非金属掺杂改性TiO2光催化剂的机理

为了扩展TiO2光催化剂对可见光的利用,以非金属元素对其进行掺杂和改性是近年来很活跃的研究内容,文献报道主要有氮、碳、硫、氟等非金属元素的改性结果.各种不同的改性方法如高温气氛还原、脉冲激光沉积、离子溅射、机械化学、溶液湿法等都可以得到非金属元素改性.本文重点探讨了氮改性TiO2光催化剂的结果,氮改性TiO2的方法和改性机理,讨论了氮改性TiO2的结构及其对可见光的利用机理等,对碳、硫、氟等元素掺杂改性也作了简要介绍.     

非金属掺杂改性TiO_2光催化剂的机理

为了扩展TiO2光催化剂对可见光的利用,以非金属元素对其进行掺杂和改性是近年来很活跃的研究内容,文献报道主要有氮、碳、硫、氟等非金属元素的改性结果。各种不同的改性方法如高温气氛还原、脉冲激光沉积、离子溅射、机械化学、溶液湿法等都可以得到非金属元素改性。本文重点探讨了氮改性TiO2光催化剂的结果,氮改性TiO2的方法和改性机理,讨论了氮改性TiO2的结构及其对可见光的利用机理等,对碳、硫、氟等元素掺杂改性也作了简要介绍。     

非金属改性可见光诱导的TiO2光催化

为拓展二氧化钛的光响应波长范围并提高其光催化活性,通常采用掺杂金属、金属氧化物或金属离子的方法.大量研究表明,掺杂金属、金属氧化物或金属离子往往以损失TiO2光催化剂在紫外光区的光催化活性为代价,而掺杂非金属离子不但能将TiO2的光响应波长拓展至可见光区域外,还能保持在紫外光区的光催化活性,在利用太阳光光催化方面展现出崭新的应用前景.本文综述了非金属氮、碳、硫、氟等掺杂改性二氧化钛光催化的最新进展.     

非金属改性可见光诱导的TiO_2光催化

为拓展二氧化钛的光响应波长范围并提高其光催化活性,通常采用掺杂金属、金属氧化物或金属离子的方法。大量研究表明,掺杂金属、金属氧化物或金属离子往往以损失TiO2光催化剂在紫外光区的光催化活性为代价,而掺杂非金属离子不但能将TiO2的光响应波长拓展至可见光区域外,还能保持在紫外光区的光催化活性,在利用太阳光光催化方面展现出崭新的应用前景。本文综述了非金属氮、碳、硫、氟等掺杂改性二氧化钛光催化的最新进展。     

非金属改性可见光诱导的TiO2光催化

为拓展二氧化钛的光响应波长范围并提高其光催化活性，通常采用掺杂金属、金属氧化物或金属离子的方法。大量研究表明，掺杂金属、金属氧化物或金属离子往往以损失TiO2光催化剂在紫外光区的光催化活性为代价，而掺杂非金属离子不但能将TiO2的光响应波长拓展至可见光区域外，还能保持在紫外光区的光催化活性，在利用太阳光光催化方面展现出崭新的应用前景。本文综述了非金属氮、碳、硫、氟等掺杂改性二氧化钛光催化的最新进展。     

氮掺杂改性二氧化钛光催化剂的研究进展

综述了近年来国内外利用氮掺杂改性二氧化钛的光催化剂性能、提高可见光的利用效率的最新研究进展;分析和讨论了氮掺杂二氧化钛的制备方法、理论计算和结构模型、掺杂机理等;总结了氮掺杂改性二氧化钛存在的问题,同时讨论了今后的研究方向.     

氟掺杂提高纳米二氧化钛光催化活性的研究进展

纳米二氧化钛(TiO2)具有光催化活性高、无毒、化学性质稳定、成本低等优点,是目前最具发展前景的光催化剂。但TiO2的宽禁带和低量子效率限制了它的实际应用。因此,对TiO2进行改性研究,实现TiO2的可见光响应和提高其量子效率成为研究的热点。氟掺杂不仅能够使TiO2具有可见光催化活性,而且可提高其紫外光催化活性。本文综述了氟掺杂TiO2的制备,氟掺杂提高TiO2光催化活性的机理、氟与其他元素共掺杂TiO2的研究进展。     

稀土掺杂TiO2光催化的研究进展

利用稀土掺杂对TiO2进行改性以实现可见光响应和提高量子效率是提高光催化剂活性的重要方法之一.总结了国内外利用稀土掺杂TiO2催化剂的制备方法及利用稀土掺杂对TiO2进行改性以提高其光催化效率的研究结果,分析了稀土元素种类、掺杂量等因素对光催化活性的影响.     

碳和钇共掺杂对混相TiO2光催化性能的影响

TiO2因其毒性低、稳定性高、制备成本低廉而获得广泛应用,特别是作为光催化剂在降解环境污染物方面受到了广泛关注;然而,纯TiO2较大的光生载流子复合率和较宽的带隙限制了其应用.元素掺杂作为一种拓宽光催化剂光吸收能力的方法广泛应用于各种光催化剂的修饰改性,而两种具有光催化性能的TiO2相共存则能有效抑制光生载流子的复合,因此采取合适的方法有效利用这两种TiO2改性的方法制备得到更具实际应用潜质的光催化剂具有一定的可行性.本文通过简单的溶胶-凝胶过程向锐钛矿相与金红石相组成的混相TiO2中共掺杂碳和钇得到了一种活性较高的可见光响应光催化剂.采用粉末X射线衍射、拉曼光谱、X射线光电子能谱和透射电镜等表征手段研究了碳和钇掺杂对TiO2结构的影响,发现碳掺杂有利于金红石相的形成且材料具有更大的晶粒尺寸,钇掺杂则有利于锐钛矿相的形成且能细化材料的晶粒尺寸,提高材料的比表面积,导致材料更好的光催化活性.材料在30 W荧光灯光照条件下的光催化降解亚甲基蓝(MB)性能的研究显示,C-Y-TiO2样品具有比单掺杂和未掺杂样品更高的光催化活性,其顺序为C-Y-TiO2>Y-TiO2>C-TiO2>TiO2≈P25.此外,降解反应动力学研究表明C-Y-TiO2样品光降解MB的速率是未掺杂样品在相同条件下降解速率的3.5倍.不同钇掺杂含量样品的结构和光催化降解MB的研究结果表明,钇掺杂显著促进了锐钛矿相TiO2的形成.这说明钇可能仅掺杂进入锐钛矿相,因此合适的钇掺杂量才能有效形成最优化的光催化性能的混相TiO2.不同热处理温度下获得的样品的光降解MB特性也表明,一定的热处理温度有利于合适的锐钛矿相和金红石相的组成,从而有利于相间的协同效应.紫外-可见光谱和荧光光谱表征分析表明,碳和钇的掺杂都拓展了其吸收光谱到可见光区域,且抑制了光生电子和空穴对的复合,进而提高了材料的光催化活性.碳和钇共掺杂的混相TiO2具有较高可见光光催化活性的主要原因有两个方面:一是元素掺杂减小了TiO2的带隙使得材料具有可见光响应;二是金属和非金属元素在锐钛矿相与金红石相TiO2中不同的掺杂特性形成的协同效应,抑制了光生电子和空穴的复合.     

N掺杂TiO_2纳米管阵列的制备及可见光光催化性能研究

分别以氨水、乙二胺、丁胺为氮源,利用阳极氧化法和湿化学法合成氮掺杂的二氧化钛(TiO2)纳米管阵列.通过扫描电镜(SEM)、X射线衍射(XRD)、X射线光电子能谱(XPS)等表征方法对氮掺杂TiO2纳米管形貌,晶型和氮元素掺杂方式进行分析,并通过可见光光催化降解六氯苯(HCB)废水,研究氮元素掺杂方式与可见光光催化活性的关系.结果表明有序排列的TiO2纳米管阵列垂直生长在钛基底表面,管长500nm左右,管径100nm左右.氮元素掺杂阻碍了TiO2晶粒的增长,抑制了锐钛矿向金红石相的转变.无机氮比有机氮更加利于氮元素进入TiO2晶格,取代态氮比间隙态氮表现出更高的可见光光催化活性.     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.