纺锤形BiVO4微米管：低温离子熔盐合成及光催化性能

以Bi(NO₃)₃·5H₂O和NH₄VO₃为原料,以氯化胆碱和尿素组成的低温离子熔盐为反应介质,采用离子热合成法成功制备出了具有纺锤状外形的BiVO₄微米管。利用XRD,SEM,UV-Vis DRS,光催化测试等手段考察了BiVO₄颗粒的物相、形貌和光催化性能。结果表明,在离子熔盐环境下可以制备出结晶良好的BiVO₄纺锤形微米管,该BiVO₄微米管长10~15 μm,直径为1.5 μm左右,管壁厚约为200 nm。同时,研究了pH值对BiVO₄颗粒物相与形貌的影响,发现随着pH值的变化可分别合成出具有柱状、纺锤形微米管、柱状微米管和针柱状单斜相BiVO₄颗粒。光催化测试结果表明,这些单斜白钨矿BiVO₄颗粒在可见光范围都具有一定的光催化活性,其中纺锤状微米管对罗丹明B的降解效果最佳,可见光照射4.5 h后罗丹明B的降解率可达到93％。     

三种形貌BiVO_4微纳材料的制备及其光催化性能研究

本文以Bi(NO_3)_3·5H_2O和NH4VO3为原料,以甲酰胺和尿素为不同碱源来调节pH值,采用水热法合成出三种不同形貌和晶型的BiVO_4微纳材料。实验结果显示,不加碱源时(反应后pH约为2.35)得到四方锆石结构和单斜晶系白钨矿结构混合相的类球状BiVO_4;加入甲酰胺时(反应后pH约为6.54)得到羽毛状单斜晶系白钨矿BiVO_4;而加入尿素时(反应后pH达到8.91)所得产物则为草垛状锆石结构和白钨矿结构的混合相BiVO_4。当以罗丹明B为降解对象,上述三种BiVO_4样品光催化性能的考察结果表明,在紫外光照射下,类球状的混合相BiVO_4微纳材料表现出最好的光催化性能,在120 min内使罗丹明B水溶液的脱色率达到98.28%。在可见光照射下,羽毛状白钨矿BiVO_4微纳材料则对罗丹明B表现出最好的降解效果,6 h内脱色率达到97.23%。     

钒酸铟分级结构微米花和纳米线的水热合成和可见光催化性能

采用水热法合成InVO4分级结构微米花和InVO4纳米线．FESEM结果表明,通过控制水热反应参数可以获得不同形貌InVO4晶体．利用可见光（λ〉420nm）照射下的罗丹明B降解实验评价了InVO4样品的光催化性能．结果表明,InVO4的光催化活性比商用P25 TiO2高得多,其中花状InVO4纳米结构光催化效率最高,经可见光照射40min,岁丹明B溶液（3μmol／L）的降解率可达100％．同时还研究了结构和形貌对不同条件下制备的InVO4样品光催化活性的影响．     

锯末模板法制备N掺杂BiVO_4及其可见光光催化性能

以锯末为模板剂合成了N掺杂BiVO_4可见光光催化剂,采用SEM、XRD、UV-vis及光降解亚甲基兰实验对合成样品的形貌、晶相结构、吸光性能及光催化性能进行了表征。结果表明,锯末模板剂对样品的生长起到了一定的抑制和导向作用,所合成的N掺杂BiVO_4样品呈蜂窝状,尺寸分布均匀,样品中BiVO_4呈单斜白钨矿结构,由于N原子进入BiVO_4晶格内部形成掺杂能级,窄化了BiVO_4的能带结构,拓宽了材料的可见光响应范围。以氙灯为光源,当N掺杂量为1.2%时,样品对MB具有良好的光催化降解效果,在3 h内对初始浓度为10 mg/L的亚甲基兰降解率可达84%左右。     

pH调控水热法合成BiVO_(4)及其可见光催化降解甲基橙

以硝酸铋为铋源,偏钒酸铵为钒源,醋酸钠调节pH值,采用水热法合成光催化剂BiVO_(4),采用X-射线衍射仪(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)对产物进行结构和形貌分析.在可见光条件下,考察BiVO_(4)对甲基橙(MO)的光催化性能.结果表明,在pH值为6.0的条件下合成的BiVO_(4)具有较优的光催化性能,可见光条件下催化反应5 h后,MO的降解率达到98.4%,并且在循环反应5次后对MO的降解率仍在95%以上.因BiVO_(4)良好的光催化活性和稳定性,在废水处理领域有非常广阔的应用前景.     

Ag_2CO_3/BiVO_4复合微米片光催化剂的制备、表征及光催化机理

采用水热法制备粒径为1~2μm的BiVO_4微米片,然后在微米片表面沉积不同含量的Ag_2CO_3颗粒,制备Ag_2CO_3/BiVO_4复合微米片光催化剂。利用X射线粉末衍射(XRD)、扫描电镜(SEM)、红外光谱(FTIR)、紫外-可见漫反射光谱(UV-Vis DRS)、光致发光(PL)光谱、瞬态光电流-时间响应对催化剂进行表征。以可见光为光源,罗丹明B为降解对象进行光催化活性测试。结果表明,复合适量Ag_2CO_3有利于提高光催化剂的比表面积,改善催化剂的表面性能。活性测试结果表明,当复合10%(w/w)Ag_2CO_3时,Ag_2CO_3/BiVO_4光催化活性最佳,比纯BiVO_4提高4.4倍。光致发光(PL)光谱、瞬态光电流-时间响应测试结果表明,复合Ag_2CO_3能有效抑制光生电子与空穴的复合。自由基捕获实验结果表明,该体系的活性氧物质为空穴和羟基自由基。Ag_2CO_3/BiVO_4复合光催化剂活性提高的原因,是较宽带隙的Ag_2CO_3与较窄带隙的BiVO_4形成的异质结有效抑制了光生电子与空穴的复合,同时两者适宜的能带结构保证产生更多的空穴,从而具有更强的氧化能力。     

二氧化锰/钒酸铋复合光催化剂的制备及性能

采用液相沉淀法制备了不同锰含量的二氧化锰(MnO_2)/钒酸铋(BiVO_4)复合光催化剂,利用XRD、SEM、XPS等对催化剂进行了表征。通过对罗丹明B的降解,研究了不同锰含量的光催化剂在太阳光下的光催化降解性能,并考察了催化剂用量对光降解率的影响。结果表明,制备出的不同Mn含量的BiVO_4光催化剂均为单斜晶型结构,且Mn元素是以MnO_2的形式存在,说明Mn元素的引入没有改变BiVO_4的晶型和结构。其中Mn含量为1.67%的BiVO_4样品具有最高的光催化活性,光催化反应90 min对罗丹明B溶液的降解率可达到26.39%,比纯BiVO_4样品的降解率(14.06%)提高了近一倍,其催化性能提高的原因可能是由于一定量MnO_2的存在使催化剂中光生电子-空穴的高效分离造成的。同时发现当MnO_2的含量过高,由于形貌分布不均,会变成光生电子和空穴的复合中心,致使催化剂的活性降低。不同用量的同种催化剂光降解实验结果表明:对罗丹明B的光降解率随催化剂用量的增加而增大,但超过一定用量后,光降解率增加速度变缓。     

四角星形BiVO4/Bi2O3催化剂的制备及性能

采用水热法合成具有四角星形貌的钒酸铋,再将钒酸铋浸渍在碱溶液里二次水热,制备出BiVO_4/Bi_2O_3催化剂。采用X射线粉末衍射(XRD)、扫描电子显微镜(SEM),紫外-可见漫反射(UV-Vis DRS)等方法对样品进行表征。可见光下,BiVO_4/Bi_2O_3复合物的光催化降解罗丹明B性能及光电流响应均优于纯BiVO_4。这是由于BiVO_4/Bi_2O_3复合材料形成了异质结构,有效抑制了光生电子与空穴的复合效率。     

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。     

Cu掺杂BiVO4催化剂的制备及其光催化性能

以Cu(NO_3)2·3H_2O为铜源,采用水热法在180 ℃条件下制备了不同Cu掺杂量的BiVO_4光催化材料,其在可见光下具有强大的氧化还原能力。通过X射线衍射、X射线光电子能谱、扫描电子显微镜、紫外可见吸收光谱、荧光光谱、电化学阻抗谱等表征手段对样品进行表征与分析,并以500 WXe灯为模拟可见光源,罗丹明B染料(RhB)为目标污染物,进行光催化性能研究。研究结果显示,Cu掺杂改变了 BiVO_4的形貌,当Cu掺杂量(质量分数)为1 %时,在500～800 nm范围内可见光吸收显著,使得光催化活性达到最佳,对RhB(10 mg·L~(-1))的降解率可达81.6%,较同条件下制备的纯BiVO_4光催化效率提高了近20%。     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

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%).     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.     

Synthesis of N-substituted carbazolones from α-iodo enaminones via Pd(0)-catalyzed intramolecular coupling under microwave irradiation

A variety of N-aryl and N-alkyl carbazolones were conveniently achieved in good to high yields via Pd₂(dba)₃-mediated intramolecular coupling of N-substituted α-iodo enaminones under microwave irradiation. The Pd(0)-catalyzed cyclization was found to proceed favorably with the more electron-deficient phenyl ring during the reactions involving unsymmetrical N,N-diaryl α-iodo enaminones. This unique property enables the construction of carbazolone skeleton containing nitro substituted benzenoid ring.     

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.     

Synthesis of substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles by intramolecular nitrilimine cycloaddition

Both substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles have been synthesized by the 3+2 intramolecular dipolar cycloaddition of nitrilimines to alkynes. This cyclization has been extended to more versatile 3-bromo derivatives by the use of alkynylbromides as dipolarophiles.