Ag/ZnO纳米纤维的制备及光催化性能

采用静电纺丝技术及煅烧法制备了氧化锌纳米纤维, 然后采用水热法将银纳米颗粒负载到了氧化锌纳米纤维表面. 利用X射线衍射(XRD)、 X射线光电子能谱(XPS)、 能量色散X射线光谱(EDX)、 扫描电子显微镜(SEM)及透射电子显微镜(TEM)等技术对合成的Ag/ZnO纳米纤维的结构和组成进行了表征. SEM结果表明, 直径在5~100 nm之间的银纳米颗粒附着在直径在80~330 nm之间的氧化锌纤维表面形成了异质结构. 以常见的有机污染物甲基橙、 亚甲基蓝和罗丹明B等为降解底物, 对Ag/ZnO纳米纤维的光催化性能进行了表征. 结果表明, 负载银纳米颗粒后, 复合催化剂的光催化性能明显提高.     

CO oxidation on the heterodinuclear tantalum-nickel monoxide carbonyl complex anions

The series of heterodinuclear metal oxide carbonyls in the form of TaNiO(CO)_n(n=5-8) are generated in the pulsed-laser vaporization source and characterized by mass-selected photoelectron velocity-map spectroscopy.During the consecutive CO adsorption,the μ~2-O-bent structure initially is the most favorable for TaNiO(CO)_5,and subsequently both μ~2-O-bent and μ~2-O-linear structures are degenerate for TaNiO(CO)_6,then the μ~2-O-linear structure is most preferential for TaNiO(CO)_7,and finally theη_2-CO_2-tagged structure is the most ene rgetically competitive one for TaNiO(CO)_8,i.e., the CO oxidation occurs at n=8.ln contrast to the literature reported CO oxidation on heteronuclear metal oxide complexes generally proceeding via Langmuir-Hinshelwood-like mechanism,complementary theo retical calculations suggest that both Langmuir-Hinshelwood-like and Eley-Rideal-like mechanisms prevail for the CO oxidation reaction on TaNiO(CO)_8 complex.Our findings provide new insight into the composition-selective mechanism of CO oxidation on heteronuclear metal complexes,of which the composition be tailored to fulfill the desired chemical behaviors.     

水溶性近红外Ⅱ区荧光Ag2Te量子点的合成

量子点具有独特的光学性质, 在生物医学领域有着广泛的应用. Ag₂Te作为Ⅰ-Ⅵ族量子点中的一员, 因具有生物毒性小和带隙窄等优势而备受关注, 但是目前直接合成水溶性Ag₂Te量子点的方法较少, 而且可调节的荧光发射波长范围有限. 本文提出了一种合成荧光发射波长位于近红外Ⅱ区窗口的水溶性Ag₂Te量子点的新方法. 该方法以硝酸银为银前体, N-乙酰-L-半胱氨酸为配体, 碲前体利用硼氢化钠还原亚碲酸钠得到, 反应条件温和(室温、 大气氛围)且不涉及有毒的有机试剂, 绿色环保. 通过进一步的阳离子处理钝化其表面缺陷, 可以得到尺寸均一的超小粒径水溶性Ag₂Te量子点, 量子点的荧光发射波长为1160 nm, 量子产率为8.0% (以IR26染料为参照). 该方法所合成的Ag₂Te量子点具有良好的生物相容性, 注入小鼠体内后能观察到明显的近红外荧光, 具有进一步生物应用的潜力.     

冷成型钢住宅结构的蒙皮效应研究

以整体结构在风荷载下侧移超过规范容许值和连接件发生破坏作为判断标准,对蒙皮(墙板)的抗剪性能进行了研究.首先以一单层冷成型钢排架为研究对象,考查其在面内荷载作用下可能出现的破坏模式.在此基础上以5层冷成型钢框架结构为例,分析其在控制荷载(风荷载)作用下的受力情况.通过比较传统柱间支撑和蒙皮这两种构造的框架整体侧移刚度,发现在螺钉连接方式和间距合理的前提下,蒙皮完全可以取代支撑.通过改变螺钉的间距和螺钉的连接方式(每波连接、隔波连接)以及板的厚度,对该5层框架的受力和侧移进行参数分析,给出了在不同板厚条件下获得理想蒙皮抗剪效果的连接方式:对于0.6mm板,螺钉与框架柱只能采用每波连接方式,并且跨度方向螺钉间距不能大于250mm;对于1.0mm板,跨度方向螺钉间距小于等于500mm,而且可以采用每波或隔波连接方式.建议在实际工程中螺钉应尽量采用每波连接方式.     

反射干涉光谱法测量固体薄膜的光学常数和厚度

本文报道一种简单的方法,从平原介质薄膜的反射干涉光谱来计算薄膜的光学常数和厚度。当一束光照射在基板上的介质膜上时,由于膜上下界面反射光的相干,会使反射光谱的曲线有一定的波动。我们对反射相干光谱进行理论分析,给出计算公式,从测量曲线中的实验值得出薄膜的光学常数ｎ、ｋ以及厚度等参数。此种方法简单可行,而且易于编程处理。     

Comparison of the chemical composition and pharmacological effects of the aqueous and ethanolic extracts from a Tibetan "Snow Lotus" (Saussurea laniceps) herb

To understand the impacts of different processing methods on the composition and effects of the herb Saussurea laniceps (SL), the present study report the first comparison of the chemical constituents of aqueous and ethanolic SL extracts using chromatographic analysis, and to compare their pharmacological effects in a mouse anti-inflammatory, anti-nociceptive model and an in vitro anti-oxidant test. Chemical comparison demonstrated that the types of chemicals in the two extracts were identical, but the contents of the main constituents in the aqueous extract were lower than those of the ethanolic extract. A transesterification of dicaffeoylquinic acids took place in the aqueous extract during boiling. As for pharmacological effects, oral administration of aqueous and ethanolic SL extracts significantly inhibited croton oil-induced mice ear edema, and significantly inhibited acetic acid-induced mice writhings, respectively. In the DPPH anti-oxidant activity test, the IC50 values were calculated as 409.6 mg/L and 523.4 mg/L for the ethanolic and aqueous extracts, respectively. The inhibitory effects of the ethanolic extract were more potent than those of the aqueous extract in all pharmacological tests, although there was no significant difference. This study suggests that the two preparations should be distinguished when used.     

Photoelectron imaging and theoretical calculations of gold-silver hydrides: comparing the characteristics of Au, Ag and H in small clusters

Structures and electronic properties of the mixed metal hydride anions AuAgH(-), Au(2)AgH(-), AuAg(2)H(-) and their neutrals are studied using anionic photoelectron imaging and theoretical calculations. The three isomers of AuAgH(-) are determined to be linear and those of AuAgH are determined to have C(s) symmetry. The structures of Au(2)AgH(-), AuAg(2)H(-) and their corresponding neutrals are determined to be planar with C(s) or C(2v) symmetries. The vertical detachment energies (VDEs) and adiabatic detachment energies (ADEs) of these anions are reported. Similar to the homonuclear Au(m)(-) and Ag(n)(-) clusters, the metal hydride anions with an even number of valence electrons have higher VDEs than those with an odd number. Variation of the VDEs of these metal hydride anions with interchange of Au, Ag and H (for example Au(m)Ag(n)(-)→ Au(m-1)Ag(n+ 1)(-), or Au(m-1)Ag(n)H(-)) will be shown to be characterized by the electronegativities of Au, Ag and H. The results presented in this study provide important insights into the similar and different characteristics of these three elements in small clusters.     

超分子双膦配体的构筑及应用研究进展

超分子双膦配体是一类新兴起的基于非共价键作用构筑的双膦配体,近年来引起人们的重视.与传统的共价键连接的双膦配体相比,利用非共价相互作用的可逆性和选择性,超分子双膦配体具有合成简便,组合灵活,易于合成超分子配体库,并利用组合化学的方法对催化体系进行优化和筛选等优点.详细综述了近几年发展的基于氢键、配位键、主客体作用和静电作用等弱相互作用的超分子双膦配体,重点讨论了它们的构建方法以及在不对称催化反应中的应用,并对其发展前景进行了展望.     

DMSO-HBr体系中二甲基苯甲酰亚甲基锍盐的合成、晶体结构及反应研究

在DMSO-HBr(二甲基亚砜-溴化氢)体系中,以苯乙酮为原料合成得到二甲基苯甲酰亚甲基锍盐,用x射线单晶衍射法测定了该化合物的晶体结构.二甲基苯甲酰亚甲基锍盐在DMSO或DMSO-HBr体系中均可以转化为苯基乙酮醛,为DMSO-HBr氧化机理研究提供了新的依据.     

Numerical simulation of Shack–Hartmann wavefront sensor to characterize the turbulence phase statistics

Shack–Hartmann wavefront sensor (SHWS) is one of the important parts in an adaptive optics system and its detection accuracy has considerable influences on the performances of the whole system. In this paper, a simulator of such type of wavefront sensor is built and tested by measuring the slope structure function of Kolmogorov turbulence simulated by random phase screens. The numerical results show that it works well to characterize the turbulence phase statistics. In combination with the noise simulation, this simulator will be a very useful tool to further investigate and optimize the system parameters to improve the detection accuracy and the performance of the whole system.