社会科学研究方法与论文写作智慧树知到期末考试答案章节题库2024年北京第二外国语学院1.What are key components of research design? （）答案:Timeframe.###Sampling Strategy.###Data Collection Methods.2.The following aspects of informed consent that are essential in researchethics include （）.答案:Researchers explaining potential risks andbenefits.###Participants being allowed to withdraw from the study.3.When should all authors be included in the in-text citation, according to theAPA style? （）答案:When there are two authors.###When there are three to fiveauthors.4.What are some essential tips for writing an effective abstract? （）答案:Use keywords###Emphasize points differently from thepaper.###Use passive verbs5.Which statements are suggested solutions for improving the Methodologysection? （）答案:Eliminate the use of first-person pronouns.###Provide a clearrationale for the chosen methods.6.What's the difference between methodology and method? （）答案:Methodology encompasses the broader theoretical framework and guiding philosophy of the research process.###Methods encompass the specific techniques and procedures employed for data collection andanalysis.###Methodology is presented as a distinct section in aresearch thesis, explaining the overall approach and rationale.7.What are the downsides of mere listing in a literature review? （）答案:It does not present themes or identify trends.###It often indicatesa lack of critical synthesis.8.The common problems to be aware of in thesis writing include（）.答案:Excessive reliance on qualitative data###Lack of theoreticalsupport###Failure to integrate theory and practice.###Misuse of tense ponents that are typically embedded in the structure of an academicpaper, especially the journal article, include （）答案:Introduction###Results and Discussion10.Which of the following examples are misconducts? （）答案:Facilitating academic dishonesty.###Unauthorizedcollaboration###Misuse of Patients11.What are the three main elements of a definition, as mentioned in the lecture?（）答案:Term, Category, and Features.12.In the Methods section, why is it important to detail the tools or materials fordata collection? （）答案:To explain how instruments to be used to answer researchquestions.13.Which is the method suggested to avoid plagiarism when summarizinginformation from sources? （）答案:Summarize immediately after reading without referring back tothe source.14.The purpose of control variables in research is （）.答案:To keep certain factors constant and prevent them frominfluencing the dependent variable.15.What is the purpose of using sampling techniques in research? （）答案:To draw conclusions about the population based on data collected from the sample.16.According to Wallwork’s tips for the final check, what is one way to ensureyour paper is as good as possible before submission? （）答案:Anticipate referees’ comments.17.What does external validity assess? （）答案:The extent to which research findings can be applied orgeneralized to other situations and populations.18.Which of the following expressions are correctly used in the Methods Section?（）答案:"We conducted the experiment in a controlled environment."19.Which of the following is NOT a recommended guideline for using tables in aresearch paper? （）答案:Using as many tables as possible to provide comprehensiveinformation.20.What does a structured abstract typically include to make it more readable?（）答案:Eye-catching font for the title21.What is the main function of the preparation stage in writing a literaturereview? （）答案:To locate relevant literature and prepare for writing.22.The primary focus of academic integrity is （）.答案:Fostering honesty and responsible behavior.23.The act of using someone else’s ideas and writings as your own can beconsidered as （）.答案:Plagiarism24.Which step is NOT part of the suggested three-step approach for revisingyour paper? （）答案:Rewrite the entire paper.25.Which is not the reason for an overly broad title being problematic? （）答案:It encourages depth in the study.26. A good thesis or dissertation should tell the reader not just “what I havedone,” but “why what I have done matters.” （）答案:对27.Coherence in academic writing refers to the clarity of the thesis statementand the organization of the paper. （）答案:对28.The research methods section helps readers and reviewers gauge thetransparency, validity, and reliability of the research. （）答案:对29.Research papers are published to share new, original results and ideas withthe academic community. （）答案:对30.Relying solely on secondary sources ensures the originality of researchfindings. （）答案:错31.In introduction writing, it is recommended to delve into an exhaustive reviewof the entire field to provide comprehensive context. （）答案:错32.The Background Method in introduction writing kicks off by presenting aproblem and then addressing the solution. （）答案:错33.Multiculturalism seeks to enhance the self-esteem and identities ofmarginalized groups. （）答案:对34. A Doctoral-level literature review is typically less comprehensive than aMaster's-level literature review. （）答案:错35."Hoaxing" involves deliberately publishing false information with theintention of deceiving others. （）答案:对36.Reflecting on the research process at the end is essential for evaluating itsstrengths and limitations. （）答案:对37. A well-crafted title should engage a wide audience effectively. （）答案:对38.In order to avoid plagiarism, it is suggested to avoid citing references. （）答案:错39.Predicting difficulties and providing countermeasures in a research proposalis essential to show the depth of thinking and enlist expected guidance. （）答案:对40.Conducting a literature review is not necessary when selecting a researchtitle. （）答案:错41.What can authors do to ensure a timely publication in a journal that reviewspapers for job hunting purposes?（）答案:Submit the manuscript without checking for errors###Seekinformation from editors about review times###Be efficient in making revisions42.When preparing a manuscript for publication, it is crucial to focus on ethicalstandards.（）答案:对43.Why do researchers want to publish their papers?（）答案:To share new results and ideas44.How can you identify an appropriate journal for publication? （）答案:Look for journals that publish work similar to your research.45.The editor-in-chief makes the final decision on whether a submitted paper isaccepted or rejected in the review process.（）答案:对ing cut and paste extensively is recommended during the final check tosave time.（）答案:错47.Exchanging texts with another student for proofreading is encouraged to findcareless errors in your own work.（）答案:对48.What is the key idea that should be remembered by the audience from yourtalk？（）答案:The key idea of your research49.Why is it important to avoid errors that may distort meaning in your writtenwork? （）答案:To enhance the quality of your writing###To ensure clarity ofcommunication50.What is the main purpose of doing a presentation?（）答案:To engage, excite, and provoke the audience51.Making academic writing more tentative involves avoiding over-generalizations and using linguistic hedges and tentative phrases.（）答案:对52.What is the purpose of the checklist questions provided for paper revision?（）答案:To help improve the writing53.Which of the following are strategies for achieving cohesion in academicwriting? （）答案:Organizing the paper logically###Using transitional words andphrases###Employing reference words54.Redundancy and colloquialisms are considered desirable features ofconciseness in academic writing. （）答案:错55.What should you do when revising your paper writing to improve clarity andspecificity? （）答案:Be self-contained56.What are the characteristics of informative abstracts? （）答案:They may replace the need for reading the full paper###Theycommunicate specific information about the paper###They provide aconcise summary of the paper’s content57.Structured abstracts may have clear subheadings to mark different sections.（）答案:对58.What is the recommended maximum word limit for a conference abstract?（）答案:250 words59.Which tense is often used when writing an abstract? （）答案:Present tense60.The primary purpose of an informative abstract is to indicate the subjectsdealt with in a paper. （）答案:错61.What are some reasons for using citations in academic writing? （）答案:To show you are a member of a particular disciplinarycommunity###To acknowledge the intellectual property rights ofauthors###To avoid plagiarism62.Self-plagiarism is not considered an ethical concern in academic writing.（）答案:错63.What is the primary purpose of citation in academic writing? （）答案:To acknowledge the intellectual property rights of authors64.What is self-plagiarism? （）答案:Presenting one's own previously published work as new65.All sources cited in the text must be documented in the References section.（）答案:对66.Which type of conclusion is more common in research papers and theses andfocuses on summarizing research outcomes and aligning them with the initial thesis? （）答案:Thesis-oriented Conclusion67.What are the four sections typically found in the Conclusion section of aresearch paper, according to the material? （）答案:Summary of findings, implications, limitations, further studies68.What is one of the purposes of the conclusions chapter? （）答案:To forestall criticisms by identifying limitations of the research69.Which of the following are types of conclusions discussed in the material? （）答案:Summary type###Field-oriented conclusion###Evaluation type of conclusion###Recommendation type of conclusion70.The conclusion section in academic papers typically follows a uniformstructure across all disciplines.（）答案:错71.What is one of the purposes of making comparisons with previous studies inacademic writing? （）答案:To justify the methods or procedures followed72.Which of the following is NOT mentioned as a common type of graphicalfigure in the material? （）答案:Map illustrations73.What can we do in demonstrating our research results in paper? （）答案:Use figures and tables to summarize data###Show the results ofstatistical analysis74.In which field are Qualitative Research methods often used?（）答案:Liberal Arts and Social Sciences75.What factors should be considered when choosing research methods for athesis? （）答案:Traditional approaches.###Research questions andobjectives.###Nature of the subject matter.76.What does "Research Design" refer to in the research process?（）答案:The overall plan guiding the research study.77.All the following moves are included in the method section except （）.答案:Describing the commonly used methods in certain field.78.The research methods section in a thesis is often presented as a distinctsection, separate from the literature review.（）答案:对79.What are the two core abilities essential for writing an effective literaturereview? （）答案:Information seeking and critical appraisal.80.Where can a literature review be placed in a research paper or thesis? （）答案:In different places depending on research goals and fieldconventions.81.Which type of literature review focuses on organizing literature aroundspecific research questions?（）答案:Question-oriented review.82.The purpose of creating a visual representation, such as a literature map, isto replace the need for drafting concise summaries.（）答案:错83.What are the recommended tenses to use when discussing the content of thesources in a literature review? （）答案:Simple Past.###Present Perfect.###Simple Present.84.What is the role of the Problem Statement in the Introduction? （）答案:Justify the importance of the research.85.Which is NOT one of the three methods could be used to write anintroduction? （）答案:Reference Method86.The location and structure of the introduction are standardized across alltypes of research theses. （）答案:错87.In Metadiscourse research, what is the recommended way for a researcher torefer to themselves in the introduction?（）答案:Refer to themselves as "this thesis" or a specific section.88.What are the key elements included in Move 2 of the "Create a ResearchSpace" (CARS) framework?（）答案:Identifying gaps in prior research.###Indicating a gap.89.What role do Research Grant Proposals play?（）答案:Both securing financial support and convincing funding agencies.90.What questions does a research proposal eloquently answer? （）答案:How are you going to do it?###What do you plan toaccomplish?###Why do you want to do it?91.The "Aims/Purposes" section in a research proposal outlines the centralissues to be tackled in the study. （）答案:对92.To whom is a research proposal usually submitted for approval and support?（）答案:Funding agencies, academic institutions, or research supervisors.93.What is the purpose of predicting difficulties and providing countermeasuresin the research proposal?（）答案:To show the depth of thinking and enlist expected guidance.94.The recency of sources is crucial in research, and older sources are alwayspreferred for their depth.（）答案:错95.Which database is specifically mentioned for searching Master's and DoctoralDissertations? （）答案:CNKI96.When conducting a critique of a study, what should be considered about themethods used?（）答案:The validity for studying the problem.97.What is the primary characteristic of primary sources in research materialcollection? （）答案:They offer synthesized information from various perspectives. 98.What are common approaches to collecting primary source materialsmentioned in the lecture? （）答案:Surveys and questionnaires###Controlled experiments###One-on-one interviews99.What are potential mistakes in the title selection process? （）答案:Having unclear titles that do not convey the subjectmatter.###Using contemporary language to make the title appearoutdated.100.How does the researcher balance the focus of a research title?（）答案:By clearly defining the scope of the study.101.What is the purpose of conducting a comprehensive literature review in the title selection process? （）答案:To identify gaps, controversies, or areas requiring furtherexploration.102.An overly narrow title might limit the potential impact and relevance of the research. （）答案:对103.What is the significance of a well-chosen title? （）答案:It significantly enhances the academic value of the work.104.What are key characteristics of deconstruction in literary theory? （）答案:Highlighting textual undecidability and paradoxes.###Challenging traditional assumptions about language and meaning.###Questioning binary oppositions.105.What distinguishes quantitative data from qualitative data in research? （）答案:Quantitative data are numerical, while qualitative data can bedescribed in words.106.What is the primary goal of case studies in applied linguistics? （）答案:To enhance understanding of a phenomenon, process, person, or group.107.Case studies use a single data source, such as interviews, to explore particular phenomena. （）答案:错108.What are the three types of cultural studies? （）答案:New historicism, postcolonialism, American multiculturalism. 109.The dependent variable in a study investigating the effects of different study methods on exam performance is （）.答案:Exam performance110.What role does a moderating variable play in a research study? （）.答案:It influences the strength or direction of the relationship between independent and dependent variables.111.External validity assesses the extent to which research findings can be applied to populations, settings, or conditions beyond the specific study. （）答案:对112.How does deduction differ from induction in research? （）答案:Deduction is the process of reasoning from general principles tospecific predictions.113.The purposes of research include （）答案:Solving real-world problems###Testing existingtheories###Meeting graduation requirements###Advancingknowledge114.The potential academic consequences for students who engage in academic dishonesty include （）.答案:Monetary fines、Academic suspension and Expulsion from theInstitute115.The three key principles that experimental researchers need to carefully consider and implement before, during and after recruiting researchparticipants are （）.答案:Anonymity###Informed consent###Confidentiality116.It is unethical to conduct research which is badly planned or poorly executed.（）答案:对117.The primary focus of academic integrity in the context of research ethics is （）.答案:Fostering responsibility and trustworthiness in academic work 118.The pillars of academic integrity include all the aspects except （）答案:Excellence119.The primary purpose of literature reviews in research articles is （）.答案:To evaluate previously published material120.Methodological articles typically present highly technical materials, derivations, proofs, and details of simulations within the main body of thearticle. （）答案:对121.In a research article, many different sections can be found in empirical studies, including （）.答案:Method###Literature review###Introduction###Discussion 122.According to the lecture, which step in the procedures of thesis writing involves drafting a title and abstract? （）答案:Step 1: Choice of Topic123.The primary use of case studies is （）.答案:To illustrate a problem or shed light on research needs。
American Mineralogist, Volume 85, pages 543–556, 20000003-004X/00/0304–543$05.00543I NTRODUCTIONThe importance of synthetic semiconductors to chemical and industrial processes has spurred a large research effort to understand the fundamentals of photochemical processes and to develop new photocatalysts. For example, synthetic photocatalysts can promote processes such as photodecompo-sition of organic and inorganic contaminants (Borgarello et al.1988; Brinkley and Engel 1998; Fox 1988; Pelizzetti et al. 1988;Serpone et al. 1988a, 1988b), photosynthesis of organic com-pounds from carbon dioxide and other inorganic substrates (Anpo et al. 1997; Inoue et al. 1979; Kanemoto et al. 1996),photodecomposition of water to hydrogen and oxygen (Lauermann et al. 1987; Reber and Meier 1984), and photore-duction of dinitrogen to ammonia (Augugliaro and Palmisano 1988; Bickley et al. 1988; Schrauzer and Guth 1977; Soria et al. 1991).In contrast, there has been relatively little research on the photocatalytic properties of mineral semiconductors. There is,however, a growing recognition of the role semiconducting minerals may play as catalysts of redox reactions in natural environments and engineered systems designed to degrade haz-ardous chemicals (Schoonen et al. 1998; Selli et al. 1996;Stumm and Morgan 1995; Sulzberger 1990). Hence, the ques-The absolute energy positions of conduction and valence bands ofselected semiconducting mineralsY ONG X U AND M ARTIN A.A. S CHOONEN *Department of Geosciences, State University of New York at Stony Brook, Stony Brook, New York 11794-2100, U.S.A.A BSTRACTThe absolute energy positions of conduction and valence band edges were compiled for about 50each semiconducting metal oxide and metal sulfide minerals. The relationships between energy levels at mineral semiconductor-electrolyte interfaces and the activities of these minerals as a cata-lyst or photocatalyst in aqueous redox reactions are reviewed. The compilation of band edge ener-gies is based on experimental flatband potential data and complementary empirical calculations from electronegativities of constituent elements. Whereas most metal oxide semiconductors have valence band edges 1 to 3 eV below the H 2O oxidation potential (relative to absolute vacuum scale),energies for conduction band edges are close to, or lower than, the H 2O reduction potential. These oxide minerals are strong photo-oxidation catalysts in aqueous solutions, but are limited in their reducing power. Non-transition metal sulfides generally have higher conduction and valence band edge energies than metal oxides; therefore, valence band holes in non-transition metal sulfides are less oxidizing, but conduction band electrons are exceedingly reducing. Most transition-metal sul-fides, however, are characterized by small band gaps (<1 eV) and band edges situated within or close to the H 2O stability potentials. Hence, both the oxidizing power of the valence band holes and the reducing power of the conduction band electrons are lower than those of non-transition metal sulfides.tion arises of whether semiconducting minerals could promote these same processes. If so, these minerals could play an im-portant role in the fate of contaminants and the chemical com-positions of atmosphere and hydrosphere of the early earth. Although all the processes mentioned above are photo-chemical processes, there is also evidence for non-photolytic catalysis of redox reactions by semiconductors (Xu 1997; Xu and Schoonen 1995; Xu et al. 1996, 1999). Semiconductors can act as a conduit for electrons between the aqueous reac-tants. Because no illumination is needed for non-photo cata-lytic processes, this mechanism may be important beneath the photic zone in aquatic systems.In photochemical reactions, as well as the non-photochemi-cal mechanism outlined in our earlier work, the crucial step is the transfer of electrons between the semiconductor and sorbed reactants. As pointed out by Morrison (1990), electrons can only be transferred between those energetic states in the semi-conductor and the electrolyte that are at approximately the same energy level. The energy level of energetic states of sorbates undergoing an electron transfer can be approximated by the standard redox potential (E 0), whereas relevant energy levels for a semiconductor are the top of the valence band (E V ) and the bottom of the conduction band (E C ). The relative energet-ics of E V and E C vs. E 0 is the fundamental property of an elec-trolyte/semiconductor system that dictates whether an electron transfer between the semiconductor and sorbate is feasible.Although band gap (E g ) is well known for most semicon-ductors, unfortunately, E V and E C have not been determined ac-*E-mail: mschoonen@XU AND SCHOONEN: SEMICONDUCTING OXIDES AND SULFIDES544curately for most semiconducting minerals. Furthermore, E V and E C values are often presented in ways that prevent a straight-forward comparison to the redox potentials of aqueous elec-trolytes. For example, in both the materials science and applied physics literature, it is customary to express the energy posi-tion of band edges with respect to the energy level midway in the band gap of the material (i.e., the Fermi level of the mate-rial), rather than on the absolute vacuum scale (AVS). In con-trast, geochemical and electrochemical literature typically reports standard redox potentials for aqueous redox couples with respect to the normal hydrogen electrode (NHE). To com-pare the energy levels of sorbates to the band edges of a semi-conductor, however, it is necessary to have all energy levels of interest (i.e., E 0, E C , E V ) expressed on a common energy scale,such as the absolute vacuum scale or the normal hydrogen elec-trode scale.The objective here is to (1) provide a compilation of the absolute energy positions of valence and conduction band edges of semiconducting metal oxide and metal sulfide minerals and (2) address the relationship between these energy positions and the catalytic activities of these minerals in various heteroge-neous electron transfer processes. For those minerals for which band edge energies have not been determined experimentally,the band edge energies were calculated using an empirical re-lationship based on the electronegativity of the elements (But-ler and Ginley 1978). More extensive reviews on the interactions between semiconductor and electrolyte and photochemistry involving semiconductors can be found elsewhere (Balzani and Scandola 1989; Bockris and Khan 1993; Grätzel 1988; Kish 1989; Lewis and Rosenbluth 1989; Mills and Le Hunte 1997;Nozik and Memming 1996; Morrison 1990; Nozik 1978; Smithand Nozik 1997; Stumm and Morgan 1995; Stumm and Sulzberger 1992; Waite 1990).T HEORETICAL BACKGROUNDEnergetics of semiconductor/electrolyte interfaces For the purpose of this study we briefly review the elec-tronic band structure of semiconductors and the energetics of the semiconductor/electrolyte interface. Comprehensive treat-ments of this topic are by Bockris and Khan (1993), Grätzel (1989), Morrison (1990), and Nozik (1978).The electronic structure of semiconductors is characterized by the presence of a bandgap (E g ), which is essentially an en-ergy interval with very few electronic states (i.e., low density of states) between the valence band and the conduction band,which each have a high density of states (Borg and Dienes 1992). In the context of electron transfer between semiconduc-tors and aqueous redox species, it is crucial to identify the high-est occupied and the lowest unoccupied electronic levels in the semiconductor because those are the energy levels involved in the transfer. In most semiconductors, all electronic levels in the valence band are occupied whereas the levels in the con-duction band are empty. Hence, the highest occupied electronic level coincides with the top of the valence band. The energy of valence band edge, E V , is a measure of the ionization potential,I , of the bulk material. The lowest unoccupied electronic level in most semiconductors coincides with the bottom of the con-duction band. Where the band edge energy, E C , is a measure of the electron affinity, A , of the compound. The Fermi level or energy, E F , represents the chemical potential of electrons in a semiconductor. In essence, the Fermi level is the absolute elec-tronegativity, –χ, of a pristine semiconductor, a value whichF IGURE 1. (a ) Position of the conduction band edge (E C ), the valence band edge (E V ) and the intrinsic Fermi level (E F ) of a semiconductor with respect to vacuum as the zero energy reference. A is electron affinity; χ is electronegativity; I is ionization energy; E g is band gap. (b )Position of energy levels at the interface of an n-type semiconductor and an aqueous electrolyte on the absolute vacuum energy scale (AVS) and with respect to normal hydrogen electrode (NHE). The E CS and E VS represent the conduction band edge and valence band edge at the interface;U ft is the flatband potential; V H is the potential drop of the Helmholtz layer; V B is the band bending; E F is the Fermi level of the system at equilibrium; ΔE F is the difference between the Fermi level and the conduction band edge; E 0F,redox , is the standard Fermi level of the redox couple; E unoc and E oc , are energies of unoccupied states and occupied states of the redox couple; and λis the reorganization energy.XU AND SCHOONEN: SEMICONDUCTING OXIDES AND SULFIDES 545corresponds to the energy halfway between the conduction and valence band edges (Fig. 1a). The relationship between band edge energies and electronegativity can be expressed as:E C = –A = –χ + 0.5 E g (1a)andE V = –I = –χ –0.5 E g(1b)Incorporation of impurities in the structure of a semiconductor leads to the presence of electron acceptor state levels and/or donor state levels within the bandgap. The presence of donor or acceptor state levels changes the position of E F so that E F lies just above E V for p -type semiconductors (presence of ac-ceptor states) and E F lies just below E C for n -type semiconduc-tors (presence of donor states) (Morrison 1990).The next step is to define the energy levels of sorbates. Aque-ous redox species exchanging electrons with a semiconductor mineral can either accept (A + e – → A –) or donate (D → D + + e –)electrons. Upon electron transfer from or to an aqueous species,the electronic structure of the species changes. Upon the accep-tance of an electron, a previously unoccupied electronic level becomes occupied, whereas upon electron donation an elec-tron is removed from an occupied level. For an electron accep-tor (A/A –), it is the energy level of the lowest unoccupied level,E unoc , that is of importance, whereas for an electron donor (D/D +)the highest occupied energy level, E oc , is of importance. Because of the polar nature of water molecules, H 2O dipoles in the solva-tion shell of a redox species will re-orientate when there is a change in the charge of the redox species. The re-orientation of the solvation shell will result in an addition energy gain or loss when an electron is transferred from or to an aqueous redox spe-cies. The free energy change associated with this re-orientation process is known as reorganization energy (λ). V alues for λ range from a few tenths of an eV up to 2 eV . Furthermore, thermal fluctuation of the solvation structure cause a corresponding ther-mal distribution of the energy levels of both E oc and E unoc , see Figure 1b (Bockris and Khan 1993; Grätzel 1989; Morrison 1990). Whereas these energy distributions are difficult to quan-tify, it is helpful to make use of the notion that the redox poten-tial, E redox , of a redox couple undergoing a one-electron transition (e.g., A/A – or D/D +) lies midway between the maxima in E oc and E unoc for these species. The Fermi level of electrons of a redox couple (E F,redox ) is equivalent to the redox potential of aqueous redox couples (E redox ) on the absolute energy scale; hence, this can be expressed as:E E E T a a F,A/A A/A A/A oA AR −−−−==+ln()(2a)E E E T a a F D/D D/D D/D o D DR +,ln()+++==+(2b)where E 0 is the standard redox potential of the aqueous redox couple with respect to the Normal Hydrogen Electrode (NHE).The Fermi level of NHE at 25 °C is –4.5 eV with respect to the vacuum level (Bockris and Khan 1993).The distribution of energy states in a redox couple (Fig. 1b)becomes more complicated if the redox couple undergoes a multi-electron tranfer, because each one-electron step has apopulation of two energy states (E oc and E unoc ) associated withit. Instead of standard redox potential of the overall reaction,the standard potential of each one-electron steps should be con-sidered for a multi-electron transfer reaction. So for a two-elec-tron transition, such as CO 2 + 2e – + 2H + = HCOOH, the standard potentials of the CO 2/CO 2·– and CO 2·–/HCOOH redox couples should be used (CO 2·– represents a CO 2 radical group with a charge of –1). The standard redox potentials for the one-elec-tron steps are mostly unavailable because the intermediate prod-ucts are often unstable. Using E 0 for the overall reaction invariably leads to a misleading comparison of energy levels between semiconductor and aqueous species. This arises from the fact that E 0 for the overall reaction does not lie midway between the maximum of E oc and E unoc populations associated with each of the one-electron transitions. For example, E 0 forCO 2/CO 2·–is estimated to lie at –2 V (NHE), whereas E 0 for CO 2/HCOOH equals –0.61 V(NHE) (Tributsch 1989).When a semiconductor is placed in a solution containing redox species, electrons will be transferred across the semi-conductor/electrolyte interface until the chemical potentials,i.e., Fermi levels, of electrons in the solid and the solution are equalized. The interfacial electron transfer generates a space charge layer in the semiconductor, and conduction and valence band edges are bent such that a potential barrier is established against further electron transfer across the interface. As a re-sult, the energies of conduction and valence band edges at the semiconductor/electrolyte interface, (E CS and E VS , respectively),deviate from their bulk values (E C and E V ). The difference be-tween E CS and E C or E V and E VS is known as band bending, V B (Fig. 1b). The thickness of the space charge layer typically ranges from 100 Å to several microns depending on the con-ductivity of the semiconductor and the amount of band bend-ing. On the solution side of the interface, the Helmholtz double layer will develop due to the sorption of counter-ions onto the charged surface of the semiconductor. The thickness of the Helmholtz layer is typically on the order of 1 Å (Morrison 1990). The Helmholtz layer results in an additional potential drop inside the semiconductor space charge layer so that the band bending adjusts to make the net rate of electron transfer across the interface equal to zero at equilibrium. Hence, the band edge positions of the semiconductor at the interface can-not be determined unless the additional potential drop associ-ated with the Helmholtz layer is quantified (Morrison 1990).To link the energy levels of the semiconductor and the elec-trolyte, an experimentally measurable quantity, flatband po-tential (U ft ), is essential. U ft is the electrode potential measured with respect to a reference electrode (e.g., normal hydrogen electrode, NHE) in an electrolyte/semiconductor system when the potential drop across the space charge layer becomes zero.U ft can be expressed as (Nozik 1978):U ft (NHE) = A + ΔE F + V H + E 0( 3)where ΔE F is the difference between the Fermi level and ma-jority carrier band edge (E C for a n-type semiconductor, and E V for a p-type semiconductor), V H is the potential drop across the Helmholtz layer, and E 0 is the scale factor relating the refer-ence electrode redox level to the A VS (E 0 = –4.5 V for NHE,Bockris and Khan 1993). Because U ft is determined not onlyXU AND SCHOONEN: SEMICONDUCTING OXIDES AND SULFIDES 546by intrinsic properties of the semiconductor (A andΔE F), but also by the electrolyte (V H), U ft is a property of the interface.Note that V H is fixed and independent of both the externally applied voltage across the semiconductor-electrolyte interface and the changes in redox condition of the system, provided the composition changes associated with electron transfer do not affect the equilibrium distribution of ions adsorbed onto the semiconductor. The independence of V H on the interfacial charge transfer is caused by the high charge density and small width of the Helmholtz layer relative to the semiconductor space charge layer (Morrison 1990). As a result, the potential drop across the interface caused by the electron transfer occurs pre-dominantly within the semiconductor space charge layer, whereas the V H remains essentially constant. Consequently, at a given electrolyte composition and semiconductor, U ft is a characteristic parameter independent of the electron transfer process. On the other hand, the potential drop within the Helmholtz layer depends on the adsorption/desorption equi-librium of electrolyte ions at the semiconductor surface. When the net adsorbed charge within the Helmholtz layer is zero, i.e., at the zero point of charge, (pH ZPC), V H is also zero. The flatband potential at the pH ZPC (U ft0) equals the intrinsic Fermi level of the semiconductor, and is the only meaningful flatband potential. Under conditions other than pH ZPC, flatbands are not really flat but contain the band bending induced by the Helmholtz layer. Hence, band edge energies can be calculated from U ft0measurements combined with E g data and an inde-pendent estimate of ΔE F (Nozik 1978).pH Dependence of band edges at semiconductor/electro-lyte interfacesFor semiconducting metal oxides, U ft varies with pH fol-lowing a linear relation known as the Nernstian relation (But-ler and Ginley 1978; Halouani and Deschavres 1982; Matsumoto et al. 1989; Morrison 1990):U fb = U fb0 + 2.303R T/(pH ZPC – pH)F(4) where R is the gas constant, T is temperature, and F is the Fara-day constant. At 25 °C and 1 atm, the Nernstian relation leads to a variation of 0.059 V/pH (Fig. 2a). It is generally accepted that the Nernstian dependence indicates that H+ and OH– are potential determining ions (PDI) adsorbed on the solid surface within the Helmholtz layer (Butler and Ginley 1978).For metal-sulfide semiconductors, the pH dependence of U fb appears more complicated than that for metal-oxides, and has not been as thoroughly studied. One unresolved issue is which ions are PDIs. If ions other than H+ and OH– are PDIs, the specific sorption of these ions can affect V H. For example, Ginley and Butler (1978) showed that dissolved sulfide (H2S and HS–) is a PDI for CdS, whereas our research has shown that dissolved sulfide and dissolved ferrous iron are PDIs for iron sulfides (Bebié et al. 1998; Dekkers and Schoonen 1994). For CdS, the flat band shows a variation in pH dependence from 0 to 59 mV/pH (Ginley and Butler 1978), with the slope depending on the concentrations of metal ions and dissolved sulfide ions. Minoura et al. (1977) reported that U ft varies with crystal face. For FeS2 and ZnS, however, the pH dependence is reported to be consistent with the Nernstian relation (Chen et al. 1991; Fan et al. 1983). We speculate that U ft for metal sul-fide semiconductors may follow the Nernstian pH dependence in aqueous solutions with low concentrations of metal ions and/ or dissolved sulfide, but that the pH dependence will switch to non-Nernstian behavior when specific sorption of metal ions and sulfide becomes important. More research in the surface chemistry of metal sulfides is needed to resolve the apparent inconsistencies highlighted above.The pH-E H relationship defined by the Nernstian slope is characterized by a constant fugacity of hydrogen, as illustrated in Figure 2b:log.fE FTHH2pHR=−−222303(5a) orlog f peH222=−−pH(5b) The constant hydrogen fugacity defined by the Equations 5a or 5b indicates a constant redox state for a linear combination of pH and E H in the Nernstian slope. On a pH-E H diagram, it is the linear combination of E H(or pe) and pH that describes the re-dox state of an aqueous redox system and not E H (or pe) alone; see also Anderson and Crerar (1993). Hence, we believe that the pH dependence of semiconductor flatband potential given by the Nernstian slope is consistent with a constant reducingF IGURE 2. pH dependence of the conduction band edge and valence band edge of pyrite in an aqueous electrolyte solution described by (a), a pH-Eh diagram, and (b) a pH-log f H2diagram. The E C and E V follow the Nernstian relation, which has a variation of 0.059V/pH at 25 °C at 1atm, and lies parallel to the water stability limits.XU AND SCHOONEN: SEMICONDUCTING OXIDES AND SULFIDES547 (oxidizing) power of the (photo)electrons (holes) in a semi-conductor. It is noteworthy that the flat-band potentials forsemiconductors are parallel to the stability limits of water inan E H-pH diagram if they follow the Nernstian behavior. Iflog f H2 is used as the parameter defining the redox conditionof a semiconductor/electrolyte system, as shown in Figure 2b, both the band edges and water stability limits are inde-pendent of pH. Hence, a pH-E H pair can be replaced with a single variable, the fugacity of hydrogen, to define the redox condition of the system.Temperature and pressure dependence of band edge energiesBecause semiconductors can catalyze non-photoreactions as well as photoreactions, their catalytic activity may extend to subsurface geochemical processes, such as in hydrothermal systems. To evaluate the potential of semiconductors as cata-lysts in subsurface environments, it is important to understand the effects of temperature and pressure on the band energies.In contrast to aqueous redox couples, which often show a considerable temperature dependence for E redox, the electronic structure of a semiconductor undergoes little change with tem-perature and pressure provided that no phase transition occurs. For example, the measured bandgap changes over temperature (d E g/d T) for PbS and ZnO range from +4 × 10–4 eV/K to –9.5 ×10–4 eV/K, respectively (Gonzalez et al. 1995). For most semi-conductors, the variation of the bandgap with pressure is also very small in the pressure ranges of interest. The experimental determined variation rates (d E g/d P) are in the order of 0.01–0.1 eV/GPa (Gonzalez et al. 1995). Therefore, the reducing power of a (photo)electron and the oxidation power of a hole are essentially constant with temperature and pressure, unless the solid itself undergoes a phase transition and changes the electronic structure altogether.Although temperature and pressure have negligible effect on the bulk band structure of semiconductors in the T-P ranges of interest, they may have a more pronounced effect on inter-facial energetics. As shown in Equation 4 the Nernstian slope is temperature dependent. Perhaps more importantly, the pH ZPC of semiconductors is also temperature dependent. Schoonen (1994) estimated pH ZPC values for several metal oxides up to 350 °C based on extrapolation of low-temperature (<95 °C) experimental data. These calculations indicate that pH ZPC values shift down by 1 to 2 pH units as temperature rises from 25 °C to 200 to 300 °C, but beyond 200 to 300 °C the pH ZPC shifts back to higher values. This general trend was confirmed experimentally for rutile up to 250 °C by Machesky et al. (1994). A 2-pH-unit decrease in pH ZPC between 25 and 250 °C would result in a shift of interfacial band edge energies to a higher energy level (with respect to vacuum) by about 0.25 eV. However, the exact tem-perature dependence of pH ZPC of semiconductors is largely un-known and more experimental investigations are needed.B AND EDGES OF SEMICONDUCTING OXIDE ANDSULFIDE MINERALSThe conduction band edges and bandgaps for common ox-ide and sulfide semiconducting minerals are given in Tables 1 and 2. This compilation includes data obtained from two dif-ferent methods: photo-electrochemical measurements, and empirical calculation based on electronegativity of constituent atoms. A comparison of experimental and empirically calcu-lated conduction band edges is shown in Figure 3. The trends in the energy positions of band edges for metal oxides and metal sulfides will be discussed below separately. Determination methodsBand edges can be derived experimentally from the flatband potential measurement using various (photo)electrochemical techniques. The classic method for flatband potential determi-nation, which is still considered as the most reliable technique, is the Schottky-Mott method (Nozik 1978). Another common method is the determination of anodic photocurrent onset po-tential by evaluating the photocurrent-potential plot (Arico et al. 1990; Butler 1977). More recently, the photocurrent-volt-age measurements have been extensively used in semiconduc-tor particle systems with electrochemical charge-collection techniques. The advantage of this technique is that the varia-tion of the steady-state photocurrent can be measured as a func-tion of pH. This allows for the estimation of interfacial energetics of the particulate system (Chen et al. 1991; Leland and Bard 1987). It is noteworthy that colloidal particles have a larger bandgap than large crystals due to the quantum size ef-fect, which results in a higher energy position of the conduc-tion band edge (Ward and Bard 1982).In the last two decades, quantitative quantum mechanical calculations have been carried out for a large number ofsemiconductor minerals (Folkerts et al. 1987; Huang and ChingF IGURE 3. Correlation between the empirically calculated conduction band edge energy and the measured flatband potential at pH ZPC for semiconducting metal oxide and sulfide minerals in absolute vacuum scale. The sources of the experimental data are given in the Tables 1 and 2.XU AND SCHOONEN: SEMICONDUCTING OXIDES AND SULFIDES5481993; Lauer et al. 1984; Santoni et al. 1992; Schroer et al. 1993;Temmerman et al. 1993). In principle, band energies can be derived from these calculations. In many studies, however, band edges are presented with the Fermi level as an arbitrary refer-ence point. Hence, although detailed electronic structures of valence and conduction band have been derived, absolute en-ergies of band edges with respect to vacuum cannot be obtained from these calculations. In the few reports in which the abso-T ABLE 1. Absolute electronegativity (x ), band gap (E g ), energy levels of caluculated conduction band edge (E CB ) and flatband potentialat pH ZPC (U ft 0) with respect to Absolute Vacuum Scale (AVS), and measured or estimated pH ZPC for semiconducting metal oxide mineralsMineralx E g E CB U ft0PH ZPC Ref. for Ref. foreV eV eV eV E g ,U ft 0pH ZPCAg 2O 5.29 1.20–4.6911.20a aAlTiO 35.44 3.60–3.648.23b BaTiO 3 5.12 3.30–4.58–4.219.00c aBi 2O 36.23 2.80–4.83–4.82 6.20d CdO 5.71 2.20–4.61–4.6211.60c aCdFe 2O 45.83 2.30–4.68–4.897.22c Ce 2O 35.20 2.40–4.008.85i CoO 5.69 2.60–4.397.59bCoTiO 35.76 2.25–4.647.41k Cr 2O 35.68 3.50–3.938.10b a CuO 5.81 1.70–4.96–4.899.50c aCu 2O5.32 2.20–4.228.53e CuTiO 35.81 2.99–4.327.29k FeO 5.53 2.40–4.338.00bFe 2O 35.88 2.20–4.78–4.698.60c a Fe 3O 45.780.10–5.736.50f a FeOOH 6.38 2.60–5.089.70g lFeTiO 35.69 2.80–4.29–4.566.30a a Ga 2O 35.35 4.80–2.958.47b HgO6.08 1.90–5.137.30b a Hg 2Nb 2O 7 6.21 1.80–5.31–5.05 6.25hHg 2Ta 2O 76.24 1.80–5.34 6.17h In 2O 35.28 2.80–3.888.64b KNbO 3 5.29 3.30–3.648.62bKTaO 35.32 3.50–3.57–3.708.55h La 2O 35.28 5.50–2.5310.40i m LaTi 2O 7 5.90 4.00–3.907.06bLiNbO 35.52 3.50–3.778.02b LiTaO 35.55 4.00–3.557.94b MgTiO 3 5.60 3.70–3.757.81b MnO 5.29 3.60–3.498.61bMnO 25.950.25–5.83 4.60j l MnTiO 3 5.59 3.10–4.047.83bNb 2O 56.29 3.40–4.59–4.16 6.06h Nd 2O 35.21 4.70–2.878.81i NiO 5.75 3.50–4.0010.30b a NiTiO 3 5.79 2.18–4.707.34d PbO 5.42 2.80–4.02–4.468.29d PbFe 12O 19 5.85 2.30–4.70–5.207.17c PdO 5.79 1.00–5.297.34bPr 2O 35.19 3.90–3.248.87i Sb 2O 36.32 3.00–4.82 5.98bSm 2O 35.26 4.40–3.078.69i SnO 5.69 4.20–3.597.59b SnO 26.25 3.50–4.50–4.55 4.30d aSrTiO 34.94 3.40–3.24–3.618.60c a Ta 2O 56.33 4.00–4.33–3.89 2.90a a Tb 2O 3 5.33 3.80–3.448.50iTiO 25.81 3.20–4.21–4.16 5.80k a Tl 2O 35.35 1.60–4.558.47b V 2O 56.10 2.80–4.70–4.84 6.54cWO 36.59 2.70–5.24–5.290.43a a Yb2O 35.47 4.90–3.028.15i YFeO 3 5.60 2.60–4.30–4.607.81a ZnO 5.79 3.20–4.19–3.918.80d aZnTiO 35.80 3.06–4.277.31k ZrO 2 5.91 5.00–3.41–3.086.70a aNotes: a = Butler and Ginley 1978; b = Quarto et al. 1997; c = Nozik 1978; d = Halouani and Deschavers 1982; e = Rodriguez et al. 1998; f = Zhang and Satpathy 1991; g = Brezonik 1993; h = Kung et al. 1977; i = Shelykh et al. 1996; j = Shuey 1975; k = Oosawa et al. 1989; l = Sverjensky 1994,m = Yoon et al. 1979.lute band energies were given, the discrepancies between cal-culated and measured band edges were as large as a few eV (Bullett 1982; Caldas et al. 1984; Fazzio et al. 1984; Tian and Shen 1989).In a much simpler approach, Butler and Ginley (1978) pro-posed that band edges at the semiconductor/electrolyte inter-face can be predicted from the electronegativity of the semiconductor. This method was based on Equations 4 and 5。
拉脊山口蛇绿混杂岩中辉绿岩的地球化学特征及SHＲIMP锆石U-Pb年龄*付长垒1闫臻1＊＊郭现轻2牛漫兰3夏文静3王宗起2李继亮4FU ChangLei1，YAN Zhen1＊＊，GUO XianQing2，NIU ManLan3，XIA WenJing3，WANG ZongQi2and LI JiLiang41.中国地质科学院地质研究所，大陆构造与动力学国家重点实验室，北京1000372.中国地质科学院矿产资源研究所，北京1000373.合肥工业大学资源与环境工程学院，合肥2300094.中国科学院地质与地球物理研究所，北京1000291.State Key Laboratory of Continental Tectonics and Dynamics，Institute of Geology，Chinese Academy of Geological Sciences，Beijing100037，China2.Institute of MineralＲesources，Chinese Academy of Geological Sciences，Beijing100037，China3.Department ofＲesources and Environment，Hefei University of Technology，Hefei230009，China4.Institute of Geology and Geophysics，Chinese Academy of Sciences，Beijing100029，China2013-01-30收稿，2013-06-24改回.Fu CL，Yan Z，Guo XQ，Niu ML，Xia WJ，Wang ZQ and Li JL.2014.Geochemistry and SHＲIMP zircon U-Pb age of diabases in the Lajishankou ophiolitic mélange，South Qilian terrane.Acta Petrologica Sinica，30（6）：1695－1706Abstract The Lajishankou ophiolitic mélange，which is an important ingredient of the ophiolitic mélange between the Central and the South Qilian terranes，contains varities of lithological units showing tectonic relationship between them.Diabases in this mélange occur as blocks and dykes respectively.The formers have SiO2contents of49.80% 50.13%，MgO contents of5.43% 5.64%，FeO T contents of10.96% 11.52%and relatively higher TiO2contents of2.38% 2.62%；the laters have SiO2contents of43.41%45.74%，MgO contents of9.04% 10.64%，FeO T contents of8.39% 9.96%and low TiO2contents of0.89% 1.02%.Theybelong to tholeiitic rocks.The diabase blocks have high totalＲEE contents（135.4ˑ10－6 150.9ˑ10－6）and（La/Yb）Nratios （3.51 4.03）with right-inclinedＲEE patterns and enrichment in large ion lithophile elements（includingＲb，Ba，K，Sr）and high field strength elements（including Th，Nb，Ta，Zr，Hf，Ti），showing typical features of OIB.However，the diabase dykes have lowtotalＲEE contents（36.10ˑ10－6 43.72ˑ10－6）and（La/Yb）Nratios（1.12 1.20）and flatＲEE patterns，indicating similar character of MOＲB.In addition，diabase blocks and dykes are lack of negative Nb，Ta and Ti anomalies.SHＲIMP zircon U-Pb dating of diabase block yields a weighted mean206Pb/238U age of491.0ʃ5.1Ma，representing the age of crystallization.These characters suggest that the mafic diabases in the Lajishankou ophiolitic mélange were probably formed in ocean island/seamount and mid-ocean ridge environments，which were mixed with other lithological units during the northward subduction-accretion of the Proto-Tethys Ocean.Key words Diabase；Ocean island/Seamount；Mid-ocean ridge；Ophiolitic mélange；Lajishan Mountain摘要拉脊山口蛇绿混杂岩是分布于中祁连和南祁连构造带之间蛇绿混杂带的重要组成部分。
