石墨烯-溴氧化铋复合物的制备及可见光光催化性能研究

采用超声-水热法在溴氧化铋(BiOBr)上负载不同含量氧化石墨来制备石墨烯-溴氧化铋(Gre-BiOBr)复合物,利用X-射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、紫外可见漫反射(UV-Vis DRS)、荧光分光光度计(PL)、比表面积仪(BET)及红外光谱仪(FT-IR)对不同负载量的Gre-BiOBr进行初步表征.发现BiOBr负载石墨烯前后均为斜四方晶型(JCPDS:78-0348),均为大小500~1 000 nm片层状.在可见光照射下(λ≥420 nm),以罗丹明B(Rhodamine B,RhB)和水杨酸(Salicylicacid,SA)作为降解底物,发现经过负载石墨烯后BiOBr的可见光活性有明显提高,且当负载质量比为10%时,Gre-BiOBr复合物表现出最好的可见光活性,此时光降解RhB反应速率(k10%Gre-BiOBr=0.046 min-1)约为单纯BiOBr(kBiOBr=0.02 min-1)的两倍.经测定10%Gre-BiOBr复合物的比表面积为10.50 m2/g,禁带宽度为2.61 eV,能吸收λ≥475 nm可见光.结合自由基捕获实验,发现该催化体系主要涉及超氧自由基(O2·-)和空穴(h+)的共同氧化作用.10%Gre-BiOBr催化剂循环使用5次,仍保持着良好光催化活性,表明该催化剂稳定性较好.     

多孔柿饼状BiOBr光催化剂的简易溶剂热法合成（英文）

以硝酸铋和十六烷基三甲基溴化铵(CTAB)为Bi和Br源,采用聚乙烯吡咯烷酮(PVP)辅助溶剂热法首次成功制备了多孔纳米片聚结的柿饼状溴氧化铋(BiOBr)。通过多种分析技术对分级微米结构BiOBr材料的物化性质进行了表征,并对其在可见光照射下降解亚甲基蓝(MB)的光催化活性进行了评价。结果表明,溶剂热时间和PVP的加入量对产物的颗粒形貌和结晶度有显著影响。当加入0.7 g PVP时,120℃溶剂热处理12 h,可得到多孔纳米片聚结的柿饼状BiOBr样品。多孔柿饼状BiOBr样品的比表面积为4 m2·g^-1,带隙能为2.64 eV,在可见光区具有较强的光吸收性能,具有良好的可见光驱动降解MB的光催化活性和稳定性。我们推断,多孔纳米片聚结的柿饼状BiOBr样品具有优良的可见光催化性能,这与该样品的较高比表面积、多孔结构、低带隙能以及独特的颗粒形貌有关。     

La掺杂在BiOBr光催化剂氧化和还原性能调控中的不同作用（英文）

同时使用有机溴源十六烷基三甲基溴化铵(CTAB)和无机溴源NaBr,通过溶剂热法合成了具有层状类囊体结构的La掺杂BiOBr光催化剂。通过第一性原理(DFT)计算了La掺杂对BiOBr能带结构的影响。采用X射线衍射、扫描电子显微镜、透射电子显微镜、X射线光电子能谱及荧光光谱对催化剂进行了表征。在可见光照射下,以光催化降解酸性橙Ⅱ和氨氮废水测试了LaBiOBr的氧化性能;以亚甲基蓝为还原指示剂,测试了La-BiOBr的还原性能。研究表明,La的掺杂可以促进晶粒的堆积。而且BiOBr的氧化性能和还原性能分别被促进和抑制,即La的掺杂促进了BiOBr光催化剂的氧化性能,抑制了其还原性能。     

溶剂对BiOBr结构和光催化降解RhB的影响

以水热法合成了不同形貌的BiOBr样品.采用X射线衍射(XRD)、扫描电子显微镜(SEM)、氮气吸附脱附曲线和紫外可见漫反射光谱(UV-Vis DRS)研究溶剂对BiOBr样品的晶形、形貌、孔径分布和比表面积、光学性质的影响;以罗丹明B(RhB)为目标降解物,研究溶剂对BiOBr的可见光催化性能的影响.实验结果表明,采用EG为溶剂的BiOBr在可见光降解RhB中表现出最佳的降解效果,因其较采用HNO_3、GL和PVP为溶剂的样品具有更高I_((001))/I_((102)),更小的禁带宽度和更均一的纳米片形貌.此外,阐述了溶剂对光催化降解RhB的影响机理.     

BiOBr的可控制备及对废水中卡马西平的有效降解

以Bi(NO₃)₃·5H₂O为原料, 乙醇为介质, KBr和/或十六烷基三甲基溴化铵(CTAB)为溴源, 采用溶剂热法合成了不同结构和性能的BiOBr微纳米材料, 通过 X射线衍射仪(XRD)、 扫描电子显微镜(SEM)、 红外光谱仪(FTIR)、 紫外-可见漫反射光谱(UV-Vis DRS)及比表面积和孔隙度分析仪对产物进行了表征. 结果表明, 溴源(KBr, CTAB)对BiOBr的结晶特性和形貌有重要影响, 其中采用双溴源且KBr与CTAB摩尔比为3∶7时制得的BiOBr(K∶C=3∶7)光催化剂在模拟太阳光下具有最优的光催化性能, 光照20 min后对废水中卡马西平的降解速率常数是以KBr为溴源制备的BiOBr(K)的4.10倍和以CTAB为溴源制备的BiOBr(C)的2.14倍. BiOBr(K∶C=3∶7)优异的光催化活性可归因于其高暴露的(110)晶面、 表面羟基、 疏松的片层状形貌及较大的比表面积和孔体积. 活性物种淬灭实验结果表明, BiOBr(K∶C=3∶7)的光催化活性主要源于光生空穴、 羟基自由基和电子.     

La掺杂在BiOBr光催化剂氧化和还原性能调控中的不同作用

同时使用有机溴源十六烷基三甲基溴化铵（CTAB）和无机溴源NaBr,通过溶剂热法合成了具有层状类囊体结构的La掺杂BiOBr光催化剂。通过第一性原理（DFT）计算了La掺杂对BiOBr能带结构的影响。采用X射线衍射、扫描电子显微镜、透射电子显微镜、X射线光电子能谱及荧光光谱对催化剂进行了表征。在可见光照射下,以光催化降解酸性橙Ⅱ和氨氮废水测试了La-BiOBr的氧化性能;以亚甲基蓝为还原指示剂,测试了La-BiOBr的还原性能。研究表明,La的掺杂可以促进晶粒的堆积。而且BiOBr的氧化性能和还原性能分别被促进和抑制,即La的掺杂促进了BiOBr光催化剂的氧化性能,抑制了其还原性能。     

单步电沉积法制备CuInS2薄膜

采用单步电沉积法在Mo基底上制备了高质量的CuInS2薄膜. 用X射线衍射仪(XRD)和扫描电子显微镜(SEM)表征了样品的结构和形貌, 研究了沉积电位、退火温度、pH值、反应物浓度等工艺条件对制备的CuInS2薄膜形貌、组分及性能的影响. 制备的CuInS2薄膜致密平整, 呈黄铜矿结构, 晶粒大小为1-2 μm. 用紫外-可见光分光光度计测试了其光学性能, 计算得到常温下禁带宽度为1.41 eV, 非常适合用作薄膜太阳电池的吸收层材料.     

导电高聚物修饰纳米尺度TiO~2多孔膜电极的光电化学研究

用光电化学方法研究了用导电高聚物修饰的纳米晶TiO~2多孔膜电极在不含氧化还原对和含不同氧化还原对体系电解质溶液中的光电转换过程。TiO~2/导电高聚物多孔膜电极为双层n型半导体结构,内层TiO~2多孔膜的禁带宽度为3.26eV,外层聚吡咯(PPy)膜的禁带宽度为2.23eV,而聚苯胺(PAn)膜的禁带宽度为2.88eV。用导电高聚物修饰半导体电极能使其在可见光区的光吸收增加,光电流增强,且起始波长红移至>600nm,使宽禁带半导体电极的光电转换效率得到明显改善。     

复合催化剂α-(Fe，Cu)OOH/RGO的制备、表征及其协同H2O2在可见光下去除环丙沙星性能

采用一步回流法制备了α-(Fe,Cu)OOH/RGO复合催化剂,通过粉末X射线衍射、扫描电子显微镜和X射线光电子能谱等对催化剂进行了表征,并以30 mg·L^-1的环丙沙星(CIP)为目标污染物,研究了不同制备条件下所得催化剂在可见光照射下协同H2O2对CIP的去除效果。结果表明,成功实现了α-(Fe,Cu)OOH纳米棒在石墨烯二维薄片上原位生长,α-(Fe,Cu)OOH/RGO复合材料的可见光吸收边发生红移,禁带宽度从2.02 eV变为1.76 eV。石墨烯复合不但增强了对污染物的吸附能力,而且加快了光生电子的分离、迁移速率,还提高了反应体系中电子的传导效率。当石墨烯复合比例(质量分数)为1%时,复合催化剂的催化性能最佳。当催化剂投加量为0.40 g·L^-1,H2O2浓度为0.10 mol·L^-1时,反应120 min,CIP被全部去除。α-(Fe,Cu)OOH/RGO循环使用5次,对CIP的去除率均在90%以上,表明催化剂具有较强的催化活性和较好的稳定性。     

La掺杂在BiOBr光催化剂氧化和还原性能调控中的不同作用

同时使用有机溴源十六烷基三甲基溴化铵（CTAB）和无机溴源NaBr，通过溶剂热法合成了具有层状类囊体结构的La掺杂BiOBr光催化剂。通过第一性原理（DFT）计算了La掺杂对BiOBr能带结构的影响。采用X射线衍射、扫描电子显微镜、透射电子显微镜、X射线光电子能谱及荧光光谱对催化剂进行了表征。在可见光照射下，以光催化降解酸性橙Ⅱ和氨氮废水测试了La-BiOBr的氧化性能；以亚甲基蓝为还原指示剂，测试了La-BiOBr的还原性能。研究表明，La的掺杂可以促进晶粒的堆积。而且BiOBr的氧化性能和还原性能分别被促进和抑制，即La的掺杂促进了BiOBr光催化剂的氧化性能，抑制了其还原性能。     

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%).     

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.     

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.     

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.     

Synthesis of pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles by Curtius reaction in Morita-Baylis-Hillman derivatives

Synthesis of substituted pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles from the Morita-Baylis-Hillman derivatives of acrylates via saponification followed by Curtius reaction is described.