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材料化学英文Materials Chemistry。
Materials chemistry is a branch of chemistry that focuses on the study of the properties and applications of materials. It involves the synthesis, characterization, and manipulation of materials to create new and improved products. The field of materials chemistry is interdisciplinary, drawing on principles from chemistry, physics, and engineering to understand and control the behavior of materials.One of the key areas of materials chemistry is the development of new materials with specific properties for various applications. This involves the design and synthesis of materials with tailored properties, such as strength, conductivity, or optical properties. For example, materials chemists may work to develop new materials for use in electronics, energy storage, or biomedical applications.In addition to creating new materials, materials chemistry also focuses on understanding the structure-property relationships of existing materials. By studying the atomic and molecular structure of materials, researchers can gain insight into their properties and behavior. This knowledge can then be used to develop strategies for improving the performance of materials or creating new materials with enhanced properties.Materials chemistry also plays a crucial role in the development of sustainable and environmentally friendly materials. With the growing concern over the environmental impact of traditional materials and manufacturing processes, materials chemists are working to develop new materials and processes that are more sustainable. This may involve the use of renewable resources, the development of biodegradable materials, or the design of materials with reduced energy and resource requirements.Another important aspect of materials chemistry is the study of materials under extreme conditions, such as high temperatures, pressures, or radiation. Understandinghow materials behave under these conditions is essential for applications in fields such as aerospace, nuclear energy, and high-performance materials.In conclusion, materials chemistry is a diverse and dynamic field that plays a critical role in the development of new materials and the improvement of existing materials. By understanding the structure-property relationships of materials and developing new materials with tailored properties, materials chemists are driving innovation and addressing important challenges in areas such as energy, healthcare, and the environment. As the field continues to evolve, materials chemistry will undoubtedly play an increasingly important role in shaping the future of technology and society.。
journal of materials and science technology简介-回复Journal of Materials and Science Technology (JMST) is a renowned scientific journal in the field of materials science and technology. With its inception in 1985, JMST has been a reputable platform for researchers and scientists to publish their groundbreaking research on various aspects of materials science. This journal focuses on the synthesis, characterization, and applications of different materials, aiming to provide valuable insights into the world of materials for the scientific community.One of the fundamental aspects of JMST is its emphasis on the synthesis of materials. Synthesis is the process of creating new materials with specific properties by combining or altering existing materials. This involves a deep understanding of thestructure-property relationship, as researchers need to control the structure at different scales to achieve desired properties. In JMST, researchers have published numerous articles outlining their novel approaches to synthesis, such as chemical vapor deposition, sol-gel methods, and nanostructuring techniques. These contributions have enhanced our knowledge and expanded our capabilities in creating advanced materials with tailored properties.Characterization is another crucial focus area of JMST. After synthesizing new materials, scientists need to thoroughly investigate and analyze their properties. Characterization techniques enable researchers to understand the structure, composition, and physical, chemical, and mechanical properties of materials. Journal articles in JMST often present innovative characterization methods, including scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and spectroscopy techniques. By describing advanced characterization techniques and their applications, the journal plays a vital role in advancing our understanding of materials at the atomic and microstructural levels.The applications of materials are a significant aspect covered by JMST. Materials science is a vast field with diverse applications, including electronics, energy storage, sensors, healthcare, and aerospace, among others. Researchers publishing in JMST often demonstrate the practical use of materials by incorporating them into various devices or systems. For example, articles have been published on the development of efficient solar cells, lightweight and high-strength materials for aerospace applications, andbiocompatible materials for tissue engineering. The journal serves as a bridge between academia and industry, promoting the transfer of knowledge from the laboratory to real-world applications.In addition to research articles, JMST also features critical reviews and perspectives from leading experts in the field. These articles provide a comprehensive overview of the current state of research in specific areas of materials science and offer valuable insights into future directions and challenges. By providing a platform for experts to share their knowledge and opinions, JMST contributes to the formation of a strong scientific community and fosters collaborations between researchers.JMST follows a rigorous peer-review process to ensure the quality and integrity of published articles. This process involves subjecting submitted manuscripts to evaluation by independent experts in the field, who assess the scientific soundness, novelty, and significance of the research. This stringent review process maintains the journal's reputation as a reliable source of high-quality research.In conclusion, the Journal of Materials and Science Technology (JMST) is a leading scientific journal that focuses on the synthesis,characterization, and applications of materials. With its comprehensive coverage of research in the field, JMST plays an essential role in advancing our understanding of materials science and technology. By publishing innovative research, critical reviews, and expert perspectives, JMST contributes to the growth of the scientific community while facilitating the transfer of knowledge from the laboratory to real-world applications.。
三联吡啶的合成及其金属配合物研究进展1 前言配位化学早期是在无机化学基础上发展起来的一门边沿学科，如今，配位化学在有机化学与无机化学的交叉领域受到化学家门广泛的关注。
有机-金属配合物在气体分离、选择性催化、药物运输和生物成像等方面都有潜在的应用前景，因此日益成为化学研究的热点领域[1-4]。
多联吡啶金属配合物在现代配位化学中占据着不可或缺的位置，常见的多联吡啶配体包括2,2'-二联吡啶（bpy）和2,2':6',2''-三联吡啶（tpy）（Fig. 1），Hosseini就把bpy 称为“最广泛应用的配体”[5]，与其类似的具有三配位点的tpy的合成及其金属配合物的研究同样是化学家们研究的热点[6-8]。
Fig 1.三联吡啶的三个吡啶环形成一个大的共轭体系，具有很强的σ给电子能力，配合物中存在金属到配体的d一π*反馈成键作用，因而能与大多数金属离子均形成稳定结构的配合物。
然而，三联吡啶金属络合物的特殊的氧化还原和光物理性质受其取代基电子效应的影响。
因此，通过引入不同的取代基，三联吡啶金属络合物可用于荧光发光装置以及光电开关等光化学领域[9-10]。
在临床医学和生物化学领域中，不管是有色金属的测定还是作为DNA的螯合试剂，三联吡啶衍生物都具有非常广泛的应用前景[11-12]。
2 三联吡啶的合成研究进展正因为三联吡啶在许多领域都具有潜在的应用价值，所以对其合成方法的研究十分重要。
三联吡啶的合成由来已久，早在1932年，Morgan就首次用吡啶在FeCl3存在下反应合成分离出了三联吡啶，并发现了三联吡啶与Fe(Ⅱ)的配合物[13]。
目前，合成三联吡啶的方法主要有成环法和交叉偶联法两种。
2.1 成环法成环法中最常用的反应是Kröhnke缩合反应（Scheme 1）[14]，首先2-乙酰基吡啶溴化得到化合物2，2与吡啶反应生成吡啶溴盐3，3与α,β-不饱和酮4进行Michael加成反应得到二酮5，在醋酸铵存在下进而关环得到三联吡啶。
pH-Responsive Biodegradable Polymers for Intracellular Drug DeliveryA。
Proposed area of researchThe aim of this proposed PhD project is to develop and evaluate pH responsive, endosomolytic polymers for efficient intracellular delivery of biological drug payloads. There is a need to better understand the mechanisms of entry into the cell cytoplasm and nucleus in order to design optimal delivery systems for biological molecules. On the one hand，this would open up significant opportunities to deliver potent drug payloads against intracellular targets to positively impact human health。
In addition the project aims to develop a more general understanding of the rules governing the uptake of biological molecules into cells。
This project proposes to investigate the use of synthetic， biodegradable polymers for intracellular delivery of drug payloads （including siRNA，therapeutic peptide and antibody) against a well-validated intracellular drug target, such as Bcl—2. The novel pH-responsive polymers have been desig ned by Dr Rongjun Chen’s Lab to mimic the activity of viruses, both in their cell entry and endosomal escape mechanisms. Using cancer cell lines （Jurkat or HL—60 cells) as a model system， the polymers would be tested with a variety of different biological payloads in a quantitative comparison of their ability to enter the cell and trigger apoptosis and subsequently cell death。
物理学院导师简介硕士教育材料物理与化学（硕士）学科、专业培养目标:具有坚实的材料物理与化学理论基础和系统的专门知识。
了解本学科的发展动向。
掌握材料结构及其物理性质和化学性质研究的基本方法和技术。
熟练掌握运用一门外国语和计算机。
有较强的知识更新能力和熟练的实验技能，掌握有关先进的材料制备技术和先进测试仪器的使用和结果分析。
具有在材料或器件的研究开发单位、高等院校或生产部门工作的能力。
主要课程: 量子力学（Ⅱ）、固体物理（Ⅱ）、高等激光技术、纳米材料与纳米技术、群论、固态电子学、激光光谱学、半导体薄膜技术、新型复合材料理论与应用、光信息存储材料、光电材料及器件物理、计算物理、材料科学前沿、激光与物质相互作用、材料化学、Matlab在工程中的应用、X射线衍射与电子显微分析。
物理电子学（硕士）学科、专业培养目标:物理电子学是近代物理学、电子学、光学、光电子学、量子电子学及相关技术的交叉学科，主要在电子工程和信息科学技术领域内进行基础和应用研究。
硕士生通过三年左右时间的学习学生应具有较坚实的数学、物理基础知识，常据本学科坚实的理论基础及系统的专门知识；掌据相关的实验技术及计算机技术。
较为熟练地掌据一门外国语，能阅读本专业的外文资料。
具有从事科学研究工作及独立从事专门技术工作的能力，以及严谨求实的科学态度和工作作风；能胜任研究机构、高等院校和产业部门有关方面儒教学、研究、工程、开发及管理工作。
主要课程: 光电子学与激光器件、微电子器件原理与应用、固体物理学Ⅱ、激光光谱学、量子力学、薄膜物理技术、声学基础、物质结构、Matlab在工程中的应用、半导体物理学、光通信技术与器件、计算物理学、物理电子技术实验等导师风采材料物理与化学：王银海朱燕娟唐新桂易双萍张欣罗莉赵韦人刘秋香物理电子学：胡义华吴福根周金运钟韶苏成悦潘永雄陈丽伍春燕王银海教授广东工业大学物理与光电工程学院副院长教授，博士,硕士生导师。
1964年3月出生，2001年在中国科学技术大学获博士学位，2002－2004年中国科学院固体物理研究所博士后。
关于聚酰亚胺方面的专著
聚酰亚胺（PI）是一种高性能聚合物材料，具有优异的热稳定性、机械性能和化学稳定性，因此在航空航天、电子、汽车等领域具有广泛的应用。
关于聚酰亚胺的专著有很多，其中一些重要的专著包括《Polyimides: Fundamentals and Applications》（作者，Sunggyu Lee）、《Handbook of Thermoset Plastics》（作者，Sidney H. Goodman）、《High Temperature Polymer Blends》（作者，Raj Das）、《Polyimides and Other High Temperature Polymers: Synthesis, Characterization and Applications》（作者，Kishor Kumar）。
这些专著涵盖了聚酰亚胺的基础知识、合成方法、性能表征以及应用领域等方面的内容。
在这些专著中，读者可以了解聚酰亚胺的化学结构、热性能、力学性能、耐化学腐蚀性能等基本特性，以及聚酰亚胺在航空航天材料、电子材料、膜材料、复合材料等方面的具体应用。
此外，这些专著还介绍了聚酰亚胺与其他高温聚合物的混合物、共混物的研究进展，以及在材料设计、加工工艺等方面的最新成果。
总的来说，这些专著为学术界和工程技术人员提供了关于聚酰亚胺的全面而深入的资料，对于从事相关领域的科研人员、工程师
以及对聚酰亚胺材料感兴趣的读者来说，都具有很高的参考价值。
希望这些专著能够帮助你更深入地了解聚酰亚胺这一重要材料。
Academic Phase BankWriting IntroductionsThere are many ways to introduce an academic essay or assignment. Most academic writers, however, appear to do one or more of the following in their introductions:∙establish the context, background and/or importance of the topic∙indicate a problem, controversy or a gap in the field of study∙define the topic or key terms∙state of the purpose of the essay/writing∙provide an overview of the coverage and/or structure of the writingExamples of phrases which are commonly employed to realise these functions are listed below. Note that there may be a certain amount of overlap between some of the categories under which the phrases are listed.Introductory sections for research dissertations, are normally much more complex than this and, as well as the elements above, may include the following: a synopsis of key literature/current state of knowledge, synopsis of methods, lists of research questions or hypotheses to be tested, significance of the study, recognition of the limitations of the study, reasons for personal interest in the topic.Establishing the importance of the topic:One of the most significant current discussions in legal and moral philosophy is ......It is becoming increasingly difficult to ignore the .....X is the leading cause of death in western industrialised countries.X is a common disorder characterised by ......X is an important component in the climate system, and plays a key role in Y.In the new global economy, X has become a central issue for ......In the history of development economics, X has been thought of as a key factor in .......Xs are one of the most widely used groups of antibacterial agents and ......Xs are the most potent anti-inflammatory agents known.X is a major public health problem, and the cause of about 4% of the global burden of disease. X is an increasingly important area in applied linguistics.Central to the entire discipline of X is the concept of .......X is at the heart of our understanding of ......Establishing the importance of the topic (time frame given):Recent developments in X have heightened the need for ......In recent years, there has been an increasing interest in ......Recent developments in the field of X have led to a renewed interest in ......Recently, researchers have shown an increased interest in ......The past decade has seen the rapid development of X in many .......The past thirty years have seen increasingly rapid advances in the field of......Over the past century there has been a dramatic increase in ......One of the most important events of the 1970s was ......Traditionally, X s have subscribed to the belief that ......X proved an important literary genre in the early Y community.The changes experienced by X s over the past decade remain unprecedented.Xs are one of the most widely used groups of antibacterial agents and have been extensivel y used for decades to .......Highlighting a problem in the field of study:However, these rapid changes are having a serious effect ......However, a major problem with this kind of application is ......Lack of X has existed as a health problem for many years.Despite its safety and efficacy, X suffers from several major drawbacks:However, research has consistently shown that first year students have not attained an adequate understanding of ......There is increasing concern that some X s are being disadvantaged ......Despite its long clinical success, X has a number of problems in use.Questions have been raised about the safety of prolonged use of ......Highlighting a controversy in the field of study:To date there has been little agreement on what ......More recently, literature has emerged that offers contradictory findings about .....One observer has already drawn attention to the paradox in ......In many X s a debate is taking place between Ys and Zs concerning ......The controversy about scientific evidence for X has raged unabated for over a century. Debate continues about the best strategies for the management of ……This concept has recently been challenged by ……. studies demonstrating …….One of the most significant current discussions in legal and moral philosophy is ......One observer has already drawn attention to the paradox in ......In many X s a debate is taking place between Ys and Zs concerning ......The controversy about scientific evidence for X has raged unabated for over a century. Questions have been raised about the safety of prolonged use of ......The issue of X has been a controversial and much disputed subject within the field of ....... The issue has grown in importance in light of recent ......One major theoretical issue that has dominated the field for many years concerns ......One major issue in early X research concerned.......Highlighting a knowledge gap in the field of study (for research):So far, however, there has been little discussion about ......However, far too little attention has been paid to ......Most studies in X have only been carried out in a small number of areas.The research to date has tended to focus on X rather than Y.In addition, no research has been found that surveyed .......So far this method has only been applied to ......Several studies have produced estimates of X (Smith, 2002; Jones, 2003), but there is still insufficient data for .....However, there have been no controlled studies which compare differences in ......The experimental data are rather controversial, and there is no general agreement about ...... However, there is no reliable evidence that ......X's analysis does not take account of ..... nor does he examine ......Focus, aim, argument:This paper will focus on/examine/give an account of ......This essay seeks to remedy these problems by analyisng the literature of ......The objectives of this research are to determine whether ......This paper seeks to address the following questions:This essay critically examines/discusses/traces ......The purpose of this paper is to review recent research into the ......This paper will review the research conducted on ......This chapter reviews the literature concerning the usefulness of using ......The aim of this paper is to determine/examine ......The aim of this study was to evaluate and validate .....In this paper I argue that .....In the pages that follow, it will be argued that ……This paper attempts to show that ......In this essay, I attempt to defend the view that ......Outline of structure:The main questions/issues addressed in this paper are: a), b and c).This paper has been divided into four parts. The first part deals with ......The essay has been organised in the following way.This paper first gives a brief overview of the recent history of X.This paper reviews the evidence for .....This paper begins by ...... It will then go on to ......The first section of this paper will examine ......Finally, .......Chapter 2 begins by laying out the theoretical dimensions of the research, and looks athow ......Chapter 3 describes the design, synthesis, characterization and evaluation of ......The last chapter assesses the ......Explaining KeywordsWhile a variety of definitions of the term X have been suggested, this paper will use the definition first suggested by Smith (1968) who saw it as .......Throughout this paper the term X will refer to/will be used to refer to .......In this article the acronym/abbreviation XYZ will be used.Referring to LiteratureOne important characteristic of academic writing is that all the sources of information that the writer has used need to be indicated, not just as a bibliography or list of references, but also in or alongside the text. In some cases the source will be the main subject of the sentence, in others the sources may be mentioned parenthetically (in brackets) or via a notation system (eg. footnotes). The more common verbs and verb phrases used in academic writing for referring to sources are given below. Note that different referencing systems are used in different disciplines. In the examples, the Harvard in-text referencing system has been used. Also note that the "author as subject" style is less common in the sciences."Ideally, your review should be evaluative and critical of the studies which have a particular bearing on your own. For example, you may think a particular study did not investigate some necessary aspect of the area, or that the authors failed to notice some problem with their results."Taken from the Manchester Good Practice Guide:/goodpractice/General descriptions of the relevant literature:A considerable amount of literature has been published on X. These studies ...... There is a large volume of published studies describing the role of ……The first serious discussions and analyses of X emerged during the 1970s with ...... The generalisability of much published research on this issue is problematic.What we know about X is largely based upon empirical studies that investigatehow ......During the past 30 years much more information has become available on ......In recent years, there has been an increasing amount of literature on .......A large and growing body of literature has investigated ......General reference to previous research/scholarly activity (usually more than one author)Many historians have argued that ...... (eg. Jones, 1987; Johnson, 1990; Smith, 1994) Numerous studies have attempted to explain ..... (for example, Smith , 1996; Kelly, 1998; Johnson, 2002)Recent evidence suggests that ....... (Smith, 1996; Jones 1999; Johnson, 2001) Recently, in vitro studies have show n that T.thermophylus EFTu can ...... (Patel et al., 1997; Jones et al., 1998).Surveys such as that conducted by Smith (1988) have show n that ......Several attempts have been made to ....... (Smith, 1996; Jones 1999; Johnson, 2001) Several studies have revealed that it is not just X that acts on ...... (Smith, 1996; Jones .......Several biographies of Harris have been published. Smith presents an ........ account, whilst Jones .....Several studies investigating X have been carried out on ......Data from several sources have identified the increased morbidity and mortality associated with obesityPrevious studies have reported ...... (Smith, 1985; Jones, 1987; Johnson, 1992). Previous research findings into X have been inconsistent and contradictory (Smith, 1996; Jones 1999, ......A number of studies have found that ...... (Smith , 2003; Jones, 2004).Twenty cohort study analyses have examined the relationship between .......At least 152 case-control studies worldwide have examined the relationship between......Other studies have considered the relationship ......The relationship between X and Y has been widely investigated (Smith, 1985; Jones, 1987, .......The causes of X have been widely investigated (Jones, 1987; Johnson, 1990; Smith, 1994).The geology of X has been addressed in several smallscale investigations and .......Xs have been identified as major contributing factors for the decline of many species (1).X has also been shown to reverse the anti-inflammatory effects of glucocorticoids in murine-induced arthritis (11).I t has been suggested that levels of X are independent of the size of the Y (Smith et al., 1995)It has conclusively been show n that X and Y increase Z (Smith et al., 1999; Jones, 2001 ......It has been demonstrated that a high intake of X results in damage to ...... (Smith, 1998; ......Reference to current state of knowledgeA relationship exists between an individual's working memory and their ability to ...... (Jones et al.,1998).GM varieties of maize are able to cross-pollinate with non-GM varieties (Smith, 1998; Jones, 1999).There is an unambiguous relationship between spending on education and economic development (Rao, 1998).X is one of the most intense reactions following CHD (Lane, 2003).MIF has been found to oppose the anti-infammatory actions of X on Y (Alourfi, 2004).Reference to single investigations in the past: researcher(s) as sentence subjectWang et al. (2004) have recently developed a methodology for the selective introduction of ......Reference to single investigations or publications in the past: time frame prominentIn 1975, Smith et al. published a paper in which they described .....In 1990 Patel et al. demonstrated that replacement of H2O with heavy water led to ...... Thirty years later, Smith (1974) reported three cases of Candida Albicans which ....... In the 1950s Gunnar Myrdal pointed to some of the ways in which …………… (Myrdal, 1957)In 1981, Smith and co workers demonstrated that X induced in vitro resistance to ....... In 1990, El-Guerrouj et al. reported a new and convenient synthetic procedure to obtain ......In 1984 Jones et al. made several amino acid esters of X and evaluated them as water-soluble pro-drugs.Reference to single publication: no time frameSmith has written the most complete synthesis to date of ......Reference to single investigations in the past: investigation prominentPreliminary work on X was undertaken by AbdulKarim (1992).The first systematic study of X was reported by Patel et al. in 1986.The study of the structural behavior of X was first carried out by Rao et al. (1986)...... Analysis of the genes involved in X was first carried out by Smith et al (1983).A recent study by Smith and Jones (2001) involved ......A longitiudinal study of X by Smith (2002) reports that ......A small scale study by Smith (2002) reaches different conclusions, finding no increase in ......Smith's cross-country analysis (2002) show ed that ......Smith's comparative study (2002) found that ......Detailed examination of X by Smith and Patel (1961) showed that ......In another major study, Zhao (1974) found that just over half of the ......In a radomised controlled study of X, Smith (2004) reported that ......In a large longitudinal study, Boucahy et al. 2004) investigated the incidence of X in Y.Reference to single investigations in the past: research topic as subjectClassical conditioning was first demonstrated experimentally by Pavlov (Smith, 2002). In his seminal study ......The electronic spectroscopy of X was first studied by Smith and Douglas 1 in 1970 The acid-catalyzed condensation reaction between X and Y w as first reported by Baeyer in 1872X formed the central focus of a study by Smith (2002) in which the author found ...... X was originally isolated from Y in a soil sample from ...... (Wang et al., 1952).The way in which the X gene is regulated was studied extensively by Ho and colleagues (Ho et al. 1995 and 1998).To determine the effects of X, Zhao et al (2005) compared ......Reference to what other writers do in their text (author as subject)Smith (2003) identifies poor food, bad housing, inadequate hygiene and large families as the major causes of ......Rao (2003) lists three reasons why the English language has become so dominant. These are: ......Smith (2003) traces the development of Japanese history and philosophy during the 19th century.Jones(2003) provides in-depth analysis of the work of Aristotle showing its relevance to contemporary times.Smith (2003) draw s our attention to distinctive categories of motivational beliefs often observed in .......Smith (2003) defines evidence based medicine as the conscious, explicit and judicious use of .....Rao (2003) highlights the need to break the link between economic growth and transport growth ......Smith (2003) discusses the challenges and strategies for facilitating andpromoting ......Toh (2003) mentions the special situation of Singapore as an example of .....Smith (2003) questions whether mainstream schools are the best environment for ...... Smith (2003) considers whether countries work well on cross-border issues suchas ......Smith (2003) uses examples of these various techniques as evidence that ......Some analysts (eg Carnoy, 2002) have attempted to draw fine distinctionsbetween ........Other authors ( see Harbison, 2003; Kaplan, 2004) question the usefulness of such an approach.Reference to other writers' ideas (author as subject)According to Smith (2003), preventative medicine is far more cost effective, and therefore better adapted to the developing world.This view is supported by Jones (2000) who writes ......Smith argues that her data support O'Brien's (1988) view that ......As Smith reminds us, ..............Elsewhere, Smith has argued that ......Some ways of introducing quotationsIn the final part of the Theses, Marx writes: "Philosophers have hitherto only interpreted the world in various ways; the point ......."Sachs concludes: "The idea of development stands today like a ruin in the intellectual landscape…" (Sachs, 1992a: 156).As Smith argues: "In the past, the purpose of education was to ......" (Smith ,2000:150).As Carnoy (2004: 215) states: "there are many good reasons to be sceptical".Being CriticalAs an academic writer, you are expected to be critical of the sources that you use. This essentially means questioning what you read and not necessarily agreeing with it just because the information has been published. Being critical can also mean looking for reasons why we should not just accept something as being correct or true. This can require you to identify problems with a writer's arguments or methods, or perhaps to refer to other people's criticisms of these. Constructive criticism goes beyond this by suggesting ways in which a piece of research or writing could be improved....... being against is not enough. We also need to develop habits of constructive thinking. Edw ard de BonoIntroducing questions, problems and limitations (theory)One question that needs to be asked, however, is whether ......A serious weakness with this argument, however, is that ......One of the limitations with this explanation is that it does not explain why... .One criticism of much of the literature on X is that ......The key problem with this explanation is that ......The existing accounts fail to resolve the contradiction between X and Y.However, there is an inconsistency with this argument.Smith's argument relies too heavily on qualitative analysis of ......It seems that Jones' understanding of the X framework is questionable.Smith's interpretation overlooks much of the historical research ......One major criticism of Smith's work is that .....Many writers have challenged Jones' claim on the grounds that .......X's analysis does not take account of ..... nor does he examine ......Introducing questions, problems and limitations(method/practice)Another problem with this approach is that it fails to take X into account.Perhaps the most serious disadvantage of this method is that .....Difficulties arise, however, when an attempt is made to implement the policy. Nevertheless, the strategy has not escaped criticism from governments, agencies and academics.One major drawback of this approach is that ......The main limitation of biosynthetic incorporation, however, is ......However, this method of analysis has a number of limitations.However, approaches of this kind carry with them various well known limitations.All the studies reviewed so far, however, suffer from the fact that .......However, there are limits to how far the idea of/concept of X can be taken. However, such explanations tend to overlook the fact that......However, one of the problems with the instrument the researchers used to measure X was ......Identifying a study's weaknessOffering constructive suggestionsA better study would examine a large, randomly selected sample of societies with ......A much more systematic study would identify how X interacts with other variables that are believed to be linked to ......Highlighting inadequacies of previous studiesMost studies in the field of X have only focussed on ......Most studies in X have only been carried out in a small number of areas.The generalisability of much published research on this issue is problematic.The experimental data are rather controversial, and there is no general agreement about ......Such expositions are unsatisfactory because they .....However, few writers have been able to draw on any structured research into the opinions and attitudes of ......The research to date has tended to focus on X rather than Y.The existing accounts fail to resolve the contradiction between X and Y. Researchers have not treated X in much detail.Previous studies of X have not dealt with ......However, these studies used non-validated methods to measure .....Half of the studies evaluated failed to specify whether ......However, much of the research up to now has been descriptive in nature …. Although extensive research has been carried out on X, no single study exists which adequately covers ......However, these results were based upon data from over 30 years ago and it is unclear if these differences still persist.Introducing other people's criticismsHowever, Jones (2003) points out that .....Many analysts now argue that the strategy of X has not been successful. Jones (2003), for example, argues that .....Non-government agencies are also very critical of the new policies.The X theory has been / vigorously / strongly challenged in recent years by a number of writers.Smith's analysis has been criticised by a number of writers. Jones (1993), for example, points out that ……Smith's meta-analysis has been subjected to considerable criticism.The most important of these criticisms is that Smith failed to note that ......Jones (2003) is probably the best known critic of the X theory. He argues that .….The latter point has been devastatingly critiqued by Jones (2003).Critics have also argued that not only do social surveys provide an inaccurate measure of X, but the......Critics question the ability of poststructuralist theory to provide ......More recent arguments against X have been summarised by Smith and Jones (1982): Jones (2003) is critical of the conclusions that Smith draws from his findings. Describing MethodsIn the Methods section of a dissertation or research article, writers give an account of how they carried out their research.The Materials and Methods section should be clear and detailed enough for another experienced person to repeat the research and reproduce the results. Typical features with examples of this language are listed below.Describing different methodsTo date various methods have been developed and introduced to measure X:In most recent studies, X is measured in four different ways.Radiographic techniques are the main non-invasive method used to determine .... Different authors have measured X in a variety of ways.Previous studies have based their criteria for selection on ......A variety of methods are used to assess X. Each has its advantages and drawbacks. Data were gathered from multiple sources at various time points during the2007–2008 academic year.Giving reasons why a particular method was adoptedThe semi-structured approach was chosen because ......Smith et al (1994) identify several advantages of the case study, .......It was decided that the best method to adopt for this investigation was to ......A case study approach was chosen to allow a ......The design of the questionnaires was based on ......The X method is one of the more practical ways of ......It was considered that quantitative measures would usefully supplement and extend the qualitative analysis.Many of the distributions were not normal so non-parametric signed rank tests were run.The X approach has a number of attractive features: ......Indicating a specific methodArticle references were searched further for additional relevant publications.Articles were searched from January 1965 until April 2008.Publications were only included if …….X was prepared according to the procedure used by Patel et al. (1957).The synthesis of X was done according to the procedure of Smith (1973).X was synthesised using the same method that was detailed for Y, using ......This compound was prepared by adapting the procedure used by Zhao et al. (1990). For this study the X was used to explore the subsurface ……An alternative method for making scales homogenous is by using …..Describing the characterisitics of the sampleThe initial sample consisted of 200 students of whom 13 did not complete all of the interviewsAll studies described as using some sort of X procedure w ere included in the analysis.A systematic literature review was conducted of studies that .....All of the participants were aged between 18 and 19 at the beginning of the study..... Two groups of subjects w ere interview ed, namely X and Y. The first group were ......A random sample of patients with ...... was recruited from .......Forty-seven students studying X were recruited for this study.The students were divided into two groups based on their performance on ......The project used a convenience sample of 32 first year modern languages students. Just over half the sample (53%) was female, of whom 69% were ......Participants were recruited from 15 clinics across ......, covering urban and rural areas ……Eligibility criteria required individuals to have received ….Five individuals were excluded form the study on the basis of ….Eligible women who matched the selection criteria were identified by ……Semi structured interviews were conducted with 17 male offenders with a mean age of 38 yearsA comparison group of 12 male subjects without any history of X was drawn from a pool of …….Indicating reasons for sample characteristicsA small sample was chosen because of the expected difficulty of obtaining ......The subjects were selected on the basis of a degree of homogeneity of their ....... Criteria for selecting the subjects were as follows:Describing the process: infinitive of purposeIn order to identify the T10 and T11 spinous processes, the subjects w ere askedto ......In order to understand how X regulates Y, a series of transfections was performed..To enable the subjects to see the computer screen clearly, the laptop was configured with ......To see if the two methods gave the same measurement, the data was plotted and ...... To control for bias, measurements were carried out by another person.To measure X, a question asking ...... was used.To determine w hether ......, KG-1 cells were incubated for ......To establish w hether ......,To increase the reliability of measures, each X was tested twice with a 4-min break between .......To compare the scores three weeks after initial screening, a global ANOVA F-test was usedThe vials were capped with ..... to prevent volatisation.In an attempt to make each interviewee feel as comfortable as possible, the interviewer ......Describing the process: other phrases expressing purposeFor the purpose of height measurement, subjects were asked to stand .....For the purpose of analysis, 2 segments were extracted from each ......For the estimation of protein concentration, 100 µL of protein sample was mixedwith ......Describing the process: typical verbs (note use of passive form)Data management and analysis w as performed using SPSS 8.0 (1999).Published studies w ere identified using a search startegy developed in .....The experiments w ere carried out over the course of the growing period from ....... Injection solutions w ere coded by a colleague to reduce experimenter bias.Drugs w ere administered by icv injection under brief CO2 narcosis;The mean score for the two trials w as subjected to multivariate analysis of variance to determine ......The subjects w ere asked to pay close attention to the characters whenever ...... Prompts w ere used as an aid to question two so that ......The pilot interviews w ere conducted informally by the trained interviewer ......Blood samples w ere obtained with consent, from 256 caucasian male patients ...... Independent tests were carried out on the x and y scores for the four years from ...... This experiment w as repeated under conditions in which the poor signal/noise ratio was improved.Significance levels were set at the 1% level using the student t-test.A total of 256 samples w ere taken from 52 boreholes (Figure 11).Describing the process: sequence words/phrases。
二氢苯并吩嗪类光催化剂的合成表征与应用摘要：随着环境污染问题的日益严重，寻找新的环境友好型的光催化剂已成为研究的热点。
二氢苯并吩嗪类化合物具有广泛的应用前景，特别是在光催化领域。
本文对二氢苯并吩嗪基光催化剂的合成表征与应用进行了详细的介绍。
首先，介绍了二氢苯并吩嗪类化合物的结构特点及其在光催化领域中的应用；接着，重点介绍了二氢苯并吩嗪基光催化剂的化学合成方法，包括溶液法和溶胶凝胶法等，同时分析了两种方法的优缺点；然后，详细探讨了二氢苯并吩嗪基光催化剂的物理化学性质及其对光催化性能的影响因素；最后，论文介绍了二氢苯并吩嗪基光催化剂在环境治理、有机合成等领域的应用，详细讨论了其对各类有机污染物的降解效果。
研究表明，二氢苯并吩嗪基光催化剂具有良好的光催化性能和广泛的应用前景。
关键词：二氢苯并吩嗪；光催化剂；化学合成；应用；影响因素。
Abstract: With the increasingly serious environmental pollution problem, finding new environmentallyfriendly photocatalysts has become a research hotspot. Dihydrophenanthroline compounds have broad prospects for application, especially in photocatalysis. This paper introduces the synthesis, characterization and application of dihydrophenanthroline-basedphotocatalysts in detail. First, the structural characteristics of dihydrophenanthroline compounds and their application in photocatalysis are introduced; then, the chemical synthesis methods of dihydrophenanthroline-based photocatalysts, including solution method and sol-gel method, are discussed, and the advantages and disadvantages of the two methods are analyzed at the same time; The physical and chemical properties of dihydrophenanthroline-based photocatalysts and the factors affecting their photocatalytic performance are discussed in detail; Finally, the paper introduces the application of dihydrophenanthroline-based photocatalysts in environmental governance, organic synthesis and other fields, and discusses in detail their degradation effect on various organic pollutants. The results show that dihydrophenanthroline-based photocatalysts have good photocatalytic performance and broad application prospects.Keywords: Dihydrophenanthroline; photocatalyst; chemical synthesis; application; influencing factors。
sci中的长难句在科学论文中，长难句常常出现，主要是为了表达复杂的概念和关系。
以下是一些常见的长难句例子：1. "The development and implementation of a robust and scalable machine learning algorithm, combined with advanced data analytics techniques, have significantly improved the accuracy and efficiency of predicting and analyzing complex biological systems, thereby enabling researchers to gain deeper insights into the underlying mechanisms driving disease progression."“强大且可扩展的机器学习算法的开发和实施，结合先进的数据分析技术，显著提高了预测和分析复杂生物系统的准确性和效率，从而使研究人员能够更深入地了解驱动疾病进展的潜在机制。
”2. "The integration of nanomaterials with traditional construction materials, such as concrete and steel, not only enhances their mechanical properties, but also provides additional functionalities, such as self-healing, self-cleaning, and energy harvesting capabilities, contributing to the development of sustainable and smart infrastructure."“将纳米材料与混凝土和钢材等传统建筑材料相结合，不仅增强了它们的机械性能，还提供了额外的功能，如自我修复、自清洁和能量收集能力，有助于可持续和智能基础设施的发展。
Synthesis,Characterization,and Adsorption Properties ofNanocrystalline ZSM-5W.Song,R.E.Justice,C.A.Jones,V.H.Grassian,*and rsen* Department of Chemistry,University of Iowa,Iowa City,Iowa52242Received February24,2004.In Final Form:June28,2004 Nanocrystalline ZSM-5with a Si/Al ratio of20was synthesized using clear solutions and a hydrothermal synthesis procedure.The resulting ZSM-5materials were characterized by powder X-ray diffraction,scanning electron microscopy(SEM),nitrogen adsorption isotherms,solid-state nuclear magnetic resonance,and toluene adsorption.A commercial ZSM-5sample was similarly characterized for comparison with the synthesized materials.The particle sizes of the synthesized ZSM-5samples were calculated using the measured external surface areas and were determined to be15and60nm.SEM images indicated that the ZSM-5samples consist of agglomerated and possibly intergrown particles.Toluene adsorption measurements showed that the ZSM-5sample with a particle size of15nm adsorbed approximately50% more toluene than the other ZSM-5samples,most likely due to the adsorption of toluene on the external surface.For the toluene adsorbed on the internal zeolite surface,approximately one toluene molecule was adsorbed per channel intersection for each of the ZSM-5samples.IntroductionMicroporous zeolite materials are widely used in ap-plications such as catalysis and chemical separations and as adsorbents.Zeolites are unique materials with pores of various shapes,sizes,and topologies that control the reactivity and shape selective properties of these materi-als.Zeolites with discrete uniform particle sizes of less than100nm are referred to as nanocrystalline zeolites. Nanocrystalline zeolites have two dimensions in the nanometer size regime:the pores which are nanometer to subnanometer in size and the crystal sizes which are also in the nanometer size range(100nm or below). Nanocrystalline zeolites are promising catalytic and adsorbent materials that have higher surface areas and reduced diffusion path lengths relative to conventional micrometer-sized zeolites.Nanocrystalline zeolites can also be assembled into thin films and other porous nanostructures for use as separation membranes,chemical sensors,and photochemical hosts.1-6ZSM-5is a zeolite that is often used as a catalyst in petroleum refining.ZSM-5has an intersecting pore network composed of straight channels and zigzag chan-nels with pore diameters of∼0.55nm.Nanocrystalline ZSM-5exhibits increased selectivity and toluene conver-sion into cresol and decreased coke formation relative to conventional ZSM-5materials.7Several strategies for the synthesis of nanocrystalline ZSM-5zeolites have been described in the literature.8-17Verduijn13and Schoeman and co-workers15,18reported the synthesis of nanocrys-talline ZSM-5using clear solutions in open beakers at low temperature and ambient pressure in contrast to the conventional hydrothermal routes.These syntheses re-sulted in the formation of colloidal solutions of zeolites with uniform,nanometer particle sizes of100nm or less. Van Grieken and co-workers recently reported a similar synthesis for ZSM-5based on clear solutions under hydrothermal conditions.17Reding and co-workers recently surveyed the synthetic methods for nanocrystalline ZSM-5 and reported a new procedure based on two crystallization steps,both under atmospheric pressure,that yielded crystals with sizes ranging from100to300nm.12 Alternative strategies based on confined space and templating methods have been adopted by other groups.8,16 Jacobsen and co-workers devised a method in which the zeolite synthesis mixture was impregnated into a porous carbon black material.16,19The growth of the zeolite crystals was then restricted by the pore size of the carbon black matrix.This method was hindered by the fact that the carbon black material is disordered and therefore zeolites with rather broad size and shape distributions were produced.Pinnavaia recently reported a method for*To whom correspondence should be addressed.E-mail:sarah-larsen@,vicki-grassian@.Phone:319-335-1346.Fax:319-335-1270.(1)Metzger,T.H.;Mintova,S.;Bein,T.Microporous Mesoporous Mater.2001,43,191-200.(2)Mintova,S.;Bein,T.Microporous Mesoporous Mater.2001,50, 159-166.(3)Huang,L.;Wang,Z.;Sun,J.;Miao,L.;Li,Q.;Yan,Y.;Zhao,D. J.Am.Chem.Soc.2000,122,3530-3531.(4)Jung,K.T.;Hyun,J.H.;Shul,Y.G.Zeolites1997,19,161-168.(5)Wang,Y.J.;Tang,Y.;Wang,X.D.;Yang,W.L.;Gao,Z.Chem. Lett.2000,1344-1345.(6)Tang,Y.;Wang,Y.J.;Wang,X.D.;Yang,W.L.;Gao,Z.In Zeolites and Mesoporous Materials at the Dawn of the21st Century:Proceedings of the13th International Zeolite Conference;Studies in Surface Science and Catalysis,Vol.135;Elsevier:Amsterdam,2001;pp3325-3332.(7)Vogel,B.;Schneider,C.;Klemm,E.Catal.Lett.2002,79,107-112.(8)Kim,S.S.;Shah,J.;Pinnavaia,T.J.Chem.Mater.2003,15, 1664-1668.(9)Yamamura,M.;Chaki,K.;Wakatsuki,T.;Okado,H.;Fujimoto, Z.Zeolites1994,14,643-649.(10)Lovallo,M.C.;Tsapatsis,M.Advanced Catalysis and Nano-structure Materials;Academic Press:San Diego,1996.(11)Mintova,S.;Bein,T.Adv.Mater.2001,13,1880-1883.(12)Reding,G.;Maurer,T.;Kraushaar-Czarnetzki,B.Microporous Mesoporous Mater.2003,57,83-92.(13)Verduijn,J.P.Exxon Chemical Patents Inc.,Patent No. WO97103019,1993.(14)Mintova,S.;Petkov,N.;Karaghiosoff,K.;Bein,T.Mater.Sci. Eng.,C2002,C19,111-114.(15)Schoeman,B.J.;Sterte,J.;Ottstedt,mun.1993, 994-995.(16)Schmidt,I.;Madsen,C.;Jacobsen,C.J.H.Inorg.Chem.2000, 39,2279-2283.(17)Van Grieken,R.;Sotelo,J.L.;Menendez,J.M.;Melero,J.A. Microporous Mesoporous Mater.2000,39,135-147.(18)Schoeman,B.J.;Sterte,J.;Ottstedt,J.E.Zeolites1994,14, 110-116.(19)Jacobsen,C.J.H.;Madsen,C.;Janssens,T.V.W.;Jakobsen,H.J.;Skibsted,J.Microporous Mesoporous Mater.2000,39,393-401.8301Langmuir2004,20,8301-8306synthesizing highly uniform ZSM-5crystals using colloid-imprinted carbon templates(CICs).8The method is based on the imprinting of carbon pitch with colloidal silica to create a carbon material with uniform pore sizes.The ZSM-5was then synthesized in the uniform carbon pores followed by burning off the porous carbon.ZSM-5with systematically varied particle sizes of13,22,42,and90 nm were synthesized using the CIC method.8In the work reported here,nanocrystalline ZSM-5was synthesized using modifications of the clear solution based procedures.The procedures were modified to produce ZSM-5with uniform crystals with sizes as small as15nm and with Si/Al)20,which is a lower ratio than previously reported.A commercial ZSM-5material was used for comparison of the properties of the synthesized nano-crystalline ZSM-5materials.The resulting materials were extensively characterized by powder X-ray diffraction (XRD),scanning electron microscopy(SEM),nitrogen adsorption isotherms,and solid-state nuclear magnetic resonance(NMR).The adsorption properties for a rep-resentative volatile organic compound(VOC),toluene,on ZSM-5samples with different particle sizes were also investigated.Experimental SectionMaterials.Tetraethyl orthosilicate(TEOS),tetrapropylam-monium hydroxide(TPAOH,40wt%aqueous solution),and aluminum isopropoxide were purchased from Alfar Aesar.Sodium hydroxide(NaOH)was purchased from Aldrich.A commercial ZSM-5sample(Si/Al)20)was provided by Zeolyst International.Nanocrystalline ZSM-5Synthesis.All synthesized ZSM-5 samples were prepared from clear gel solutions following the general procedure described by Van Grieken and co-workers.17 Detailed conditions such as gel composition,synthesis vessel, temperature,and time duration are listed in Table1.The rela-tive ratio of reagents in the synthesis gel was similar to that in our previous report on silicalite-1synthesis,20except that an aluminum source,aluminum isopropyloxide,was added.ZSM-5 samples synthesized in this study have a starting Si/Al)25 which is lower than that used by Van Grieken(Si/Al)60).17 Overall,the general procedure follows Van Grieken,but the specific synthesis gel composition and synthesis conditions were modified to prepare nanocrystalline ZSM-5with a lower Si/Al ratio.To start a synthesis,measured amounts of chemicals(H2O, NaOH,TPAOH solution,TEOS,and aluminum isopropyloxide) were mixed and stirred at room temperature(RT)overnight to ensure complete TEOS and aluminum isopropyloxide hydrolysis to ethanol and isopropyl alcohol,respectively.For the larger particle size(60nm),the ethanol and isopropyl alcohol were removed by heating the solution to80°C until the weight loss expected for complete alcohol removal was reached.For the smaller particle size(15nm),the alcohols were not removed from the solution.Next,the clear solution was transferred into a25mL autoclave equipped with a Teflon liner for the hydrothermal treatment specified in Table1.ZSM-5crystals were recovered after three cycles of centrifuging and washing with deionized water,followed by drying at120°C.The ZSM-5 crystals were calcined at600°C under air flow to remove the TPAOH template.The ZSM-5samples are labeled according to average particle size as calculated from their external surface areas,measured using the Brunauer-Emmett-Teller(BET)method.For ex-ample,the sample labeled ZSM-5(15nm)consists of ZSM-5with an average particle size of15nm.Scanning Electron Microscopy.SEM images of the ZSM-5 crystals were acquired using a Hitachi S-4000scanning electron microscope.To prepare the sample for SEM,a drop of dilute colloidal solution of the sample was dropped onto the SEM sample stud surface and the sample stud was then dried at60°C for3 h.Shortly before an SEM image was acquired,the sample was coated with gold.Elemental Analysis.A Perkin-Elmer Plasma400inductively coupled plasma atomic emission spectrometer(ICP/AES)was used to determine the Si/Al ratio of the ZSM-5samples.ZSM-5 samples were acid digested by dilute HF solution followed by neutralization in NaBO3.Four standard solutions with known silicon and aluminum concentrations were prepared as calibration standards.Atomic emission peak intensities at wavelengths of 309.2nm for aluminum and203.9nm for silicon were recorded for all four standard solutions and the sample solutions.Exact concentrations of aluminum and silicon in the sample solution were obtained by projection from the working curve generated from standard solution data.X-ray Diffraction.A Siemens D5000X-ray diffractometer with a Cu K R target and a nickel filter was used to collect XRD powder patterns for the samples.XRD patterns were collected between2θangles of5and55°.To estimate crystal sizes from Scherrer’s equation,a slower,high-resolution scan between7.7 and7.8°for each sample was also collected.The full width at half-maximum(fwhm)of the peak from the slow scan of each sample was obtained by simulation and was used to estimate the crystal size of each ZSM-5sample from Scherrer’s equation(with K)1.0)given below:where T is the crystal size(nm),K is the crystal shape factor,λis the wavelength of X-rays(for the Cu target,λ)1.542Å), is the full width at half-maximum,andθis Bragg’s angle.Nitrogen Adsorption Isotherms.Nitrogen adsorption isotherms were obtained on a Quantachrome Nova1200mul-tipoint BET apparatus using approximately0.2g of sample for each measurement.Immediately prior to the N2adsorption,each sample was vacuum degassed at120°C for1h.The specific surface area was measured by the BET method,which was performed automatically by the instrument.BET adsorption isotherms were collected for ZSM-5samples before and after calcination to remove the template.Solid-State Magic Angle Spinning NMR.29Si(59.595MHz) and27Al(78.172MHz)solid-state magic angle spinning(MAS) NMR spectra were obtained using a300MHz wide bore magnet with a TecMag Discovery Console with a Chemagnetics double-resonance7.5mm pencil MAS probe with a spinning speed of∼6 kHz.Typically,0.2g of sample was used to load the rotor.Each single pulse spectrum was acquired by signal averaging1000 scans with a3s pulse delay for27Al and1000scans with a60 s pulse delay for29Si.Probe Molecule Adsorption.Toluene was selected to examine VOC adsorption as a function of the particle size of ZSM-5.The experimental setup has been described previously.20 Each experiment consists of three regions:Region I,room-temperature adsorption;Region II,room-temperature purge withTable1.Synthesis Conditions for ZSM-5sample a gel composition vessel temp(°C)time(h)Si/Al ZSM-5(15nm)9TPAOH/0.16NaOH/Al/25Si/495H2O/100EtOH autoclave16512020 ZSM-5(60nm)9TPAOH/0.16NaOH/Al/25Si/300H2O autoclave16512020 Zeolyst ZSM-5N/A N/A N/A N/A20 a The number in parentheses denotes the average particle size(nm)of the sample calculated from the external surface area.T)Kλ cosθ8302Langmuir,Vol.20,No.19,2004Song et al.with quartz wool to minimize breakthrough.The sample bed was heated at 300°C under helium prior to the adsorption at room temperature.During room-temperature adsorption,25sccm helium was directed through a toluene bubbler and then through the sample bed.After the sample was saturated with toluene,the toluene bubbler was bypassed to start purging the sample by helium flow at room temperature;then the sample was heated at 5K/min to do the TPD experiment.Throughout the experiment,the concentration of toluene in the gas stream was monitored by the thermal conductivity detector (TCD)of a Varian 3400CX gas chromatograph (GC),which was calibrated to give a quantitative measurement of toluene passing through the detector.Results and DiscussionSynthesis and Characterization of Nanocrystal-line ZSM-5.The two nanocrystalline ZSM-5samples have different average particle sizes and were synthesized by varying the relative amounts of water in the synthesis solution as listed in Table 1.In addition,the alcohol hydrolysis products were removed prior to the thermal synthesis treatment for the larger ZSM-5crystal size,but not for the smaller crystal size sample.Aluminum was added to the synthesis gel in order to prepare ZSM-5with a Si/Al ratio of 20.The powder XRD patterns of two synthesized ZSM-5samples and a Zeolyst ZSM-5sample for comparison are shown in Figure 1.The diffraction patterns agree with the diffraction pattern expected for ZSM-5.21Close inspection of the diffraction patterns in Figure 1reveals that the line widths decrease from top to bottom,suggesting that the ZSM-5particle size is increasing such that the Zeolyst ZSM-5sample has the largest particle size.The particle sizes estimated from the XRD line width and Scherrer’s equation are listed in Table 2with the shape factor K equal to ing Scherrer’s equation,the particle sizes are estimated to be 14,28,and 32nm for the two synthesized ZSM-5samples and the Zeolyst sample,respectively.The SEM images of the ZSM-5samples are shown in Figure 2.The SEM images show the size,particle morphology,and aggregation of the synthesized and commercial ZSM-5crystals.The ZSM-5particles grow into larger aggregates as shown in the SEM images,and it is therefore difficult to determine the primary particle size from the SEM images alone.The larger aggregates may be composed of many individual zeolite particles or of intergrown zeolite particles.The larger aggregates range from 100-200nm for ZSM-5(15nm)to 400-600nm for ZSM-5(60nm)to 700-1000nm for Zeolyst ZSM-5.Nitrogen adsorption isotherms for the synthesized ZSM-5samples were measured both before and after calcination to remove the template.Total surface areas of both calcined and as-synthesized samples were obtained from the nitrogen adsorption isotherms using the BET method and are listed in Table 2.The total surface area of the as-synthesized samples in which the internal surface is blocked by template molecules represents the external surface area of the zeolite sample.20,22The total surface area obtained from the calcined samples should containTable 2.Particle Sizes of ZSM-5Determined from SEM Images and XRD Line Widthssample BET area (as synthesized)aBET area (calcined)adifference bparticle size (calculated)cXRD Scherrer particle size d(nm)ZSM-5(15nm)2085563481514ZSM-5(60nm)534193636028Zeolyst ZSM-5N/A396N/AN/A32aAll surface areas are provided in m 2/g.Standard deviations of surface areas were measured to be between 0.4and 1.4m 2/g;the larger errors are associated with the higher surface areas measured.b Difference )BET area (calcined)-BET area (as synthesized).c Calculated particle sizes are obtained using the following equation:particle size (nm))3216/BET surface area of as-synthesized ZSM-5samples.d K )1.0in Scherrer’sequation.Figure 1.XRD patterns of three ZSM-5samples:(a)Zeolyst ZSM-5;(b)ZSM-5(60nm);(c)ZSM-5(15nm).2θangles between 5and 55°werecollected.Figure 2.SEM images of three ZSM-5samples:(a)Zeolyst ZSM-5;(b)ZSM-5(60nm);(c)ZSM-5(15nm).In each image,the scale bar is equal to 100nm.Nanocrystalline ZSM-5Langmuir,Vol.20,No.19,20048303contributions from both the internal and the external surfaces.Therefore,the difference between the surface area of the uncalcined and the calcined ZSM-5should provide the internal surface area.For the Zeolyst ZSM-5 sample,only the total surface area was measured since the material was only available in the calcined form. Examination of the data in Table2shows that the total surface area of the calcined ZSM-5samples increases as particle size decreases,as expected.The total surface area can be separated into contributions from the internal and external surface area.The internal surface area obtained by taking the difference in total surface area of the calcined and the as-synthesized ZSM-5samples is constant with an average value of approximately355m2/g.The external surface area increases from a value of approximately53 to208m2/g for the two synthesized ZSM-5samples.Onlythe total surface area of396m2/g was obtained for the Zeolyst sample.Using a simple approximation for external surface area, the particle size for the synthesized ZSM-5samples can be estimated from the external surface areas measured from the BET method.20To establish a correlation between external surface area and the particle size,a simple model assuming a cubic particle shape for ZSM-5was used.Then, a particle with a size of x nm will have an external surface area of6x2(nm2).ZSM-5has the MFI framework structure with a unit cell volume of5.21nm3and a chemical formula for the unit cell of92Si/4Al/192O,which gives a unit cell formula weight of5852.For a ZSM-5particle with x nm size,the chemical formula weight can then be calculated to be(x3/5.21)×5852)1123x3.For1g of ZSM-5,the number of crystals is6.02×1023/1123x3,and the total external surface area can then be calculated as6x2×6.02×1023/1123x3.After adjusting the units,a particle of size x of a ZSM-5sample iswhere S ext is the external surface area in m2/g and x is the ZSM-5particle size in ing this relationship,the particle size can be estimated from external surface area the particle sizes for the synthesized ZSM-5samples were determined to be15and60nm,respectively.An analogous relationship was derived for nanocrystalline silicalite,and the experimentally determined external surface areas and particle sizes(from SEM)agreed remarkably well with the results of the calculation assuming cubic silicalite crystals.20The method of using the external surface area to determine the particle size for the nanocrystalline zeolites appears to provide a very good approximation of the particle size.The particle size obtained from the external surface area is similar to the particle size obtained from Scherrer’s equation for the smallest synthesized ZSM-5sample but deviates significantly for the larger sample.This was also found to be the case in our study on nanocrystalline silicalite-120and was attributed to the intergrowth of multiple particles.22As observed in the SEM images in Figure2,the intergrown particles are present in these samples.Solid-State29Si and27Al MAS NMR.The29Si MAS NMR spectra of calcined ZSM-5samples are shown in Figure4.Peaks at-110and-100ppm are observed and can be assigned to Q4and Q3silicon atoms,respectively. The Q n nomenclature is used,where n represents the number of siloxane bonds and(4-n)provides the numberFigure3.Correlation between external surface area in m2/g and particle size in nm for ZSM-5.The solid line represents the calculated external surface area as a function of particle size assuming a cubic particle as described in the text.The open triangles represent the data points for the two ZSM-5samples synthesized in this study assuming the relationship between external surface area and particle size described in the text. The dotted lines indicate how the theoretical curve is used to determine the particle size from the external surface area for the two synthesized ZSM-5samples.x)3216/Sext Figure4.29Si solid-state NMR spectra of calcined ZSM-5 samples:(a)Zeolyst ZSM-5;(b)ZSM-5(60nm);(c)ZSM-5 (15nm).Figure5.27Al solid-state magic angle spinning NMR spectra of as-synthesized and calcined ZSM-5samples:(a)calcined Zeolyst ZSM-5;(b)as-synthesized ZSM-5(60nm);(c)as-synthesized ZSM-5(15nm);(d)calcined ZSM-5(60nm);(e) calcined ZSM-5(15nm).8304Langmuir,Vol.20,No.19,2004Song et al.samples to compensate the charge from the templating agent,and a terminal silanol site.23-25Only a small number of Q 3sites remain after calcinations as can be seen in Figure 4.The 27Al MAS NMR spectra of calcined and as-synthesized ZSM-5samples are shown in Figure 5.Peaks at ∼50and ∼0ppm in 27Al NMR spectra are assigned to aluminum in tetrahedral sites and extraframework alu-minum in octahedral coordination,respectively.The main peak present in the 27Al NMR spectra of as-synthesized and calcined samples is at ∼50ppm and is assigned to aluminum in tetrahedral sites.This peak broadens as the particle size decreases,as has been observed previously for HZSM-5.26A second peak is present in the 27Al NMR spectrum of Zeolyst ZSM-5at approximately 0ppm and is assigned to extraframework aluminum.Very little extraframework aluminum is observed for the ZSM-5samples synthesized as part of this study.VOC Adsorption.The adsorption of a typical VOC,toluene,on ZSM-5was investigated using the flow apparatus described previously.20Representative results from toluene adsorption/desorption on ZSM-5samples are shown in Figure 6.The TCD signal of the GC is at a maximum when the sample bed is bypassed or when the sample is saturated and at a minimum when no toluene passes through the sample bed.In Region I of the experiment,toluene adsorption on the ZSM-5sample was monitored.In Region II of the experiment,the ZSM-5sample bed was purged with helium while monitoring the desorption of toluene,and in Region III of the experi-ment,a temperature-programmed desorption of the toluene was conducted.The amount of toluene adsorbed was obtained by measuring the area between the maxi-mum baseline and the experimental curve,while the amount of toluene desorbed was obtained from the area between the minimum baseline and the experimental curve profiles after the temperature ing this method,the amounts of toluene adsorbed and desorbed in this experiment were calculated and are listed in Table 3.The total toluene adsorption in Region I of the experi-ment ranged from 1.65to 1.04to 1.03mmol/g for the ZSM-5(15nm),ZSM-5(60nm),and Zeolyst ZSM-5samples,respectively.The amount of toluene removed during the helium purge was 1.07mmol/g for ZSM-5(15nm),0.46mmol/g for ZSM-5(60nm),and 0.46mmol/g for Zeolyst ZSM-5.The amount of toluene desorbed during the room-temperature helium purge trends with the external surface area for the synthesized ZSM-5samples,sug-gesting that the toluene desorbed during the helium purge is due to toluene adsorbed on the external surface of the ZSM-5.The area under the desorption peak in Region III of the experiment is approximately the same for all three samples and is 0.65-0.67mmol/g.This corresponds extremely well with the calculated density of channel intersections of the ZSM-5framework which is 0.68mmol/g,suggesting that approximately one toluene molecule is adsorbed per channel intersection of ZSM-5.In a previous study of toluene adsorption on siliceous ZSM-5,toluene was found to adsorb at channel intersections at low toluene loadings (1-4molecules/unit cell)and at both channel intersections and midsections of channels at higher toluene loadings (>4molecules/unit cell).27However,while the area of the TPD peak is ap-proximately the same for all three samples,the shape of the TPD peak is different for the different samples.The TPD peak for ZSM-5(60nm)and Zeolyst ZSM-5has two maxima,suggesting that the toluene is adsorbed at two different sites in the zeolite.However,the TPD peak for ZSM-5(15nm)only has the lower temperature desorption component.The shapes of the peaks suggest that the toluene is adsorbing at different sites in the zeolite such as proton acid sites versus sodium cation sites or channel intersection sites versus channel sites.Given that the concentration of adsorbed toluene corresponds so well with the number of channel intersections,it seems most likely that the toluene is adsorbed at different sites in the channel intersection such as proton acid sites or sodium cation sites.(23)Koller,H.;Lobo,R.F.;Burkett,S.L.;Davis,M.E.J.Phys.Chem.1995,99,12588-12596.(24)Dessau,R.M.;Davis,M.E.;Kerr,G.T.;Wooley,G.L.;Alemany,L.B.J.Catal.1987,104,484-489.Figure 6.Toluene adsorption on nanocrystalline ZSM-5and commercial ZSM-5.Each experiment consists of three regions:Region I,room-temperature adsorption;Region II,room-temperature purge with helium;and Region III,temperature-programmed desorption.Solid line,ZSM-5(15nm);dotted line,ZSM-5(60nm);dashed line,Zeolyst ZSM-5.Table 3.Amount of Toluene Adsorption/Desorption onZSM-5samples adsorption (mmol/g)RT purge (mmol/g)TPD (mmol/g)total desorption (mmol/g)ZSM-5(15nm) 1.65 1.070.66 1.73ZSM-5(60nm) 1.040.460.65 1.11Zeolyst ZSM-51.030.460.671.13Nanocrystalline ZSM-5Langmuir,Vol.20,No.19,20048305These results indicate that the overall adsorption capacity of ZSM-5(15nm)is approximately50%greater than that of the other samples tested,largely due to the higher external surface area and the weakly adsorbed toluene that desorbs during the room-temperature helium purge of the sample.The strongly adsorbed toluene that desorbs during the temperature-programmed desorption is quantitatively the same for all of the samples,suggesting that this toluene is adsorbed on the internal zeolite surfaces,most likely at the channel intersections.27ConclusionsNanocrystalline ZSM-5samples with different particle sizes and Si/Al)20were synthesized.The resulting ZSM-5 samples had particle sizes of15and60nm and were compared to a commercial ZSM-5sample.For each of the samples,the framework structures,particle sizes,internal and external surface areas,and VOC adsorption properties were characterized by XRD,SEM,solid-state NMR,and N2and toluene adsorption.The external surface areas of the samples were determined from the BET measurement and were used to determine the particle sizes for the two synthesized ZSM-5samples.The external surface areas of as-synthesized samples were208and53m2/g for the 15and60nm samples,respectively.No extraframework aluminum was detected by27Al MAS NMR of the synthesized nanocrystalline ZSM-5zeolites in contrast to the commercial ZSM-5sample,which exhibited a peak due to extraframework aluminum.ZSM-5with a15nm average particle size showed significantly higher adsorp-tion capacity for toluene relative to the other ZSM-5 samples examined in this study due to adsorption of toluene on the external zeolite surface.The toluene adsorbed on the internal surface was the same for all three ZSM-5samples examined and quantitatively corresponded to the number of channel intersections in ZSM-5,sug-gesting that the toluene adsorbed on the internal zeolite surface was preferentially located at the channel inter-sections.Acknowledgment.The research described in this article has been funded by the Environmental Protection Agency through EPA Grant No.R82960001to S.C.L.and V.H.G.Gonghu Li is acknowledged for assistance in setting up the flow reactor used for the adsorption experiments. LA049516C8306Langmuir,Vol.20,No.19,2004Song et al.。
