in the standard CIAO tools. To identify periods of enhanced background(“flar-ing”),which seriously degrades the signal-to-noise(S/N) and complicates background subtraction(e.g.Marke-vitch2002),we accumulated background lightcurves for each exposure from low surface-brightness regions of the active chips.We excluded obvious diffuse emission and data in the vicinity of any detected point-sources(see below).Periods offlaring were identified by eye and ex-cised.Any residualflaring which is not removed by this procedure will be sufficiently mild to have negligible im-pact in the centres of bright galaxies.However,in the fainter systems even very mild background variation can have a significant impact on our results,and so we treat these systems with extra care(§5.2).Thefinal exposure times are listed in Table1.Point source detection was performed using the CIAO tool wavdetect(Freeman et al.2002).In order to im-prove the likelihood of identifying sources with peculiarly hard or soft spectra,full-resolution images were created of the region of the ACIS focal-plane containing the S3 chip in the energy-band0.1–10.0keV and,so as to iden-tify any unusually soft or hard sources,also in the bands 0.1–3.0keV and3.0–10.0keV.Sources were detected sep-arately in each image.In order to minimize spurious detections at node or chip boundaries we supplied the detection algorithm with exposure-maps generated at en-ergies1.7keV,1.0keV and7keV respectively(although the precise energies chosen made little difference to the results).The detection algorithm searched for structure over pixel-scales of1,2,4,8and16pixels,and the de-tection threshold was set to∼10−7spurious sources per pixel(corresponding to∼0.1spurious detections per im-age).The source-lists obtained within each energy-band were combined and duplicated sources removed,and the final list was checked by visual inspection of the images.A full discussion of the point source populations will be given in a subsequent paper.In the present work,the data in the vicinity of any detected point source were removed so as not to contaminate the diffuse emission. As discussed in Humphrey&Buote(2004,see also Kim &Fabbiano2004a)a significant fraction of faint X-ray binary sources will not have been detected by this pro-cedure,and so we include an additional component to 2/ciao/threads/index.html4Humphrey&Buote.TABLE1The sampleGalaxy Type Dist D25L B log10L X N H ObsID Instr.Date Exposure (Mpc)(′)(1010L⊙)(log10(erg s−1))(1020cm−2)(dd/mm/yy)(ks) High-L X galaxiesIC4296E Radio gal50.82 3.812.141.54 4.13394S10/09/0125 NGC507SA(r)082.63 3.214.943.03 5.42882I08/01/0243 NGC741E075.83 2.914.242.32 4.42223S28/01/0130 NGC1132E98.24 2.18.342.76 5.2801S10/12/9913 NGC1399cD;E1pec18.51 6.9 4.242.09 1.3319S18/01/00564174I28/05/0345 NGC1600E357.43 3.29.842.19 4.84283S18/09/0222 NGC4472E2/S0(2)Sy215.119.77.541.52 1.7321S12/06/0032322I19/03/0010 NGC5846E0-1;LINER HII21.11 3.8 3.141.57 4.3788S24/05/0023 NGC7619E49.21 2.6 6.942.06 5.03955S24/09/0331 NGC7626E pec51.23 2.7 6.941.51 5.02074I20/08/0126 Moderate-L X galaxiesNGC720E525.71 4.6 3.141.33 1.5492S12/10/0029 NGC1332S(s)021.31 4.1 2.340.95 2.24372S19/09/0245 NGC1387SAB(s)018.91 3.3 1.240.78 1.34168I20/05/0345 NGC1407E026.81 5.3 6.541.32 5.4791S16/08/0040 NGC1549E0-118.31 4.7 2.940.66 1.52077S08/11/0022 NGC1553SA(rl)0LINER17.21 5.3 3.740.64 1.5783S02/01/0014 NGC1700E441.11† 3.0 4.641.20 4.82069S03/11/0027 NGC3607SA(s)021.21 4.5 3.440.94 1.52073I12/06/0138 NGC3923E4-521.31 6.4 4.941.03 1.51563S14/06/018.8 NGC4365E319.01 5.8 3.740.83 6.22015S02/06/0140 NGC4552E;LINER HII14.31 5.0 2.040.65 2.62072S22/04/0154 NGC5018E342.63 3.67.140.967.02070S14/04/0128 Low-L X galaxiesNGC3115S09.017.3 1.439.86 4.32040S14/06/0136 NGC3585E7/S018.61 6.1 3.340.35 5.62078S03/06/0135 NGC3608E2LINER21.31 3.2 1.740.39 1.52073I12/06/0138 NGC4494E1-2LINER15.81 4.5 2.340.36 1.52079S05/08/0115 NGC4621E517.01 5.0 2.540.14 2.22068S01/08/0125 NGC5845E24.010.90.4540.17 4.34009S03/01/0330Note.—Listed above are all of the galaxies in our sample.Distances were obtained from1—SBF:Tonry et al.(2001),corrected for the the new Cepheid zero-point(see text),2—SBF:Jensen et al.(2003),3—D n-σ:Faber et al.(1989),4—redshift distance(LEDA);†—uncertain. L B was determined from the face-on,reddening-corrected B-band magnitude given by LEDA.L X was computed in the0.1–10.0keV band self-consistently in the present work(§3.2),excluding obvious emission from any low-luminosity AGN,and extrapolating the surface brightness to a fiducial300kpc radius.The galaxy type was taken from NED.N H is the nominal Galactic column-density along the line-of-sight.We show the Chandra observation identifier(ObsID),the ACIS instrument(I or S)and the net exposure-time,having excluded periods offlaring.account for it in our spectralfitting.3.1.Background estimationOne of the key challenges in spectral-fitting diffuse X-ray emission is ensuring proper background subtraction. For Chandra a set of blank-field eventfiles have been made available as part of the standard Caldb distribu-tion,from which background spectra can be accumulated corresponding to similar regions of the detector.For each observation,we prepared from these a suitably projected background eventsfile.We were able to extract from this file“template”background spectra for each region of the detector in which our“source”spectra were obtained. However,these background spectra are unlikely to rep-resent perfectly the background in any one observation. There are known to be significant long-term secular vari-ations in the non X-ray components of the background, substantialfield-to-field variation in the cosmic compo-nent,and there may be some residual mildflaring.It is also worth noting that the hard(power law)component of the cosmic X-ray background arises from undetected background AGN,so its absolute normalization is also a strong function of the point source detection complete-ness;in turn this is a function of the surface brightness of the galaxy and the total exposure time(Kim&Fabbiano 2004a).Several authors have adopted the practice of renor-malizing the background template to ensure good agree-ment with the instrumental background at high energies (∼>10keV).Such a procedure,however,also renormal-izes the(uncorrelated)cosmic X-ray background and in-strumental line features,which can lead to serious over or under-subtraction.Given these reservations we chose to use an alternative background estimation procedure. Our method involved modelling the background,some-what akin to the approach of Buote et al.(2004).For each observation,we extracted a spectrum from a“source free”region of the ACISfield of view.We chose a∼2′region centred on the S1chip if the galaxy was cen-tred on S3,or on the S2chip where the galaxy was centred on ACIS-I.If the S1or S2chips were turned off,we chose a small,∼<1′region on the S3or ACIS-I chips,as appropriate,positioned to be in a regionISM abundances in early-type galaxies.5of as low surface-brightness as possible.We excluded data from the vicinity of any point-sources found by the source detection algorithm.Additionally,we extracted a “source+background”spectrum from the CCD on which the source was centred,in an annulus centred at the galaxy centroid and with an inner and outer radii typi-cally∼2.5′and3.3′.We adopted two spectra since we found that this procedure enabled us most cleanly to constrain the background.Some of the brightest galax-ies are so extended in the X-ray that even in our“source free”region there is a small contribution from hot gas at large radii.We found that using two spectra with different hot gas contributions allowed this to be read-ily disentangled from the actual background components. In order to constrain the model,wefitted both spectra simultaneously,without background subtraction,using Xspec.Our model consisted of a single APEC plasma (to take account of the diffuse emission from the galaxy; the“source”),plus background components.These com-prised a power law withΓ=1.41(to account for the hard X-ray background),two APEC models with solar abun-dances and kT=0.2and0.07keV(to account for the soft X-ray background)and,to model the instrumental con-tribution,a broken power law model and two Gaussian lines with energies1.7and2.1keV and negligible intrin-sic widths.We have found that this model can be used to parameterize adequately the template background spec-tra.In order to disentangle the source and background components,given the general lack of photons in these spectra,we tied the abundances and temperatures of the “source”APEC components between both extraction re-gions,but allowed the normalizations to be free.In the fainter galaxies the normalization of the source compo-nent in the“source free”region tended,as expected,to zero.We also assumed that the background model nor-malization scales exactly with the extraction area.In general,we found that this was able tofit both spectra very well.In our subsequent spectral analysis,we did not background-subtract the data using the standard tem-plates,but took into account the background by using an appropriately scaled version of this model.Even if the background spectrum varies substantially over thefield-of-view,our background modelling is most correct at largest distances from the source centroid, where the results are most sensitive to the background. In fact,we found that the standard background tem-plates fared much worse than these modelled background estimates when the data were from regions of low surface brightness.We discuss this issue further,and how the choice of background can affect our results in§5.2.3.2.L X estimationIn order to provide a self-consistent analysis of the galaxies in this sample,we obtained estimates of L X based on the Chandra data.First,we estimated the flux within our chosen spectral extraction regions from our the best-fitting spectral models(§4.3–4.4).Fluxes were computed separately for the gas and undetected point-sources in the energy-band0.1–10.0keV.Since the adopted aperture will not contain all of the diffuseflux from the galaxy,we extrapolated the emission out to a projected radius of300kpc,i.e.the Virial radius for a 1.6×1012M⊙galaxy.We assumed spherical symmetry and parameterized the surface brightness with a single or doubleβ-model.Theβ-model parameters were de-termined fromfits to the radial surface brightness in the 0.3–2.0keV band,using dedicated software which can fold in the instrumental point-spread function,which we computed at1keV.Data from the vicinity of any de-tected point-sources were excluded from thefit,and we assumed that the hot gas and undetected sources had the same radial brightness distribution.The results of the surface brightnessfits to each galaxy will be discussed in detail in a subsequent paper.This procedure typically corrects theflux upwards by a factor∼1.1–4,depending on the shape of the surface brightness profile.Since it is by no means certain that this extrapolation is valid out to∼300kpc,we expect this to introduce some uncer-tainty into the estimated L X.However,for our present purposes we believe this approach is sufficiently accurate. To compute the total L X of the galaxy,we also included theflux of all detected point-sources within the B-band twenty-fifth magnitude(D25)isophote,all of which were assumed to be associated with the galaxy for these pur-poses.Wefitted the composite spectrum of all these sources with our canonical(kT=7.3keV bremsstrahlung) model.In most cases this gave a goodfit to the data, although in a few instances a single power law or power law plus disk blackbody components were used instead to obtain a goodfit.In the event a significant low-luminosity AGN appears to be present in the galaxy(i.e. NGC1553,IC4296),we omitted theflux from the AGN. The total luminosity of the(detected,plus undetected) point-sources within D25was typically in agreement with the estimate of Kim&Fabbiano(2004a),based on ex-trapolating the resolved X-ray luminosity functions in nearby early-type galaxies.We found a mean L X(point sources)/L B∼0.9×1030erg s−1L⊙−1,in excellent agree-ment with these authors.The point-source populations will be discussed in detail in a subsequent paper. Comparing with thefluxes given in O’Sullivan et al. (2001)wefind broad agreement,although our estimates tend to be∼0.25dex higher.We attribute this discrep-ancy to differences in spectral modelling and our extrap-olation procedure.4.SPECTRAL ANALYSIS4.1.Solar abundances standard Throughout this paper,we adopt the solar photo-spheric abundances of Asplund et al.(2004),which de-viate significantly for many of the key species from the previous standard of Grevesse&Sauval(1998).The in-corporation of detailed3D line transfer modelling(and, in some cases,treatment of non-LTE conditions)has tended to reconcile so-called“meteoritic”and photo-spheric abundances(for non-volatile species),so that dis-crepancies remaining are typically at∼<0.1dex,i.e.ap-proximately the same level as the statistical uncertain-ties.We therefore adopt these abundances as our stan-dard.This does,however,introduce some complications when comparing with results reported in the literature since most authors adopt either the older abundances standard of Grevesse&Sauval(1998)or the outdated abundances of Anders&Grevesse(1989).For comparison with our work,Z Fe,Z O/Z Fe,Z Ne/Z Fe, Z Mg/Z Fe,Z Si/Z Fe,Z S/Z Fe and Z Ni/Z Fe referenced to the standard of Grevesse&Sauval(1998)should be scaled。

Investigating the properties of metalalkylsMetal alkyls are a group of compounds consisting of a metal atom and an organic alkyl group. They are widely used in industry as catalysts, reagents and precursors for the synthesis of organic compounds. In this article, we will be investigating the properties of metal alkyls, including their reactivity, stability and applications.Reactivity:Metal alkyls are highly reactive compounds due to the presence of a polar metal-carbon bond. They can react with a variety of reagents, such as water, oxygen, acids and halogens, to form different products. For example, when a metal alkyl is exposed to air, it undergoes oxidation to form metal oxides and alkyl radicals. This can lead to a loss in activity of the compound, making it less effective as a catalyst.Stability:The stability of metal alkyls depends on the nature of the metal and alkyl group. Generally, smaller alkyl groups tend to form more stable metal alkyls compared to larger alkyl groups. This is because smaller alkyl groups have a higher degree of steric hindrance, which reduces the reactivity of the metal-carbon bond. In addition, metals such as aluminum, magnesium and zinc tend to form more stable alkyls compared to transition metals such as titanium and zirconium. This is due to differences in the electronegativity and size of the metal atoms.Applications:Metal alkyls have a wide range of applications in industry, including as catalysts for polymerization reactions, metal organic chemical vapor deposition (MOCVD), and as intermediates for the synthesis of organic compounds. For instance, aluminum alkyls, such as triethylaluminum, are commonly used in the production of polyolefins. Incontrast, zirconium alkyls, such as zirconium tetra-tert-butoxide, are used as precursors for the synthesis of ceramics.Conclusion:In conclusion, metal alkyls are a diverse group of compounds with important industrial applications. Their reactivity and stability depend on the nature of the metal and alkyl group, and they have various functionalities as catalysts, precursors and intermediates in organic synthesis. Further research into the properties and applications of metal alkyls is essential for developing new and improved catalysts and materials.。

The properties and uses of metalcarbidesMetal carbides are a type of material that is formed when a metal reacts with carbon to form a compound. They have a wide range of properties that make them useful in a variety of applications, ranging from cutting tools to wear-resistant coatings. In this article, we will explore the properties and uses of metal carbides in more detail.Properties of Metal CarbidesMetal carbides are unique in that they are both metallic and ceramic in nature. They are often classified as a type of ceramic material because of their high melting points and hardness. However, they also exhibit metallic conductivity, making them useful as electrical conductors. Some of the key properties of metal carbides include:1. High melting points: Most metal carbides have very high melting points, making them suitable for use in extremely high-temperature applications. For example, tungsten carbide melts at around 2,870°C, making it one of the highest melting point materials known.2. Hardness: Metal carbides are also very hard materials, with a hardness that is typically greater than that of steel. This property makes them useful for cutting tools and wear-resistant coatings.3. Chemical stability: Metal carbides are generally very chemically stable, which means that they are resistant to corrosion and oxidation. This makes them suitable for use in harsh environments where other materials may degrade quickly.4. Electrical conductivity: Despite their ceramic nature, many metal carbides are also good electrical conductors. This makes them useful for electrical contacts, electrodes, and other applications where good electrical conductivity is required.Uses of Metal CarbidesMetal carbides are used in a wide range of applications, thanks to their unique properties. Some of the most common uses of metal carbides include:1. Cutting tools: Metal carbides are widely used in cutting tools, such as drill bits and saw blades. Their hardness and wear resistance make them ideal for cutting through tough materials like metals and ceramics.2. Wear-resistant coatings: Metal carbides are also useful as coatings for parts that experience high levels of wear and tear. For example, carbide coatings can be used on engine parts to improve their durability and reduce friction.3. Electrical contacts: Many metal carbides have good electrical conductivity, making them useful for electrical contacts in a variety of applications.4. Refractory materials: Metal carbides are often used as refractory materials, which are materials that are able to withstand high temperatures without degrading. Refractory metal carbides are often used in the production of ceramics, glass, and other materials.ConclusionIn conclusion, metal carbides are a unique type of material that exhibit a range of properties that make them useful in a variety of applications. They are both metallic and ceramic in nature, with high melting points, hardness, chemical stability, and electrical conductivity. Common uses of metal carbides include cutting tools, wear-resistant coatings, electrical contacts, and refractory materials. As new applications for these materials are discovered, their popularity is likely to continue to grow.。

DOI: 10.1016/S1872-5813(23)60352-4Associated Data DOI: 10.57760/sciencedb.j00124.00015Influence of pretreatment conditions on the structure and catalytic performance ofsupported cobalt catalysts derived from metal-organic frameworksSUN Jia-qiang 1,2，ZHENG Shen-ke 3,*，CHEN Jian-gang1,*（1. State Key Laboratory of Coal Conversion , Institute of Coal Chemistry , Chinese Academy of Sciences , Taiyuan 030001, China ；2. University of Chinese Academy of Sciences , Beijing 100049, China ；3. Hubei Key Laboratory for Processing and Application of Catalytic Materials , College of Chemistry and ChemicalEngineering , Huanggang Normal University , Huanggang 438000, China ）Abstract: Supported cobalt catalysts (Co@C-ZnZrO 2 and Co/ZnZrO 2) were prepared through a metal-organic frameworks (MOFs)-mediated synthesis strategy. The influence of MOFs pyrolysis on the structure and Fischer-Tropsch synthesis performance of supported cobalt catalysts was investigated. The crystalline phase and microstructure of supported cobalt catalysts were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), N 2 adsorption-desorption and X-ray photoelectron spectroscopy (XPS). The Co/ZnZrO 2 showed the CO conversion of 18.1% and the C 5 + selectivity of 77.4%, whereas the Co@C-ZnZrO 2 exhibited the CO conversion of 8.5% and the C 5 + selectivity of 35.2%. The excellent CO conversion for Co/ZnZrO 2 was attributed to the more exposure of active Co sites. Meanwhile, the activity of Co sites on Co@C-ZnZrO 2 catalyst was restricted by the carbon layer, suppressing the adsorption and activation of syngas on Co sites.Key words: pyrolysis ；metal-organic frameworks ；supported cobalt catalysts ；Fischer-Tropsch synthesis CLC number: O643 Document code: ASupported metal catalysts are objects of great interest in heterogeneous catalysis due to their uniquechemical and physical properties [1]. They can catalyze the synthesis of bulk chemicals and transportation fuels. Especially, supported cobalt catalysts are widelyused for Fischer-Tropsch synthesis (FTS)[2−5]. For supported cobalt catalysts, their performance depends strongly on the nature of the active metal sites on thecatalyst surface and support [6−9]. The nature of active site is closely correlated to the size of Co nanoparticles(NPs), size distribution and crystal phase [10,11]. The supports with high specific surface area are expected to disperse the active phase giving a high metal specific surface area and stabilize the active phase against lossof specific surface area during the reaction [12,13]. Thus,an ideal supported cobalt catalyst would exhibit not only uniform Co distribution but also highly reducedand dispersed Co sites [14]. These factors strongly depend on the preparation method of the catalysts. In this respect, it is not surprising that the development of synthetic methods for the supported cobalt catalysts has received tremendous attentions. Impregnation [15,16],deposition-precipitation [17], and sol-gel methods [18]are among the most commonly used methods to control and tune these factors. By using such methods, the structure performance relationships are also established, aiming to develop better catalysts.However, it is not easy to achieve high Co dispersion by using traditional preparation methods, because it usually means smaller Co particles. The derived stronger interaction between metal and support often leads to the decreased reduction of Co, which lowersthe catalytic activity for FTS [19].Metal-organic frameworks (MOFs), a new class of porous coordination polymer, which are self-assembled by metal nodes and organic ligands through chemical coordination bonds, have been extensively investigated in a number of fields including catalysis, gas adsorption, gas separation, sensors, and drugdelivery [20]. In particular, MOFs have attracted significant attentions for their application in heterogeneous catalysts design due to the highReceived ：2023-01-12；Revised ：2023-02-06*Corresponding author. E-mail: ，.The project was supported by the National Natural Science Foundation of China (21503256, 22072175), “Strategic Priority Research Program” of the Chinese Academy of Sciences (XDA21021000), Sanju Environmental Protection New Material Company and the Research Foundation of Huanggang Normal University (2042020026).本文的英文电子版由 Elsevier 出版社在 ScienceDirect 上出版 (/science/journal/18725813)第 51 卷 第 9 期 燃 料 化 学 学 报 （中 英 文）Vol. 51 No. 92023 年 9 月Journal of Fuel Chemistry and TechnologySept. 2023dispersion of active sites, highly uniform porous structure, large specific surface area and tunable porosity[21−23]. In addition to direct applications, MOFs have been widely developed as promising sacrificial templates/precursors to fabricate supported cobalt catalysts with high porosity, high specific surface area and distinctive morphology by applying different thermal and/or chemical treatments. Typically, Co@C catalysts can be prepared by high-temperature pyrolysis of MOFs in inert atmosphere[24]. The Co@C catalysts could present a small crystalline size even at high metal loading. Unfortunately, the Co NPs are usually covered by the graphitic carbon shells, which makes the surface of metal NPs difficult to access. Thus, their application in FTS is restricted since the activity and selectivity are unsatisfying[25−28]. In order to improve the FTS performance of MOF-derived Co@C catalysts, the Co NPs supported by porous carbon or silica as the FTS catalysts have also been prepared from Co MOF-74 and ZIF-67 by direct pyrolysis or multi-step approaches (pyrolysis, calcination and reduction), and show very competitive activity and selectivity[29,30]. In addition, due to the flexibility of MOFs in structure and chemical composition, supported cobalt catalysts derived from MOFs can also be designed rationally by selecting versatile metal centers and ligands. The interesting results demonstrate that the MOF-mediated synthesis strategy is a promising route for the preparation of supported cobalt catalysts with outstanding FTS performance.Herein, we investigated the MOFs-derived Co@C-ZnZrO2 and Co/ZnZrO2 catalysts to determine the influence of the thermal treatment methods of the MOFs precursors on the structure and catalytic performance of the supported cobalt catalysts. Detailed characterizations were used to establish the relation between the catalytic performance and structure. By using multi-step approach, Co/ZnZrO2 catalysts with highly exposed active sites were synthesized, and exhibited high activity and selectivity.1 Experimental1.1 Catalysts preparationZCZ-MOFs were prepared by a one-pot solvothermal method. Firstly, certain amounts of Co(NO3)2·6H2O, Zr(NO3)4·5H2O, Zn(NO3)2·6H2O with molar ratios of Co∶Zr∶Zn=1∶1∶2 were dissolved with 200 mL water. Then, 40 mmol 1, 4-benzenedicarboxylic acid were dissolved in 200 mL DMF to form a clear solution. Afterwards, the as-prepared two solutions were mixed under a magnetic stirring. The reaction mixture prepared above was transferred directly into a Teflon-lined stainless steel autoclave and heated at 120 °C for 12 h. The as-prepared samples were filtered out and washed with DMF and water and finally dried at 80 °C for 12 h.The as-prepared ZCZ-MOFs were carbonized at 800 °C for 2 h under Ar. The obtained samples were denoted as Co@C-ZnZrO2 (39% Co, 0.5% Zn, 42% Zr).The as-prepared ZCZ-MOFs were calcinated at 400 °C for 4 h under air to form CoZnZrO2. The CoZnZrO2 was further reduced to Co/ZnZrO2 in H2 at 400 °C for 4 h. When the temperature decreased to room temperature, the samples were passivated with 1% O2/N2 for 1 h, forming CoO x/ZnZrO2 (20% Co, 31% Zn, 31% Zr).1.2 CharacterizationsThe transmission electron microscopy (TEM) images and high-resolution TEM (HRTEM) images were obtained on a JEM 2100F HRTEM. The X-ray diffraction (XRD) experiments were performed on a Bruker D8 Advance provided Cu Kα radiation (λ=1.5418 Å). The N2 adsorption-desorption measurement was carried out on a Micromeritics Tristar II 3020 gas adsorption analyzer. The X-ray photoelectron spectroscopy (XPS) studies were performed on the Kratos Axis Ultra DLD. The elemental composition of the sample was collected on the inductively coupled plasma atomic emission spectroscopy (ICP-AES, Thermo iCAP6300). Hydrogen temperature-programmed desorption (H2-TPD) tests were performed on the Quantachrome Chembet TPR/TPD.1.3 Catalytic performance evaluationThe catalytic behavior was investigated in a fixed bed reactor. The catalysts diluted with quartz powders (60–80 mesh) were reduced at 400 °C for 4 h by H2 with a gas hourly space velocity (GHSV) of 2 L/(g·h). After reduction, the reactor was cooled to 100 °C, the syngas (H2/CO=2, v/v) with a GHSV of 1 L/(g·h) was fed into the catalyst bed and the temperature was increased to 200 °C at 4 °C/min. The composition of the reactants and tail gas were analyzed online by gas chromatography (GC). The H2, CO, CO2, CH4 and N2 were analyzed by using a TDX column and thermal conductivity detector (TCD). The light hydrocarbons were analyzed using a Al2O3 capillary column with a1292 燃 料 化 学 学 报 （中 英 文）第 51 卷flame ionization detector (FID). The oil and wax were analyzed offline using GC with an OV-101 capillary column and an FID.2 Results and discussion2.1 Catalyst characterizationWe used ZCZ-MOFs as the precursors to synthesize the Co@C-ZnZrO2 and Co/ZnZrO2 catalysts for FTS. Firstly, the well-defined ZCZ-MOFs were synthesized via a one-pot solvothermal method according to a literature procedure with a few modification[31]. As shown by TEM image in Figure 1, the obtained ZCZ-MOFs show a nanosheet morphology. The crystalline phase of the ZCZ-MOFs was demonstrated by XRD (Figure 2). All the peaks of the ZCZ-MOFs can be indexed to MOF-5∙5H2O[31]. Secondly, the MOFs were calcined under different atmospheres, during which the solvent molecules were decomposed and discharged. The ZCZ-MOFs were transformed into Co@C-ZnZrO2 by the direct high-temperature pyrolysis in inert atmosphere (Ar, 800 °C). Meanwhile, the ZCZ-MOFs were transformed into mixed metal oxides (CoZnZrO2) by calcination in air, and were further reduced in H2, forming the Co/ZnZrO2 catalysts. Noteworthily, the obtained reduced samples were then passivated with 1% O2/N2 to form the CoO x/ZnZrO2 samples, for the convenience of structural characterization. Their crystalline nature was also confirmed by XRD. As shown in Figure 3, Co@C-ZnZrO2 displays characteristic peaks of monoclinic ZrO2 (JCPDS No. 65-1023), cubic ZrO2 (JCPDS No. 49-1642) and face-centered cubic (fcc) Co (JCPDS No. 15-0806). CoO x/ZnZrO2 displays characteristic peaks of hexagonal phase ZnO (JCPDS No. 36-1451), cubic ZrO2 (JCPDS No. 49-1642) and fcc Co3O4 (JCPDS No. 43-1003). In addition, we can find the fcc Co peaks (JCPDS No. 15-0806) for Co/ZnZrO2 (Figure 4).The morphology and crystal structure of Co@C-ZnZrO2 and CoO x/ZnZrO2 were evaluated by TEM and HRTEM. As shown in the TEM image of Co@C-ZnZrO2 catalysts (Figure 5), the sizes of the metallic Co NPs are in the range from 5 to 80 nm. Clearly, metallic Co nanoparticle with the lattice spacing of 0.205 nm is covered by carbon (Figure 5(c)). The CoO x/ZnZrO2 catalysts possess a highly porous texture (Figure 6(a)) and some CoO x NPs disperse on the surface of the catalysts (Figure 6(b)). The sizes of the CoO x NPs in CoO x/ZnZrO2 are in the range from 2 to 28 nm. HRTEM images further confirm the crystalline feature. The lattice spacing of 0.202 nm corresponds to (400) planes of fcc Co (Figure 6(c)).500 nmFigure 1 TEM image of ZCZ-MOFs51015202530352θ /(°)Intensity/(a.u.)Figure 2 XRD pattern of ZCZ-MOFs1020304050607080♠m-ZrO2♥c-ZrO2* fcc Co♥♥♥∗∗∗♠♠♠♠2θ /(°)Intensity/(a.u.)Figure 3 XRD pattern of Co@C-ZnZrO2♣Co/ZnZrO2CoO x/ZnZrO2♣♣♦♦♥♦♥♣♣♣♣♥♥♥♦♦♦♦♦♦♦♦♦∗∗∗♥c-ZrO2♦ ZnO ♣ Co3O4* fcc Co♦♦♦♦♦♦10203040506070802θ /(°)Intensity/(a.u.)Figure 4 XRD patterns of CoO x/ZnZrO2 and Co/ZnZrO2第 9 期SUN Jia-qiang et al.：Influence of pretreatment conditions on the structure and catalytic performance of (1293)Co d(111)=0.205 nm100 nm10 nm 5 nmFigure 5 TEM ((a), (b)) and HRTEM (c) images of Co@C-ZnZrO2CoO x d(400)=0.202 nm100 nm20 nm 2 nmFigure 6 TEM ((a), (b)) and HRTEM (c) images of CoO x/ZnZrO2The textural properties of the MOFs and thederived catalysts were investigated by N2 adsorption-desorption measurement (Table 1). The MOFsprecursors show the Brunauer-Emmett-Teller (BET)specific surface area of 67.2 m2/g and an average poresize of 8.7 nm. Notably, the Co@C-ZnZrO2 catalystsobtained by thermal decomposition of the MOFs showthe BET specific surface area of 132.6 m2/g and anaverage pore size of 10.4 nm. Compared with theCo@C-ZnZrO2 catalysts, CoO x/ZnZrO2 catalysts showsmaller BET specific surface area of 28.3 m2/g and anaverage pore size of 17.5 nm.Table 1 N2 adsorption-desorption measurement resultsof the catalystsSample SBET /(m 2·g−1)vmic /(cm3·g−1)dave /nmZCZ-MOF67.20.028.7 Co@C-ZnZrO2132.60.2110.4 CoO x/ZnZrO228.30.1117.5XPS was performed to investigate the surface elemental composition as well as chemical properties of those samples. From the full spectra of Co@C-ZnZrO2, it is observed that the samples show the existence of Co, Zr, O and C species (Figure 7). It is clear that the Co@C-ZnZrO2 catalysts show a large amount of C species compared with Co/ZnZrO2 catalysts. Meanwhile, CoO x/ZnZrO2 and Co/ZnZrO2 show the existence of Co, Zr, Zn and O species. As for Co 2p XPS spectra of Co/ZnZrO2 and Co@C-ZnZrO2, apart from the existence of Co2 + characteristic peaks, the peaks at 778.5 and 792.7 eV corresponding to metallic Co0 can also be observed (Figure 8). The Co 2p3/2 peak of Co0 for Co/ZnZrO2 shows lower binding energies compared with that of Co@C-ZnZrO2. In addition, the Zr 3d XPS peaks of Co/ZnZrO2 exhibit higher binding energies compared with that of Co@C-ZnZrO2, indicating the stronger electronic interaction between Zr and Co NPs in Co/ZnZrO2 (Figure 9). The XPS peaks of Zn exhibit the same binding energies in all the catalysts (Figure 10).Binding energy /eVFigure 7 XPS full spectra of the catalysts1294 燃 料 化 学 学 报 （中 英 文）第 51 卷810805800795790785780775Co/ZnZrO 2Binding energy /eVI n t e n s i t y /(a .u .)CoCo 2+sat.sat.Co 3+Co 2+Co 2+Co 0sat.Co 2p 1/2Co@C-ZnZrO 2CoO x /ZnZrO 2sat.Co 2+Co 0Co 2p 3/2Figure 8 Co 2p XPS spectra of the catalysts190188186184182180178176Binding energy /eVCo@C-ZnZrO 2I n t e n s i t y /(a .u .)CoO x /ZnZrO 2Zr 3dCo/ZnZrO 2Figure 9 Zr 3d XPS spectra of the catalysts10501045104010351030102510201015Binding energy /eVI n t e n s i t y /(a .u .)Zn 2pCo@C-ZnZrO 2CoO x /ZnZrO 2Co/ZnZrO 2Figure 10 Zn 2p XPS spectra of the catalysts2.2 Catalytic performanceThe catalytic activity of the prepared catalysts with time on stream is shown in Figure 11. The CO conversion of the Co/ZnZrO 2 catalyst reaches to 18.1%after 24 h at 200 °C. The catalytic activity of Co/ZnZrO 2 is over 2 times than that of Co@C-ZnZrO 2.The turnover frequency (TOF) value of Co/ZnZrO 2 is1.0 × 10−2 s −1, while the TOF value of Co@C-ZnZrO 2 is0.8 × 10−2 s −1. The reason of the high activity for Co/ZnZrO 2 may be explained by the fact that Co/ZnZrO 2 have more active sites than Co@C-ZnZrO 2.Furthermore, the activity of the Co/ZnZrO 2 catalyst did not decrease after 120 h, showing better stability of the catalysts. The selectivity of hydrocarbon products is shown in Figure 12. The CH 4 selectivity of the Co/ZnZrO 2 catalyst is about 13%, which is lower thanthat of the Co@C-ZnZrO 2 catalyst. The Co/ZnZrO 2catalyst exhibits the highest C 5 + selectivity of 77.4%.On the other hand, the Co@C-ZnZrO 2 catalyst only exhibits C 5 + selectivity of 35.2%. The product distributions results show the chain growth probability (α) values of 0.74 for Co/ZnZrO 2 and 0.45 for Co@C-ZnZrO 2 , respectively (Figure 13).051015202530Time on stream /hC O c o n v e r s i o n /%Figure 11 Catalytic activity of the catalystswith time on streamReaction conditions: v (H 2)/v (CO)=2, GHSV=1 L/(g·h),2 MPa, 200 °C20406080100120140Time on stream /hS e l e c t i v i t y /%Figure 12 Hydrocarbon product selectivity of the catalystswith time on streamReaction conditions: v (H 2)/v (CO)=2, GHSV=1 L/(g·h),2 MPa, 200 °C−10−8−6−4−2024Carborn numberl n (W n /n )Figure 13 Hydrocarbon product distributionsof the catalystsTo get a thorough understanding of the enhanced activity of Co/ZnZrO 2, H 2-TPD tests were used for estimating the number of surface active sites of the catalysts. The Co/ZnZrO 2 shows the hydrogen第 9 期SUN Jia-qiang et al.：Influence of pretreatment conditions on the structure and catalytic performance of ……1295adsorption amount of 38 μmol/g, while the Co@C-ZnZrO 2 shows that of 22 μmol/g, indicating that the Co/ZnZrO 2 catalyst has more active sites than Co@C-ZnZrO 2 catalyst. Despite Co/ZnZrO 2 exhibits the lower BET specific surface area, the more active sites for Co/ZnZrO 2 catalyst are responsible for the higher activity. The H 2 desorption temperature of Co/ZnZrO 2is higher than that of Co@C-ZnZrO 2, implying that the H 2 chemisorption on the surface of Co NPs is enhanced for Co/ZnZrO 2 catalyst, resulting in the higher activity (Figure 14). In addition, it is claimed that zirconium could enhance the activity and heavy hydrocarbonselectivity of Co-based catalysts [32]. As clarified by the XPS results, Zr and Co NPs in Co/ZnZrO 2 have the stronger electronic interaction, which promotes CO adsorption, weakens C−O bond and promotes the chain growth processes, resulting in the higher heavy hydrocarbon selectivity. Zr and Co NPs in Co@C-ZnZrO 2 present the weaker interaction. This is because the active Co sites are surrounded by the carbon layer,which suppresses the adsorption of syngas, resulting in the lower activity and heavy hydrocarbon selectivity.Furthermore, Co/ZnZrO 2 catalyst has the higher chain growth probability than Co@C-ZnZrO 2, which reveals that the chain growth on Co/ZnZrO 2 catalyst is favored,leading to the higher heavy hydrocarbon selectivity.50100150200250300350Co@C-ZnZrO 2Co/ZnZrO 2Temperature /℃I n t e n s i t y /(a .u .)Figure 14 H 2-TPD profiles of the catalysts3 ConclusionsIn summary, Co/ZnZrO 2 catalysts were synthesized by a MOFs-mediated synthesis strategy,which exhibited an excellent catalytic performance for FTS. 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Treatment of Wastewater from the Metal IndustryThe metal industry is one of the most significant contributors to industrial wastewater. The wastewater generated from this industry contains a high concentration of heavy metals, chemicals, and other pollutants that are harmful to the environment and human health. Therefore, it is essential to treat the wastewater before discharging it into the environment. This article discusses the treatment of wastewater from the metal industry, including the challenges and solutions.The wastewater generated from the metal industry contains various pollutants, including heavy metals, oils, grease, and chemicals. These pollutants can cause severe environmental and health problems if not treated correctly. The treatment of wastewater from the metal industry is a complex process that requires the use of various treatment technologies. The primary goal of the treatment process is to remove the pollutants from the wastewater and make it safe for discharge.One of the significant challenges in the treatment of wastewater from the metal industry is the high concentration of heavy metals. Heavy metals are toxic and can cause severe health problems, such as cancer and neurological disorders. Therefore, the removal of heavy metals from wastewater is of utmost importance. Various treatment technologies, such as chemical precipitation, ion exchange, and membrane filtration, can be used to remove heavy metals from wastewater.Another challenge in the treatment of wastewater from the metal industry is the high concentration of oils and grease. Oils and grease can cause clogging in the treatment equipment, which can lead to operational problems and reduced efficiency. Therefore, it is essential to remove oils and grease from the wastewater before treatment. Various treatment technologies, such as gravity separation, dissolved air flotation, and biological treatment, can be used to remove oils and grease from wastewater.The treatment of wastewater from the metal industry also requires the removal of chemicals. Chemicals can be toxic and can cause severe health and environmental problemsif not treated correctly. Various treatment technologies, such as chemical oxidation, adsorption, and biological treatment, can be used to remove chemicals from wastewater.In conclusion, the treatment of wastewater from the metal industry is a complex process that requires the use of various treatment technologies. The primary goal of the treatment process is to remove pollutants from the wastewater and make it safe for discharge. The challenges in the treatment of wastewater from the metal industry include the high concentration of heavy metals, oils and grease, and chemicals. However, various treatment technologies, such as chemical precipitation, ion exchange, and membrane filtration, can be used to remove heavy metals from wastewater. Additionally, various treatment technologies, such as gravity separation, dissolved air flotation, and biological treatment, can be used to remove oils and grease from wastewater. Finally, various treatment technologies, such as chemical oxidation, adsorption, and biological treatment, can be used to remove chemicals from wastewater.。