氧化亚铜微纳米结构的制备及光催化性能研究

以氨基酸为还原剂及配位剂,在碱性溶液中通过水热还原二价铜离子,制备了不同形貌的氧化亚铜微晶。考察了氨基酸对氧化亚铜微晶结构、尺寸、形貌的影响,提出了氧化亚铜微晶在水热条件下的可能形成机理,结果表明氨基酸是良好的形貌调节剂。以亚甲基蓝为探针分子,对所制备的氧化亚铜微晶的光催化性能进行了研究,发现其催化性能与形貌间存在着密切联系。     

基于柱芳烃的超分子催化研究进展

利用超分子识别与组装的基本原理，发展新型超分子催化剂以实现催化反应的超分子选择性调控是当今催化领域研究的热点和前沿。柱芳烃是一类具有刚性骨架结构的新型大环主体分子，其富电子的空腔和优异的主客体化学性质能够对客体分子进行选择性识别，使其在超分子催化中显示了独特的催化性能。综述了近十年来柱芳烃在超分子催化领域的应用研究进展，重点阐述主-客体相互作用对超分子催化选择性的调控作用，并对其存在问题进行总结及发展前景进行展望。     

一种适用于检测水相中肼的荧光探针研究

肼是一种重要的化工原料,具有广泛的用途。肼的毒性对环境和生物体具有重要影响,然而能够检测水相中肼的荧光探针非常有限。设计合成了一种新的反应型荧光探针,通过核磁共振和高分辨质谱对中间产物和探针分子进行了结构表征。研究发现探针能够特异性的检测水相中的肼,具有较高的灵敏度和强抗干扰能力。通过荧光光谱和理论计算相结合,探究了探针的检测机理和发光性质。研究发现探针分子与肼接触,发生肼解反应,导致荧光团恢复激发态分子内质子转移(ESIPT)发光,从而实现对肼的特异性检测。     

乙苯脱氢过程中催化剂表面碱性研究

本文应用程序升温脱附技术(TPD),以乙酸作为分子探针,考察了无铬Fe—K系混合氧化物乙苯脱氢催化剂的表面碱性。Fe—K系催化剂表面至少存在两种强度不同的碱中心,其中强碱中心b态对乙苯催化脱氢贡献较大;而催化剂表面同时具有适当的碱强度和密度是获得较好催化性能的重要条件。研究结果还发现,乙苯脱氢反应可能类似于强碱催化的双分子消除E2反应,其中催化剂表面碱位起着类似于E2历程中强碱试剂的作用。     

基于萘酚席夫碱结构的荧光增强型铝离子探针

金属离子Al3+在生命系统中起着非常重要的作用并影响着人类的健康,荧光分子探针由于方法简单、选择性和灵敏度高、现场实时监测、检出限低等优点吸引了更多的研究关注.通过一步缩合反应制备了基于萘酚席夫碱结构的荧光分子探针,该分子探针在DMSO/H2 O溶液中对Al3+具有较好的选择性.加入Al3+后分子探针溶液的荧光强度明显...     

烃分子动力学直径与分子筛择形催化性能的相关性

作为分子筛研究领域的一个热点,择形催化理论在工业上已经被研究了近60年。尽管在理论上很多研究还不够深入,但随着对催化反应类型、新型催化材料合成、分子筛结构测定、催化性能表征、催化反应作用机理等方面研究的深入,对择形催化反应的认识仍取得了令人欣慰的进步。本文在现有的研究基础上,对不同尺寸的烃分子在分子筛孔道内的吸附和扩散行为进行了总结,并对烃分子反应动力学直径与分子筛的择形相关性做了一定的探究。分析表明,烃分子的反应动力学直径与分子筛择形催化相关性存在一个适用规律区间,当其略小于或接近分子筛孔径时,分子筛的择形催化性能表现最好。此外,分子筛本身的拓扑结构等因素也会对分子筛催化性能造成影响。     

TiO2催化正丁醛自缩合反应机理

为明晰锐钛矿TiO_2催化正丁醛自缩合反应机理,采用原位反应红外分析和探针分子中毒催化剂酸碱活性位相结合的方法对酸碱活性位的作用进行了研究。气态正丁醛在TiO_2表面的吸附及物种变化结果表明,正丁醛分别通过Ti-OH和Ti4+两种活性位吸附在TiO_2表面,进而发生羟醛缩合反应。分别采用NH_3和CO_2作为探针分子中毒TiO_2的酸碱活性位,并评价中毒后催化剂对正丁醛自缩合反应的催化效果,发现TiO_2的酸性位起主要催化作用,而碱性位会促进副反应发生。在此基础上,提出了锐钛矿TiO_2催化正丁醛自缩合的反应机理。     

基于苯并噻唑用作分析物检测的小分子荧光探针

苯并噻唑及包含苯环和噻唑环的衍生物上的某些结构或官能团的引入可用于构建苯并噻唑荧光探针。基于光致电子转移、激发态分子内质子转移(ESIPT)、分子内电荷转移、聚集诱导发射的机理,获得的荧光探针可以与分析物特异性相互作用,从而改变其发光特性以实现对分析物。苯并噻唑荧光探针可用于物质检测,有害物质分析和细胞成像。综述了近5年来苯并噻唑荧光探针的研究现状,主要分为金属离子、阴离子、小分子和生物大分子,根据分析物的类型而定。总之,分析了基于苯并噻唑小分子荧光探针当前面临的挑战和进一步的应用。     

双取代催化发夹自组装介导的microRNA荧光比率分析

基于荧光共振能量转移的检测策略由于具有高精度、高灵敏度和强可控性等优势,在内源性分子检测中受到越来越多的关注。利用荧光共振能量转移以及双取代的催化发夹自组装技术,构建了一种用于microRNA(miRNA)比率分析的DNA分子探针。在验证探针可行性的同时,对探针浓度进行了优化,在最优条件下对目标物miRNA-21进行了检测,检测限为59.56 pmol/L,并证明了所设计的探针具有良好的选择性。     

基于TCF的荧光探针的设计与应用研究进展

2-二氰基亚甲基-3-氰基-4,5,5-三甲基-2,5-二氢呋喃(TCF)是一个强电子供体,广泛应用于光学材料和分子荧光探针。同时,TCF结构简单,活性位点少,能通过简单的反应与苯基偶联。并且基于TCF的分子荧光探针一般具有大的斯托克斯位移和较高的量子产率。根据TCF荧光探针的检测对象,将其分为阴阳离子、生物分子和其他分子,并从分子结构、性能、机理出发,综述了近5年来国内外基于TCF的荧光探针在设计和检测方面的新进展。最后提出了构建新型TCF类分子荧光探针面临的挑战和发展方向。     

探针分子3-乙基-十一烷的合成

针对SAPO- 11的一维十元环直孔道结构,设计了具有特殊分子结构的长链烷烃3-乙基-十一烷.3-乙基-十一烷与目前常用的长直链探针分子相比,具有能卡在SAPO- 11分子筛孔口的特点,因此可以作为特殊的长链探针分子,结合直链探针分子,对SAPO-11负载催化剂在长链正构烷烃异构化反应中的孔口催化机理进行研究.3-乙基...     

Chemisorption of Probe Molecules on Metal Oxides

A more complete understanding of the structural and mechanistic details of a catalyzed heterogeneous reaction leads both directly and indirectly to the development of new and better catalysts. For catalyst technology, the most sensitive probe of catalysts performance will continue to be the rate and selectivity of a chemical reaction. However, these macroscopic observations, adequate for determining how good a catalyst is, require supplementary microscopic information to remove ambiguity in the deduction of a catalytic mechanism. This information, almost down to the atomic level, concerning the structure and reactivity of the intermediates, the nature of adsorption sites (and sometimes the active sites) and their number, is the main objective of the science of catalysis. The most promising approach to this problem is the use of suitable probe molecules for the quantitative titration of site density and qualitative characterization of their nature by means of surface spectroscopies of the chemisorbed probe molecules [1, 21. This framework of action is schematically represented in Fig.1.     

Chemisorption of Probe Molecules on Metal Oxides

A more complete understanding of the structural and mechanistic details of a catalyzed heterogeneous reaction leads both directly and indirectly to the development of new and better catalysts. For catalyst technology, the most sensitive probe of catalysts performance will continue to be the rate and selectivity of a chemical reaction. However, these macroscopic observations, adequate for determining how good a catalyst is, require supplementary microscopic information to remove ambiguity in the deduction of a catalytic mechanism. This information, almost down to the atomic level, concerning the structure and reactivity of the intermediates, the nature of adsorption sites (and sometimes the active sites) and their number, is the main objective of the science of catalysis. The most promising approach to this problem is the use of suitable probe molecules for the quantitative titration of site density and qualitative characterization of their nature by means of surface spectroscopies of the chemisorbed probe molecules [1, 21. This framework of action is schematically represented in Fig.1.     

Models for the formation of poly(butylene terephthalate): effect of water on the kinetics of the titanium tetrabutylate-catalysed reactions: 3

In an effort to investigate the mechanism of catalysis of titanium tetrabutoxide on the polycondensation of poly(butylene terephthalate), alcoholysis and hydrolysis reactions were studied with the aid of model molecules. The retarding effect of water has also been taken into account. Appropriate kinetic equations are derived and discussed and the results compared with experimental data obtained at different molar ratios of reactants.     

Reactivity of surface alkoxy species on acidic zeolite catalysts

[Reaction: see text]. A solid understanding of the mechanisms involved in heterogeneously catalyzed reactions is of fundamental interest for modern chemistry. This information can help to refine modern theories of catalysis and, in a very practical way, can help researchers to optimize existing industrial processes and develop new ones. To understand the mechanisms of heterogeneous catalysis, we need to observe and identify reaction intermediates on a working catalyst. Motivated by this goal, we have monitored the catalytic events in heterogeneous systems using in situ magic-angle-spinning (MAS) NMR under flow conditions. In this Account, we describe the reactivity and possible intermediate role of surface alkoxy species in a variety of zeolite-catalyzed reactions. First, we isolate the surface alkoxy species on a working zeolite catalyst and then investigate the chemical reactivity with different probe molecules under reaction conditions. Finally, we investigate reaction mechanisms facilitated by these intermediate surface alkoxy species. We examined the reactivity of surface methoxy species (SMS) in terms of C-O bond and C-H bond activation. SMS on acidic zeolite catalysts act as an effective methylating agent when reacted with different probe molecules (including methanol, water, ammonia, alkyl halides, hydrochlorides, aromatics, carbon monoxide, and acetonitrile) through C-O bond activation. At higher reaction temperatures (ca. 523 K and above), the C-H bond activation of SMS may occur. Under these conditions, intermediates such as surface-stabilized carbenes or ylides are probably formed. This C-H bond activation is directly related to the initiation mechanism of the methanol-to-olefin (MTO) process and invites further investigation. Based on our experimental results, we also discuss the reactivity and the carbenium-ion-like nature of surface alkoxy species and recent theoretical investigations in this area.     

Acidity characterization by microcalorimetry and relationship with reactivity

In the area of acid catalysis, adsorption microcalorimetry studies have allowed a significant insight in surface studies under certain experimental conditions. Consideration is given to the interpretation of the heat evolved when a basic probe molecule is adsorbed on the surface of crystalline or amorphous silica-aluminas. In particular, the number and strength of acid sites are discussed as functions of lattice structure, concentration and nature of framework cation and basicity of the probe molecules. This revised version was published online in June 2006 with corrections to the Cover Date.     

分子噻蒽化修饰及偶联反应研究进展

噻蒽盐是近几年来研究较为热门的一个偶联模块,其具有制备简单、活性高、选择性好、转化模式多样等特点.该盐可通过多种未活化的芳烃或者烯烃与噻蒽亚砜直接噻蒽化合成,并可兼容多种官能团,尤其适合多种复杂分子的后期噻蒽化修饰,所得到的噻蒽盐结构可通过金属偶联以及光氧化还原偶联等模式引入多种重要官能团.综述了近3年噻蒽盐的...     

Models for the formation of poly(butylene terephthalate): Kinetics of the titanium tetrabutylate-catalysed reactions: 2

In order to investigate the mechanism of catalysis of titanium tetrabutoxide on the polycondensation of poly(butylene terephthalate), this reaction has been studied with the aid of model molecules. The catalytic and retarding effects of benzoic acid have also been taken into account. Appropriate kinetic equations are derived and discussed and the results compared with experimental data obtained at different temperatures and molar ratios of reactants.     

硅氢加成反应催化机理的研究进展

综述了硅氢加成反应的三大催化机理(自由基加成机理)、离子加成机理、配位加成机理的研究动向及发展,着重介绍了配位加成机理中的铂催化机理(Chalk-Harrod机理、硅基迁移、铂胶体过渡态机理、钴催化机理、铑催化机理、钌催化机理、钯催化机理、镍催化机理等.)