Bi2Ti2O7/TiO2/Bi4Ti3O12多异质结的构筑及其增强的可见光催化性能

以静电纺丝技术制备的TiO₂纳米纤维为基质,硝酸铋为铋源,KOH为矿化剂,成功制备了多异质结Bi₂Ti₂O₇/TiO₂/Bi₄Ti₃O₁₂复合纳米纤维光催化剂。通过X射线衍射(XRD)、扫描电子显微镜(SEM)、紫外可见漫反射光谱(UV-Vis DRS)等一系列表征,对其物相组成、微观形貌和光学性质等进行分析。结果表明：TiO₂纳米纤维的介入,将Ⅰ型异质结Bi₂Ti₂O₇/Bi₄Ti₃O₁₂分离为2个Ⅱ型异质结Bi₂Ti₂O₇/TiO₂和Bi₄Ti₃O₁₂/TiO₂。Bi₂     

β-Bi2O3修饰Bi2WO6光催化降解苯酚及其可能机理

采用简单混合法制备了一系列Bi₂O₃/Bi₂WO₆复合光催化剂. 在紫外光降解水中苯酚的过程中, Bi₂O₃/Bi₂WO₆的光催化活性随Bi₂O₃含量的增加呈现先增大后减小的趋势. 当Bi₂O₃最佳负载量等于12.5% (质量分数, w)时, 该复合光催化剂的活性大约是单一Bi₂WO₆的4 倍. 固体样品表征表明, Bi₂O₃主要以β-Bi₂O₃存在, 复合光催化剂是Bi₂O₃和Bi₂WO₆的简单混合物. 此外, 在电催化氧化水的过程中, β-Bi₂O₃/Bi₂WO₆薄膜电极的光电流远大于β-Bi₂O₃和Bi₂WO₆薄膜电极的光电流之和. Bi₂O₃对Bi₂WO₆光催化的促进作用是由于前者接受后者的光生空穴, 提高Bi₂WO₆光生载流子的分离效率, 从而加快了O₂的还原和苯酚的降解.     

TiO2/Bi2O3纳米复合体的制备及可见光催化产氢性能

首先采用相分离的水解-溶剂热法制备了Bi₂O₃纳米粒子,然后利用简单的湿化学法在Bi₂O₃表面负载不同比例的TiO₂纳米颗粒,进而得到TiO₂/Bi₂O₃纳米复合体。通过气氛调控的表面光电压谱(SPS)等测试表明,表面负载适量的TiO₂后能够提高Bi₂O₃光生电荷分离。可见光催化产氢和降解污染物测试结果进一步证明,表面负载适量的TiO₂后可显著提高其可见光催化活性,其中Ti/Bi摩尔比为7%时具有最高的光催化活性。这主要归因于TiO₂具有较为合适的导带能级位置,可以接收Bi₂O₃在可见光激发下所产生的高能级电子,从而抑制光生电子-空穴对复合,并且维持了高能级电子较高的还原能力。     

微波液相法一步合成H3PW12O40/Bi2WO6光催化剂及其脱氮性能

采用微波液相法一步合成了固载型H₃PW₁₂O₄₀/Bi₂WO₆光催化剂. 通过紫外-可见漫反射光谱(UV-Vis)、 场发射扫描电子显微镜(SEM)、 表面积及孔隙度(BET)测定、 氨气程序升温脱附(NH₃-TPD)、 吡啶吸附红外光谱(Py-FTIR)和X射线衍射(XRD)对所合成催化剂的结构和性质进行了考察, 并以吡啶浓度为15 mg/g的模拟油对光催化剂的脱氮效果进行评价. 结果表明, 与传统浸渍固载法相比, 微波液相一步法不仅能高效合成H₃PW₁₂O₄₀/Bi₂WO₆光催化剂, 且所合成的催化剂能被低能量的光激发. 固载H₃PW₁₂O₄₀不但能提高Bi₂WO₆纳米颗粒的表面酸量, 还能通过改变Bi₂WO₆前驱液的酸强度来调控催化剂形貌. 在H₃PW₁₂O₄₀固载量为15%(质量分数), 微波功率为800 W, 反应时间为90 min条件下得到的H₃PW₁₂O₄₀/Bi₂WO₆的光催化脱氮活性最高, 在催化剂与模拟油质量比为1/300, 500 W氙灯光照60 min的最佳光催化反应条件下, 模拟油脱氮率达到92.63%.     

锌掺杂OV-β-Bi2O3可见光催化活性的提高:能带结构的调节和电荷分离的促进

采用溶胶-凝胶-原位碳热还原处理的方法,制备了一种含有氧空位(OV)的新型Zn掺杂β-Bi₂O₃纳米材料(OV-Zn∶Bi₂O₃),氧空位的浓度可以通过改变Zn²⁺的掺杂量进行调节。作为参照,只有氧空位没有Zn²⁺的新型β-Bi₂O₃(OV-β-Bi₂O₃)也通过类似的方法制得。通过紫外可见漫反射光谱、X射线光电子能谱、电子顺磁共振、光致发光光谱和光电化学测试,系统研究了氧空位和Zn²⁺掺杂对OV-Zn∶Bi₂O₃降解亚甲基蓝(MB)和2,4,6-三氯苯酚(2,4,6-TCP)可见光催化活性的综合影响。结果表明,氧空位的引入不仅可以使光吸收向长波方向拓展,而且可以促进光生载流子的分离。因此,与传统的β-Bi₂O₃相比,OV-β-Bi₂O₃对亚甲基蓝(MB)和2,4,6-三氯苯酚(2,4,6-TCP)的降解活性显著增强。对于OV-Zn∶Bi₂O₃催化剂,Zn²⁺掺杂可使光催化剂的价带边缘向下移动,增强了光激发空穴的氧化能力,并且适量的锌掺杂也能提高光生载流子的分离效率。因此,OV-Zn∶Bi₂O₃的可见光活性优于OV-β-Bi₂O₃,而且当Zn与Bi物质的量之比为0.3时,OV-Zn∶Bi₂O₃-0.3对MB和2,4,6-TCP的降解活性最高。     

沉淀法制备Bi2O3的晶相转变过程及其光催化性能

以硝酸铋为原料,氨水为沉淀剂,通过液相沉淀法制得前驱体Bi(OH)₃,并将Bi(OH)₃分别在不同温度和时间下焙烧。利用X射线衍射(XRD)、拉曼光谱、热重(TG)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)及紫外-可见漫反射光谱(UV-Vis DRS)详细研究了Bi(OH)₃转变为Bi₂O₃的过程及相变过程中粒子形貌、大小、光吸收性质等。结果表明,前驱体Bi(OH)₃经过焙烧之后,发生了如下的转变过程:Bi(OH)₃→Bi₅O₇NO₃→β-Bi₂O₃/Bi₅O₇NO₃→β-Bi₂O₃/Bi₅O₇NO₃/α-Bi₂O₃→α-Bi₂O₃,而且转变过程伴随着粒子长大。在上述转变过程中,与Bi₅O₇NO₃向β-Bi₂O₃转变的过程相比,从β-Bi₂O₃到α-Bi₂O₃相变过程更为迅速。此外,以光催化降解罗丹明B(RhB)为模型反应,考察了不同晶相的Bi₂O₃光催化活性,结果表明Bi₅O₇NO₃和β-Bi₂O₃材料具有优异的光催化性能,而α-Bi₂O₃具有较低的光催化活性。     

纳米晶(CeO2)1-x(BiO1.5)x固溶体的水热合成与离子输运性质研究

在240℃水热体系中首次合成出系列纳米晶固溶体(CeO₂)_1-x(BiO_1.5)_x(x=0.0～0.50).产物采用X射线衍射,扫描电子显微镜和X射线光电子能谱仪进行表征.Bi₂O₃在CeO₂中的固溶限约为50%.所有固溶体结晶属立方萤石结构,粒度范围为10～18nm.当Bi₂O₃掺杂量小于固溶限时,于800℃烧结不会导致结构转变.而对于(CeO₂)_0.5(BiO_1.5)_0.5,于800℃在空气中烧结将导致固溶限降低.Bi₂O₃含量低于固溶限时,固溶体只具有体电导,而(CeO₂)_0.6(BiO_1.5)_0.4的总电导可分为体电导和晶界电导.体电导为氧离子,而晶界为来自电极的银离子.     

表面活性剂修饰碳酸氧铋的制备及光催化性能

采用水热法,以阳离子表面活性剂十六烷基三甲基溴化铵(CTAB)、非离子型表面活性剂聚乙二醇8000(PEG8000)、阴离子表面活性剂十二烷基硫酸钠(SDS)及SDS与CTAB耦合修饰Bi₂O₂CO₃。 系统地研究了表面活性剂种类及用量对Bi₂O₂CO₃晶面、形貌、光吸收特性及光催化降解效率的影响。 以紫外光下降解罗丹明B(RhB),考察样品的光催化性能。 结果表明,当Bi盐投加量为6 mmol(2.9106 g)时,SDS对Bi₂O₂CO₃的修饰对其光催化活性有所抑制;0.6 g CTAB修饰Bi₂O₂CO₃能有效提高其光催化活性;0.3 g SDS与CTAB耦合修饰Bi₂O₂CO₃就能有效提高其光催化活性;0.3 g PEG8000修饰Bi₂O₂CO₃也能使其光催化活性有所提高。     

光生电荷梯度连续传递链的构筑及对光催化性能的增强作用

选取能带位置匹配的γ-Bi₂O₃, α-Bi₂O₃和Bi₄Ti₃O₁₂, 采用等体积浸渍法原位构筑了具有梯度能级的Bi₄Ti₃O₁₂@α/γ-Bi₂O₃三元同素结光催化剂. 光催化降解高浓度罗丹明B(RhB)和四氯苯酚(4-CP)的实验结果表明, 相比于γ-Bi₂O₃和α/γ-Bi₂O₃, Bi₄Ti₃O₁₂@α/γ-Bi₂O₃显示出优异的光催化活性, 其中0.5%Bi₄Ti₃O₁₂@α/γ-Bi₂O₃显示了最佳的光催化性能, 光降解RhB(或4-CP)的活性是γ-Bi₂O₃的32倍(或10.4倍)和α/γ-Bi₂O₃的4.4倍(或2.2倍). 光电性质表征结果证实, Bi₄Ti₃O₁₂@α/γ-Bi₂O₃三元同素结具有高效的光生电荷分离和迁移效率, 这是Bi₄Ti₃O₁₂@α/γ-Bi₂O₃三元同素结具有较高光催化性能的主要原因之一.     

纳米Al2O3包覆富锂锰基正极材料Li1.2Ni0.13Co0.13Mn0.54O2的性能研究

采用纳米三氧化二铝(Al₂O₃)对富锂锰基正极材料Li_1.2Ni_0.13Co_0.13Mn_0.54O₂进行表面均匀包覆, 并考察了最优纳米Al₂O₃包覆量下材料的电化学性能. 扫描电子显微镜(SEM)和透射电子显微镜(TEM)显示了纳米Al₂O₃对富锂锰基正极材料表面均匀包覆, X射线衍射分析(XRD)结果表明包覆后富锂材料依然具有良好的层状结构. 恒流充/放电循环测试发现, 包覆后的Li_1.2Ni_0.13Co_0.13Mn_0.54O₂材料的首次放电比容量为249.7 mA·h/g, 循环100次后的容量保持率为89.5%, 与未包覆的Li_1.2Ni_0.13Co_0.13Mn_0.54O₂材料相比, 容量保持率提升约13%. 循环伏安(CV)和电化学阻抗(EIS)测试结果表明, 纳米Al₂O₃包覆可有效抑制材料极化, 降低界面阻抗和电荷转移阻抗, 进而提升富锂锰基正极材料的电化学性能.     

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%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.     

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.     

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.     

Microwave-assisted copper-catalyzed stereoselective ring expansion of three-membered heterocycles with α-diazo-β-dicarbonyl compounds

Microwave-assisted copper-catalyzed ring expansions of three-membered heterocycles with α-diazo-β-dicarbonyl compounds were investigated. Thiiranes generated 3-acyl-5,6-dihydro-1,4-oxathiines in the presence of copper sulfate and trans-3-acyl-5,6-dihydro-1,4-oxathiines as stereospecific products for 1,2-disubstituted cis-thiiranes through an intramolecular S_N2 process. Oxiranes gave rise to 2-acyl-5,6-dihydro-1,4-dioxines under the catalysis of copper hexafluoroacetylacetonate and cis-3-acyl-5,6-dihydro-1,4-dioxines as stereospecific products for 1,2-disubstituted cis-oxiranes via an intimate ion-pair mechanism. The current method provides a direct and simple strategy in efficient preparation of 3-acyl-5,6-dihydro-1,4-oxathiines and 2-acyl-5,6-dihydro-1,4-dioxines, important agents in medicinal and agricultural chemistry, from readily available thiiranes and oxiranes, respectively.     

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.