GdBa_2Cu_(3-x)Fe_xO_(7-δ)超导体系结构相变及拉曼谱特征

采用固态反应法制备了GdBa2Cu3-xFexO7-δ(x=0.00-0.30)系列样品,利用X射线衍射、拉曼光谱以及电测量技术对体系的晶体结构、拉曼散射谱特征以及电输运特性进行了系统研究。结果表明,当Fe掺杂量在x=0.05-0.10区间时,体系的晶体结构发生了从正交相到四方相的转变。通过对拉曼光谱中典型振动模的指认及振动模随Fe掺杂量的变化规律,得到了拉曼谱随体系正交-四方结构相变的变化特征:对于具有正交相的x=0.00-0.05样品,拉曼谱具有五个与正交相结构相对应的特征峰;而对于具有四方相的x=0.10-0.30样品,随Fe掺杂量增加,振动模强度变弱,且典型振动模发生了不同程度的展宽或频移。电输运测量表明,随Fe掺杂量的增加,超导临界温度Tc降低,正常态电阻率增加且发生了金属-半导体相变。     

Eu2+掺杂浓度对Ca2MgSi2O7∶Eu2+荧光粉发光特性的影响

采用化学共沉淀法制备了Ca_2-xMgSi₂O₇:xEu²⁺绿色荧光粉.用X射线衍射仪、荧光分光光度计及光色综合测试系统对Ca_2-xMgSi₂O₇:xEu²⁺绿色荧光粉的相结构、发光性能进行了测试.结果表明:其激发光谱分布在300–480 nm波长范围,谱峰位于389,430 nm处,可以被InGaN管芯产生的360–480 nm辐射有效激发;在波长为430 nm蓝光激发下,其发射光谱谱峰位于531 nm处.Ca_2-xMgSi₂O₇:xEu²⁺绿色荧光粉的发光强度随Eu²⁺掺杂量的增加而增强,当Eu²⁺掺杂量x为0.04时,发光强度达到最大值,而后开始降低,发生浓度猝灭.根据Dexter能量共振理论,浓度猝灭是由电偶极-电偶极相互作用引起的. 关键词： 2MgSi₂O₇∶Eu²⁺')" href="#">Ca₂MgSi₂O₇∶Eu²⁺ 绿色荧光粉 发光特性 白光发光二极管     

有序介孔碳CMK-3微波负载NiO及其电容性能研究

微波法负载具有简便、快速、均匀的优点. 本文尝试以乙二醇为还原剂, Ni(Ac)₂为Ni源, 通过微波辐射负载及低温空气煅烧在CMK-3上形成NiO. 对样品进行X射线衍射(XRD)、透射电子显微镜(TEM)、N₂吸脱附等结构表征及循环伏安(CV)等电化学性能测试. 结果显示, 微波法并经低温空气煅烧后有序介孔碳CMK-3的小角XRD峰强度变弱、比表面积下降、孔容减小, 但却使其比电容从229.3 F/g提高到295.9 F/g, 大于文献报导中介孔碳负载MnO₂, RuO₂•xH₂O后的比电容值. 由此说明微波法是有效的负载方法, 具有较好的应用前景.     

Facile Synthesis of Hierarchical Nanosized Single‐Crystal Aluminophosphate Molecular Sieves from Highly Homogeneous and Concentrated Precursors

The synthesis of hierarchical nanosized zeolite materials without growth modifiers and mesoporogens remains a substantial challenge. Herein, we report a general synthetic approach to produce hierarchical nanosized single‐crystal aluminophosphate molecular sieves by preparing highly homogeneous and concentrated precursors and heating at elevated temperatures. Accordingly, aluminophosphate zeotypes of LTA (8‐rings), AEL (10‐rings), AFI (12‐rings), and ‐CLO (20‐rings) topologies, ranging from small to extra‐large pores, were synthesized. These materials show exceptional properties, including small crystallites (30–150 nm), good monodispersity, abundant mesopores, and excellent thermal stability. A time‐dependent study revealed a non‐classical crystallization pathway by particle attachment. This work opens a new avenue for the development of hierarchical nanosized zeolite materials and understanding their crystallization mechanism.     

Facile Synthesis of Hierarchical Nanosized Single-Crystal Aluminophosphate Molecular Sieves from Highly Homogeneous and Concentrated Precursors

The synthesis of hierarchical nanosized zeolite materials without growth modifiers and mesoporogens remains a substantial challenge. Herein, we report a general synthetic approach to produce hierarchical nanosized single-crystal aluminophosphate molecular sieves by preparing highly homogeneous and concentrated precursors and heating at elevated temperatures. Accordingly, aluminophosphate zeotypes of LTA (8-rings), AEL (10-rings), AFI (12-rings), and -CLO (20-rings) topologies, ranging from small to extra-large pores, were synthesized. These materials show exceptional properties, including small crystallites (30–150 nm), good monodispersity, abundant mesopores, and excellent thermal stability. A time-dependent study revealed a non-classical crystallization pathway by particle attachment. This work opens a new avenue for the development of hierarchical nanosized zeolite materials and understanding their crystallization mechanism.     

Maximizing the Number of Interfacial Sites in Single‐Atom Catalysts for the Highly Selective,Solvent‐Free Oxidation of Primary Alcohols

The solvent‐free selective oxidation of alcohols to aldehydes with molecular oxygen is highly attractive yet challenging. Interfacial sites between a metal and an oxide support are crucial in determining the activity and selectivity of such heterogeneous catalysts. Herein, we demonstrate that the use of supported single‐atom catalysts (SACs) leads to high activity and selectivity in this reaction. The significantly increased number of interfacial sites, resulting from the presence of individually dispersed metal atoms on the support, renders SACs one or two orders of magnitude more active than the corresponding nanoparticle (NP) catalysts. Lattice oxygen atoms activated at interfacial sites were found to be more selective than O₂ activated on metal NPs in oxidizing the alcohol substrate. This work demonstrates for the first time that the number of interfacial sites is maximized in SACs, providing a new avenue for improving catalytic performance by developing appropriate SACs for alcohol oxidation and other reactions occurring at metal–support interfacial sites.     

介孔分子筛V-MCM-41的水热法制备与合成机理

 以十六烷基三甲基溴化铵为模板剂,廉价的工业级高模数比(3.3)的硅酸钠为硅源,通过水热法合成了V-MCM-41介孔分子筛. 考察了合成条件对产物织构的影响,并采用低温氮吸附法分析探讨了介孔分子筛V-MCM-41的合成机理. 结果表明,模板剂用量、 pH值、加料方式、晶化温度、晶化时间、陈化时间和焙烧气氛等合成条件对介孔分子筛的制备均有影响,其中晶化温度、 pH值和模板剂用量的影响最为明显. X射线衍射谱表明合成的介孔分子筛具有六方晶体结构. 红外光谱和紫外可见光谱表明V进入了介孔分子筛的骨架结构.     

Use of zwitterionic buffer additives to improve the separation of proteins in capillary zone electrophoresis

In CZE, the adsorption of the proteins on the capillary wall is a common problem. This paper describes the simple method of utilizing zwitterionic buffer additives to improve the separation of proteins in untreated fused silica capillaries at neutral pH. Three kinds of zwitterion are evaluated in the separation of acidic, neutral, and basic proteins, including their effect on protein efficiency, mobility, separation, and resolution; the difference between the effects of the different additives are also highlighted. The method has proved to be a possible means of reducing protein adsorption, especially for basic proteins.     

Effect of Sulfate on an Iron Manganese Catalyst for Fischer-Tropsch Synthesis

The effect of sulfate on Fischer-Tropsch synthesis performance was investigated in a slurry- phase continuously stirred tank reactor(CSTR)over a Fe-Mn catalyst.The physiochemical properties of the catalyst impregnated with different levels of sulfate were characterized by N_2 physisorption,X-ray photoelectron spectroscopy(XPS),H_2(or CO)temperature-programmed reduction(TPR),Mφssbauer spectroscopy,and CO_2 temperature-programmed desorption(TPD).The characterization results indicated that the impregnated sulfate slightly decreased the BET surface area and pore volume of the catalyst, suppressed the catalyst reduction and carburization in CO and syngas,and decreased the catalyst surface basicity.At the same time,the addition of small amounts of sulfate improved the activities of Fischer- Tropseh synthesis(FTS)and water gas shift(WGS),shifted the product to light hydrocarbons(C_1-C_(11)) and suppressed the formation of heavy products(C_(12 )).Addition of SO_4~(2-)to the catalyst improved the FTS activity at a sulfur loading of 0.05-0.80 g per 100 g Fe,and S-05 catalyst gave the highest CO conversion(62.3%),and beyond this sulfur level the activity of the catalyst decreased.     

血清CLDN5、OCLN和ZO1与颅脑损伤急性期患者损伤程度及预后的关系

目的探讨非开放性颅脑损伤急性期患者血清中封闭蛋白5（CLDN5）、密封蛋白（OCLN）和紧密连接蛋白1（ZO1）的含量与患者损伤严重程度及预后的关系。方法收集2014年2月至2015年2月非开放性颅脑损伤急性期患者92例。患者入院后立即留取外周血,检测血清中CLDN5、OCLN和ZO1的含量,分析三者与患者格拉斯哥昏迷评分（GCS）、颅内血肿体积的关系以及对患者预后的判断价值。结果不同GCS的患者间血清CLDN5和OCLN含量均有统计学差异（均P＜0.05）;不同血肿体积的患者间CLDN5和OCLN含量均有统计学差异（均P＜0.05）;死亡患者的血清CLDN5和OCLN含量明显高于存活组（均P＜0.05）,在不同GCS、血肿体积和预后的患者间比较,ZO1含量均无统计学差异（均P＞0.05）。GCS与血清CLDN5、OCLN含量均呈负相关（rCLDN5=-0.84,rOCLN=-0.85,均P＜0.01）,与ZO1无相关性（rZO1=0.14,P＞0.05）;血肿体积与血清CLDN5、OCLN和ZO1含量均呈正相关（rCLDN5=0.82,rOCLN=0.93,rZO1=0.82,均P＜0.01）。结论血清CLDN5、OCLN可以作为急性颅脑损伤患者病情严重程度和预后判断的有效生物标志物。