CdS/石墨烯复合材料的制备及其可见光催化分解水产氢性能

以氧化石墨烯和CdS为原料, 在乙醇水溶液中采用CdS光催化还原法制备了CdS/石墨烯复合光催化材料, 并用透射电子显微镜(TEM)、X射线衍射(XRD)、傅里叶变换红外(FTIR)光谱、X射线光电子能谱(XPS)和瞬态光电流等技术对复合材料的结构和光电性能进行了表征. 可见光照射下(λ≥420 nm), 研究了该复合材料光催化分解水产氢的性能. 结果表明, 可见光照射下CdS的光生电子可有效地还原氧化石墨烯, 得到CdS与石墨烯之间具有强相互作用力的CdS/石墨烯复合材料. 与CdS相比, 复合材料中石墨烯作为良好的电子受体和传递介质, 可明显加快CdS光生电子的迁移速率, 提高光生载流子的分离效率, 从而增强复合材料的光电性能和光催化分解水产氢的活性.     

CdS/石墨烯纳米复合物的可见光催化效率和抗光腐蚀行为

制备了一系列CdS纳米晶/石墨烯(CdS/GR)复合物,并在可见光照条件下评价了其光催化降解亚甲基蓝的光催化效率和抗光腐蚀行为. 研究表明,石墨烯的引入加速了CdS纳米晶(NCs)光生电子的迁移速率,抑制了其光生电子-空穴的复合,有效改善了其光催化降解有机污染物的性能. CdS/GR复合物中的石墨烯含量显著影响其光催化效率,其中石墨烯含量为4.6%的光催化剂效率最高,其光电流是CdS NCs的2.3倍. 利用光电化学和X射线衍射技术进一步证实,石墨烯的引入抑制了CdS NCs光腐蚀的发生,提高了CdS/GR复合物的光催化稳定性.     

TiO2/石墨烯复合材料的光生电荷分离调控与光催化产氢性能研究

半导体光生电荷分离是光催化过程中的关键步骤之一,其效率极大地影响了最终光催化性能.将TiO₂纳米片与石墨烯复合,能够促进TiO₂中光生电子和空穴的分离,从而提高其光催化活性.为了研究光生电荷的分离对TiO₂/石墨烯复合材料光催化性能的影响,通过调控TiO₂纳米片的尺寸来调节TiO₂/石墨烯复合材料中光生电荷分离的能力,然后研究其对TiO₂/石墨烯复合材料光催化性能的影响.合成了一系列不同厚度的TiO₂纳米片,将其与石墨烯复合,并通过光沉积负载Pt纳米颗粒作为助催化剂,用于光催化产氢.实验结果显示,随着TiO₂纳米片厚度减小,其与石墨烯形成的复合结构的光催化性能显著提高.这主要是由于TiO₂纳米片厚度减小时,光生电子沿厚度方向穿过TiO₂纳米片迁移到石墨烯的距离缩短,从而减少了光生电子在迁移过程中与空穴的复合;同时TiO₂纳米片厚度减小使其比表面积增大,使得TiO₂/石墨烯界面面积增大,从而使石墨烯更好地分离出TiO₂中的光生电子,有更多的光生电子到达石墨烯参与催化反应,提高TiO₂/石墨烯复合材料的光催化性能.此研究表明通过控制TiO₂纳米片的尺寸来调控TiO₂/石墨烯复合材料中光生电子和空穴的分离,是显著提高其光催化性能的有效途径.     

纳米复合材料CdS/TiO_2制备与不同模式光催化降解多种染料

采用化学水浴沉淀法再结合溶胶-凝胶和程序升温溶剂热两步法制备了一系列不同比例的CdS/TiO2纳米复合材料。通过X-射线衍射(XRD)、X-射线光电子能谱(XPS)、扫描电镜(SEM)、紫外-可见漫反射吸收光谱(UV-Vis/DRS)和氮气吸附-脱附测试等手段对所合成纳米复合材料的组成、结构和形貌进行了表征。结果表明,该系列CdS/TiO2纳米复合材料为锐钛矿TiO2和六方相CdS的混合晶相,其对可见光有较强吸收,并且随着复合材料中TiO2比例的增加,BET值明显增大。另外,所合成的CdS/TiO2复合材料呈圆球形,颗粒比较均匀。紫外光催化降解甲基橙的实验结果表明,摩尔比为1∶4的CdS/TiO2复合材料的活性明显高于CdS、P25以及其他不同比例的CdS/TiO2。同时,1∶4 CdS/TiO2纳米复合材料在紫外光、可见光和微波辅助光催化等不同模式下对多种结构的染料均有较好的降解效果。     

ZnO/CdS复合材料的合成与可见光催化性能

采用喷雾辅助气相沉积法在水热法合成的ZnO纳米线上沉积CdS纳米颗粒。采用X射线衍射仪（XRD）、激光拉曼仪（Raman）、扫描电镜（SEM）、透射电镜（TEM）、X射线光电子能谱分析谱（XPS）和紫外可见漫反射光谱等测试手段对复合光催化剂进行表征。结果表明,3~10 nm的CdS纳米粒子修饰在直径约为100 nm ZnO纳米线的表面。XPS和Raman表明复合材料中ZnO和CdS之间存在化学相互作用。可见光催化降解罗丹明B实验结果表明ZnO/CdS复合材料的催化性能优于单相CdS或ZnO,沉积时间为30 s合成的ZnO/CdS速率常数分别是CdS和ZnO的2.91和4.03倍,且具有较高的稳定性。ZnO/CdS复合材料光催化性能增强的可能原因为光吸收范围的拓展和光生载流子分离效率的提高。     

n-p异质结型CdS/BiOBr复合光催化剂的制备及性能

采用两步水热法制备了CdS/BiOBr复合光催化剂,并通过X射线粉末衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和紫外-可见漫反射光谱(UV-Vis DRS)等手段对其物相、表面结构、光响应性等性质进行了表征.结果表明,合成的CdS/BiOBr复合材料是n-p型异质结,由CdS颗粒裹附在BiOBr纳米球的表面构成,这种结构不仅具有良好的可见光响应范围,且有利于光生电子的迁移,并有效地抑制光生电子/空穴对的复合.通过光催化降解模拟染料废水和光催化脱除模拟含硫燃料评价了CdS/BiOBr复合材料的可见光催化性能.结果表明,6%(质量分数)CdS/BiOBr降解次甲基蓝的拟一级动力学常数分别为BiOBr和CdS的5.3和9.6倍,脱除噻吩的拟一级动力学常数分别为BiOBr和CdS的1.9和3.2倍.CdS/BiOBr具有良好的光催化稳定性,循环使用5次后,降解率仍能达到90%以上.     

CdS/TiO2纳米管复合结构的制备与光电性能研究

利用阳极氧化法在钛金属基底表面制备一层TiO2纳米管阵列薄膜,然后通过水热反应在TiO2纳米管上负载CdS纳米粒子,形成CdS/TiO2纳米管的复合结构。利用SEM、XRD、XPS、UV-Vis等手段对其形貌和结构进行表征。进一步考察了CdS/TiO2纳米管的光电性能和光催化活性,结果表明,相比于TiO2纳米管,CdS/TiO2纳米管复合结构在紫外光和可见光下都具有更好的光催化活性及光电性能。     

0D/1D碳点修饰硫化镉纳米线异质结增强可见光光催化性能（英文）

硫化镉(CdS)作为一种对可见光响应的窄带隙半导体(带隙宽度约为2.4 eV),具有合适的能带位置,近年来受到越来越多的重视.然而在光催化过程中,光生电子与空穴的快速复合极大地限制了CdS的实际应用,如何提高光生电子-空穴对的分离效率成为研究重点.一维CdS纳米棒(1D CdS NWs)具有较大的长径比,能快速有效地转移光生载流子.零维碳点(0D C-dots)是一种粒径在10 nm以下的新型纳米碳材料,其作为助催化剂能够加快光生载流子传递速率,可提高材料光催化性能.因此,通过C-dots对CdS NWs进行修饰并形成异质结,利用C-dots助催化剂的作用以提升CdS NWs的光催化性能,具有一定的可行性.本文成功构建了一种0D/1D碳点修饰CdS NWs异质结(C-dots/CdS NWs),并考察其光催化性能.通过X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)和紫外-可见(UV-Vis)吸收光谱等技术对系列C-dots/CdS NWs样品进行表征.研究发现,C-dots成功负载在CdS NWs的表面并形成异质结.通过测试系列样品在可见光照射下光催化降解罗丹明B(RhB)以及光催化产氢性能发现,C-dots的修饰能够有效增强CdS NWs的光催化性能,其中0.4%C-dots/CdS NWs表现出最佳的光催化降解RhB活性,其经可见光照射60 min即可实现对RhB的完全降解(相同条件下CdS NWs需要180 min).同时自由基捕获实验表明,·O_2~–是降解罗丹明B过程中的主要活性基团.在光催化产氢性能测试中,0.4%C-dots/CdS NWs样品表现出最高的光催化产氢能力,产氢速率可达1633.9μmol g~(-1) h~(-1),比纯CdS的(196.9μmol g~(-1) h~(-1))提高了8.3倍,并且C-dots/CdS NWs具有良好的稳定性.研究发现,在可见光照射下,C-dots/CdS NWs能够产生较强的光生电流,且形成的0D/1D C-dots/CdS NWs异质结具有良好的电子传输能力,实现了C-dots/CdS NWs光生电子与空穴的有效分离,从而增强了光催化性能.     

CdS/BiVO4复合半导体制备及其光催化性能

采用水热法以BiVO_4纳米片为基体原位生长CdS晶体,得到CdS/BiVO_4复合光催化剂,利用XRD、SEM、UV-Vis DRS等方法对材料进行了表征,通过降解亚甲基蓝对样品的光催化性能进行评价。结果表明,BiVO_4为方形片状颗粒,其表面附着棒状CdS纳米颗粒,分散较好。CdS/BiVO_4复合光催化剂表现出较高的光催化活性,在可见光照射下,利用CdS/BiVO_4光催化降解亚甲基蓝,60 min后的降解率达94.79%,相比于纯相BiVO_4和CdS有显著提高,且对多种有机染料均有良好的降解效果,重复使用性较好。机理研究发现,超氧自由基(·O_2~-)是CdS/BiVO_4光催化降解亚甲基蓝的主要活性物种。     

核壳结构CdS/CuS纳米复合材料的制备及光催化性能

以乙酸镉、 2-巯基苯并噻唑、 硫化钠和氯化铜为原料, 依次利用液相热分解与离子吸附法, 改变CdS晶化时间及含量, 制备了4种CdS/CuS纳米复合材料. 研究结果表明: CdS/CuS纳米复合材料呈类球形核壳结构, 改变CdS晶化时间可以控制CdS/CuS纳米复合材料粒径大小; CdS的晶化时间为10 min, CdS与CuS摩尔比为4∶1的纳米复合材料光催化活性最佳, 25 min内对RhB和MB的降解效率均达到99%.     

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.     

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%).     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

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.     

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.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

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.