钒元素的化学和应用

钒元素是稀有金属元素,也是人体必需的微量元素。钒元素化学已有200年的历史。简要介绍了钒元素化学,重点介绍了钒元素在工业催化、二次电池、酶催化等领域的应用,以及在医学领域中作为抗糖尿病药物和抗癌药物的应用及研究。     

钒氧酞菁的合成及其薄膜结构与光电性能的研究

自从60年前^[1]金属酞菁被发现以来,就引起人们的广泛兴趣,其原因主要在于它们在染料颜料、光化学、催化、和成像中的应用. 和许多其它酞菁衍生物一样,钒氧酞菁具有光导和半导体特性,这使得它在光电子学、电子成像、化学传感器、甚至于微电子器件中有潜在的十分光明的应用前景^[2]. 例如, 钒氧酞菁在电子成像体系中已成为有用的感光材料. 近年来,金属酞菁等有机材料的结晶薄膜开始不断地吸引人们的注意力. 人们考察了不同的金属酞菁如: 酞菁铜、酞菁铅、酞菁镍、和酞菁锡 等的光电导和光电压^[3]. 通常酞菁以几种不同的多晶异构体、即以不同的晶体排列结构方式存在. 因此,其光电特性不仅取决于分子中心的金属原子、而且取决于它们的晶体结构. 总之,值得我们研究钒氧酞菁薄膜的光电特性以及它与吸收光谱和薄膜晶体结构的关系.     

单原子催化——概念、方法与应用

单原子催化体系的成功构建将催化领域研究深入到更小的尺度范围,不仅可以从原子层次认识复杂的多相催化反应,而且由于其优越的催化性能在工业催化中具有巨大的应用潜能。本文基于近年来国内外研究者在单原子催化领域的研究工作,总结归纳了单原子催化剂的性能特征,介绍了单原子催化剂的制备手段、表征技术、理论研究及其在CO氧化、选择性加氢和光电催化等反应中的应用研究进展,分析了单原子催化剂特殊的电子结构对催化性能和反应机理的影响及其作用机制,指出了单原子催化体系在研究领域取得的突破与不足,对于深刻认识单原子催化的概念与原理、完善实验与理论研究方法、拓展应用范围和尽早实现工业应用提出了建议与展望。     

三氟化硼修饰载体负载茂金属催化乙烯聚合

用BF3对载体硅胶和氧化铝进行了表面修饰,考察了修饰的载体负载茂金属催化剂后催化乙烯聚合的特性.研究表明,用BF3修饰过的载体负载二氯二茂锆催化乙烯的聚合,聚合活性有较大提高,具有工业应用前景,并且提出了这一催化体系的负载机理.     

二氧化碳催化还原反应中的光催化剂

总结了CO2光催化还原反应中催化剂的应用，主要涉及TiO2,CdS以及铁氧化物，由于它们自身在反应中存在着一定的缺陷，因而在应用中往往需要对其进行改性，以改变其电子结构和光响应特性，从而提高反应的光催化效率，另外，对催化反应过程所涉及的机理也相应作了介绍。     

太阳能光解水制氢的研究进展

本文概述了利用光催化技术催化分解水制氢的反应机理和研究进展。结合作者的最近研究,重点描述了TiO2及过渡金属氧化物,层状金属氧化物以及某些能利用可见光的光催化材料的结构和光催化特性,阐述了核课题的意义和今后的研究方向。     

TiO_2和ZrO_2担载的钒氧化物对柴油炭黑催化燃烧的原位紫外激光拉曼光谱研究

利用紫外激光拉曼(UV-Raman)光谱表征了担载TiO2或ZrO2表面的钒氧化物催化剂的分子结构,采用原位UV-Raman光谱考察了V4/TiO2和V4/ZrO2催化剂对柴油炭黑催化燃烧的真实反应状态.结果表明:随着反应温度的升高,TiO2发生了从锐钛矿相到金红石相的晶相转移;然而,ZrO2载体没有观察到明显的相转移过程发生.担载钒氧化物的结构也与钒的载量有关,当钒的载量m(m是每100个载体金属离子中所含的钒离子数)等于4时,钒氧化物在TiO2或ZrO2载体上达到了单层饱和分散,此时催化剂的氧化还原能力最强.所以,在TiO2或ZrO2担载的钒氧化物催化剂中,V4/TiO2和V4/ZrO2是各自系列催化剂中对炭黑燃烧活性最高的催化剂.在炭黑的催化燃烧过程中,原位UV-Raman光谱检测到表面含氧络合物(SOC)的形成,而且SOC主要以羧基功能团的形态存在.反应气体中NO的存在能够促进SOC的生成.     

TiO2和ZrO2担载的钒氧化物对柴油炭黑催化燃烧的原位紫外激光拉曼光谱研究

利用紫外激光拉曼（UV-Raman）光谱表征了担载TiO2或ZrO2表面的钒氧化物催化剂的分子结构,采用原位UV—Raman光谱考察了V4/TiO2和V4/ZrO2催化剂对柴油炭黑催化燃烧的真实反应状态．结果表明：随着反应温度的升高,TiO2发生了从锐钛矿相到金红石相的晶相转移;然而,ZrO2载体没有观察到明显的相转移过程发生．担载钒氧化物的结构也与钒的载量有关,当钒的载量m（m是每100个载体金属离子中所含的钒离子数）等于4时,钒氧化物在TiO2或ZrO2载体上达到了单层饱和分散,此时催化剂的氧化还原能力最强．所以,在TiO2或ZrO2担载的钒氧化物催化剂中,V4／TiO2和V4／ZrO2是各自系列催化剂中对炭黑燃烧活性最高的催化剂．在炭黑的催化燃烧过程中,原位UV—Raman光谱检测到表面含氧络合物（SOC）的形成,而且SOC主要以羧基功能团的形态存在．反应气体中NO的存在能够促进SOC的生成．     

层状氯氧化铋纳米片的制备及其光催化性能测试*——大学综合化学实验的设计

以五水硝酸铋和氯化钾为原料,通过一步式水热合成法制备具有较高光催化活性的层状氯氧化铋催化剂,应用X射线衍射、电子场扫描电镜和紫外可见光谱的表征方法进行材料表征,通过光催化反应研究催化剂对罗丹明B的光催化降解特性。本实验涉及纳米材料的一步式水热合成、纳米材料的结构表征和光催化降解有机污染物的实际应用,综合化学学科知识点于一体。通过实验,本科生能够深入了解并掌握层状氯氧化铋材料的合成和催化性能测试,并且熟悉相关仪器的操作流程,能够把实际教学知识和科研内容有机结合起来,培养并提升学生的化学科研信念和知识储备。     

催化波在矿物原料分析中的应用——催化法极谱测定矿石中微量钒

本文提出微量的五价钒在苦杏仁酸-氯酸钾的微酸性介质中产生灵敏度为0.001微克/毫升的催化极谱波,半波电位为-0.965伏(对饱和甘汞电极)。从溶液酸度、底液组份、汞柱高度、温度等因素对波高的影响以及从极谱波的对数分析确定:由五价钒产生的极谱波系由它催化生成的苯甲醛在电极上进行单电子扩散还原的可逆波,不具有动力波特性。讨论并通过实验证实产生催化扩散电流的电极过程和反应机理。拟定了无须经过分离和富集手续测定矿石中0.000x—0.5％的五氧化二钒的快速简便操作流程。     

V2O5·xH2O-BiVO4纳米复合材料的可控合成和可见光响应的光催化性质

以单斜相V2O5·xH2O纳米线为前驱物,在温和条件下合成出V2O5·xH2O-BiVO4复合光催化剂.为理解产物的物相含量、形貌和光催化性质随合成时间延长而变化的情况,利用X射线衍射仪、场发射扫描电子显微镜、紫外-可见漫反射光谱仪以及光催化性质测试实验对三个典型的V2O5·xH2O-BiVO4样品(分别在反应6、12和24 h获得)进行了研究.分析结果表明:V2O5·xH2O-BiVO4纳米复合材料由V2O5·xH2O纳米线和BiVO4纳米晶组成,并且随合成反应时间的延长,产物中V2O5·xH2O纳米线的含量逐渐减少而BiVO4纳米晶的含量逐渐增加.光催化性质测试结果表明:V2O5·xH2O-BiVO4复合光催化剂在可见光(λ>400 nm)辐射下降解亚甲基蓝时表现出了提高的光催化效率,其中在反应12 h获得的V2O5·xH2O-BiVO4样品体现出最好的光催化活性,这可能是由于其适当的组分含量和特殊的微结构有利于半导体激发和染料激发两种光催化机理的协同作用.     

Preparation and Characterization of Divanadium Pentoxide Nanowires inside SBA-15 Channels

One-dimensional V2O5 nanowires have been synthesized inside the channels of mesoporous silica SBA-15 through chemical approach, which involves aminosilylation of silanol groups on the silica surface, anchoring of isopoly acid, H6V10O28, by neutralization of basic amine groups, and thermal decomposition. The formation and physicochemical properties of the nanowires were monitored and studied by TG-DTA, variable temperature in situ XRD, TEM, N2 sorption measurements and UV-Vis DRS. The results indicate that V2O5 nanowires formed within SBA-15 channels belong to orthorhombic polycrystal domains. The oxygen-to-metal charge transfer band of V2O5 nanowires shows a blue shift in comparison with bulk V2O5, which clearly exhibits the quantum size effect of nanowires.     

Synthesis of Fe(3)O(4)/PdO heterodimer nanocrystals in silica nanospheres and their controllable transformation into Fe(3)O(4)/Pd heterodimers and FePd nanocrystals

The thermal annealing of silica nanospheres encapsulating Fe(3)O(4) nanocrystals and Pd(2+) complexes led to the formation of heterodimers consisting of Fe(3)O(4) and PdO nanoparticles encapsulated in a silica shell, allowing for their controllable transformation into either Fe(3)O(4)/Pd heterodimers or FePd alloy nanocrystals through a solid state reduction process.     

3-Aminopropyltriethoxysilane-functionalized manganese doped ZnS quantum dots for room-temperature phosphorescence sensing ultratrace 2,4,6-trinitrotoluene in aqueous solution

New strategies for silica coating of inorganic nanoparticles became a research hotspot for enhancing the mechanical stability of colloidal particles and protecting colloidal particles against oxidation and agglomeration, and so on. In this paper, 3-aminopropyltriethoxysilane (APTES)-functionalized Mn doped (AF MnD) ZnS QDs was prepared to be firsyly through the use of silane coupling agents to form an active layer of silica, then sol-gel reaction of TEOS co-deposited with APTES on the surface of resultant active layer of silica. The emitted long lifetime room-temperature phosphorescence (RTP) of the resultant nanomaterials allows an appropriate delay time so that any fluorescent emission and scattering light can be easily avoided. The APTES anchored on the layer of silica can bind 2,4,6-trinitrotoluene (TNT) species to form TNT anion through acid-base pairing interaction, the TNT anion species may increase the charge-transfer pathways from the nanocrystals to nitroaromatic analytes, therefore further enhance the quenching efficiency of RTP. Moreover, APTES as capped reagents can enlarge the spectral sensitivity and enhance RTP response of nanocrystals to the electron-deficient nitroaromatic and nitrophenol species. Meanwhile, AF MnD ZnS QDs also exhibited a highly selective response toward TNT analyte through significant color change and quenching of ⁴T₁ to ⁶A₁ transition emission. This AF MnD ZnS QDs based sensor showed a very good linearity in the range of 0.05-1.8 μM with detection limit down to 50 nM (quenching percentage of phosphorescence intensity of 8%) and RSD of 3.5% (n = 5). The reported QDs-based chemosensors here open up a promising prospect for the sensitive and convenient sensing of TNT explosive.     

Structural and redox properties of VOx and Pd/VOx thin film model catalysts studied by TEM and SAED

The oxidation of pure V(2)O(3) and Pd/V(2)O(3) films was studied by Transmission Electron Microscopy (TEM) and Selected Area Electron Diffraction (SAED) in the temperature range 673-773 K. Thin films of V(2)O(3) were prepared by reactive deposition of V metal in 10(-2) Pa O(2) on NaCl(001) cleavage faces. Pd particles were epitaxially grown on NaCl(001) and subsequently embedded in V(2)O(3). Oxidation of both pure V(2)O(3) and Pd/V(2)O(3) at 673 K transforms V(2)O(3) into a platelet-like V(2)O(5) structure. At temperatures T>or= 773 K, a reconstruction of the platelet-like V(2)O(5) structure into an array of oblong and needle-type V(2)O(5) nanocrystals of different size occurs. Subsequent reduction of the so-prepared structures in 1 bar H(2) at 573-673 K results in the formation of the cubic VO phase, whereby the external shape of the original crystals is partially maintained. Upon oxidation at 723 K, Pd is transformed into PdO, but its formation is suppressed in comparison with Pd supported on Al(2)O(3) and occurs only at an about 100 K higher temperature than on Pd/Al(2)O(3). The Pd particles are stabilized against oxidation up to 673 K, PdO decomposes upon reduction in hydrogen between 573 and 673 K.     

Maghemite nanocrystal impregnation by hydrophobic surface modification of mesoporous silica

Here, we report the design of a hybrid inorganic/organic mesoporous material through simultaneous pore engineering and hydrophobic surface modification of the intramesochannels to improve the uptake of superparamagnetic maghemite nanocrystals via impregnation techniques. The mesoporous material of the SBA-15 type was functionalized in situ with thiol organo-siloxane groups. Restricting the addition of the thiol organo-siloxane to 2 mol % yielded an inorganic/organic hybrid material characterized by large pores and a well-ordered hexagonal p6mm mesophase. The hydrophobic surface modification promoted the incorporation of 7.5 nm maghemite (gamma-Fe2O3) nanocrystals, prepared through temperature-controlled decomposition of iron pentacarbonyl in organic solvents. The hydrophobic, oleic acid capped superparamagnetic maghemite nanocrystals were incorporated into the porous network via wet impregnation from organic suspensions. Combining diffraction, microscopy, and adsorption data confirmed the uptake of the nanocrystals within the intramesochannels of the silica host. Magnetization dependencies on magnetic field at different temperatures show a constriction in the loop around the origin, which indicates immobilization of maghemite nanocrystals inside the thiol-functionalized silica host.     

Interface structure of silicon nanocrystals embedded in an amorphous silica matrix

We performed molecular dynamics simulations of the atomic structure of silicon nanocrystals embedded in a stoichiometric amorphous silica matrix. The atom–atom interactions are described by a combination of well-assessed potentials for bulk silicon and SiO₂, plus a mixing term to allow adjusting the charge transfer at the interface between Si and silica. For the free-standing Si nanocrystals, we find that the spherical structure is favoured with respect to the faceted one, up to at least a diameter of 6 nm. Correspondingly, the surface layer shows a higher diffusivity than the bulk. When embedded in the silica matrix, nanocrystals are under severe mechanical stress which is released by the combined formation of porosity at the interface and of bridging Si–O–Si bonds, whose density increases with the nanocrystal size. Vibrational frequencies specific to the interface bonding are identified and discussed.     

Analytical and mechanistic aspects of the room-temperature fluorescence and phosphorescence of benzo(f)quinoline adsorbed on silica gel chromatoplates with humidified gases

The solid-matrix room-temperature fluorescence and room-temperature phosphorescence properties of benzo(f)quinoline adsorbed on silica gel chromatoplates were investigated over a wide range of humidities in N(2), air and O(2). Both neutral and acidic conditions were used and even at the highest relative humidity used, 93% relative humidity, the room-temperature fluorescence and phosphorescence intensities from benzo(f)quinoline were not totally quenched. However, in all experiments, the room-temperature phosphorescence was much more sensitive to humidity quenching than the room-temperature fluorescence. The results gave rather detailed information on quenching of the room-temperature fluorescence and phosphorescence in the different gases at a variety of humidities. It was possible to calculate the contribution to the percent decrease in luminescence due to moisture or a quenching gas. Thus, a more detailed assessment could be made about the quenching of moisture and individual quenching gases on the solid-matrix fluorescence and phosphorescence.     

甲烷部分氧化制甲醛催化剂MoO_3／SiO_2及MoO-3·MxOy／SiO_2的程序升温还原研究

利用程序升温还原（ＴＰＲ）方法，研究了甲烷部分氧化制甲醛催化剂ＭｏＯ３／ＳｉＯ２及添加金属氧化物的ＭｏＯ３·ＭｘＯｙ／ＳｉＯ２（Ｍ＝Ｖ、Ｆｅ、Ｎｉ、Ｃｒ、Ｃｕ）催化剂上，活性组分在载体上的分散及ＭｏＯ３与ＭｘＯｙ的相互作用．发现钼含量的提高不利于ＭｏＯ３在ＳｉＯ２上的分散，催化剂表面晶相ＭｏＯ３随钼含量的提高而增多．ＳｉＯ２上担载的活性组分有一个最佳值，对应于最佳催化活性．ＭｏＯ３·ＭｘＯｙ／ＳｉＯ２催化剂中ＭｏＯ３与ＭｘＯｙ发生了不同的相互作用，影响催化剂表面的活性氧物种，导致它们对甲烷氧化活性和甲醛选择性的不同．ＭｏＯ３·Ｖ２Ｏ５／ＳｉＯ２是比较好的催化剂，且Ｖ２Ｏ５添加量有最佳值，对应甲烷氧化制甲醛也有较高的活性和选择性．     

硅胶负载H6PMo9V3O40催化合成5-硝基水杨醛

采用硅胶负载Keggin型H6PMo9V3O40催化水杨醛与硝酸反应合成5-硝基水杨醛,考察了催化剂负载量、反应时间、反应温度、催化剂用量、硝酸用量和溶剂对反应的影响及催化剂的重复使用性能。实验结果表明,m(水杨醛)∶m(质量分数65%硝酸)∶m(负载量20%H6PMo9V3O40/SiO2)=2.44∶3.00∶3.00,用石油醚作为溶剂,45℃反应2.5 h,水杨醛的转化率为98%,5-硝基水杨醛的选择性为96.8%。催化剂回收容易,重复使用5次后,活性基本不变。