掺Cu对MoO3-TiO2/SiO2上光促甲烷和水表面反应的影响

 在固定床环隙反应器中,借助紫外光的激发,气相甲烷和水在MoO3-TiO2/SiO2催化剂表面生成了甲醇和氢气,当在催化剂中掺杂Cu2+后,光催化剂的活性明显提高. XRD,IR,UVDRS和TPD的研究结果表明,在催化剂表面形成了具有Mo-O-Ti和Mo-O-Cu基元的高度分散物种,不但使得吸光带边明显蓝移,而且扩展了催化剂的光响应范围. 所形成的复合结构还可以优化单组分的吸光性能并促进对反应物分子的吸附活化,同时可以有效地转移光生电子和空穴. 掺杂Cu2+能够进一步延长光生电子-空穴对的寿命,进而提高反应的量子产率.     

水分子团簇结构的改变及其生物效应

概述了近30年来从水分子团簇结构的发现到水分子簇的稳定结构及相关理论计算的研究进展;总结了改变水分子团簇结构的四种方法．包括外加磁场、外加电场、激光辐射以及直接加热法．分别讨论了这四种方法的作用机理;最后简要介绍了改变水分子团簇结构所诱发的生物效应,并对该领域的研究前景作了展望。     

K2CO3-Na2CO3-Li2CO3-H2O四元体系288K的相平衡

水盐体系;碳酸盐;溶解度;盐湖卤水;K2CO3-Na2CO3-Li2CO3-H2O四元体系288K的相平衡     

A DNA crystal designed to contain two molecules per asymmetric unit

We describe the self-assembly of a DNA crystal that contains two tensegrity triangle molecules per asymmetric unit. We have used X-ray crystallography to determine its crystal structure. In addition, we have demonstrated control over the colors of the crystals by attaching either Cy3 dye (pink) or Cy5 dye (blue-green) to the components of the crystal, yielding crystals of corresponding colors. Attaching the pair of dyes to the pair of molecules yields a purple crystal.     

层状复合氢氧化物对乙酰苯甲酸的负载与体外释放

共沉淀-微波晶化法合成层状复合氢氧化物(LDH)后, 用不同方式将乙酰苯甲酸(ASP)组装到LDH层间制成载药体LDH-ASP, 通过对合成及药物释放前后的液相分析与固相表征数据研究了LDH对ASP的负载及载药体LDH-ASP在磷酸盐介质的溶释现象. 结果表明: LDH层间通道是负载、贮存及控制药物释放的微观基础; 载体选择、药物配比、反应能量供给方式及搅拌强度是决定并影响LDH-ASP载药效率的基本因素, LDH-ASP结构参数可以反映药物负载情况、并与其释放性能明确相关; LDH对ASP的负载与释放均致晶胞参数改变、结晶度下降; 载药体与前体的晶态属性、热力学行为及表面特性相似, 而释放药物后固相的晶态性征减弱、无定形性增强、通道吸附活性降低, 有利于使命后载体在体内降解消除.     

Synthesis of a Nine-atom Germanium Cluster K_(0.5)[K(18-crown-6)]_(1.5)Ge_9·1.5en with Unprecedented “up” and “down” Chain Arrangement of Unit [-(Ge_9-K-Ge_9)~(3-)-]

A new complex K0.5[K(18-crown-6)]1.5Ge9·1.5en(1) which contains unprecedented "up" and "down" chain arrangement of unit [-(Ge-9-K-Ge9)3-] has been prepared by the reaction of K4Ge9 with HgS in ethylenediamine(en) in the presence of 18-crown-6(1,4,7,10,13,16-hexaoxacyclooctadecane), and characterized by X-ray structure analysis. The color of the title crystals(black), which is darker than that of the reported three compounds with chains of germanium clusters, may result from the naked K+ and their interactions with the chain. And the structure differences between 1 and the reported three compounds with chains of germanium have also been discussed.     

反应烧结碳化硅复合材料的磨损机理研究

采用销－盘摩擦磨损试验机考察了反应烧结碳化硅及含Ｎｉ碳化硅复合材料在不同温度下的干摩擦磨损性能。结果表明,Ｎｉ有利于改善反应烧结碳化硅复合材料的摩擦磨损性能。ＳＥＭ磨损表面和亚表面分析表明,复合材料在常温下的磨损机理为削和犁沟;６００℃下反应烧结碳化硅的磨损机理为表面裂纹形成及断裂;而含Ｎｉ碳化硅复合材料的磨损机理为亚表面裂纹扩展导致表面局部剥落。     

GaN基p-i-n型雪崩探测器的制备与表征

制备和表征了p-i-n型的GaN基雪崩探测器.器件在-5V下的暗电流约为0.05 nA,-20 V下的暗电流小于0.5 nA.响应增益-偏压曲线显示,可重复的雪崩增益起始于80 V附近,在85 V左右增益达到最大为120,表明所制备的器件具有较好的质量.C-V测量用来确定载流子的分布和耗尽信息,结果显示,P型层在15 ...     

AlGaN-Based Solar-Blind Schottky Photodetectors Fabricated on AlN/Sapphire Template

We report AlGaN-based back-illuminated solar-blind Schottky-type ultraviolet photodetectors with the cutoff- wavelength from 280nm to 292nm without bias. The devices show low dark current of 2.1× 10^-6A/cm^2 at the reverse bias of 5 V. The specific detectivity D＊ is estimated to be 3.3 × 10^12cmHz^1/2 W^-1 . To guarantee the performance of the photodetectors, the optimization of AlGaN growth and annealing condition for Schottky contacts were performed. The results show that high-temperature annealing method for Ni/Pt Schottky contacts is effective for the reduction of leakage current.     

In气氛下晶体生长对Mg掺杂p-Al_xGa_(1-x)N激活能的影响

Ⅲ-Ⅴ族氮化物宽禁带半导体材料体系中,普通方法生长的p型外延层电导率一般都很低,成为了制约器件性能提高的瓶颈。在p-AlxGa1-xN材料中,Mg受主的激活能较大,并且随Al组份增加而增大。通过在p-AlxGa1-xN材料生长过程中引入三甲基铟(TMIn),发现能有效地降低AlxGa1-xN材料中受主态的激活能。为研究不同In气氛下生长的p-AlxGa1-xN材料的性质,在使用相同二茂基镁(CP2Mg)的情况下,改变TMIn流量,生长了A,B,C和D四块样品。X射线衍射(XRD)组份分析表明:在1100℃下生长AlxGa1-xN外延层时,In的引入不会影响晶体组份。利用变温霍尔(Hall)测试研究了p-AlxGa1-xN材料中受主的激活能,结果表明:In气氛下生长的外延层相比无In气氛下生长的外延层,受主激活能明显降低,电导率显著提高。采用这种方法改进深紫外发光二极管(LED)的p-AlxGa1-xN层后,LED器件性能明显提高。