Bi2WO6量子点(QDs)修饰Bi2MoO6-xF2x异质结的构筑及其催化活性增强机理

采用简单沉积-沉淀法合成了Bi₂WO₆@Bi₂MoO_6-xF_2x（BWO/BMO6-xF2x）异质结,借助XRD、XPS、TEM、SEM、EDS、UV-Vis-DRS、PC和EIS等测试技术对其组成、形貌、光吸收特性和光电化学性能等进行系统表征,并以模型污染物罗丹明B（RhB）的光催化降解作为探针反应来评价Bi₂WO₆@Bi₂MoO_6-xF_2x异质结的光催化活性增强机制。形貌分析表明,所得Bi₂MoO₆微球由大量厚度为20~50 nm的纳米片组成;FE-SEM和HR-TEM分析表明,尺寸约为10 nm的Bi₂WO₆量子点均匀沉积在Bi₂MoO_6-xF_2x微球表面,形成新颖的Bi₂WO₆@Bi₂MoO_6-xF_2x异质结;与纯Bi₂MoO₆或者Bi₂WO₆相比,1∶1Bi₂WO₆@Bi₂MoO_6-xF_2x异质结表现出更好的光催化活性和光电流性质,其对RhB光催化降解的表观速率常数分别为纯BMO和BWO的6.4和11.6倍。PC和EIS图谱分析表明,Bi₂WO₆量子点表面沉积显著提高Bi₂MoO_6-xF_2x光生电子/空穴的分离效率和迁移速率;活性物种捕获实验证明了·O₂^-和h⁺是主要的活性物种。根据实验结果,探讨了F^-掺杂和Bi₂WO₆量子点之间的协同效应对Bi₂MoO₆的光催化活性的影响机制。     

三元体系YCl3-CdCl2-H2O和四元体系YCl3-CdCl2-HCl(～8.8%)-H2O (25 ℃)的相平衡及其固相新化合物的研究

The equilibrium solubilities of the ternary system YCl₃-CdCl₂-H₂O, the quaternary system YCl₃-CdCl₂-HCl(～8.8%)-H₂O were determined at 25 ℃ and the phase diagrams were constructed. The results show that the ternary system was complicated with six equilibrim solid phases CdCl₂·2.5H₂O, CdCl₂·H₂O, 8CdCl₂·YCl₃·15H₂O (8∶1 type), 4CdCl₂·YCl₃·13H₂O(4∶1 type), 5CdCl₂·2YCl₃·26H₂O (5∶2 type) and YCl₃·6H₂O. The quaternary system was also complicated with four equilibrim solid phase CdCl₂·H₂O, 4CdCl₂·YCl₃·13H₂O (4∶1 type), 5CdCl₂·2YCl₃·26H₂O(5∶2 type) and YCl₃·6H₂O. Among the three new compounds 8CdCl₂·YCl₃·15H₂O, 4CdCl₂·YCl₃·13H₂O and 5CdCl₂·2YCl₃·26H₂O, 8CdCl₂·YCl₃·15H₂O was a kind of metastable compound only in ternary system, and it was changed into 4CdCl₂·YCl₃·13H₂O with time. Both 4∶1 type and 5∶2 type existed in ternary and quaternary system, but they were also congruently soluble compounds in quaternary system. They have been prepared from the system and have been characterized by XRD, TC-DTG and DSC.     

纳米Mn-Zn铁氧体的制备和研究

Nanosize manganese zinc ferrites were fabricated by hydrothermal precipitation route using Fe₂(SO₄)₃, ZnSO₄·7H₂O, MnSO₄·H₂O as material, then some calcinated at 500 ℃ and studied by XRD, TEM, IR and VSM. The results showed that the products were spinel crystal structure and uniformly sized nanoparticles (15～25 nm) with little aggregation. The analysis of IR showed that the superficial water can be eliminated, but that was embedded in crystal lattice can not be removed by calcinating. The effect Zn content x on the lattice (a) of nanosize Mn_1-xZn_xFe₂O₄ was also discussed. The lattice of nanosize Mn_1-xZn_xFe₂O₄ decreases with x increasing; and its value deviated the standard lattice (a₀) of normal size manganese zinc ferrites. A lot of water was absorbed during the hydrothermal process owing to the large surface of nanosize particles. The change of magnetic properties of Mn_xZn_1-xFe₂O₄ with x increasing was studied: nanosize Mn_xZn_1-xFe₂O₄ particles synthesized by us exhibited peculiar magnetic properties curve with Zn content (x) increasing, Superparamagnetic behaviors of the synthesized ZnFe₂O₄ samples were confirmed by magnetic characterization, which can be explained by the difference between the distribution of the metal ions (Mn²⁺, Zn²⁺ and Fe³⁺) among the tetrahedral (A) and the octahedral (B) sites of nanosize ferrite and that of bulk ferrite.     

掺杂和取代对红色荧光材料SrAl12O19:Mn4+发光性能的影响

SrAl₁₂O₁₉：Mn⁴⁺是一种用于高显色性白光发光二极管的候选红色荧光材料。本论文研究了Mg²⁺、Zn²⁺和Ge⁴⁺离子的掺杂效应以及Ga³⁺、Ca²⁺和Ba²⁺离子的取代效应对SrAl₁₂O₁₉：Mn⁴⁺荧光材料性能的影响。样品通过高温固相反应制备,焙烧温度在1 250~1 500 ℃之间。利用X射线衍射技术表征了材料的相纯度,用荧光激发光谱和发射光谱表征了材料的荧光性能。研究结果指出,与未进行Mg²⁺或Zn²⁺掺杂的样品相比,Mg²⁺或Zn²⁺离子对Al³⁺格位的掺杂可以使材料的发光强度提高~60%,其原因被认为是掺杂促进了激活剂Mn⁴⁺离子进入晶格,其过程可以表示为：MO+MnO₂⇔M_Al^''+M_Al^·+3O_O^×（M=Mg,Zn）,电子顺磁共振谱支持这一结果。Ge⁴⁺离子的掺杂使材料的发光性能明显下降。Ga³⁺离子可以取代Al³⁺离子形成全范围的固溶体,其中少量Ga³⁺离子的掺杂可以使材料的荧光发射强度提高~13%,而掺杂量进一步提高使材料的荧光性能下降。Ca²⁺和Ba²⁺对Sr²⁺的取代仅形成有限范围的固溶体。Ca²⁺的取代使材料的发光性能提高;而 Ba²⁺的取代使材料的发光强度下降。     

电荷补偿对Ba2ZnGe2O7：Bi3+荧光粉发光性质的影响

采用高温固相法制备了2个系列的荧光粉样品：Ba_2-xZnGe₂O₇：xBi³⁺（系列Ⅰ）和Ba_1.994-yK_yZnGe₂O₇：0.006Bi³⁺（系列Ⅱ）。X射线衍射（XRD）测试结果表明,少量Bi³⁺、K⁺的掺杂不会明显改变材料的物相结构。样品的荧光光谱测试结果表明,虽然2个系列样品的发光光谱都随组成成分变化有少量变化,但发光颜色基本上均为黄绿色。在358 nm的激发下,荧光粉的发射光谱呈现一个峰值在500 nm的宽发射带,归属于³P₁→¹S₀能级跃迁。在500 nm监测下,荧光粉的最强激发峰位于358 nm,归属于¹S₀→³P₁能级跃迁,此外还有一个位于320 nm的肩峰归属于O^2--Bi³⁺电荷转移带。系列Ⅰ样品的光谱数据结果指出,Bi³⁺的最佳掺杂量x为0.006。在该基质中,Bi³⁺掺杂取代Ba²⁺属于不等价取代,会在晶格中产生Ba²⁺空位或间隙O^2-,对材料的发光强度产生负面影响。对此,采用K⁺与Bi³⁺协同掺杂起到电荷补偿的作用,填补Ba²⁺空位或捕获间隙O^2-缺陷。空位被填补或间隙被捕获均减少了晶格畸变,从而使发光强度明显提高。系列Ⅱ样品的光谱数据表明,完全电荷补偿的荧光粉样品相比于没有掺K⁺的样品,其发光强度提高了约2.5倍。     

g-C3N4/CaTi2O5复合材料制备及其光催化性能

利用类石墨氮化碳（g-C₃N₄）和亚稳相钙钛氧化物（CaTi₂O₅）固相法制备C₃N₄/CaTi₂O₅复合材料。利用X射线衍射（XRD）、金相显微镜、扫描电子显微镜（SEM）及附带能谱分析仪（EDS）和N₂吸附-脱附对样品的显微结构和比表面积进行检测分析,并用紫外-可见吸收光度计（UV-Vis）测试了样品的光吸收性能,研究C₃N₄与CaTi₂O₅物质的量之比（n_C3N4/nCaTi₂O₅）对C₃N₄/CaTi₂O₅复合样品的物相结构和微观形貌的影响,同时考察C₃N₄/CaTi₂O₅复合样品在可见光照射下光催化降解罗丹明染料效果。实验结果表明：相比纯C₃N₄和CaTi₂O₅样品,C₃N₄/CaTi₂O₅复合样品在可见光下具有较高的光催化性能,随着n_C3N4/nCaTi₂O₅增加,样品的光催化降解率随之增加而后降低,当n_C3N4/nCaTi₂O₅=1：1时,样品的光催化降解率达到最大值99.5%,并且循环重复利用5次后,样品的光催化剂降解率仍几乎保持不变。复合样品光催化性能提高主要归因于复合能级结构有效地抑制了电子和空穴复合所致。     

CO2在纳米SiO2/TiO2悬浮体系中的光催化还原

用水热法合成了氧化硅改性的具有高比表面积、高催化活性的锐钛型二氧化钛, 并在其悬浮体系中将CO₂光催化还原合成甲醇. 采用XRD, TEM, 物理吸附, UV-Vis吸收光谱和FTIR等表征手段对催化剂结构特征进行了研究. 结果表明: 添加氧化硅后, 氧化硅和二氧化钛之间形成Si—O—Ti键, 抑制了TiO₂晶粒生长, 提高了锐钛型TiO₂的比表面积, 且随着含硅量的增加, SiO₂/TiO₂的UV吸收逐步蓝移, 禁带宽度增加. 还原反应结果表明: SiO₂/TiO₂具有光催化还原活性, 且随着含硅量的增加先增加后减小, 当SiO₂质量分数为3.5%时, SiO₂/TiO₂复合催化剂反应活性最强, 5 h内甲醇产量可达到21.0 mg/L, 并有少量甲醛生成.     

四种Keggin型多酸纳米材料的制备及其吸附有机染料的性能

以4种Keggin型多酸作为原料(分别为H₃PW₁₂O₄₀·36H₂O(简写为PW₁₂^a)、H₃PMo₁₂O₄₀·34H₂O(简写为PMo₁₂^a)、H₄SiW₁₂O₄₀·35H₂O(简写为SiW₁₂^a)和H₄GeW₁₂O₄₀·40H₂O(简写为GeW₁₂^a)),采用表面活性剂智能化控制的软化学法制备了相应的4种Keggin型多酸纳米材料,分别为Ag₃PW₁₂O₄₀·36H₂O(简写为PW₁₂^b)、Ag₃PMo₁₂O₄₀·34H₂O(简写为PMo₁₂^b)、Ag₄SiW₁₂O₄₀·35H₂O(简写为SiW₁₂^b)和Ag₄GeW₁₂O₄₀·40H₂O(简写为GeW₁₂^b)。采用IR、UV-Vis、XRD和SEM表征多酸的结构和纳米粒子的形貌。在室内黑暗条件下,100mg样品可在5min内把20mg·L^-1的100mL亚甲基蓝(MB)染料溶液脱色,使其变为接近无色,吸附效率最高可达96.3%,吸附效率大小为PMo₁₂^b >PW₁₂^b >GeW₁₂^b >SiW₁₂^b。相同条件下,100mg样品使20mg·L^-1的100mL罗丹明B(RhB)染料溶液30min内脱色完全,脱色效率最高可达96.1%,吸附效率大小为PW₁₂^b >PMo₁₂^b >SiW₁₂^b >GeW₁₂^b。说明该4种多酸纳米材料具有较高的吸附有机染料性能。     

ZnAl2O4:Mn材料的制备及发光性能

以共沉淀法与煅烧法联用,成功制备了一系列ZnAl₂O₄:xMn样品。通过扫描电镜和X射线粉末衍射测试研究了样品的形貌和物相特征,结果表明尖晶石结构的ZnAl₂O₄中[AlO₆]的八面体位可以有效被Mn⁴⁺替代。通过荧光激发和发射光谱研究了样品的发光性能,发现Mn⁴⁺在ZnAl₂O₄体系中掺杂可以显示出明亮的红色发光(发射峰值位于680 nm处)。比较不同Mn⁴⁺浓度(Mn与Al的物质的量之比)掺杂样品的发光强度时发现,Mn⁴⁺最佳掺杂浓度为0.06%。通过德克斯特公式分析了发光强度与浓度关系,探究浓度猝灭机制,结果表明最邻近离子之间能量传递造成Mn⁴⁺浓度猝灭的发生。为了提高Mn⁴⁺的发光强度,选择了7种金属离子(Li⁺、Na⁺、K⁺、Ca²⁺、Sr²⁺、Sn²⁺和Ga³⁺)与Mn⁴⁺共掺杂进入ZnAl₂O₄基质中,其中效果较突出的为Li⁺和Ga³⁺,其共掺杂使Mn⁴⁺发光强度分别增强0.6倍和1倍。     

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%.     

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.     

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.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

Copper catalyzed/mediated synthetic methodology for ebselen and related isoselenazolones

Scope of the copper catalyzed/mediated selenium-nitrogen coupling reaction has been studied for the synthesis of isoselenazolones. It is noticed that the 2-chloro, 2-bromo-, and 2-iodo-aryl amides substrates can be exploited in the selenium-nitrogen coupling reaction by employing 25-100 mol % of CuI/1,10-phenanthroline (L) and potassium carbonate as a base in DMF. Furthermore, electron rich 2-chloro-arylamides also underwent selenium-nitrogen coupling reaction to give biologically important selenium-nitrogen heterocycles. Also, copper-catalyzed selenium-nitrogen coupling reaction has been meticulously applied for the synthesis of diaryl diselenides having methoxy, amine, and amide functionality from respective aryl iodides in the presence of stoichiometric amount of succinimide as an external Se-N coupling partner.     

Knoevenagel condensation catalyzed by novel Nmm-based ionic liquids in water

A series of novel N-methyl morpholine (Nmm) based ionic liquids with 1,2-propanediol group were synthesized and used as catalysts for Knoevenagel condensation at room temperature in water. Under the effect of the catalyst, various aldehydes or aliphatic ketones could react with a wide range of activated methylene compounds well, including malononitrile, alkyl cyanoacetate, cyanoacetamide, β-diketone, barbituric acid, 2-arylacetonitrile and thiazolidinedione. Furthermore, most of the products could be separated just by filtrating and washing with water. Additionally, the catalyst is recyclable and applicable for the large-scale synthesis.     

Construction of polyheterocyclic spirotetrahydrothiophene derivatives via sulfa-Michael/aldol cascade reaction

A series of polyheterocyclic spirotetrahydrothiophene derivatives were obtained in moderate to excellent yields via a catalyst-free sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 under mild conditions. We also present the first asymmetric sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 with moderate to good enantioselectivities catalyzed by readily available chiral phase-transfer catalysts (PTCs).     

Suzuki-Miyaura reactions of the soluble guanylate cyclase inhibitor NS2028: a non-product specific route to C-8 substituted analogues

Both soluble guanylate cyclase (sGC) inhibitors ODQ 1 and NS2028 2 are synthesized via improved protocols. In the former case treating 3,4-dihydroquinoxalin-2(1H)-one oxime 8, which can be prepared in two steps from 1,2-benzenediamine, with 1,1′-carbonyldiimidazole (CDI) gives the dihydro-ODQ 10 that in the presence of KMnO₄ oxidises to give ODQ 1 in an overall yield of 46% starting from 1,2-benzenediamine. In the latter case, the synthesis affords NS2028 2 from 2-amino-4-bromophenol 3 in three steps with an overall yield of 85% and avoids the need for chromatography. Furthermore, Suzuki-Miyaura reaction conditions are described that enable the preparation of 8-aryl and 8-heteroaryl derivatives of NS2028 directly from NS2028 2. Finally, demethylation of the 8-(methoxyphenyl) substituted analogues afforded the 8-(hydroxyphenyl) derivatives 40-42. All new products are fully characterised.