准二维钙钛矿晶体中自限域激子发光机制研究

通过冷却结晶法成功地合成了准二维钙钛矿(C₄H₁₀N)₂(CH₃NH₃)Pb₂Br₇晶体，并研究了该晶体的晶体结构以及自由激子和自限域激子复合发光行为。单晶XRD结构分析表明，该晶体中PbBr₆八面体单元具有极大的结构扭曲。通过光谱分析发现，该准二维钙钛矿材料在紫外光激发下表现为蓝色发光，并且具有两个荧光峰，峰位分别为440 nm和477 nm。其中，较强的荧光峰(440 nm)和较弱的荧光峰(477 nm)分别来源于准二维钙钛矿材料的自由激子和自限域激子的复合发光。该研究结果将有助于深入理解钙钛矿晶体中激子自限域过程和发光机制。     

低碳烷烃烯烃在超微孔柔性Cu(Qc)2上的吸附行为

采用实验研究与分子模拟相结合的方法研究了低碳烷烃烯烃在超微孔柔性Cu(Qc)₂上的吸附热力学、动力学和吸附分离机理。用常温合成方法制备了超微孔金属-有机骨架材料Cu(Qc)₂,测定了低碳烷烃烯烃（CH₄/C₂H₄/C₂H₆/C₃H₆/C₃H₈）在Cu(Qc)₂上的吸附相平衡和吸附动力学。使用Materials Studio中的Fortcite模块模拟低碳烷烃烯烃在超微孔柔性Cu(Qc)₂上的吸附机理以及材料的结构形变。结果表明Cu(Qc)₂具有优良的C₂H₆ /C₂H₄吸附选择性和吸附动力学,而对C₃H₈ /C₃H₆的吸附选择性很低。273 K和0.1 MPa下,C₂H₆/C₂H₄在Cu(Qc)₂上的IAST选择性达4.6。298 K和0.05 MPa下C₂H₆/C₂H₄在Cu(Qc)₂上的扩散时间常数分别达1.42×10^-3和1.48×10^-3_{s^-1,扩散活化能分别为16.62 和16.43 kJ/mol。应用装填Cu(Qc)2的固定床可在常温条件下实现C2H6 /C2H4二元混合气的完全分离。模拟结果显示Cu(Qc)2为二维堆叠结构,材料会由于吸附不同分子而发生不同程度的结构形变。甲烷易从变大的层间扩散脱附,导致其在材料上的吸附量很低;C2H6/C2H4两者都能稳定吸附在层中的孔道中,其分离推动力主要来源于两种气体在材料上明显的吸附热差异;C3H8/C3H6会分别吸附在两种不同的环境,吸附热差异小导致Cu(Qc)2对C3H8 /C3H6的吸附选择性低。}     

Study on the epoxidation of olefins with H2O2 catalyzed by biquaternary ammonium phosphotungstic acid

Selective epoxidation of olefins is an important field in chemical industry. In this work, we developed a new phosphotungstic acid catalyst {[(C₈H₁₇)(CH₃)₂N]₂(CH₂)₃}_1.5{PO₄[WO(O₂)₂]₄} with long carbon chain and biquaternary ammonium cation. Cyclohexene could be epoxidized to cyclohexene oxide in 96.3% conversion and 98.2% selectivity. The catalyst type, solvent type...     

Zn/Cu单晶转换MOF材料的CO2/CH4分离性能研究

CO₂的捕获和分离具有重要的工业和环境意义。采用溶剂热法,以羧基和路易斯碱位点功能修饰的配体和锌离子构筑了阴离子型金属有机框架材料{[Zn₂(N)·(DMF)₃·(CH₃)₂NH₂]·(DMF)₂}_n (NEM-7-Zn)。为了提高骨架的稳定性,通过金属离子置换工艺,将NEM-7-Zn转化为高稳定性的铜基框架材料NEM-7-Cu。采用EA、PXRD、TGA及比表面积分析等技术对多孔材料进行综合表征,并测定了NEM-7-Cu对二氧化碳、乙炔和甲烷单组分气体的吸附等温线。实验结果表明,NEM-7-Cu不仅具有较高的CO₂ 吸附性能（74 cm³·g^-1）,更表现出优异的CO₂/CH₄（11.5）和C₂H₂/CH₄（7.1）吸附选择性。通过巨正则Monte Carlo方法（GCMC）计算得到CO₂在NEM-7-Cu中的主要吸附位点为功能基团羧基与路易斯碱位点附近以及Cu的金属团簇附近。     

CH4/C2H6/C3H8在MOF-505@5GO上吸附相平衡和选择性

应用溶剂热法合成了不同氧化石墨烯（GO）负载量的MOF-505@GO复合材料,分别采用全自动表面积吸附仪、P-XRD、SEM和Raman对材料进行了性能表征,测定了CH₄、C₂H₆和C₃H₈在MOF-505@GO上的吸附等温线,并进行Langmuir-Freundlich方程拟合,依据IAST理论模型计算了C₂H₆/CH₄和C₃H₈/CH₄二元混合气在MOF-505@5GO上的吸附选择性。研究结果表明,随着GO负载量增大,MOF-505@GO复合材料的孔容及BET比表面积先增大后减小,当GO负载量为5%（质量）时,复合材料MOF-505@5GO的孔容及BET比表面积达到最大,当GO负载量进一步增大至8%（质量）和10%（质量）时,复合材料的孔容及BET比表面积逐渐降低。在0.1 MPa和298 K条件下,MOF-505@5GO对CH₄、C₂H₆和C₃H₈的吸附容量分别为0.88、4.81和5.17 mmol·g^-1,相比MOF-505分别提高了14.9%、30.7%和13.1%。MOF-505@5GO对C₂H₆/CH₄和C₃H₈/CH₄的吸附选择性分别为40.1和3056.1,其对C₂H₆/CH₄和C₃H₈/CH₄具有极高的吸附选择性。     

[(C2H5)3NH]Cl/ZnCl2离子液体催化合成维生素E

维生素E合成过程中催化剂用量大、损失严重且不能循环使用, 后处理过程产生大量废液导致严重的环境问题。实验合成了几种Lewis酸性离子液体, 并应用于维生素E合成。研究发现, [(C₂H₅)₃NH]Cl/ZnCl₂离子液体催化合成维生素E效果最好, 该离子液体中无机阴离子起主要催化作用, 季铵阳离子易与异植物醇的羟基形成氢键, 能使异植物醇与主环发生定向缩合反应。采用FT-IR研究了[(C₂H₅)₃NH]Cl/ZnCl₂离子液体结构和酸性, 并系统考察了其对维生素E合成的影响。随着ZnCl₂摩尔分数增加, 离子液体的Lewis酸性增强。在ZnCl₂摩尔分数为0.66的[(C₂H₅)₃NH]Cl/ZnCl₂离子液体催化作用下, 维生素E的产率可达到87.4%, 该离子液体重复使用5次, 催化性能没有明显下降。     

3种PLA/OMLS纳米复合材料的结构、结晶行为与力学性能的对比研究

采用同向旋转啮合双螺杆制备了3种不同有机改性剂改性的纳米蒙脱土(OMLS)与聚乳酸(PLA)纳米复合材料。采用X射线衍射仪和透射电子显微镜、差示扫描量热仪等研究了复合材料的结构和结晶行为。结果表明,3种PLA/OMLS纳米复合材料(OMLS质量分数为2%)均具有剥离结构,且OMLS的有机改性剂分子链越长,插层的OMLS间距越大;3种OMLS都大大加速了PLA的结晶,减小了PLA晶体尺寸;3种OMLS中,CH₃(CH₂)₁₇N(CH₃)[(CH₂CH₂OH)₂]~+改性的OMLS对PLA的结晶行为影响最大,其纳米复合材料的冲击强度最高;而CH₃(CH₂)₁₇NH₃~+和HOOC(CH₂)₁₇NH₃~+改性的OMLS对PLA的增强效果明显。     

[C16H33N(CH3)3]3[PO4(WO3)4]催化脂肪酸甲酯环氧化性能

在无酸、无溶剂条件下,以[C₁₆H₃₃N(CH₃)₃]₃[PO₄(WO₃)₄]为反应控制相转移催化剂,研究各因素对脂肪酸甲酯(FAME)环氧化反应的影响。结果表明,水相pH对环氧化反应的影响最大,反应适宜pH为4;适宜反应条件为过氧化氢与脂肪酸甲酯中双键摩尔比为1.05:1,反应温度50～60℃,反应时间5 h。在此反应条件下催化剂循环5次不失活,产品环氧值大于4.0%,碘值小于5 g I·(100 g)^-1。并通过元素分析与红外光谱,研究了催化剂在反应过程中的变化,认为磷钨杂多阴离子的分解是导致催化剂失活的关键原因。     

TiO2-ZrO2聚合溶胶形成过程的小角X射线散射研究

由金属醇盐（M（OR）₄）水解制备溶胶的方法已广泛应用于溶胶-凝胶法制备纳米孔无机膜。通过控制异丙醇钛[Ti（i-OC₃H₇）₄]和正丙醇锆[Zr（n-OC₃H₇）₄]的混合物在异丙醇（i-C₃H₇OH）中水解制备聚合型TiO₂-ZrO₂溶胶,利用小角X射线散射方法（SAXS）研究了初始反应混合物Ti（i-OC₃H₇）₄：Zr（n-OC₃H₇）₄：H₂O：i-C₃H₇OH=0.9：0.1：m：30（摩尔比,m=1.8,2.0,2.2）形成TiO₂-ZrO₂溶胶的过程,探讨了水与醇盐摩尔比H₂O/M（OR）₄（M=Ti+Zr）、反应温度和正丙醇锆对TiO₂-ZrO₂溶胶形成的影响。研究结果表明,H₂O/M（OR）₄=1.8时,只有少量胶粒形成;H₂O/M（OR）₄=2.0～2.2时,TiO₂-ZrO₂溶胶中胶粒具有质量分形结构,分形维数1.2 ≤ D_m < 1.4;随着H₂O/M（OR）₄增加,胶粒的形成时间缩短,胶粒大小和分形维数均增大,溶胶的稳定性显著下降。升高反应温度有利于胶粒形成。[Ti（i-OC₃H₇）₄+Zr（n-OC₃H₇）₄]混合物比Ti（i-OC₃H₇）₄水解快,H₂O/M（OR）₄相同时,TiO₂-ZrO₂溶胶比TiO₂溶胶稳定性差。     

Zn(Ⅱ)配合物催化C—C键裂解和原位合成2-甲基-4(3H)-喹唑酮

在配合物的水热合成过程中往往可以发现新的化学反应和催化机理。本文通过[Zn(L)₂·(H₂O)₂·(NO₃)₂]（L=4(3H)-喹唑酮）配合物在130℃催化乙腈分子中的CC键断裂,原位合成化合物2-甲基-4(3H)-喹唑酮。利用红外、元素分析和X射线单晶衍射表征分析2-甲基-4(3H)-喹唑酮和[Zn(L)₂·(H₂O)₂·(NO₃)₂]的结构,结果表明[Zn(L)₂·(H₂O)₂·(NO₃)₂]和2-甲基-4(3H)-喹唑酮属于三斜晶系,P-1空间群。三组温度控制实验表明,温度对2-甲基-4(3H)-喹唑啉酮的形成有着重要的影响,并且温度高于130℃有利于该催化反应的进行。采取电喷雾质谱表征2-甲基-4(3H)-喹唑酮的形成机理发现,[Zn(L)₂·(H₂O)₂·(NO₃)₂]催化乙腈分子中的CC键断裂,生成(CN)₂和·CH₃。·CH₃有选择性地引入到4(3H)-喹唑酮中的C原子和N原子之间。本文对原位引入CH₃有着指导作用。     

Ferroelectric phase transitions of (CH3NH3)5Bi2Cl11

The spontaneous polarization of (CH₃NH₃)₅Bi₂Cl₁₁ single crystals was measured in the range 80-315 K revealing the existence of a ferro-ferroelectric type transition at 170 K.     

Ferroelectric and ferroelastic phase transitions in (CH3NH3)3Sb2Br9 crystals

(CH₃NH₃)₃Sb₂Br₉ crystals were studied by pyroelectric method in the temperature range 10 - 200 K. Pyroelectric measurements revealed reversal spontaneous polarization below 141 K along the a-axis. The optical observations showed that MABA possesses ferroelastic domains in all low temperature phases.     

A raman and infrared spectroscopic study of the ferroelectric phase transition of (CH3NH3)5 Bi2 Br11

The Phase transition of (CH₃NH₃)₅ Bi₂ Br₁₁ from a ferroelectric to a paraelectric state has been followed by infrared and Raman spectroscopy. The libration mode of the (CH₃ NH₃)⁺ cation shows changes in the Raman spectrum probably due to order-disorder processes.     

甲胺铅碘钙钛矿物性及制备过程的分子模拟

应用分子动力学方法分析了甲胺铅碘晶体的结构特征与机械性质等相关物性,模拟了用蒸气沉积法在TiO₂基底上制备甲胺铅碘晶体的过程,探讨了生成的PbI₄^2-、PbI₅^3-和PbI₄^6-多面体的排布方式,结合周围CH₃NH₃⁺的分布筛选出满足结构要求的初生晶核,分析了前驱盐配比对甲胺铅碘初生晶核产量的影响。结果表明,在拉伸过程中,甲胺铅碘晶体经历弹性形变、塑性形变以及断裂三个阶段,拟合计算得到的弹性模量与实验值符合较好;大部分初生晶核以PbI₅^3-金字塔的结构存在。前驱盐配比对各系统中PbI_x多面体的总含量影响较小,但对其中排布有效的PbI_x结构以及初生晶核的产量影响较大,二者产量随着配比PbI₂∶CH₃NH₃I的增加而迅速减小,这一关系与研究者发现的实验现象相符。     

Dielectric and Ferroelectric Properties of [(CH3)2NH2]3CuCl5 Single Crystal

The detailed studies of dielectric properties of [(CH₃)₂NH₂]₃CuCl₅ single crystal were performed. Distinct anomalies of permittivity along three crystallographic direction were observed at 277.5 K and 252.7 K on cooling. The observed permittivity behaviour evidenced the first order character of both phase transitions. The hysteresis loops characteristic of a ferroelectric phase were observed in the range of temperature 277.5-252.7 K. An appearance and disappearance of spontaneous polarization confirms the first order phase transitions in this crystal. The permittivity measured along the ferroelectric a-axis under influence of external electric field in paraelectric phase showed clearly a nonlinear increase with increase of electric field intensity applied to the crystalline sample.     

Ultrasonic investigations of [(CH3)2NH2]5Cd3Cl11

The temperature dependences of ultrasound velocities along the crystallographic a, b and c axis in [(CH₃)₂NH₂]₅Cd₃Cl₁₁ were studied in the vicinity of phase transition at 178.5 K. The results obtained for the longitudinal and shear ultrasonic velocities confirmed clearly the existence of the second-order phase transition at this temperature and the quadratic relation between δV₄ and δV₆ and phase transition parameter was observed.     

CBD方法制备的Zn(O,S)薄膜的微结构表征及性能

对低温化学浴沉积方法制备的Zn（O,S）薄膜进行了研究,通过XPS、SEM、XRD、拉曼光谱、PL谱、紫外-可见吸收光谱等手段对薄膜的形貌、结构及组成进行系统表征,探究了其作为钙钛矿电池电子传输层的可能性。研究表明：化学浴沉积（CBD）方法制备的Zn（O,S）薄膜为ZnO、ZnS和ZnOS合金的复合膜;该薄膜对CH₃NH₃PbI₃光吸收层具有与TiO₂相当的电子抽提能力,是一种可供选择的高效柔性钙钛矿电池电子传输层材料。     

Phase transitions in R2 SnCl6-type crystals (R = NH3 C2H3, NH3C2H5 and N(CH3)4)

The thermal dilatation in (NH₃ ·CH₃) SnCl₆, (NH₃ · C₂H₅) SnCl₆ and [N(CH₃)] SnCl₆ was measured, and as the results it has turned out that (NH₃ ⁶·C₂H₅) SnCl₆ and [N(CH₃)₄]₂ SnCl₆ undergo the first order transitions at 128 K and 158 K, respectively. The low temperature phases of (NH · C₂H₅) SnCl₆ and [N(CH₃)₄]₂ SnC1₆ are found to be monoclinic and tetragonal, respectively, No phase transition was observed in (NH₃ ·CH₃)₂ SnCl₆ down to 77 K.     

(CH3CH[NH3]CH2NH3)1/2·ZnPO4, a zincophosphate analogue of aluminosilicate zeolite thomsonite

The synthesis and structure of (CH₃CH[NH₃]CH₂NH₃)_1/2·ZnPO₄, an organically templated zincophosphate (ZnPO) analogue of aluminosilicate zeolite thomsonite (THO), are described. The ZnPO framework is built up from an alternating, vertex-sharing, network of ZnO₄ and PO₄ groups (d_av(Zn–O)=1.944 (8) Å, d_av(P–O)=1.535 (9) Å, θ_av(Zn–O–P)=130.5°) involving distinctive 4=1 secondary building units. The 1,2-diammonium propane cations are highly disordered in the [0 0 1] 8-ring channels. Crystal data: (CH₃CH[NH₃]CH₂NH₃)_1/2·ZnPO₄, M_r=198.42, orthorhombic, space group Pncn (no. 52), a=14.119 (6) Å, b=14.136 (5) Å, c=12.985 (5) Å, V=2591 (3) ų, Z=10, R(F)=0.057, R_w(F)=0.061 (for a twinned crystal).     

Preparation and characterization of indium based complex perovskites-Pb(In1/2Nb1/2)O3 (PIN), Ba Ba(In1/2Nb1/2)O3 (BIN), and Ba(In1/2Nb1/2)O3 (BIT)

The processing of order-disorder perovskites Ba(In_1/2Nb_1/2)O₃ (BIN), Ba(In_l/2Ta_1/2)O₃ (BIT), and the lead analogue Pb(In_1/2Nb_1/2)O₃ (PIN) was investigated with an emphasis on improving and expanding our knowledge of microwave dielectric materials. Both BIN and BIT were shown to be paraelectric perovskites. The processing and annealing of PIN were related to the perovskite and its transformation to pyrochlore. Dielectric and physical characteristics were examined by X-ray diffraction profiles (XRD), scanning electron microscopy (SEM), and dielectric behavior. Attempts to enhance B-site cation order in PIN by thermal annealing were unsuccessful due to a pyrochlore formation.