Au nanoparticles as a novel coating for solid-phase microextraction

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Au、Ag金属纳米颗粒、纳米棒、多面体、核壳结构合成的几篇经典文献,colloidal 合成

eometry control of metal particles at the nanoscale is a crucial step in the development of nanoplasmonic materials and devices.1,2 Among all the reported synthetic routes, the seeded growth method can be considered as the most versatile one, since it allows ﬁne-tuning of both the morphology and size of the nanoparticles by simply reducing additional metal ions on preformed nanoparticle seeds.3,4 Such seeded growth process can be implemented either in aqueous solution or in organic solvents such as N,N-dimethylformamide (DMF) or polyols,5 usually mediated by surfactants or polymers, respectively.6 Typically, reduction in organic solvents (which are the actual reducing agents) requires diﬀerent experimental conditions, such as higher temperatures or the presence of (apparently) spectator ions. Although both approaches cannot be easily compared, it is widely accepted that the ﬁnal particle shape, regardless of the synthetic approach, is mainly dictated by the crystalline structure of the seed, as well as by the eﬀect of ligands (surfactants/polymers) and other additives (ions in general). The preferential adsorption of ligands or additives onto the seeds makes certain crystallographic facets thermodynamically more stable, reducing their surface free energy. As a consequence, the relative free energies for diﬀerent facets and thus their relative growth rates may change as compared to surface energies in vacuum. Although the fast development of spectroscopic techniques has

普鲁士蓝衍生物Cd2[Fe（CN）6]·2H2O纳米棒的合成与表征

普鲁士蓝衍生物Cd2[Fe（CN）6]2H2O纳米棒的合成与表征钱江华;王金敏【摘要】Using polyethylene glycol (PEG-400) as the surfactant, Prussian blue analogue Cd2[Fe(CN)6]· 2H2O nanorods with a diameter of around 500 nm were synthesized by hydrothermal process. The products were coated on indium tin oxide (ITO) coated glasses by spin-coating. Cyclic voltammetry curves of the films were measured by electrochemical workstation. The results show that the oxidation and reduction potentials of the film are 0.32 V and 0.26 V.%以聚乙二醇(PEG-400)为表面活性剂,采用水热法合成了直径约为500 nm的普鲁士蓝衍生物Cd2[Fe(CN)6]·2H2O纳米棒。

将其旋涂到氧化铟锡(ITO)玻璃上制成薄膜,用电化学工作站对薄膜进行循环伏安测试,测得该薄膜的氧化电位为0.32 V,还原电位为0.26 V。

【期刊名称】《上海第二工业大学学报》【年(卷),期】2016(033)002【总页数】4页(P118-121)【关键词】普鲁士蓝衍生物;水热法;纳米棒【作者】钱江华;王金敏【作者单位】上海第二工业大学环境与材料工程学院，上海201209;上海第二工业大学环境与材料工程学院，上海201209【正文语种】中文【中图分类】O614.24+2普鲁士蓝（Prussian Blue，PB），又称柏林蓝，其分子式为Fe4［Fe（CN）6］3，是人们熟知的一种蓝色染料。

Au-Pt

Au–Pt alloy nanocrystals incorporated in silica filmsGoutam De {and C.N.R.Rao *Received 11th August 2004,Accepted 23rd November 2004First published as an Advance Article on the web 15th December 2004DOI:10.1039/b412429dAu,Pt and Au–Pt alloy nanocrystals have been prepared in thin SiO 2film matrices by sol–gel spin-coating,followed by heating at 450u C in 10%H 2–90%Ar.X-Ray diffraction patterns reveal that the Au and Au–Pt nanocrystals have a preferential (111)orientation.Upon increasing the Pt concentration,part of the Pt does not alloy with Au,but instead forms a shell around the Au–Pt alloy core.The alloy composition itself goes up to Au(50):Pt(50),and the Pt shells are formed around the alloy above an alloy composition of Au(75):Pt(25).The surface plasmon resonance (SPR)band at 544nm of Au gradually disappears due to the formation of Au–Pt alloys and core–shell structures.IntroductionMetal nanocrystals embedded in appropriate glassy hosts are known to exhibit enhanced nonlinear optical properties,with a large intensity-dependent refractive index related to the real part of the third-order susceptibility,x (3).1Such materials have potential optoelectronic applications in optical switching and limiting devices because of the ultrafast nonlinear response.1–3Optical properties of these composites are greatly influenced by the interface between the nanocrystals and the matrix.4Accordingly,the shape,size and composition of the nanocrys-tals play an important role in modulating the properties.5–8There is considerable interest today in synthesizing Au–Pt bimetallic nanoparticles from solution.9–11Au–Pt bimetallic nanoparticles supported on inorganic oxides 12and zeolites 13are also reported for their improved catalytic properties.Of these,Au–Pt core–shell type nanoparticles have been prepared by the deposition of Pt on Au or vice-versa .9–11Although core–shell Au–Pt nanoparticles are formed readily by the solution process,their formation inside a glassy film matrix has not yet been accomplished.For real nonlinear optical applications,however,the nanocrystals have to be embedded in a matrix which can withstand high intensity laser light.Sol–gel derived metal nanocrystals incorporated in SiO 2films are known to exhibit high x (3)values with good reproducibility.2In this article we report a sol–gel synthesis of oriented nanoparticles of Au and Au–Pt alloys as well as of core (alloy)–shell (Pt)particles embedded in thin SiO 2films.Such oriented composite nanocrystals belonging to the quantum-size regime embedded in thin transparent SiO 2film could be interesting for nonlinear optical applications.ExperimentalAu,Pt and Au–Pt alloy nanocrystals embedded in silica hosts were prepared from sols starting from tetraethylorthosilicate (TEOS),HAuCl 4?3H 2O,H 2PtCl 6?x H 2O (40%Pt),n -propanol,i -butanol and water,by the sol–gel spin-coating technique.The compositions of the films are listed in Table 1.The molar ratio of the metal (M 5Au,Au–Pt or Pt)to SiO 2was kept constant in all the films,being of 6equivalent mol%M :94%SiO 2.The general method of preparation of the films was as follows.To a solution of TEOS in n -propanol (50%of the total)of the appropriate concentration,an aqueous-n -propanol solution containing HAuCl 4?3H 2O or/and H 2PtCl 6?x H 2O (40%Pt)was added under stirring,and the stirring continued for 2h at 22¡2u C.After this period,i -butanol was added and the sol stirred for another 1h.The total H 2O/TEOS molar ratio was maintained at 8.The total equivalent SiO 2and metal content of the sols was about 4.5wt%in all cases.Films were deposited on clean silica glass slides (type II,Heraeus),silicon wafers and ordinary soda-lime glass slides by spin-coating,employing a spinning rate of 1000–1500rpm.The resulting films were dried at 75u C in air.The dried films were then heated to 450u C for 30min in air (to remove the organic matter)and then in 10%H 2–90%Ar (gas flow was controlled by mass flow controller)for 1h.The films were allowed to cool naturally in the flow of the 10%H 2–90%Ar gas mixture.Powder X-ray diffraction (XRD)patterns of the thin film samples were recorded with a diffractometer operating at 40kV and 30mA using Ni-filtered Cu K a radiation.Transmission electron microscopy (TEM)was done using a Jeol (model JEM 3010).Optical spectra of the coated films were obtained on a Perkin Elmer UV-VIS spectrophotometer (model Lambda 900).Scanning electron microscopy (SEM)was done using a scanning electron microscope (model Leica S440i).Results and discussionThe silica-gel films air-dried at 75u C are completely trans-parent and colourless.AuCl 42and/or a mixture of AuCl 42and PtCl 622ions remain in the gel-films trapped as in other sol–gel derived films.14After heat-treatment of the films at 450u C the AuCl 42/PtCl 622ions are reduced,precipitating Au/Pt metallic nanoparticles in glassy SiO 2film matrices.It may be noted here that annealing in air could reduce AuCl 42and PtCl 622ions to their corresponding metallic states in individual systems.8,15However,in a mixed system,the large{Permanent address:Sol–Gel Division,Central Glass and Ceramic Research Institute,Jadavpur,Kolkata 700032,India.*cnrrao@jncasr.ac.inPAPER /materials |Journal of Materials ChemistryD o w n l o a d e d b y BE I J I N G I N S T I T U T E OF T E C H N O L OG Y o n 16 F e b r u a r y 2012P u b l i s h e d o n 15 D e c e m b e r 2004 o n h t t p ://p u b s .r s c .o r g | d o i :10.1039/B 412429DView Online / Journal Homepage / Table of Contents for this issueredox potential (+0.99V)of the AuCl 42ions could inhibit the reduction process of platinum ions.To avoid this complex situation,films were heated in a reducing atmosphere (H 2–Ar gas mixture),as was also followed by other workers for the preparation of supported Au–Pt bimetallic catalysts by reduction of the HAuCl 4/H 2PtCl 6mixture.12a ,13The heat-treated films are homogeneous and transparent.The film containing Au alone is reddish-blue in colour.The colour gradually disappears on increasing the Pt loading.The film containing Pt alone is light brown in colour.The thickness of the films,estimated by cross-sectional scanning electron microscopy (SEM)was in the 145–175nm range.As also pointed out earlier,one would expect that the gold ions are reduced first,followed by platinum ions since the standard redox potential E 0for the AuCl 42/Au 0couple is higher than that of the PtCl 622/Pt 0couple.9,16,17AuCl 42+3e 2«Au 0+4Cl 2E 05+0.99V PtCl 622+4e 2«Pt 0+6Cl 2E 05+0.74VAs a result,the Au nanoparticles form first and the Pt atoms are deposited on to the gold nanoparticles in the SiO 2film matrix.Transmission electron microscope (TEM)images of the Au and Au–Pt nanocrystals are shown in Fig.1.The images show the presence of trigonal or prismatic Au nanocrystals with a size range of 10–40nm [Fig.1(a)].The inclusion of Pt causes a drastic decrease in the size of the nanoparticles to 3–4nm.Interestingly,we observe the presence of a large number of bigger clusters in the case of Au 4.5Pt 1.5[Fig.1(b)],whereas in Au 3Pt 3the number of such big clusters is reduced [Fig.1(c)].In the case of Au 1.5Pt 4.5,the bigger clusters are absent [Fig.1(d)].Instead,we observe uniform-sized nanoparticles of 3–4nm.In Fig.2,we show the XRD patterns of the SiO 2films containing Au,Pt and Au–Pt alloy nanocrystals deposited on silica glass substrates.The patterns show only the (111)Bragg reflection,18indicating a highly oriented growth of the nanocrystals.The other Bragg reflections are hardly visible.The decrease in the d (111)value with increasing Pt loading is consistent with the formation of Au–Pt solid solutions (Table 1).Thus,in the case of Au the (111)reflection is at2.354A˚corresponding to a 50.4078nm,while in Au 4.5Pt 1.5it is at 2.344A˚corresponding to a 50.4060nm.The a value calculated from Vegard’s law for Au 0.75Pt 0.25(Au 4.5Pt 1.5)is 0.4060nm.19,20For Au 3Pt 3and Au 1.5Pt 4.5,the observed dvalues are at 2.339and 2.331A˚respectively corresponding to a values of 0.4051and 4037nm respectively.These values are higher,indicating a lower Pt content than indicated by the nominal composition of the solid solution (Table 1).In these cases,the a values calculated from Vegard’s law give thecompositions as Au 0.666Pt 0.333and Au 0.54Pt 0.46respectively.It appears that in the latter,a major proportion of the Pt atoms does not enter the alloy structure.It may be noted that bulk Au–Pt solid solutions are generally formed only at tempera-tures above 1100u C.The compositions of the alloys derived from the respective d values obtained from the XRD patterns are listed in Table 1.By simple arithmetic,we see that about 50and 66mol%of the Pt remains out of the solid solutions in Au 3Pt 3and Au 1.5Pt 4.5respectively.The XRD peaks in these systems should therefore show the Pt reflection as well.We,do not,however,see a peak due to Pt because of the small particle size (see Fig.2in the case of pure Pt).Fig.3shows the optical spectra of the films annealed at 450u C for 1h in 10%H 2–90%Ar.The pure Au film shows a band at 544nm with a broad tail extending towards higher wavelengths due to surface plasmon resonance (SPR).The SPR band of well-dispersed spherical Au nanocrystals is generally sharp and appears around 520nm.The broadening of this band at higher wavelengths may be due to the anisotropy of the trigonal/prismatic shape (non-spherical)of the Au nanocrystals.6,21The pure Pt film does not have aTable 1Composition of the films obtained after annealing at 450u C for 1h in 10%H 2–90%ArStarting composition(mol Au :mol Pt :mol Si)Sample name Composition (nominal)Lattice parameter/nm (XRD)Calculated alloy composition from Vegard’s law Cluster composition 6:0:94AuAu0.4078AuAu4.5:1.5:94Au 4.5Pt 1.5Au 0.75Pt 0.250.4060Au 0.75Pt 0.25Au 4.5Pt 1.53:3:94Au 3Pt 3Au 0.5Pt 0.50.4051Au 0.666Pt 0.333Au 3Pt 1.5core–Pt 1.5shell 1.5:4.5:94Au 1.5Pt 4.5Au 0.25Pt 0.750.4037Au 0.54Pt 0.46Au 1.5Pt 1.5core–Pt 3shell 0:6:94PtPt0.3924PtPtFig.1TEM images showing the nanoparticles embedded in SiO 2films:(a)Au,(b)Au 4.5Pt 1.5,(c)Au 3Pt 3and (d)Au 1.5Pt 4.5.The alloy compositions are nominal (see Table 1).D o w n l o a d e d b y BE I J I N G I N S T I T U T E OF T E C H N O L OG Y o n 16 F e b r u a r y 2012P u b l i s h e d o n 15 D e c e m b e r 2004 o n h t t p ://p u b s .r s c .o r g | d o i :10.1039/B 412429Ddistinguishable SPR band.The dampening of the Au SPR band due to the introduction of Pt indicates the formation of either a Au–Pt solid solution or a Au core–Pt shell type structure.Since the calculated and observed lattice parameters agree well in the case of Au 4.5Pt 1.5(Table 1),we suggest that this is a good solid solution rather than a Au core–Pt shell.For Au 3Pt 3and Au 1.5Pt 4.5,the optical spectra show that the Au-SPR band is very weak or absent.This observation may be taken to indicate either the formation of a Au–Pt solid solution or a Au core–Pt shell type structure.However,in Au 3Pt 3,the a value calculated from Vegard’s law gives the composition of the alloy to be Au 0.666Pt 0.333showing that about 50mol%of the Pt remains outside the Au–Pt alloy.Similarly,in the case of Au 1.5Pt 4.5,the d (111)value is consistent with formation ofthe Au 0.54Pt 0.46core with about 66%of the Pt remaining as the shell.The core–shell type structure is shown schematically in Fig.4.It is of interest to know whether the Au,Au–Pt alloy and Pt nanoparticles remain as separate clusters in the thin film silica matrix.It was pointed out earlier that the Au nanoparticles are formed first,with the Pt atoms precipitating on to the gold nanoparticles.The Pt atoms close to the Au atoms would be expected to form solid solutions under the experimental conditions.When the Pt concentration is low (as in Au 4.5Pt 1.5),we obtain only a Au–Pt solid solution while in Au 3Pt 3and Au 1.5Pt 4.5part of the Pt forms a solid solution with the Au,the remaining part forming a shell around the alloy.The deposition of Pt atoms on to the surface of the gold nanoparticles can be understood from the optical spectra of the composite films as well.A significant dampening of the gold surface plasmon resonance is known to occur by a surface layer of platinum.9–11This is clearly evidenced in the absorption spectra of the annealed films shown in Fig. 3.The SPR band of gold (544nm)gradually disappears with increasing Pt content.If a mixture of discrete Au and Pt nanoparticles were present,the Au SPR band would continue to occur in the Au–Pt films.ConclusionsAu,Au–Pt alloys and core (alloy)–shell (Pt)nanoparticles have been generated in glassy silica films by the sol–gel method.The nanoparticles are oriented in the (111)crystalline plane.By the low-temperature method employed,nanocrystal alloys are formed up to a Au :Pt ratio of about 1:1,but with an increase in Pt content,Pt shells are formed around the alloy cores.Formation of Au,Pt and their alloy nanoparticles in the silica film matrix is noteworthy and could be of potential technological value.Goutam De {and C.N.R.Rao *Chemistry and Physics of Materials Unit,Jawaharlal Nehru Centre for Advanced Scientific Research,Jakkur P.O.,Bangalore 560064,India.E-mail:cnrrao@jncasr.ac.inReferences1H.Hache,D.Ricard and C.Flytzanis,J.Opt.Soc.Am.B ,1986,3,1647; C.Flytzanis, F.Hache,M. C.Klein, D.Ricard and Ph.Roussignol,Prog.Opt.,1991,29,321;T.Tokizaki,A.Nakamura,S.Kaneko,K.Uchida,S.Omi,H.Tanji and Y.Asahara,Appl.Phys.Lett.,1994,65,941.2G.De,L.Tapfer,M.Catalano,G.Battaglin, F.Caccavale,F.Gonella,P.Mazzoldi and R.F.Haglund,Jr.,Appl.Phys.Lett.,1996,68,3820andP.P.Kiran,G.De and D.N.Rao,IEE Proc.-Circuits Devices System ,2003,150,559.3Y.-P.Sun,J. E.Riggs,K. B.Henbest and R. B.Martin,J.Nonlinear Opt.Phys.Mater.,2000,9,481.Fig.2XRD patterns of nanocrystals of Au,Pt and Au–Pt alloys embedded in SiO 2thin film matrices.Nominal compositions of the alloys are shown (see Table1).Fig.3Optical absorption spectra of Au,Pt and Au–Pt alloys embedded in SiO 2thin filmmatrices.Fig.4Schematic diagram of a core (Au–Pt alloy)–shell (Pt)nanocrystal.D o w n l o a d e d b y BE I J I N G I N S T I T U T E OF T E C H N O L OG Y o n 16 F e b r u a r y 2012P u b l i s h e d o n 15 D e c e m b e r 2004 o n h t t p ://p u b s .r s c .o r g | d o i :10.1039/B 412429D4P.N.Butcher and D.Cotter,The Elements of Nonlinear Optics ,Cambridge University Press,Cambridge,UK,1990;J.A.Creighton and D.G.Eadon,J.Chem.Soc.,Faraday Trans.,1991,87,3881;F.Gonella,G.Mattei,P.Mazzoldi,G.Battaglin,A.Quaranta,G.De and M.Montecchi,Chem.Mater.,1999,11,814;R.H.Doremous,Langmuir ,2002,18,2436.5U.Kreibig and M.Volmer,Optical Properties of Metal Clusters ,Springer-Verlag,Berlin,1995.6 A.I.Kirkland, D. A.Jefferson, D.G.Duff,P.P.Edwards,I.Gameson,B.F.G.Johnson and D.J.Smith,Proc.R.Soc.London,Ser.A ,1993,440,589.7 C.N.R.Rao,G.U.Kulkarni,P.J.Thomas and P.P.Edwards,Chem.Eur.J.,2002,8,29.8G.De,G.Mattei,P.Mazzoldi, C.Sada,G.Battaglin and A.Quaranta,Chem.Mater.,2000,12,2157.9L.M.Liz-Marza ´n and A.P.Philipse,J.Phys.Chem.,1995,99,15120.10 C.Damle,K.Biswas and M.Sastry,Langmuir ,2001,17,7156.11 A.Henglein,J.Phys.Chem.B ,2000,104,2201.12(a )A.Va ´zquez-Zavala,J.Garcı´a-Go ´mez and A.Go ´mez-Corte ´s,Appl.Surf.Sci.,2000,167,177;(b )ng,S.Maldonado,K.J.Stevenson and B.D.Chandler,J.Am.Chem.Soc.,2004,126,12949.13G.Riahi,D.Guillemot,M.Polisset-Thfoin,A.A.Khodadadi and J.Fraissard,Catal.Today ,2002,72,115.14G.De and D.Kundu,Chem.Mater.,2001,13,4239.15H.Kozuka,G.Zhao and S.Sakka,J.Sol–Gel Sci.Technol.,1994,2,741;G.Fo ´ti,C.Mousty,K.Novy,ninellis and V.Reid,J.Appl.Electrochem.,2000,30,147.16R.C.Weast,Handbook of Chemistry and Physics,56th edn.,CRC Press,Cleveland,OH,1975,p.D-141.17 A.I.Vogel,Quantitative Inorganic Analysis,3rd edn.,Addison Wesley Longman Ltd,England,1961,p.87.18 D. F.Leff,L.Brandt and J.R.Heath,Langmuir ,1996,12,4723.19M.Hansen,Constitutions of Binary Alloys ,McGraw-Hill,New York,1958.20H.Okamoto, D.J.Chakrabarti, D. ughlin and T. B.Massalski,Phase Diagrams of Binary Gold Alloys,Monograph Series of Alloy Phase Diagrams ,ASM Internationals,Metals Park,OH,1987.21G.De and C.N.R.Rao,J.Phys.Chem.B ,2003,107,13597.D o w n l o a d e d b y BE I J I N G I N S T I T U T E OF T E C H N O L OG Y o n 16 F e b r u a r y 2012P u b l i s h e d o n 15 D e c e m b e r 2004 o n h t t p ://p u b s .r s c .o r g | d o i :10.1039/B 412429D。

纳米银的合成及其抗菌应用研究进展

纳米银的合成及其抗菌应用研究进展叶伟杰;陈楷航;蔡少龄;陈利科;钟同苏;王小英【摘要】病原微生物严重威胁着人类的健康安全,纳米银作为一种新型抗菌材料,其制备与应用已成为纳米材料领域的研究热点.本文综述了纳米银的主要合成方法,包括多糖法、Tollens试剂法、辐射法、生物法和多金属氧酸盐法等,具有原料广泛、反应温和、成本低廉和环境友好等优点.基于纳米银的优异抗菌性能,总结了纳米银的抗菌机理及其抗菌应用,并展望了纳米银在抗菌涂料、抗菌包装等领域的发展前景.%Pathogenic microorganism is a serious threat to human health.As a novel kind of antibacterial materials, silver nanoparticles involving their preparation approaches and applications are of great research interest in the field of nanomaterials.This review summarized a summary of synthesis methods of silver nanoparticles, including polysaccharide, Tollens, irradiation, biological and polyoxometalates, which enjoy numerous advantages such as wide range of raw materials, gentle reaction condition, low-cost and environmental-friendly and etc..Furthermore, based on the antibacterial property of silver nanoparticles, the antibacterial mechanism and applications were described.The development of silver nanoparticles in antibacterial application was also prospected, such as antibacterial coating and antibacterial packaging.【期刊名称】《材料工程》【年(卷),期】2017(045)009【总页数】9页(P22-30)【关键词】纳米银;合成;抗菌机理;抗菌应用【作者】叶伟杰;陈楷航;蔡少龄;陈利科;钟同苏;王小英【作者单位】华南理工大学轻工科学与工程学院制浆造纸国家重点实验室,广州510640;华南理工大学轻工科学与工程学院制浆造纸国家重点实验室,广州510640;华南理工大学轻工科学与工程学院制浆造纸国家重点实验室,广州510640;深圳市美盈森环保科技股份有限公司,广东深圳 518107;深圳市美盈森环保科技股份有限公司,广东深圳 518107;深圳市美盈森环保科技股份有限公司,广东深圳 518107;华南理工大学轻工科学与工程学院制浆造纸国家重点实验室,广州510640【正文语种】中文【中图分类】TB331近年来，环境微生物灾害事件频繁发生，造成了巨大的经济损失和社会危害。

纳米技术可以运用在衣服地方英语作文

纳米技术可以运用在衣服地方英语作文全文共3篇示例，供读者参考篇1Nanotechnology: The Future of FashionAs a student passionate about science and technology, I find the field of nanotechnology absolutely fascinating. The potential applications of manipulating matter at the atomic and molecular level seem boundless, with the ability to revolutionize industries from electronics to medicine. However, one area that often gets overlooked is the fashion industry and how nanotechnology could completely transform the clothes we wear every day.At its core, nanotechnology for clothing is about engineering fabrics at the nanoscale to give them enhanced properties and functionalities. This could mean weaving nanomaterials into the fabric itself during production, or applying nanoparticle coatings and treatments to existing textiles. The unique physical and chemical properties that emerge at the nanoscale allow for incredible advances in areas like stain and water resistance, insulation, durability, and even embedded electronics and sensors.One of the most promising applications is making fabrics virtually impervious to stains and liquids through the use of nanowhiskers or nanotubes. These ultra-thin cylindrical structures can be woven into fabric or applied as a coating to create a tightly packed rough surface that causes liquids to bead up and roll off rather than penetrating the material. Companies have already developed nano-based stain-resistant dress shirts and pants that stay clean and fresh for weeks without washing.Building on this, nanotechnology could lead to self-cleaning clothes that use compounds like titanium dioxide or zinc oxide nanoparticles. When exposed to sunlight, these nanoparticles create powerfully oxidizing conditions that break down organic stains at the molecular level. Clothing brands are actively pursuing photocatalytic self-cleaning technology that could make manually washing clothes a rarity.Staying on the topic of cleanliness, one major issue with clothing is its tendency to absorb odors from sweat and environmental sources. Researchers are looking at embedding odor-fighting nanoparticles like silver, copper, or carbon-based compounds into fabrics. These have natural antimicrobial and deodorizing properties to keep clothes fresher for longer. Bonus:the nanoparticles can also help reduce bacteria growth that causes fabric deterioration.Regulating temperature and insulation is another huge potential benefit of nanotechnology in clothing. Nanoporous materials allow for extremely fine-tuning of air permeability, enabling garments that keep you cool by letting heat escape or provide warming insulation by trapping heat. Scientists have developed nanofiber insulation that is 10x warmer than traditional materials. Winter coats and athletic wear could be revolutionized.The nanoscale also opens up possibilities for smart fabrics embedded with electronics, sensors, and computing capabilities. Clothes could have tiny nanodevices woven into the threads that track biometrics like heart rate and body temperature. Or nanosensors could detect environmental conditions like UV exposure and automatically adjust for protection. Futuristic "smart clothes" may even be able to charge devices, change color based on your mood, or release medications through the skin.Of course, one concern with engineering clothing at the nanoscale is potential toxicity risks. After all, nanoparticles are able to penetrate cells and tissues in ways that larger particlescannot. There are open questions around how some nanomaterials may interact with the body and environment that require further research and safety testing. As with many emerging technologies, responsible development and regulation will be critical.However, the immense benefits and potential of nanotechnology in fashion seem to outweigh the risks. In addition to enhancing the functionality of clothes, nanoengineered fabrics could drastically reduce the environmental impact of clothing manufacturing and cleaning through reduced chemical usage, water conservation, and extended product lifespans. The apparel industry is notorious for massive waste, pollution, and energy consumption - so solutions like self-cleaning nanogarments could be a huge sustainability win.Furthermore, clothes enhanced with nanotechnology could have profound humanitarian applications by providing advanced protective properties. Imagine affordable uniforms for doctors and nurses that shield against pathogens and contaminants. Or gear for soldiers and first responders with smart insulation, integrated electronics, and self-decontamination capabilities.Nanotech apparel could even filter out pollution particles from the air in smoggy cities.As a student always trying to blend my interests in STEM fields with creative pursuits, I find the concept of nanoengineering fashion endlessly fascinating. I can't wait to see how clothing brands and research teams push the boundaries of what's possible by tapping into the unique properties of materials at the nanoscale. From rugged outdoor wear that never gets muddy to sleek business suits that stay impeccably clean, nanotechnology holds the potential to reinvent how we think about and utilize the clothes we wear.Just a few decades ago, nanotechnology belonged solely in the realm of science fiction. Now, it's very much a scientific reality poised to upend countless industries - including the multi-billion dollar fashion world. While many may associate nanotech with advanced semiconductors or cancer treatments, I believe the application of nano-engineered smart fabrics could be one of the most ubiquitous and impactful reviolutions. After all, clothing is something we all use every single day and nanotechnology promises to vastly improve its functionality, durability, and environmental footprint.As both a STEM student and self-professed clothes enthusiast, I can't wait to see what the future holds fornano-enhanced textiles and apparel. The ability to control matter at the atomic level is truly the next frontier of human ingenuity and design. The unique properties that emerge at these tiny scales open up realms of possibility - like coats that effortlessly insulate, shirts that clean themselves, and clothes that monitor our vitals. With continued research and innovation, mundane fabrics could soon possess almost magical qualities thanks to the power of nanotechnology. The clothes of tomorrow may very well outperform and outlast anything from today.篇2The Future of Fashion: Nanotechnology in ClothingTechnological advancements have revolutionized nearly every aspect of our lives, from communication and transportation to healthcare and entertainment. However, one area that has seen significant transformations due to the integration of cutting-edge technologies is the fashion industry. Nanotechnology, in particular, has opened up a realm of possibilities for innovative textiles and clothing that were once confined to the realms of science fiction.As a passionate student of both fashion and science, I find the convergence of these two worlds absolutely fascinating. Nanotechnology, the manipulation of matter at the molecular or atomic scale, has the potential to create fabrics with extraordinary properties that could change the way we think about clothing forever.Imagine a world where your clothes not only look stylish but also possess incredible functionalities. Envision a shirt that can regulate your body temperature, keeping you cool in the sweltering heat and warm in the biting cold. Or a dress that can repel stains and dirt, ensuring it remains pristine and fresh throughout the day. These seemingly futuristic concepts are rapidly becoming a reality thanks to the advancements in nanotechnology.One of the most promising applications of nanotechnology in clothing is the development of self-cleaning fabrics. Through the incorporation of nanoparticles with photocatalytic properties, these textiles can break down dirt and stains when exposed to sunlight or specific wavelengths of light. This technology could revolutionize the way we care for our garments, reducing the need for frequent washing and extending the lifespan of our clothing.Another exciting development is the creation of fabrics with enhanced durability and strength. Nanofibers, which are thousands of times thinner than human hair, can be woven into textiles, resulting in materials that are remarkably strong yet lightweight. This technology could pave the way for clothing that is resistant to tearing, abrasion, and other forms of wear and tear, making it ideal for outdoor activities, sports, and even protective gear.But nanotechnology's potential in clothing goes beyond functional benefits. It also offers exciting opportunities for aesthetic enhancements. Imagine clothes that can change color or pattern at the touch of a button, or fabrics that can display intricate designs or even moving images. This technology, known as electrochromic or electrowetting, utilizes nanostructures to manipulate the way light interacts with the material, creating dynamic and customizable visual effects.Furthermore, nanotechnology has the potential to revolutionize the way we approach sustainability in the fashion industry. By developing textiles that are biodegradable or made from renewable resources, we can reduce the environmental impact of clothing production and disposal. Additionally, nanoparticles can be used to create fabrics with enhancedmoisture-wicking and antimicrobial properties, reducing the need for frequent washing and extending the lifespan of garments.However, as with any emerging technology, there are concerns about the potential risks and implications of nanotechnology in clothing. The long-term effects of nanoparticles on human health and the environment are still being studied, and there is a need for rigorous testing and regulation to ensure the safety of these materials.Despite these challenges, the potential benefits of nanotechnology in clothing are too significant to ignore. As a student passionate about both fashion and science, I am excited to witness the ongoing developments in this field and to contribute to the innovation and responsible implementation of these technologies.In conclusion, nanotechnology is poised to revolutionize the fashion industry, offering unprecedented opportunities for functional, aesthetic, and sustainable clothing. Fromself-cleaning fabrics and temperature-regulating textiles to dynamic visual effects and biodegradable materials, the possibilities are endless. As we continue to explore and harness the power of nanotechnology, we are shaping the future offashion, creating garments that not only look stunning but also provide remarkable functionalities and environmental benefits.篇3The Nanotech Clothing RevolutionNanotechnology is often discussed in relation to fields like computing, medicine, and engineering. However, one area where nanoscale materials and devices could have a huge impact that is less frequently talked about is the clothing and textiles industry. By integrating nanotech into fabrics and garments, we could see a revolutionary new generation of high-performance "smart clothing" emerge in the coming years and decades.At its core, nanotechnology involves manipulating matter at the molecular or atomic scale to create new materials and products with enhanced properties. When applied to clothing, nanotech can improve fabrics in several key ways - making them stronger, more durable, better insulated, moisture-wicking, stain-resistant, anti-microbial, and even imbuing them with tech capabilities like integrated sensors, energy storage, and data processing.Let's take a look at some of the exciting potential applications of nanotechnology in clothing and apparel:Strength and DurabilityOne of the most obvious benefits nanotech could provide clothing is increased strength and resistance to tearing or fraying. This is achieved by incorporating high-strength nanomaterials like carbon nanotubes into the fabric fibers. Clothes made with nanotech-reinforced textiles would be much harder to rip or damage, greatly improving their lifespan.For example, researchers have already created cotton fabrics reinforced with carbon nanotubes that are over 10 times stronger than untreated cotton. Dresses, pants, jackets and other garments made with such super-strong nanotech fabrics could withstand rough use and heavy activity far better than today's clothing.Stain and Water ResistanceAnother awesome capability is making fabrics highlystain-resistant and waterproof using nanotech coatings and treatments. Clothes could literally have a nano-scale protective coating that causes water, oil, and other liquids to bead up and roll off rather than being absorbed into the fabric.The U.S. military is already issuing nanotech-treated combat uniforms to soldiers that are extremely water-repellent. Start-upshave also begun selling nanotech dress shirts for businessmen that can simply be rinsed under a tap to remove stains like red wine or grease. In the future, we may have suits, ties, dresses and more that never stain or get soaked, no matter what liquid spills on them.Odor and Germ ResistanceBody odor from sweating and bacterial growth is a perpetual problem with clothing, especially activewear. However, researchers are developing nano-coatings and nanoparticles that can be integrated into fabrics to neutralize odor-causing compounds and kill bacteria, fungi and other microbes.Some companies already sell "anti-odor" workout clothes utilizing nanoparticles of materials like silver that have natural antimicrobial properties. But even more advanced solutions could emerge, like responsive fabrics that only releaseanti-microbial nanoparticles when they detect sweat or bacterial growth. With nanotech, our clothes could stay fresher longer without odor build-up.Temperature RegulationAnother incredible potential is clothing that dynamically adapts to outside conditions to keep the wearer optimally warmor cool. This could be achieved by embedding smart fabrics with layers of different nanomaterials that change their thermal insulating properties in response to temperature fluctuations.For instance, you could have a jacket made of a fabric interwoven with two different types of nanomaterials - one that traps heat well, and one that allows heat to easily escape. When it's cold out, the heat-trapping nanomaterial expands to increase insulation. But when it's hot, the other nanomaterial takes over, opening pathways for body heat to vent outwards.We're already seeing early examples of this in "self-heating" winter jackets that use electrically-conductive nanofilaments to generate warmth without bulky battery packs or wiring. But in the future, our clothes could dynamically adapt to any climate or environment with perfectly tuned insulation and ventilation enabled by smart nanomaterials.Wearable TechnologyPerhaps the most sci-fi application of nanotechnology is using clothing and textiles as substrates for wearable electronics and computing devices. This could allow for tight integration of technologies like health sensors, communications, data displays, energy harvesting, and more right into the fabric of our shirts, pants, jackets, socks and other garments.Picture a dress shirt that not only resists stains and odors, but also contains flexible nanowire circuits interwoven throughout. These could continuously monitor your heart rate, body temperature, and other vital signs while displaying info on a shoulder-mounted fiber-optic display. Or workout clothes with integrated nanosensors tracking your exercise and calorie burn. Or a winter jacket with solar nanomaterials efficiently harvesting energy to power heated gloves or Bluetooth headphones built right into the collar.The possibilities of cloth-based wearable nanotech are mind-boggling and could change how we interact with devices and sensors in our everyday lives. Instead of wrist-worn wearables, the wearable could become the clothes themselves - a second skin of smart, responsive fabrics enhancing our comfort and capabilities.These are just a few examples of how nanotechnology could revolutionize clothing and apparel in the decades ahead. While much of this is still in the research phase today, the core nanomaterials and fabrication methods already exist. As they mature further, we're likely to see nanotech threads, coatings and electronics increasingly woven into our shirts, pants, jackets and more.Perhaps 20 or 30 years from now, we'll look back and marvel at how primitive and low-tech today's clothing was. Ourgreat-grandchildren may grow up never knowing scratchy, stain-prone fabrics, or clothes that can't automatically regulate temperature or monitor health. Instead, their ultra high-tech nanogarments could make today's athletic wear look as dated as a burlap sack.Of course, realizing the full potential of nanotech clothing isn't without its challenges - from high costs and scalability hurdles to toxicity concerns over the nanomaterials used. But if the breakthroughs continue, nanotechnology could spark a true revolution in what we wear and how clothing enhances our lives. We may barely recognize the smart, adaptive, multifunctional nanotech outfits of the future.。

基于聚苯乙烯微球阵列模板法制备有序纳米结构及表面增强拉曼应用

基于聚苯乙烯微球阵列模板法制备有序纳米结构及表面增强拉曼应用吕志成;李琴【摘要】以规则排列聚苯乙烯微球阵列为模板,在平面衬底上获得了六角形排列的开口球腔结构,在微观曲面衬底上制备了3种不同纳米球腔结构.偏振紫外可见吸收光谱表明,开口纳米球腔阵列光学性质以π/3为周期.两种基底对4-巯基苯甲酸(4-MBA)表面增强拉曼散射(SERS)增强能力的差异证明球腔型纳米结构的拉曼增强能力来源于开口部分.利用球腔型SERS基底实现了对农药甲基对硫磷的检测,此类基底具有用于农药残留分析的潜力.%In this paper,hexagonally ordered arranged spherical nanocavity structure with opened mouth on plane substrate and three different spherical nanocavity structures on micro-convex substrate were prepared using ordered array of polystyrene microsphere as a template.Polarized ultraviolet-visible absorption spectra of spherical nanocavity array showed a optical property regular change with π/3 as a period.The difference in surface enhanced Raman scattering(SERS) intensity of 4-mercaptobenzoic acid(4-MBA) on these two type of substrates clearly indicated that enhance of Raman signal came from opened mouth region.The spherical nanocavity SERS substrates were used to detect pesticide methyl parathion and revealed a potential for analyzing pesticide residues.【期刊名称】《化学与生物工程》【年(卷),期】2017(034)001【总页数】5页(P44-47,61)【关键词】聚苯乙烯微球阵列;纳米球腔;表面增强拉曼散射;农药残留【作者】吕志成;李琴【作者单位】华中农业大学理学院,湖北武汉430070;华中农业大学理学院,湖北武汉430070【正文语种】中文【中图分类】O657.37表面增强拉曼散射(surface enhanced Raman scattering，SERS)以其灵敏度高、结构鉴定能力强等特点在化学分析[1]、环境污染物检测[2]、生物分子结构鉴定[3]等领域发挥了重要作用。

双金属纳米颗粒的英文文献2000字左右

双金属纳米颗粒的英文文献2000字左右Dual-metallic nanoparticles have gained increasing attention in various fields due to their unique properties and wide range of applications. These nanoparticles, composed of two different metals, exhibit synergistic effects that enhance their catalytic, optical, and magnetic properties. In this review, we discuss the synthesis, properties, and applications of dual-metallic nanoparticles, focusing on their importance in nanotechnology.Synthesis methods for dual-metallic nanoparticles include chemical reduction, thermal decomposition, and galvanic replacement. These methods allow for control over the size, shape, composition, and structure of the nanoparticles, which ultimately influences their properties and applications. For example, alloying two metals can induce a shift in the surface plasmon resonance of the nanoparticles, leading to enhanced catalytic activity for various reactions.The properties of dual-metallic nanoparticles can be tailored by adjusting the ratio of the two metals, the nanoparticle size, and the synthesis conditions. For instance, bimetallic nanoparticles can exhibit improved stability, selectivity, and activity compared to their monometallic counterparts. The presence of two different metals also enables multifunctionality,allowing for applications in catalysis, sensing, imaging, and drug delivery.In catalysis, dual-metallic nanoparticles have shown great potential as efficient and selective catalysts for a wide range of reactions, including hydrogenation, oxidation, and coupling reactions. The synergistic effects between the two metals enhance the catalytic activity, while the unique structure of the nanoparticles provides a high surface area for catalysis. These properties make dual-metallic nanoparticles ideal candidates for sustainable and green chemistry applications.In addition to catalysis, dual-metallic nanoparticles have been used in other fields such as optoelectronics and photonics. The plasmonic properties of these nanoparticles can be tuned to absorb and scatter light in specific wavelengths, enabling applications in sensing, imaging, and photothermal therapy. Moreover, the magnetic properties of dual-metallic nanoparticles make them promising candidates for magnetic separation, drug delivery, and hyperthermia treatments.Overall, dual-metallic nanoparticles represent a versatile class of nanomaterials with significant potential for a wide range of applications. Their unique properties, tunable nature, and multifunctionality make them promising candidates for variousfields, including catalysis, sensing, imaging, and therapy. With further research and development, dual-metallic nanoparticles have the potential to revolutionize nanotechnology and contribute to the advancement of science and technology.。

Au-Pd双金属核壳结构————表征十分清晰

Green ChemistryDynamic Article LinksCite this:Green Chem.,2011,13,/greenchemPAPEROne-step room-temperature synthesis of Au@Pd core–shell nanoparticles with tunable structure using plant tannin as reductant and stabilizer†Xin Huang,a ,b Hao Wu,a Shangzhi Pu,c Wenhua Zhang,b ,c Xuepin Liao*a ,b and Bi Shi*bReceived 23rd October 2010,Accepted 8th February 2011DOI:10.1039/c0gc00724bBayberry tannin (BT),a natural plant polyphenol,is used for the one-step synthesis of Au@Pd core–shell nanoparticles (Au@Pd NPs)in aqueous solution at room temperature.Due to its mild and stepwise reduction ability,BT was able to preferentially reduce Au 3+to Au NPs when placed in contact with an Au 3+/Pd 2+mixture,and subsequently,the formed Au NPs served as in situ seeds for the growth of a Pd shell,resulting in the formation of Au@Pd NPs.Importantly,it is feasible to adjust the morphology of the Pd shell by varying the Pd 2+/Au 3+molar ratio.Au@Pd NPs with a spherical Pd shell were formed when the Pd 2+/Au 3+molar ratio was 1/50,while Au@Pd NPs with cubic Pd shell predominated when the ratio was increased to 2/1.The core–shell structure of synthesized Au@Pd NPs was characterized by TEM,HAADF-STEM,EDS mapping,an EDS line scan,and EDS point scan.Furthermore,density functional theory (DFT)calculationssuggested that the localization of BT molecules on the surface of the Au clusters was the crucial factor for the formation of Au@Pd NPs,since the BT molecules increased the surface negative charges of the Au NPs,favoring the attraction of Pd 2+over Au NPs and resulting in the formation of a Pd shell.IntroductionThe construction of core–shell bimetallic nanoparticles (NPs)has attracted growing interest in recent decades because their unique optical,electrical,and catalytic properties have great potential in diverse ﬁelds such as biomedical,information storage and catalysis.1–3The most distinct advantages of core–shell bimetallic NPs are their tunable structural and electronic properties compared with their monometallic counterparts.4,5By changing the composition,core size,and shell thickness,one can rationally control the physicochemical properties of the shell metal,and thus design various functional core–shell NPs.6–8Core-shell bimetallic NPs are generally prepared by a two-step seeding–growth method where pre-synthesized metal NPs are used as seeds for the overgrowth of second metal.9According to this method,various core–shell bimetallic NPs,such asaDepartment of Biomass chemistry and Engineering,Sichuan University,Chengdu,610065,P .R.China.E-mail:xpliao@;Fax:+862885460356;Tel:+862885400382bNational Engineering Laboratory of Clean Technology for Leather Manufacture,Sichuan University,Chengdu,610065,P .R.China.E-mail:shibi@;Fax:+862885460356;Tel:+862885400356cCollege of Chemistry,Sichuan University,Chengdu,610064,China.E-mail:Huawenzhang@†Electronic supplementary information (ESI)available:TEM,EDS,XRD and surface charge calculation of the materials.See DOI:10.1039/c0gc00724bRh@Pt,10Au@Pd and Au@Ag,11have been successfully syn-thesized by choosing different metal NPs as seeds.Although the seeding–growth method is a useful methodology for preparing core–shell bimetallic NPs,the synthetic procedures are some-what tedious due to the stepwise nature of this method (the metal seeds need to be prepared beforehand),and the strict reaction conditions that are often employed (such as high temperature and high vacuum).12–14Therefore,much effort has been devoted to develop a more facile strategy,such as one-step synthesis method,15for the preparation of core–shell bimetallic NPs.However,it is in principle extremely difﬁcult to construct core–shell bimetallic NPs without seeds,because the simultaneous reduction of bimetallic precursors often leads to the formation of a bimetallic alloy.Very recently,the in situ seeding–growth method was devel-oped for the one-step aqueous synthesis of core–shell bimetallic NPs.16,17The basic principle of this novel approach is to take advantage of the difference in reduction potentials of metal ions,by which the metal ions with higher reduction potential are reduced ﬁrst and then serve as the in situ seeds for the successive reduction of shell metal ions.To achieve such a synthesis,a suitable reductant is essential because strong reductants inevitably lead to the formation of binary alloys,while reducing agents that are too weak cannot effectively reduce the metal precursors.18In this regard,important achieve-ments have been made by the use of ammonium compounds.For example,Lee et al.16successfully synthesized Au@PdD o w n l o a d e d b yE a s t C h i n a U n i v e r s i t y o f S c i e n c e & T e c h n o l o g y o n 15 J u l y 2011P u b l i s h e d o n 28F e b r u a r y 2011 o n h t t p ://p u b s .r s c .o r g | d o i :10.1039/C 0G C 00724BView Onlinecore–shell nanooctahedra via the simultaneous reduction of Au 3+and Pd 2+using cetyltrimethylammonium chloride (CTAC)as the reductant.However,this reaction system needs to be sealed and heated at high temperature to promote the complete reduction of metal ions owing to the weak reducing power of the reductant employed.Yan and co-workers 17prepared Au@Co core–shell NPs using ammonia–borane to simultaneously re-duce Au 3+and Co 2+precursors.Although the synthetic process was rapidly completed at room temperature,the reductant is expensive,and additional stabilizers are required to protect the NPs.Another important issue for the preparation of core–shell nanoparticles is control of their core–shell structure,but so far this has been a big challenge.In the present investigation,we wish to propose a green strategy for the synthesis of core–shell Au@Pd bimetallic NPs by using plant tannins (also called plant polyphenols)as a reductant and stabilizer.The interesting feature of this method is that Au@Pd NPs can be synthesized in one step at room temperature under an ambient atmosphere without additional stabilizer.More importantly,the core–shell structure of Au@Pd NPs can be rationally designed by varying the molar ratio of Au 3+/Pd 2+and the concentration of plant tannin.Plant tannins,extracted from plants,are soluble polyphenols with multifunctional groups,which are generally classiﬁed into condensed tannins and hydrolysable tannins.The molecular structure of condensed tannins mainly consists of polymerized ﬂavan-3-ols.The unique electronic properties of condensed tannins are that they are able to gradually donate the electrons of ortho -phenolic hydroxyls,thus exhibiting mild and stepwise reduction ability.19Additionally,the molecular backbone of condensed tannins consists of aromatic rings,which can provide steric hindrance to prevent the aggregation of metal particles,thus acting as an effective stabilizer.20,21More recently,we devel-oped a green strategy for the one-step room-temperature synthe-sis of gold nanoparticles (Au NPs)by using condensed tannin as the reductant and stabilizer.22Our research demonstrated that condensed tannins can rapidly reduce Au 3+to metallic nanoparticles,and simultaneously stabilize them by attaching to their surface.At higher tannin concentrations,the excess tannin molecules could form a supramolecular tannin shell around the Au NPs due to the strengthened intermolecular interactions (hydrogen bonds and/or hydrophobic bonds)between tannins.Considering these unique properties of condensed tannins,we therefore hypothesized that,if the condensed tannins localized on the surface of Au NPs can successively reduce second metal ions with lower reduction potential,core–shell Au@M NPs (M represents other metals)would be easily prepared under mild conditions by using condensed tannins as reductant and stabilizer.In order to verify our hypothesis,we ﬁrst investigated the reduction rate of bayberry tannin (BT,a typical condensed tannin)upon individual Au 3+and Pd 2+precursors.Subsequently,a series of Au 3+/Pd 2+mixtures with different molar ratios were blended with BT solution at room temperature under ambient atmosphere.The resultant nanoparticles were examined by transmission electron microscopy (TEM),and analyses of the core–shell structure were performed using a high-angle annular dark-ﬁeld scanning TEM (HAADF-STEM)technique.Subsequently,theoretical calculations were used to provide understanding of the formation of Pd shell over the Au core.Much to our delight,Au@Pd NPs with core–shell structure can be easily synthesized under mild conditions by using BT,a typical natural non-toxic polyphenol,as the reductant and stabilizer,which is much more environmentally benign than the conventional ‘bottom-up’methods of nanoparticle preparation that need toxic chemical reducing agents and/or stabilizers.Moreover,the morphology of the Pd shell could be tuned from sphere to cube by varying the molar ratio of Au 3+/Pd 2+and the BT concentration.Consequently,our investigations have provided the ﬁrst successful example of a ‘green’synthesis of Au@Pd core–shell nanoparticles by using plant tannins (plant polyphenols)as the reductant and stabilizer.Experimental sectionAll the reactions were carried out at room temperature under ambient atmosphere without N 2protection.HAuCl 4,PdCl 2and other chemicals were purchased and used as received.Distilled water was used for the preparation of all solutions.Synthesis of BT-stabilized nanoparticles(a)BT 0.4-Au 0.5NPs.10.0mL of HAuCl 4solution (0.025mmol)was directly added to 40.0mL of BT solution (0.02g)at 30◦C under ambient atmosphere.The resulting solu-tion was denoted as BT 0.4-Au 0.5NPs,in which the concentration of Au 3+was 0.5mmol L -1and that of BT was 0.4g L -1.(b)BT 0.4-Pd 0.5NPs and BT 0.4-Pd 1.0NPs.BT 0.4-Pd 0.5NPs were simply obtained by mixing 10.0mL of PdCl 2solution (0.025mmol)with 40.0mL of BT solution (0.02g),followed by shaking at 30◦C under ambient atmosphere for 24h.For the preparation of BT 0.4-Pd 0.5NPs,the concentration of Pd was 0.5mmol L -1and that of BT was 0.4g L -1.The BT 0.4-Pd 1.0NPs were synthesized by the same procedures used for the preparation of BT 0.4-Pd 0.5NPs,except that the amount of Pd 2+was increased to 0.050mmol.In the case of BT 0.4-Pd 1.0NPs,the concentration of Pd 2+was 1.0mmol L -1and that of BT was 0.4g L -1.(c)Core-shell BT 0.4-Au x @Pd y NPs.10.0mL of HAuCl 4/PdCl 2mixture with different molar ratios (0.025mmol Au 3+/0.0005mmol Pd 2+,0.050mmol Au 3+/0.0010mmol Pd 2+,0.025mmol Au 3+/0.025mmol Pd 2+,0.025mmol Au 3+/0.050mmol Pd 2+,and 0.050mmol Au 3+/0.025mmol Pd 2+)was mixed with 40.0mL of BT solution (0.02g).The resultant mixture was subsequently shaken at 30◦C under ambient atmosphere for 24h.As a result,a series of BT-stabilized Au x @Pd y NPs (denoted BT 0.4-Au x @Pd y NPs)were prepared,where x and y are the molar concentrations (mmol L -1)of Au and Pd,respectively,and the concentration of BT was ﬁxed at 0.4g L -1.Herein,Au x @Pd y -BT 0.4NPs with different Au/Pd molar ratios were synthesized includingBT 0.4-Au 0.5@Pd 0.01,BT 0.4-Au 1.0@Pd 0.02,BT 0.4-Au 0.5@Pd 0.5,BT 0.4-Au 0.5@Pd 1.0,and BT 0.4-Au 1.0@Pd 0.5.(d)Core-shell BT x -Au 0.5@Pd 0.5NPs.To investigate the effects of BT concentration on the morphology of Au@Pd NP,BT solution with different concentrations was used in the preparation process.The detailed synthetic procedures were theD o w n l o a d e d b yE a s t C h i n a U n i v e r s i t y o f S c i e n c e & T e c h n o l o g y o n 15 J u l y 2011P u b l i s h e d o n 28F e b r u a r y 2011 o n h t t p ://p u b s .r s c .o r g | d o i :10.1039/C 0G C 00724BTable 1Experimental parameters for the preparation of BT-stabilized nanoparticles aAu 3+(mmol)Pd 2+(mmol)BT (g)Deionized water (ml)Particle shape BT 0.4-Au 0.50.025—0.0250.0Spherical BT 0.4-Pd 0.5—0.0250.0250.0Spherical BT 0.4-Pd 1.0—0.0500.0250.0Cubic BT 0.4-Au 0.5@Pd 0.010.0250.00050.0250.0Spherical BT 0.4-Au 1.0@Pd 0.020.0500.00100.0250.0SphericalBT 0.4-Au 0.5@Pd 0.50.0250.0250.0250.0Spherical/cubic BT 0.4-Au 0.5@Pd 1.00.0250.0500.0250.0Spherical/cubic BT 0.4-Au 1.0@Pd 0.50.0500.0250.0250.0Spherical BT 0.1-Au 0.5@Pd 0.50.0250.0250.00550.0SphericalBT 0.8-Au 0.5@Pd 0.50.0250.0250.0450.0Spherical/cubicaThe whole synthetic process was carried out 303K under ambient atmosphere.same as used for Au x @Pd y -BT 0.4,but the ﬁnal concentration of BT was varied from 0.1g L -1to 0.8g L -1by changing the BT dosage.The synthetic parameters of BT-stabilized nanoparticles are summarized in Table 1.CharacterizationThe UV/vis spectra were recorded on a Shimazu TU-1901spectrophotometer.Wide-angle X-ray diffraction (XRD)mea-surements were obtained by an X’Pert PRO MPD diffractometer (PW3040/60)with Cu-K a radiation.Transmission electron microscopy (TEM)observation was carried out on a FEI-Tecnai G2microscope.Density functional calculationsIn order to theoretically investigate the effect of BT molecules on the surface charges of Au NPs,density functional theory (DFT)calculations were performed using the program package Dmol 3in the Accelrys Materials Studio.Considering that the actual BT-stabilized Au nanopaticles are too large for the DFT calculations,the model Au 43cluster was constructed based on a face-centered-cubic (fcc)octahedral to represent Au NP .Additionally,due to the complexity of molecular structure of BT,pyrogallol was used as a model compound to simulate the interaction of ortho -phenolic hydroxyls of BT with the Au 43cluster.Metal atom core electrons were treated using the quasi-relativistic pseudopotentials,in which the mass-velocity and Darwin relativistic corrections were introduced.During the calculations,the generalized gradient approximation (GGA)and localized double-numerical basis sets with polarizationfunctions (DNP)were employed.A real-space cutoff of 4.5A˚was used,with convergence criteria of 2¥10-5hartree (1hartree =27.2eV),4¥10-3hartree A˚-1,and 5¥10-3A ˚for energy,energy gradient,and geometry,respectively.The self-consistent ﬁeld (SCF)calculations were conducted with the spin-polarization Kohn–Sham formalism,and molecular symmetry was not enforced to allow for geometry relaxation.Results and discussionOne-step synthesis of BT-stabilized Au NP (BT-Pd)and BT-stabilized Pd NP (BT-Pd)Bayberry tannin (BT)is a typical kind of condensed tannin,which consists of polymerized ﬂavan-3-ols and ﬂavan-3-gallate,as shown in Fig.1.There are a large number of ortho -phenolic hydroxyls on the B-ring of the BT molecule,which can be gradually oxidized to benzoquinones when exposed to air or electrophilic ions;23it thus exhibits mild and stepwise reduction ability.On the other hand,the reduction potentials of Au 3+(E 0AuCl 4-/Au =+1.002eV vs.SHE)is much higher than that of Pd 2+(E 0PdCl 4-/Pd =+0.591eV vs.SHE).24Therefore,it can be rationally assumed that Au 3+will be preferentially reduced over the Pd 2+when Au 3+and Pd 2+are simultaneously exposed to BTsolution.Fig.1Molecular structure of BT and its reduction properties.To verify this assumption,assessment of the reduction rate of Au 3+or Pd 2+with BT solution was carried out,where the concentration of BT was ﬁxed at 0.4g L -1,and those of Au 3+and Pd 2+were both 0.5mmol L -1.For the preparation of BT 0.4-stabilized Au NP 0.5(BT 0.4-Au 0.5),complete reduction of Au 3+can be achieved within several minutes.Upon the mixing of Au 3+with BT solution,the color rapidly changed from yellow to purple–red,which suggested the formation of Au NPs.The fast reduction rate is also reﬂected on the UV-vis spectra of BT 0.4-Au 0.5.In Fig.2a,the surface plasmon resonance (SPR)peak of Au NP is clearly observed at 524nm,25and its absorbance intensity rapidly reaches equilibrium in the ﬁrst 3min (inset in Fig.2a).The transmission electron microscopy (TEM)image of BT 0.4-Au 0.5in Fig.2b clearly shows the roughly spherical Au NPs with an average diameter of 11±2nm (see Fig.S1for details†).Importantly,the EDS mapping analyses of BT 0.4-Au 0.5in Fig.2c–e reveal that the O mapping image has a similar shape to that of Au,which directly conﬁrms the encapsulation of Au NP in the supramolecular BT shell.In contrast to the fast rate of Au 3+reduction,Pd 2+exhibited a much slower reduction rate under the same conditions.InD o w n l o a d e d b yE a s t C h i n a U n i v e r s i t y o f S c i e n c e & T e c h n o l o g y o n 15 J u l y 2011P u b l i s h e d o n 28F e b r u a r y 2011 o n h t t p ://p u b s .r s c .o r g | d o i :10.1039/C 0G C 00724BFig.2UV-vis spectra,TEM and HRTEM images of BT 0.4-Au 0.5(a,b,c)and BT 0.4-Pd 0.5(g,h,i).HAADF-STEM image (d)and EDS mapping images (e and f)of BT0.4-Au 0.5.Fig.2g,the characteristic peak of BT 0.4-Pd 0.5at 416nm takes almost 12h to reach equilibrium.This strongly suggests that BT can preferentially reduce Au 3+when treated with an Au 3+/Pd 2+mixture.Additionally,it is somewhat surprising that the Pd NPs synthesized from the slow reduction process have a small particle size of 5–12nm (Fig.S2).Possibly,BT molecules have strong stabilizing effect toward Pd NPs at such concentrations (BT =0.4g L -1,Pd 2+=0.5mmol L -1).When further increasing the Pd concentration to 1.0mmol L -1,cubic Pd particles are found to be predominant in the diameter range of 300–800nm (Fig.S3).According to the literature,26the shape of Pd NPs can vary between spheres,cubes,triangles and pentagons,depending on the species of reducing agent,the reducing speed,and the ratio of metal precursor to stabilizer/reducing agent.In the current work,the Pd NPs have two shapes –spheres and cubes.Consequently,we inferred that it was feasible to adjust the morphology of the Pd shell by varying the ratio of Pd 2+concentration and BT concentration when preparing BT-stabilized Au@Pd core–shell NPs.Synthesis of BT-stabilized Au@Pd NP (BT-Au@Pd)with spherical and cubic Pd shellsWe have shown above that the reduction rate of Au 3+with BT solution was faster than for Pd 2+.Therefore,when a Au 3+/Pd 2+mixture is exposed to BT,Au 3+will be ﬁrst reduced to Au NPs in solution,and then serve as the in situ nucleation center for the growth of the Pd shell.The proposed preparation mechanism is depicted in Fig.3.As documented in the literature,27,28the low-coordinated surface atoms of Au NP are characterized by negative charges.Our density functional theory (DFT)calculations (see below)also show that the surface atoms of the Au NP carry more negative charges when stabilized by BT,which is due to the electron transfer from BT to Au NP .Hence,after Au 3+is reduced to Au NP,the positively charged Pd 2+(with a slow reduction rate)will be preferentially absorbedon Fig.3Schematic outline of the preparation of BT-stabilized Au@Pd NP with tunable structure.the negatively charged Au NP via electrostatic attractions.27,29Following this,the Pd 2+slowly reduces to Pd over the Au NP via the action of the supramolecular BT shell.It should be noted that the BT shell on the surface of the Au NP is the crucial factor for this synthetic route because individual Pd nuclei will be randomly formed in solutions if no BT molecules are located on Au NP .The above element mapping analyses of BT 0.4-Au 0.5have conﬁrmed the presence of BT shell over Au NP .Thus,it is feasible to prepare Au@Pd core–shell NP via one-step reduction of Au 3+/Pd 2+mixture by using BT as the stabilizer and reductant.Additionally,the morphology of Pd shell should be tunable in principle,since the reducing ability of supramolecular BT shell can be adjusted by controlling the initial concentration of BT,and the Au 3+/Pd 2+molar ratio also inﬂuences the reduction extent of Pd 2+.To achieve a spherical Pd shell,the Pd 2+/Au 3+molar ratio was ﬁxed at 1/50(0.01mmol L -1/0.5mmol L -1)to ensure a thin shell of Pd over Au NP .Spherical core–shell Au@Pd NPs were synthesized by mixing BT solution (0.4g L -1)with a Pd 2+/Au 3+mixture (0.01mmol L -1/0.5mmol L -1),followed by shaking at room temperature for 24h.A TEM image of BT 0.4-Au 0.5@Pd 0.01is shown in Fig.4a.Spherical nanoparticles are clearly formed,the average diameter being in the range 10±4nm (Fig.4b).Further EDS mapping analysis demonstrates the formation of a supramolecular BT shell on Au@Pd NP,since the O mapping image in Fig.4d is similar to the corresponding HAADF-STEM image (Fig.4c).In Fig.4e–f,EDS mapping images of Au and Pd have similar shapes,which conﬁrms that all particles are bimetallic in nature.However,the EDS line analysis of a distinct nanoparticle (Fig.4g)clearly shows that Au has a much higher intensity than Pd.The EDS line of Au exhibits an ‘K ’-shaped distribution with the maximum intensity at the particle center,whereas the Pd distribution is much wider without a maximum intensity at the particle center.Subsequent EDS point spectra (Fig.S4)acquired from the edge and center of the nanoparticle show the higher atomic percentage of Au at the center with a higher atomic percentage of Pd at the edge,which is consistent with the EDS line analysis.All these results strongly conﬁrm the core–shell structure of obtained NPs.10Subsequently,we doubled the concentration of Pd 2+and Au 3+,but still ﬁxed the Pd 2+/Au 3+molar ratio at 1/50(0.02mmol L -1/1.0mmol L -1).D o w n l o a d e d b yE a s t C h i n a U n i v e r s i t y o f S c i e n c e & T e c h n o l o g y o n 15 J u l y 2011P u b l i s h e d o n 28F e b r u a r y 2011 o n h t t p ://p u b s .r s c .o r g | d o i :10.1039/C 0G C 00724BFig.4TEM image (a)and the corresponding size distribution (b)of spherical BT 0.4-Au 0.5@Pd 0.01.HAADF-STEM image (c)and EDS map-ping images (d,e,f)of BT 0.4-Au 0.5@Pd 0.01.Cross-sectional compositional line spectra (g)of a distinct BT 0.4-Au 0.5@Pd 0.01nanoparticle.Under such synthetic conditions,spherical Au@Pd NPs were still prepared based on the TEM and EDS mapping analyses (Fig.S5),and the corresponding particle diameter range is similar to that of BT 0.4-Au 0.5@Pd 0.01.In addition,a stepwise reduction of Au 3+and Pd 2+was also performed to prepare BT 0.4-Au 0.5@Pd 0.01NPs by adding Pd 2+to solutions after the reduction of Au 3+in BT solutions.The corresponding TEM and EDS line analysis (Fig.S6)suggested that the core–shell BT 0.4-Au 0.5@Pd 0.01NPs were produced by the step-wise reduction method,which further conﬁrmed the proposed mechanism in Fig.3.To synthesize Au@Pd NPs with cubic Pd shell,the Pd 2+/Au 3+molar ratio was increased to 1/1(0.5mmol L -1/0.5mmol L -1)while the BT concentration was kept at 0.4g L -1.The TEM image of BT 0.4-Au 0.5@Pd 0.5is shown in Fig.5a,showing that a considerable number of Au@Pd NPs with a cubic Pd shell were formed,while others have spherical morphologies.Clearly,the increase of Pd content in solutions favors the sufﬁcient growth of Pd shell over the Au NP .Another interesting phenomenon is that multi-Au cores can be contained in a single Pd cube (Fig.5b and d),apart from the expected formation of Au@Pd NPs with single Au core (Fig.5c and e).To speciﬁcally explain the formation of multi-Au cores is difﬁcult,but one can speculate that the BT shells of adjacent Au NPs may interact via intermolecular interactions (hydrogen bonds and/or hydrophobic bonds)to form a supramolecular tannin network,22,30,31and that such BT network allows the reductive growth of Pd over the adjacent Au NPs,which leads to the formation of Au@Pd NP containing multi-Au cores.The corresponding core and shell size distributions of cubic Au@Pd NPs are illustrated in Fig.5f and g,respectively.The spherical Au core has an average diameter of 20±5nm while that for the cubic Pd shell is 150±50nm.Subsequently,we furtherincreasedFig.5TEM image (a)of BT 0.4-Au 0.5@Pd 0.5.High-magniﬁcation TEM images (b,c,d,e)of cubic Au@Pd core–shell NPs marked in (a).The corresponding core (f)and shell (g)size distributions of cubic BT 0.4-Au 0.5@Pd 0.5.the Pd 2+/Au 3+molar ratio to 2/1(1.0mmol L -1:0.5mmol L -1)in order to promote the formation of more cubic Au@Pd NPs (Fig.S7).A large number of cubic Au@Pd NPs are formed,for which the corresponding average sizes for core (20±7nm)and shell (150±60nm)are close to those of cubic BT 0.4-Au 0.5@Pd 0.5.In addition,the Au@Pd NPs with multi-Au cores are still observed in BT 0.4-Au 0.5@Pd 1.0.Subsequent element analyses conﬁrm the formation of Au core and cubic Pd shell,as well as the presence of BT shell over the Au@Pd NP .All these results suggest a similar formation mechanism for cubic BT 0.4-Au 0.5@Pd 0.5and BT 0.4-Au 0.5@Pd 1.0except that higher content of Pd 2+is provided during the preparation of BT 0.4-Au 0.5@Pd 1.0,which results in the sufﬁcient growth of Pd shell over more Au cores.The wide-angle XRD patterns of BT 0.4-Pd 1.0,BT 0.4-Au 0.5and BT 0.4-Au 0.5@Pd 1.0are presented in Fig.S8.The characteristic peaks of a face-centered-cubic (fcc)metallic gold (38.2◦,44.4◦,64.6◦,77.6◦and 81.7◦,JCPDS-4784)are clearly observed,which conﬁrm the reduction of Au 3+to Au(0)in BT 0.4-Au 0.5.32Apart from the characteristic peaks of metallic gold,the characteristic peaks of metallic Pd are also observed at 39.7◦,46.7◦,and 82.1◦.These peaks correspond to the {111},{200},and {311}planes of a fcc lattice,respectively,indicating the fcc structure of Pd shell in BT 0.4-Au 0.5@Pd 1.0.33,34Compared with the {111}reﬂection of Au core at 38.2◦,the intensity of the {111}reﬂection of Pd shell at 39.7◦is relatively weak,which is possibly due to the BT shell on the surface of the Au core disturbing the ordered crystallization of the Pd shell during the relatively slow reduction of Pd 2+.35To conﬁrm that the reduction extent of Pd 2+is mainly dependent on the residual BT molecules,a mixture of Au 3+/Pd 2+with molar ratio of 2/1(1.0mmol L -1/0.5mmol L -1)was added to 0.4g L -1of BT solution,followed by constant shaking at room temperature for 24h.The resultant BT 0.4-Au 1.0@Pd 0.5was characterized by TEM and EDS analyses,and the corresponding results are shown in Fig.6.All the BT 0.4-Au 1.0@Pd 0.5particles are spherical rather than cubic,which is completely different fromD o w n l o a d e d b yE a s t C h i n a U n i v e r s i t y o f S c i e n c e & T e c h n o l o g y o n 15 J u l y 2011P u b l i s h e d o n 28F e b r u a r y 2011 o n h t t p ://p u b s .r s c .o r g | d o i :10.1039/C 0G C 00724BFig.6TEM image (a)and the corresponding size distributions (b)of spherical BT 0.4-Au 1.0@Pd 0.5.HAADF-STEM image (c)and EDS mapping images (d,e,f)of BT 0.4-Au 1.0@Pd 0.5marked in (a).Cross-sectional compositional line spectra (g)of BT 0.4-Au 1.0@Pd 0.5in (c).the BT 0.4-Au 0.5@Pd 1.0.The average diameter of BT 0.4-Au 1.0@Pd 0.5is 12±6nm,which is very similar to that of BT 0.4-Au 1.0@Pd 0.02.EDS mapping images of O,Au and Pd all exhibit similar shapes,which conﬁrm the presence of the BT shell and the binary nature of BT 0.4-Au 1.0@Pd 0.5NPs.However,subsequent EDS line analysis (Fig.6c)suggests that the intensity of Au with a ‘K ’-shaped distribution is much higher than that of Pd (‘M’-shaped distribution).These results are quite different from those of BT 0.4-Au 0.5@Pd 1.0,but very similar to those of BT 0.4-Au 1.0@Pd 0.02.According to the preparation mechanism proposed in Fig.3,it is reasonable to explain the difference in morphologies between BT 0.4-Au 0.5@Pd 1.0and BT 0.4-Au 1.0@Pd 0.5.After the addition of Au 3+/Pd 2+mixture into BT solution,Au 3+with higher reduction potential was ﬁrst reduced,along with partial oxidation of BT,and then the Pd 2+in solution was gradually reduced by the residual BT.Under such conditions,the reduction extent of Pd is mainly dependent on the content of remaining BT.When the molar ratio of Au 3+/Pd 2+is 1/2,the residual BT is sufﬁcient enough to reduced the Pd 2+,and thus,considerable amounts of cubic Au@Pd NPs were formed.However,in the case of high molar concentrations of Au 3+,as in BT 0.4-Au 1.0@Pd 0.5,the majority of BT molecules are consumed by the reduction of Au 3+,which leads to the insufﬁcient reduction of Pd 2+,resulting in a thin shell of Pd over the spherical Au core.As a result,BT 0.4-Au 1.0@Pd 0.5exhibited a similar morphology and particle size distribution to BT 0.4-Au 1.0@Pd 0.02.Clearly,the BT in BT 0.4-Au 1.0@Pd 0.02and BT 0.4-Au 1.0@Pd 0.5was insufﬁcient even for the complete reduction of 0.02mmol L -1Pd 2+,otherwise their particle size should not be similar because of the different reduction extent of Pd 2+.This strongly suggests that the morphology of Au@Pd NP is signiﬁcantly affected by the molar ratio of Au 3+/Pd 2+as well as the BT concentration.Effect of BT concentration on the synthesis of Au@Pd NPs To verify the effect of BT on the synthesis of Au@Pd NPs,the molar ratio of Au 3+/Pd 2+mixture was ﬁxed at 1/1(0.5mmol L -1/0.5mmol L -1)while the concentration of BT was decreased to 0.1g L -1.The TEM image of BT 0.1-Au 0.5@Pd 0.5is shown in Fig.7a,which shows that spherical nanoparticles have been formed.However,the particle diameters vary widely,from 15to 70nm (Fig.7b),and the particle aggregation is obvious.These results can be related to the insufﬁcient reducibility and stabilizing effect of BT,since low concentrations of BT are unable to rapidly reduce the metal precursors,and in addition,they cannot provide enough steric hindrance to suppress the aggregation of the nanoparticles.36,37Further EDS mapping analyses conﬁrm the binary nature of the prepared nanoparticles (Fig.7d–f)while the EDS line analysis shows that Au element has much higher intensity than Pd (Fig.7g),which is similar to those observed in BT 0.4-Au 1.0@Pd 0.5.Additionally,it is also found that some Au NPs covered with insufﬁcient growth of Pd shell are aggregated (Fig.S9).All these facts suggest the insufﬁcient reduction of Pd 2+under such BTconcentrations.Fig.7TEM image (a)and the corresponding size distribution (b)of spherical BT 0.1-Au 0.5@Pd 0.5.HAADF-STEM image (c)and EDS mapping images (d,e,f)of BT 0.1-Au 0.5@Pd 0.5marked in (a).Cross-sectional compositional line spectra (g)of a distinct BT 0.1-Au 0.5@Pd 0.5nanoparticle.Subsequently,the concentration of BT was increased to 0.8g L -1while the molar ratio of the Au 3+/Pd 2+mixture was kept at 1/1(0.5mmol L -1/0.5mmol L -1).It was found that the morphology of BT 0.8-Au 0.5@Pd 0.5shows a bimodal distribution where more than 96%of the particles are in the diameter range of 9±2nm,and less than 4%of the particles have large diameters (average 300–600nm;Fig.S10).Additionally,transparent ﬂoc-cules are clearly observed surrounding the small nanoparticles (Fig.S10a);this is the supramolecular BT network formed from the aggregation of excess free BT molecules in solution.Due to the presence of the supramolecular BT network,each small nanoparticle in Fig.S10a is isolated,and the corresponding EDS mapping analyses conﬁrm the binary nature of theseD o w n l o a d e d b yE a s t C h i n a U n i v e r s i t y o f S c i e n c e & T e c h n o l o g y o n 15 J u l y 2011P u b l i s h e d o n 28F e b r u a r y 2011 o n h t t p ://p u b s .r s c .o r g | d o i :10.1039/C 0G C 00724B。

Ph.D.StudentsRecruitmentforDr

Ph.D. Students Recruitment for Dr. LuDr. Yuerui Lu is relocating to the Australian National University (ANU), Research School of Engineering, as a Research Fellow and Lecturer. His research focuses on nanotechnologies, including micro/nano-electro-mechanical sensors and actuators, nano-scale energy conversion devices, biomedical devices, novel nano materials, etc.He is looking for highly motivated Ph.D. graduate students who are majoring in applied physics, electrical engineering, mechanical engineering, chemistry, materials science engineering, biomedical engineering, or other closely related areas to join his research team. If you are interested, please send your inquires and detailed CV directly to Dr. Lu through email *****************.au, as soon as possible. Please refer to the following webpage for his detailed research directions:https://.au/researchers/lu-yxAdditional Information about ANU:(Please refer to the following URL for more detailed information:/wiki/Australian_National_University):The Australian National University (ANU) is a university in Canberra, Australian Capital Territory. Established by an Act of the Parliament of Australia in 1946, it is the only Australian university to be established by Federal, rather than State or Territory, legislation.In 2012, ANU was ranked 1st and 2nd among Australian universities, and 24th and 38th among the world's universities by the QS World University Rankings and the Times Higher Education World University Rankings, respectively. Canberra is a wonderful place for living and studying, with pleasant climate (not too cold, not too hot).Areas of expertise•Micro-/Nano-electro-mechanical System (MEMS/NEMS)•Nanolithography•Nano-electronics•Nano-structured thin-film solar cells•Nano-scale sensors and actuators•Nano-materials•Energy harvesting•MEMS/NEMS based biomedical novel devicesBiographyYuerui Lu received his Ph.D. degree from Cornell University, the school of Electrical and Computer Engineering, in 2012. He holds a B.S. degree from department of Applied Physics at University of Science and Technology of China. In 2013, he joined the Australian National University as research fellow and lecturer under the Future Engineering Research Leadership Fellowship. Before that, he worked as a postdoc research associate in Sonic MEMS Laboratory at Cornell University. His research interests include MEMS/NEMS sensors and actuators, nano-manufacturing technologies, renewable energy harvesting, biomedical novel devices, nano-materials, nano-electronics, etc. He was the recipient of several awards, including MRS Graduate Student Award(Silver) in 2012 from Materials Research Society, Best Poster Award in 2012 from Cornell NanoScale Facility Annual Meeting, Daisy Yen Wu Scholarship in 2012 from Cornell University, Chinese Government Award for outstanding Ph.D. students in 2010, Guo Moruo Presidential Award in 2003 from University of Science and Technology of China, etc. He is serving as a reviewer for several journals, including Advanced Materials, Small, Applied Physics Letters, Nanotechnology, Optics Express, Optics Letters,Sensors and Actuators A: Physical, etc.Research ProjectsMy research focuses on nanotechnologies, including micro/nano-electro-mechanical sensors and actuators, nano-scale energy conversion devices, biomedical devices, novel nano materials, etc. I am looking for highly motivated Ph.D. graduate students who are majoring in applied physics, electrical engineering, mechanical engineering, chemistry, materials science engineering, biomedical engineering, or other closely related areas to join my research team. We always look for dedicated undergraduate or master students to join us, to do creative work in rapidly growing field and generate co-authored publications.1. MEMS/NEMS based novel biomedical devicesThe ability to detect bio-molecule at ultra-low concentrations (e.g. atto-molar) will enable the possibility of detecting diseases earlier than ever before. A critical challenge for any new bio-sensing technology is to optimize two metrics --- shorter analysis time, and higher concentration sensitivity in clinically relevant small volumes. Moreover, practical considerations are equally important: simplicity of use, mass producible (low cost), and ease of integration within the clinical structure. Compared with other methods, nano-electro-mechanical system (NEMS) based bio-sensors are promising in clinical diagnostics because of their extremely high mass sensitivity, fast response time and the capability of integration on chip. We have demonstrated a low concentration DNA (atto-molar sensitivity) optically interrogated ultrasonic mechanical mass sensor, which has ordered nanowire (NW) array on top of a bilayer membrane. This method represents a mass-based platform technology that can sense molecules at low concentrations, which could be useful for early-stage disease detection. We can develop this sensor further to measure an array of biomarkers (e.g. DNA or proteins), by providing both the needed specificity and sensitivity in physiological disease (e.g. cancer) detection.Recommended references:[1]B. Ilic et al., Enumeration of DNA molecules bound to a nanomechanical oscillator. Nano Letters 5, 925-929 (2005).[2]T. P. Burg et al., Weighing of biomolecules, single cells and single nanoparticles in fluid. Nature 446, 1066-1069 (2007).[3]H. G. Craighead, Nanoelectromechanical systems. Science 290, 1532-1535 (2000).[4]A. K. Naik, M. S. Hanay, W. K. Hiebert, X. L. Feng, M. L. Roukes, Towards single-molecule nanomechanical mass spectrometry. Nature Nanotechnology 4, 445-450 (2009).[5]Y. Lu, S. Peng, D. Luo, A. Lal, Low-concentration mechanical biosensor based on a photonic crystal nanowire array. Nature Communications 2, 578 (2011).2. Nonlinearity engineering for nano-electro-mechanical systemA nano-electro-mechanical system (NEMS) that integrates various nano-scale mechanical sensors onto a single chip, has attracted exceptional interest among research and engineering communities. Among other remarkable characteristics, these tiny mechanical structures possess strong nonlinear properties. Typically, device nonlinearity is intentionally avoided, because higher amplitude fluctuations in the nonlinear region could be translated into frequency variability. Recently, we found that nonlinearity bifurcation could be used to stabilize our membrane oscillator with nanowire (NW) arrays. As a consequence, we propose to use our NEMS device as a platform to investigate its nonlinear dynamics and gain a deeper understanding of the origins of that nonlinearity. This could present a general mechanism to assist oscillation frequency stabilization and improve NEMS resonator performance for bio-molecular sensing applications. These nanowire arrays could also be embedded into suspended micro-channels. Coupled with the nonlinearity-assisted frequency stabilization result, the sensitivity of the mass sensor could be improved by orders of magnitude.[1] A. K. Naik, M. S. Hanay, W. K. Hiebert, X. L. Feng, M. L. Roukes, Towards single-molecule nanomechanical mass spectrometry. Nature Nanotechnology 4, 445-450 (2009).[2] I. Kozinsky, H. W. C. Postma, O. Kogan, A. Husain, M. L. Roukes, Basins of attraction of a nonlinear nanomechanical resonator. Physical Review Letters 99, 207201 (2007).[1] D. Antonio, D. H. Zanette, D. Lopez, Frequency stabilization in nonlinear micromechanical oscillators. Nature Communications 3, 806 (2012).[4] Y. Lu, S. Peng, D. Luo, A. Lal, Low-concentration mechanical biosensor based on a photonic crystal nanowire array. Nature communications 2, 578 (2011).[5] Y. Lu, and A. Lal, Nonlinearity-assisted frequency stabilization for nanowire array membrane oscillator. Proceedings of the 26th IEEE International Conference on Micro ElectroMechanical Systems (MEMS 2013), pp. 653-656, Taipei, Taiwan, January 20-25, 2013.(a) (b) (c) (d)3. Nano-electro-mechanical system based on novel two dimensional nano-materials Two-dimensional (2D) nano-materials, such as molybdenum disulfide (MoS 2) and graphene, have atomic or molecular thickness, exhibiting promising applications in nano-electro-mechanical systems. Graphene is a one-atom thick carbon sheet, with atoms arranged in a regular hexagonal pattern. Molybdenum disulfide (MoS 2) belongs to transition metal dichalcogenides (TMD) semiconductor family YX 2 (Y=Mo, W; X=S, Se, Te), with a layered structure. These 2D nano-materials can be integrated into nano-electro-mechanical systems, enabling ultra-sensitive mechanical mass sensors, with single molecule or even single atom sensitivities. Moreover, the mechanical resonators based on these 2D nano-materials would be a perfect platform to investigate quantum mechanics, opto-mechanics, material internal friction force, nonlinear physics, etc.Recommended references:[1] J. S. Bunch et al., Electromechanical resonators from graphene sheets. Science 315, 490-493 (2007).[2] R. A. Barton et al., Photothermal self-oscillation and laser cooling of graphene optomechanical systems. Nano Letters 12, 4681-4686 (2012).[3] Radisavljevicb, Radenovica, Brivioj, Giacomettiv, Kisa, Single-layer MoS 2 transistors. Nature Nanotechnology 6, 147-150 (2011).[4] M. Osada, T. Sasaki, Two-dimensional dielectric nanosheets: Novel nanoelectronics from nanocrystal building blocks. Advanced Materials 24, 210-228 (2012).0.7 nm thick S D SiO4. High-throughput Nano-manufacturingNanolithography is important for nano-scale device fabrication, both in academia and in the semiconductor industry. The fundamental challenge in developing nanolithography systems is to create a system with high resolution (sub-20 nm), high throughput (4-inch wafer exposure within 30 seconds), high controllability and low cost. I have demonstrated the proof of concept for a new lithography system --- Radioisotope-powered Parallel Electron Lithography (RIPEL). This system uses high energy electrons emitted from radioisotope thin films to expose resist through a stencil mask. The RIPEL system simultaneously exposes the entire substrate, making it a parallel system, as opposed to the serial raster scanning electron beam lithography system. This will enable the rapid exposure of nano-scale features over very large substrates. However, there are still several significant hurdles in preventing RIPEL’s practical uses. We will study these hurdles and propose developing building blocks to overcome these hurdles, through radioisotope electron sources development, new mask design, and investigation of new electron resist. These building blocks will enhance RIPEL’s throughput by four orders of magnitude. The progress will significantly benefit the areas that need volumetric nanostructures with high spatial density and good controllability, such as plasmonics, nanoelectronics, micro/nano-electro-mechanical systems, nano-structured thin film solar cells, biomedical devices, etc.Recommended references:[1] Y. Lu, N. Yoshimizu, A. Lal, Self-powered near field electron lithography. Journal of VacuumScience & Technology B 27, 2537-2541 (2009).[2] Y. Lu, A. Lal, Vacuum-free self-powered parallel electron lithography with sub-35-nmresolution. Nano Letters 10, 2197-2201 (2010).[3] Y. Lu, A. Lal, High-efficiency ordered silicon nano-conical-frustum array solar cells by self-powered parallel electron lithography. Nano Letters 10, 4651-4656 (2010).5. High-efficiency nano-structured thin film solar cellsNanostructured silicon thin film solar cells are promising, due to the strongly enhanced light trapping, high carrier collection efficiency, and potential low cost. Ordered nanostructure arrays, with large-area controllable spacing, orientation, and size, are critical for reliable light-trapping and high-efficiency solar cells. Available top-down lithography approaches to fabricate large-area ordered nanostructure arrays are challenging due to the requirement of both high lithography resolution and high throughput. Here, a novel ordered silicon nano-conical-frustum array structure, exhibiting an impressive absorbance over broad band wavelengths by a thickness of only 5 µm, is realized by our recently reported technique radioisotope-powered parallel electron lithography. Moreover, high-efficiency (up to 10.8%) solar cells are demonstrated, using these ordered ultrathin silicon nano-conical-frustum arrays.Although these nano-structure arrays have high light absorption efficiency, the solar cell efficiency is still less than half of that for bulk crystalline Si solar cells and the open circuit voltage and fill factor are lower too. This is probably due to the high surface recombination losses, which are introduced by the highly enhanced surface area from the nanostructures, although a thin passivation oxide layer was used. Therefore, how to reduce the surface loss through appropriate surface passivation is critical to further enhance the conversion efficiency. In addition, it will be also interesting to transfer the related fabrication techniques to low-cost substrate.Recommended references:[1] J. Zhu et al., Optical absorption enhancement in amorphous silicon nanowire and nanocone arrays. Nano Letters 9, 279-282 (2008).[2] Y. Lu, A. Lal, High-efficiency ordered silicon nano-conical-frustum array solar cells by self- powered parallel electron lithography. Nano Letters 10, 4651-4656 (2010).[3] J. Oh, H.C. Yuan, H. M. Branz, An 18.2%-efficient black-silicon solar cell achieved through control of carrier recombination in nanostructures. Nature Nanotechnology 7, 743-748 (2012).[4] K. X. Wang, Z. Yu, V. Liu, Y. Cui, S. Fan, Absorption enhancement in ultrathin crystalline silicon solar cells with antireflection and light-trapping nanocone gratings. Nano Letters 12,1616-1619 (2012). (a) (b) (c) (d)6. High-efficiency betavoltaic cells by novel semiconductor nano-materials Betavoltaics are generators that convert energy from a radioactive beta source to electricity. A beta radioisotope atom gives off a beta high energy particle (e.g., electron) through beta decay, which is governed by Poisson statistics emission event. Radioactive decay is independent of temperature and pressure. Only near nuclear fusion temperatures can the fundamental decay processes be modified. Furthermore the half-lives of many radioisotopes are several years to decades to even centuries. When the high energy beta particles traverse a semiconductor, electron-hole pairs are produced and separated by the built in electrical field of the pn junction, leading to energy conversion. Betavoltaic power sources have very promising applications in harsh environments where long life of the energy source is required. Novel semiconductor nano-materials, such as porous silicon, GaN nano-crystals, etc, have great potential to realize high efficiency betavoltaic cells.Recommended references:[1] M. V. S. Chandrashekhar, C. I. Thomas, H. Li, M. G. Spencer, A. Lal, Demonstration of a 4h sicbetavoltaic cell. Applied Physics Letters 88, 033506 (2006).[2] G. Hang, L. Hui, A. Lal, J. Blanchard, Nuclear microbatteries for micro and nano Devices,Proceedings of 9th International Conference on Solid-State and Integrated-Circuit Technology, pp. 2365-2370 (2008).[3] G. Hang, Y. Hui, Z. Ying, Proceedings of IEEE 20th International Conference on Micro ElectroMechanical Systems, pp. 867-870, 2007.[4] T. Wacharasindhu, J. W. Kwon, D. E. Meier, J. D. Robertson, Radioisotope microbattery basedon liquid semiconductor. Applied Physics Letters 95, 014103 (2009).。

The Chemical Properties of Gold Nanoparticles

The Chemical Properties of GoldNanoparticlesIntroductionGold nanoparticles (AuNPs) are a promising material in various fields due to their unique chemical and physical properties. In recent years, AuNPs have gained attention for their potential applications in biomedical sciences such as cancer therapy, drug delivery, and imaging. In this article, we will discuss the chemical properties of AuNPs and how they affect their behavior in different applications.Size and Shape DependenceThe size and shape of AuNPs play a crucial role in determining their chemical properties. Small particles (less than 10 nm) exhibit a high surface area-to-volume ratio, leading to enhanced reactivity. As the particle size increases, the surface area-to-volume ratio decreases, resulting in lower reactivity.The shape of AuNPs also influences their chemical properties. For instance, spherical nanoparticles are more stable than other shapes and have a uniform surface, allowing for better surface chemistry modification. However, certain shapes such as nanorods or nanocubes have different surface energies and can exhibit unique optical properties.Surface ChemistryThe surface of AuNPs is essential for determining their chemical behavior. AuNPs have a high affinity for thiol molecules, leading to the formation of a self-assembled monolayer (SAM) on their surface. The SAMs can serve as a template for further surface modification such as the attachment of biomolecules for targeted drug delivery or imaging.AuNPs also have a high affinity for oxygen-containing functional groups such as carboxylic acids, alcohols, and amines. These functional groups can be used to attach various molecules, polymers, or biomolecules to the surface of AuNPs. The surface chemistry of AuNPs can be manipulated to create various properties, allowing for applications in imaging, sensing, and drug delivery.Optical PropertiesAuNPs have unique optical properties, including surface plasmon resonance (SPR), which is the collective oscillation of electrons on the surface of the nanoparticle. SPR results in the absorption and scattering of light, leading to a change in color and intensity. The SPR wavelength depends on the size and shape of the particles, allowing for tunable optical properties for various applications such as sensing and imaging.AuNPs also exhibit enhanced fluorescence when excited by light due to their electromagnetic field enhancement effect, making them useful in bioimaging and sensing applications.ConclusionIn conclusion, AuNPs have unique chemical properties that make them suitable for various biomedical applications. The size and shape of the particles, along with their surface chemistry, influence their properties, allowing for tunable behaviors. AuNPs' unique optical properties, such as SPR and electromagnetic field enhancement effect, make them useful in sensing and imaging applications. Future research is needed to explore the potential of AuNPs in various biomedical applications.。

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Journal of Chromatography A,1217 (2010) 8079–8086Contents lists available at ScienceDirectJournal of ChromatographyAj o u r n a l h o m e p a g e :w w w.e l s e v i e r.c o m /l o c a t e /c h r o maAu nanoparticles as a novel coating for solid-phase microextractionJuanjuan Feng a ,b ,Min Sun a ,b ,Hongmei Liu a ,b ,Jubai Li a ,Xia Liu a ,Shengxiang Jiang a ,∗aKey Laboratory of Chemistry of Northwestern Plant Resources,CAS/Key Laboratory for Natural Medicine of Gansu Province,Lanzhou Institute of Chemical Physics,Chinese Academy of Sciences,Lanzhou 730000,China bGraduate University of Chinese Academy of Sciences,Beijing 100039,Chinaa r t i c l e i n f o Article history:Received 28July 2010Received in revised form 28September 2010Accepted 25October 2010Available online 30 October 2010Keywords:Au nanoparticles Stainless steel wireSolid-phase microextraction Gas chromatographyHydrophobic organic chemicalsa b s t r a c tA novel solid-phase microextraction ﬁber based on a stainless steel wire coated with Au nanoparticles was prepared and has been applied,coupled with gas chromatography,to the extraction of aromatic hydrophobic organic chemical pollutants in rainwater and soil extract.The solid-phase microextraction ﬁber exhibited excellent extraction efﬁciency and selectivity.Effects of extraction time,extraction tem-perature,ionic strength,stirring rate and desorption conditions were investigated and optimized.Single ﬁber repeatability and ﬁber-to-ﬁber reproducibility were less than 7.90%and 26.40%,respectively.The calibration curves were linear in a wide range for all analytes.Correlation coefﬁcients ranged from 0.9941to 0.9993.The as-established SPME-GC method was used successfully to two real natural samples.Recov-ery of analytes spiked at 10␮g L −1and 100␮g L −1ranged from 78.4%to 119.9%and the relative standard deviations were less than 11.3%.© 2010 Elsevier B.V. All rights reserved.1.IntroductionSolid-phase microextraction (SPME),ﬁrstly introduced by Belardi and Pawliszyn [1],has got many applications in food [2,3],environment [4],biochemistry [5,6]and medicine [7]because of its sensitivity,rapidity,simplicity and free of solvent [8].It has been coupled with various instruments and analytical technologies such as GC [9],HPLC [10,11],CE [12],UV [13,14]and MS [15].Further development of SPME related intimately to the preparation and characterization of new sorbent materials.Molecular imprinted polymer [16],mesoporous materials [17],nanomaterials [18,19]and some organic polymers [20]have been used successfully as functional coatings over fused-silica ﬁber or metal wire supports.Nanomaterials possessing excellent physical and chemical properties have attracted great attention lately in the separation science.Carbon nanotubes [8],fullerenes [21],nanoporous silica [18]and some nano-structured metal oxides [19,22]have been suc-cessfully used as SPME ﬁber coatings.Au nanoparticles (Au NPs)share many important properties with materials mentioned above and keep some special properties such as long term stability,eas-iness in chemical modiﬁcation,compatibility with biomolecules∗Corresponding author at:Key Laboratory of Chemistry of Northwestern Plant Resources,CAS/Key Laboratory for Natural Medicine of Gansu Province,Lanzhou Institute of Chemical Physics,Chinese Academy of Sciences,No.18,Tianshui Road,Lanzhou,Gansu 730000,China.Tel.:+869314968266.E-mail address:sxjiang@ (S.Jiang).[23],and so anic molecules containing thiol (SH)or amino (NH 2)groups can be adsorbed spontaneously onto the Au sur-face to form a well organized self-assembled monolayer (SAM)[24].Researchers have made use of these properties to develop applications of Au NPs in analytical and separation science for a long time.Chi et al.[25]used a sensitive and simple colorimetric visualization method to detect melamine easily with citrate sta-bilized Au NPs,in which trace melamine of 25ppb in real milk samples was quickly detected.Au NPs have been widely used in capillary electrochromatography and capillary electrophoresis as pseudo-stationary phase or stabilized on modiﬁed fused-silica cap-illary to separate neutral steroid drugs [7],polycyclic aromatic hydrocarbons (PAHs)[26]and biomolecules [5,6].Currently avail-able utilization in the sample preconcentration is mainly focused on solid-phase extraction [27],nanoparticle-single drop microex-traction [28]and solid-phase nanoextraction [29].Extraordinary properties of Au NPs deserve further investigations in other sample preparation method such as in SPME.Based on these considerations,we prepared a novel Au NPs/SPME ﬁber through a simple layer by layer (LBL)self-assembly process.A new way to extract and preconcentrate PAHs,diphenyl and terphenyls in aqueous solution was developed using the physicochemical afﬁnity between aromatic hydrophobic organic chemicals (HOCs)and Au NPs.The inherent chemical stability of gold makes the novel Au NPs/SPME ﬁber show high stability and durability towards acid,alkali and high temperature.The sin-gle ﬁber repeatability and ﬁber-to-ﬁber reproducibility are both satisfactory.The as-prepared ﬁber also has remarkable selec-0021-9673/$–see front matter © 2010 Elsevier B.V. All rights reserved.doi:10.1016/j.chroma.2010.10.0898080J.Feng et al./J.Chromatogr.A1217 (2010) 8079–8086Fig.1.Schematic diagram of Au NPs/SPME ﬁber preparation process.tivity towards compounds with high hydrophobicity and large ␲-electron systems.2.Experimental 2.1.InstrumentsAn Agilent 7890A series gas chromatograph (Agilent Tech-nologies,USA)equipped with a ﬂame ionic detector was used.Chromatographic separation was carried out on an AT.SE-54capil-lary column (30m ×0.32mm id.×0.33␮m ﬁlm thickness).Ultrapure nitrogen (>99.999%)was used as the carrier and make-up gas at 1ml min −1and 30ml min −1,respectively.Both the injector and detector temperatures were ﬁxed at 300◦C.Separation was achieved using temperature programs as follows:for PAHs,diphenyl and two terphenyls,the column temperature was ini-tially held at 100◦C,and programmed at 5◦C min −1to 215◦C,being held for 5min,then at the rate of 1◦C min −1to 223◦C,ﬁnally at 15◦C min −1to 260◦C;for n -alkanes,phenols and amines,the col-umn temperature was initially held at 50◦C,and programmed at 5◦C min −1to 300◦C.Scanning electron microscope micrographs of the Au NP ﬁber were obtained on a ﬁeld emission scanning electron microscope (FESEM,JSM-6701F,Japan).Energy dispersive X-ray ﬂuorescence (XRF)analysis was performed on a XRF spectrometer (EDAX-Genesis XMZ,USA)with a 20kV of applied voltage and 10␮A of current.2.2.Chemicals and solutionsThe stainless steel wire (SUS304, 140␮m)was purchased from the Yixing Shenglong Metal Wire Net Co.(Jiangsu,China).Naph-thalene,anthracene,ﬂuorene,ﬂuoranthene,1-bromonaphthalene,diphenyl,m -terphenyl and p -terphenyl were obtained from the Shanghai Chemical Reagent Factory (Shanghai,China);n -hexane,n -octane,n -nonane,n -undecane,n -tridecane,n -hexadecane and n -heneicosane were purchased from the Tianjin Guangfu Fine Chemical Research Institute (Tianjin,China);aniline,4-toluidine,4-chloroaniline and 1-naphthylamine were purchased from the Tianjin Chemical Reagent No.1Plant (Tianjin,China);phenol,4-methylphenol,4-chlorophenol,and 1-naphthol were purchased from the Beijing Chemical Reagent Factory (Beijing,China);1,8-octanedithiol was obtained from the Alfa Aesar,chloroau-ric acid (HAuCl 4·4H 2O)was purchased from the Shenyang Keda Chemical Reagent Factory (Liaoning,China);trisodium citrate (C 6H 5Na 3O 7·2H 2O)was purchased from the Wuxi Minfeng Chem-ical Reagent Factory (Jiangsu,China).All chemicals were of analytical grade.1,8-Octanedithiol was dissolved in ethanol with concentration of 30%(w/w)as stock solution.HAuCl 4·4H 2O of 1%(w/w)was prepared using distilled water as solvent.Analytes were dissolved in ethanol with concentration of 250mg L −1.All the stock solutions were stored at 4◦C for use.2.3.Preparation procedures2.3.1.Preparation of Au nanoparticlesAu nanoparticles were prepared through the reduction of HAuCl 4by trisodium citrate as described by Frens and Kolliod [30].Brieﬂy,30mL of HAuCl 4aqueous solutions (0.01%,w/w)was heated at 115◦C under vigorous stirring.While boiling,0.6mL of trisodium citrate aqueous solution (1%,w/w)was added very quickly.The solution turned to wine red in 2min.After a 15min reaction,the heating was stopped but the stirring was kept until the solution was cooled to room temperature.Nanoparticles prepared under these conditions were proved to be more regular and stable.The product was stored at 4◦C.2.3.2.Preparation of Au NPs/SPME ﬁberPreparation steps of Au NPs/SPME ﬁber are shown in Fig.1brieﬂy and detailed as follows:(1)One end of the stainless steel wire (2cm)was ﬁrstly washed with acetone,ethanol and distilled water in an ultrasonic bath for 10min respectively and then dried at room temperature.Secondly,the wire was dipped in a HAuCl 4solu-tion (0.05%,w/w)for 3h and then washed with deionized water.(2)The stored dithiol solution (30%,w/w)was diluted to 0.1%with ethanol.The pretreated stainless steel wire was then put into it for 12h to form a SAM of dithiol;the excess 1,8-octanedithiol was removed through washing with ethanol.Afterwards,the ﬁber was immersed in the Au NPs gel (as prepared in Section 2.3.1)for another 48h to absorb Au NPs onto the SAM;the excess AuNPsFig.2.Effect of repeat times on extraction capability.Conditions:concentration,200␮g L −1;extraction time,50min;extraction temperature,60◦C;NaCl content,20%(w/w);stirring rate,800rpm;desorption temperature,300◦C;desorption time,6min.J.Feng et al./J.Chromatogr.A 1217 (2010) 8079–80868081Fig.3.FESEM images of stainless steel wire after modiﬁcation by Au NPs at magniﬁcation of 500(a);50,000(b);100,000(c).were removed by washing with deionized water.This procedure was repeated for about eight times.The color of stainless steel wire was turned to dark bluish-grey after the entire preparation procedures.2.4.Solid-phase microextractionBefore the SPME experiment,the Au NPs/SPME ﬁber was aged at 300◦C for 0.5h under nitrogen.The ﬁber was installed into a homemade SPME device which was a modiﬁcation of a 5␮mFig.4.Energy dispersive XRF analysis of Au NPs/SPME ﬁber.syringe [31].20mL of sample solution (0.2␮g mL −1)was put in a 25mL glass vial with a rubber cork.The modiﬁed syringe was placed into the sample vial and the ﬁber was dipped in the sam-ple solution directly.A magnetic agitator was used to accelerate the extraction.The extraction was performed under optimized conditions (temperature,time,ionic strength,and stirring rate).After the extraction,the ﬁber was withdrawn into the needleandFig.5.Effect of extraction time on peak area of analytes.Conditions:concentration,200␮g L −1;extraction temperature,60◦C;NaCl content,20%(w/w);stirring rate,800rpm;desorption temperature,300◦C;desorption time,6min.8082J.Feng et al./J.Chromatogr.A1217 (2010) 8079–8086Fig.6.Effect of extraction temperature on peak area of analytes.Conditions:con-centration,200␮g L −1;extraction time,50min;NaCl content,20%(w/w);stirring rate,800rpm;desorption temperature,300◦C;desorption time,6min.introduced into the GC inlet [32].Desorption conditions were also optimized.3.Results and discussion3.1.Preparation of Au NPs/SPME ﬁberFig.1shows the preparation process of Au NPs/SPME ﬁber.It mainly included two sections.3.1.1.Pretreatment of the stainless steel wirePurpose of this procedure was to form an Au ﬁlm on the wire surface through a reduction reaction between chloroauric acid (HAuCl 4)and the wire.HAuCl 4is high caustic and the stainless steel wire easily broke in a concentrated HAuCl 4solution or after a long-time reaction.The optimum HAuCl 4concentration was inves-tigated:we immersed the stainless steel wire in HAuCl 4solutions with concentrations at 1%,0.5%,0.1%,0.05%,0.005%and0.001%,Fig.7.Effect of NaCl content on peak area of analytes.Conditions:concentration,200␮g L −1;extraction time,50min;extraction temperature,60◦C;stirring rate,800rpm;desorption temperature,300◦C;desorption time,6min.Fig.8.Fiber-to-ﬁber reproducibility for Au NPs/SPME ﬁber preparation.Conditions:concentration,200␮g L −1;extraction time,50min;extraction temperature,60◦C;content of NaCl,20%(w/w);stirring rate,800rpm;desorption temperature,300◦C;desorption time,6min.respectively.As the experiment shows,more diluted solution (≤0.005%,w/w)needed a longer time reaction and more concen-trated solution (≥0.1%,w/w)strongly corroded the stainless steel wire in a short time.So we chose 0.05%as the ﬁnal concentration and the time was ﬁxed at 3h to obtain a satisfactory coverage of Au ﬁlm and avoid mortal damage of stainless steel wire at the same time.Reaction between the wire and HAuCl 4is shown as follows:Fe +AuCl 4−→Fe 3++Au +Cl −(1)After the reaction,the surface of the stainless steel wire was covered with a thin ﬁlm of Au and the color turned into pale pink.Untreated stainless steel wire could not form SAM of 1,8-octanedithiol and no Au NPs could be coated on it.So the process of reduction reaction was necessary and crucial.3.1.2.Assembly of Au NPs onto the pretreated stainless steel wireConcentration of dithiol in SAM formation was usually mil-limolar [33],so we dipped the pretreated ﬁber into the 0.1%(w/w)solutions of 1,8-octanedithiol and the time was ﬁxed at 12h according to some reports [34,35].To obtain a higher Au NP immo-bilization efﬁciency on the SAM,the ﬁber was immersed in Au NP sol for 48h.Thickness of the Au NP coatings determined the extraction efﬁciency to a great extent.As shown in Fig.2,peak areas increase greatly with repeat times from four to eight.After eight times assembly,extraction efﬁciency increases slightly.In the view of saving preparation time,preparation of Au NPs/SPME ﬁber completed after eight times assembly of Au NPs.Fig.3shows the FESEM images of the stainless steel wire after modiﬁcation.It can be clearly seen that Au NPs are immobilized on the wire surface tightly.Au NPs are extremely uniform and the grain size is about 20nm.Surface area of the ﬁber was very large because of the tiny nanoparticles,and this was favorable for efﬁ-cient extraction.Tiny grain size also made the coating too thin to be measured by our available method.Energy dispersive XRF was used to verify the adsorption of Au NPs onto the ﬁber.As shown in Fig.4,2.1keV is an M ␣1peak of gold [36].Peaks at 9.6and 11.3keV are assigned to the L ␣and L ␤of gold respectively [7].These results clearly demonstrated the successful immobilization of Au NPs on the stainless steel wire.Since the detection depth of XRF analysis is about 1␮m,peaks of the matrix elements (Fe,Cr,Ni,and Mn)can also be seen in Fig.4.J.Feng et al./J.Chromatogr.A1217 (2010) 8079–80868083Table1Enhancement factors(EFs)and log P a for different analytes extracted on Au NPs/SPMEﬁber.Compounds ACD b/log P EF(n=3)Compounds ACD/log P EF(n=3)Compounds ACD/log P EF(n=3)Naphthalene 3.4539.4±1.3n-Hexane 3.94Not detected Phenol 1.48Not detected Diphenyl 3.9866.1±4.1n-Octane 5.01Not detected4-Methylphenol 1.94Not detected 1-Bromonaphthalene 4.2277.6±13.6n-Undecane 6.6011.4±3.04-Chlorophenol 2.43Not detected Fluorene 4.1658.0±4.4n-Tridecane7.6627.7±6.71-Naphthol 2.71Not detected Anthracene 4.68105.2±7.14n-Hexadecane9.26170.9±9.0Aniline0.94Not detected Fluoranthene 5.17202.5±10.6n-Octadecane10.32189.7±2.24-Methylamine 1.40Not detected m-Terphenyl 6.02256.3±7.2n-Heneicosane11.91222.2±9.14-Chloroaniline 1.76Not detected p-Terphenyl 5.63158.0±13.51-Naphthylamine 2.17Not detecteda Octanol/water partition coefﬁcient,measurement of how hydrophilic or hydrophobic a chemical substance is.b Advanced Chemistry Development,maker of related database.Conditions:for aromatic HOCs,sample concentration,200␮g L−1;extraction time,50min;extraction temperature,60◦C;NaCl content,20%;desorption temperature,300◦C;desorption time,6min.For n-alkanes,sample concentration,200␮g L−1;extraction time,40min; extraction temperature,60◦C;NaCl content,30%(w/w);desorption temperature,300◦C;desorption time,6min.Table2Analytical parameters of the Au NPs/SPME-GC method for the determination of analytes under the same conditions as in Table1and comparisons of the LODs with other methods.Compounds Linear range(␮g L−1)Linearity/R2LOD(ng L−1)Repeatability(n=3,%)(singleﬁber)Reproducibility(n=3,%)(ﬁber-to-ﬁber)LODs a withcommercialﬁber[42](ng L−1)LODs a of Xu’smethod(ng L−1)[43]LODs of EPAmethod601(ng L−1)[44]PDMS PANaphthalene1–3000.9984250 2.4926.401502202401800b Diphenyl0.5–3000.998750 4.2712.27––––1-Bromonaphthalene0.5–3000.996850 5.727.3––––Fluorene0.5–2500.994850 4.27 4.288080300210b Anthracene0.5–2500.999325 6.4211.13180110–660c Fluoranthene0.05–2000.9964257.90 5.6250170580210c m-Terphenyl0.05–2000.997112.5 4.248.34––––p-Terphenyl0.05–2000.994112.5 3.5513.58––––a SPME-GC-FID.b LLE-HPLC-UV.c LLE-HPLC-FLD.3.2.Optimization of SPME parameters3.2.1.Extraction timeThe absorption and desorption of sample molecules on SPME ﬁber is a dynamic equilibrium.Normally,the time needed for equi-librium is the best for the extraction.As can be seen from Fig.5, peak areas increase as the time increase from30to50min and reach a relatively stable stage after a50min extraction.So50min was chosen as the suitable extraction time.3.2.2.Extraction temperatureTemperature has double inﬂuence on the SPME extraction:a higher temperature increases the values of diffusion coefﬁcient and Henry’s constant but decreases the distribution coefﬁcient. Elevated diffusion coefﬁcient is favorable for the diffusion of ana-lytes to theﬁber coatings and decreases the time for equilibrium, while decrease of the distribution coefﬁcient reduces the adsorp-tion capacity of the coating.So there will be a platform or a summit on the temperature–extraction capability curve.From the correla-tion studies on temperature and peak areas shown in Fig.6,for most of analytes,the highest extraction efﬁciency is reached at60◦C while some of them need a long time to reach equilibrium.Under the comprehensive consideration on analytical time and extraction capability,60◦C was chosen as the optimum temperature.3.2.3.Ionic strengthIonic strength also has double effects on the extraction.With the increase of ionic strength,salting-out effect and procompet-itive effect will inﬂuence the extraction diversely.We used NaCl to change the ionic strength of the sample solution in the range of0–30%(w/w).As shown in Fig.7,when the content of NaCl is lower than20%,salting-out effect plays the major role and peak area increases with the increase of NaCl content.When the content of NaCl is higher than20%,procompetitive effect is principal,and peak areas decrease with the increase of NaCl content.So,20%was selected as the suitable content ofNaCl.Fig.9.Stability of Au NPs/SPMEﬁber.Conditions:concentration,200␮g L−1;extrac-tion time,50min;extraction temperature,60◦C;content of NaCl,20%(w/w);stirring rate,800rpm;desorption temperature,300◦C;desorption time,6min.8084J.Feng et al./J.Chromatogr.A 1217 (2010) 8079–8086Table 3Aromatic HOC concentration and recovery in real samples (n =3)under the same conditions as in Table poundsRainwaterSoil extractConcentration (␮g L −1)Recovery (%)Concentration (␮g L −1)Recovery (%)Spiked 10␮g L −1Spiked 100␮g L −1Spiked 10␮g L −1Spiked 100␮g L −1Naphthalene Not detected 110.1±5.798.6±5.084.0±10.0111.4±6.8119.9±3.0Diphenyl Not detected92.4±6.384.5±0.75Not detected 87.3±4.776.8±2.4Fluorene Detected but not quantiﬁed 86.1±2.5102.4±10.2Not detected 94.8±1.985.5±3.3Anthracene 17.2±1.586.6±9.2113.9±4.040.5±3.798.6±4.9108.8±4.4Fluoranthene 18.1±2.3101.2±10.796.8±1.615.3±3.6106.0±9.980.7±1.4m -Terphenyl 20.8±4.099.5±6.9110.2±4.924.0±1.598.3±10.587.8±5.7p -Terphenyl 18.8±7.788.0±6.278.4±5.720.2±2.1114.2±11.3114.3±6.5Total54.1184.03.2.4.Effect of stirring rateStirring,improves the extraction through accelerating the trans-ference of sample molecules from the solution to the ﬁber,thus improves the extraction.As our experiment showed,extraction efﬁciency increased with the stirring rate.However,a stirring rate above 800rpm caused the bubble formation in the solu-tion.So the magnetic agitator was ﬁxed at 800rpm during the extraction.3.2.5.Effect of desorption conditionsComplete desorption of analytes from the ﬁber enhances the sensitivity of the method as well as ensures that no crossover pol-lution for the next GC analysis [32],so we investigated the effects of injector temperature (from 250to 300◦C)and desorption time (from 4to 7min)carefully.Based on these results,desorption at 300◦C for 6min was chosen as the optimum desorption conditions.3.3.Extraction selectivity studies of Au NPs/SPME ﬁberFour types of organic compounds including aromatic HOCs (naphthalene,diphenyl,1-bromonaphthalene,ﬂuorine,anthracene,ﬂuoranthene,m -terphenyl,and p -terphenyl),n -alkanes (n -hexane,n -octane,n -undecane,n -tridecane,n -hexadecane,n -octadecane,and n -heneicosane),phenols (phenol,4-methylphenol,4-chlorophenol,and 1-naphthol)and amines (aniline,4-toluidine,4-chloroaniline,and 1-naphthylamine)were chosen to test the extraction selectivity of the Au NPs/SPME ﬁber.The results are shown in Table 1.In this work,the novel SPME ﬁber could not extract phenols and amines from aqueous solutions no matter what extraction conditions were used,but it had a preconcentration effect on aromatic HOCs and n -alkanes (n c ≥13).Comparisons among the octanol/water partition coefﬁcient (log P s)of these compounds were carried out in order to ﬁnd the relation-ship between their hydrophobicity and the enhancementfactorFig.10.GC chromatograms of aromatic HOCs in soil extract (a),rainwater (b)and standard solutions (c)extracted by Au NPs/SPME ﬁber.(1)Naphthalene,(2)diphenyl,(3)1-bromonaphthalene,(4)ﬂuorene,(5)anthracene,(6)ﬂuoranthene,(7)m -terphenyl,(8)p -terphenyl.Conditions:concentration,200␮g L −1;extraction time,50min;extraction temperature,60◦C;content of NaCl,20%(w/w);stirring rate,800rpm;desorption temperature,300◦C;desorption time,6min.J.Feng et al./J.Chromatogr.A1217 (2010) 8079–80868085values[37](EF,the ratio of theﬁnal concentration to the original). From Table1,it is seen that only analytes with large log P s(except phenols and amines)can be extracted by theﬁber,and larger log P s give bigger EFs among the same kind of compounds.These results can be attributed to the hydrophobic characteristic of the Au surface[38].Analytes with higher hydrophobicity have stronger afﬁnity with the Au NPs/SPMEﬁber,which is favorable to the extraction.It seemed that hydrophobicity was the dominative factor to be extracted by theﬁber.Meanwhile,the Au NPs/SPME ﬁber gave much bigger EFs for PAHs with larger␲-system.This suggested the existence of an additional interaction between aromatic HOCs and the Au NP surface.In theoretical and computational chemistry,gold is“anoma-lous”due to its very large relativistic effects[39].The relativistic effects lead to excellent electronic mobility,which makes it eas-ier to use its empty valency shell to form coordinate bond with atoms having lone pair electrons,or use its valency elec-trons to form feedback-coordinate bond with atoms having unoccupied orbital.Hoffmann[40]modeled the chemisorptive molecule–surface interactions and explained the molecule–metal interaction in terms of the interaction of the frontier orbits,HOMO and LUMO.Pérez-Jiménez et al.[41]found the occurrence of electron transference from Au to the fullerene LUMO by a scan-ning tunneling spectroscopy experiment.Based on these theories and researches,we ascribed the selective extraction of PAHs on the Au NPs/SPMEﬁber to the interaction between␲-system of PAHs and Au.There may be an electron transference between PAHs(␲-donor system)and Au which strengthened the afﬁnity beyond the hydrophobic effect,thus the extraction capacities were improved.To sum up,the Au NPs/SPMEﬁber exhibited superb selectiv-ity to some aromatic HOCs,which was favorable to its practical utilization.3.4.Analytical evaluationThe analytical evaluation parameters for the Au NPs/SPME-GC method were studied under optimized conditions and results are shown in Table2.Solutions used in linearity studies were prepared by diluting the stored solution with distilled water with concentra-tion from0.01to500␮g L−1for each analyte.As can be seen from Table2,good linearity is achieved in a wide range for all analytes with correlation coefﬁcients(R2)ranging from0.9941to0.9993. Determination limits are in the range of12.5–250ng L−1,which is deﬁned as three times the baseline noise.These are relatively lower than the commercially availableﬁber and other method as shown in Table2.The relative standard deviations(RSDs)for singleﬁber are from2.49%to7.90%.Theﬁber-to-ﬁber reproducibility was also evaluated using threeﬁbers prepared in the same procedure and the results are shown in Fig.8.RSDs for all the compounds are in the range of4.28–26.40%.3.5.Durability and stabilityDurability and stability of the SPMEﬁber correlate to its life-time and are very important for its practical applications.The ﬁber was exposed overnight in solutions of0.1mol L−1NaOH and 0.01mol L−1HCl respectively.Thermal stability of theﬁber was evaluated through heating theﬁber at350◦C for3h in the GC inlet.We compared the peak area before and after the treatment to evaluate theﬁber stability and the results are shown in Fig.9.As can be seen from Fig.9,no signiﬁcant peak area change is observed after the treatments.Au NPs/SPMEﬁber shows well dura-bility and stability towards harsh conditions.These characteristics can be ascribed to the chemical stability of gold and the strong Au–S bond.Furthermore,since the support of the novel Au NPs/SPME ﬁber is theﬂexible and strong stainless steel wire,thus prolonging the lifetime at the same time.3.6.Application to real samplesAromatic HOCs are important environmental contaminants in air,soil and water.Many national organizations and government departments have developed laws and regulations to set limits of them to protect public health.For example,United States Envi-ronmental Protection Agent(US EPA)has provided estimates of levels of total cancer-causing PAHs(16kinds of PAHs,including naphthalene,ﬂuorene,anthracene,ﬂuoranthene and so on)and the total maximum contaminant level is0.2mg L−1.The as-established Au NPs/SPME-GC method was applied for the analysis of PAHs, diphenyl,and two terphenyls in rainwater and soil extract.Rainwa-ter was collected in Lanzhou,China on May20,2010.The soil extract was obtained from the garden of Lanzhou Institute of Chemical Physics and was treated using the following procedure:put335g of soil in335mL of water and stirred dramatically for60min;keep still and the supernatant was transferred to another vessel.Both water samples wereﬁltered through ordinaryﬁlter paper and0.45␮m membranes and stored at4◦C.The experimental results are shown in Table3.Anthracene,ﬂuoranthene,m-terphenyl,and p-terphenyl are detected and quantiﬁed in rainwater and soil extract and the concentrations in soil extract are higher than those in rainwater. This dropped a hint of enrichment effect of these compounds in soil.Total amount of the pollutions in the two samples was54.1 and184.0␮g L−1respectively,which was lower than the regulation limits.Fluorene in rainwater is detected but the quantity is not in the linear range.The recoveries spiked in two samples at10and 100␮g L−1are in the range from78.4%to119.9%.Chromatograms of the real samples and standard solution are shown in Fig.10. 4.ConclusionA novel Au NPs/SPMEﬁber has been prepared using a simple layer by layer self-assembly method.Coupled with GC analysis,the ﬁber exhibitsﬁne extraction efﬁciency and selectivity.The estab-lished Au NPs/SPME-GC method has been used to extract several aromatic HOC pollutants in aqueous solutions,which achieved a wide linearity ranges and low LODs.The method was then applied to two real natural samples;four analytes were detected and quan-tiﬁed.The novel Au NPs/SPMEﬁber showed high stability and durability towards acid,alkali and under high temperature.Both the singleﬁber repeatability andﬁber-to-ﬁber reproducibility were satisfactory.Au NPs can be a good sorbent for SPME. AcknowledgementsThis work was supported by the National Natural Science Foun-dation of China(No.20905073),the National Science&Technology Major Project of China(No.2008ZX05011and No.2008ZX05010) and the Technology R&D Program of Gansu Province of China (0804GKCA034).References[1]R.P.Belardi,J.Pawliszyn,Water Pollut.Res.J.Can.24(1989)179.[2]A.A.Boydboland,J.B.Pawliszyn,J.Chromatogr.A704(1995)163.[3]L.M.Ravelo-Pérez,J.Hernández-Borges,M.Á.Rodríguez-Delgado,J.Chro-matogr.A1211(2008)33.[4]L.Pan,J.M.Chong,J.Pawliszyn,J.Chromatogr.A773(1997)249.[5]M.R.Ivanov,H.R.Bednar,A.Haes,J.ACS Nano3(2009)386.[6]C.Y.Lin,C.H.Liu,H.C.Chang,W.L.Tseng,Electrophoresis29(2008)3024.[7]F.K.Liu,Y.T.Hsu,C.H.Wu,J.Chromatogr.A1083(2005)205.[8]H.M.Liu,J.B.Li,X.Liu,S.X.Jiang,Talanta78(2009)926.[9]C.L.Arthur,L.M.Lillam,K.D.Buchbolz,Anal.Chem.64(1992)1960.[10]J.Chen,J.B.Pawliszyn,Anal.Chem.67(1995)2530.。

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