The effects of pyridine derivative additives on interface processes at nanocrystalline TiO2 thin film in dye‐sensitized solar cells

2‐Methyl‐4‐propoxypyridine, a new pyridine derivative, has been synthesized and used as an additive in the liquid electrolyte of dye‐sensitized solar cells (DSSCs). Compared with 2‐methylpyridne and 4‐tert‐pyridine, they were employed to study the influence of the pyridine derivative additives on the rate of recombination at the electrode/dye/electrolyte interfaces and band edge shift of TiO₂, which were measured by time‐resolved mid‐infrared absorption spectroscopy and Mott–Schottky analysis, respectively. It was found that the rate of interfacial charge recombination was enhanced when the pyridine derivative additives were present in the electrolyte. Meanwhile, the additives caused a negative shift of the band edge. However, the net effect of pyridine derivative addition was to improve the open‐circuit photovoltage according to the photoelectrochemical measurement, indicating that negative shift of conduction band of TiO₂ was a predominant factor in improving the open‐circuit photovoltage. Also, the result was strongly supported by the dark current measurement. Therefore, it provides a microscopic account for the function of the pyridine derivative additives on the open‐circuit photovoltage enhancement of the DSSCs. Furthermore, the decrease of the short‐circuit photocurrent of the cells was also attributed to the slower dye regeneration due to the addition of additives from the results of cyclic voltammetry measurement. Copyright © 2007 John Wiley & Sons, Ltd.     

微波溶样火焰和石墨炉原子吸收法测定样品中的金属元素

本文采用全聚四氟乙烯高压消化弹结合微波溶样技术消化食物，植物和河流沉积物样品，用火焰和石墨炉子原子吸收法测定了样品中的Ｃｕ，Ｚｎ，Ｆｅ，Ｍｎ，Ｃａ，Ｍｇ，Ｐｂ，Ｓｅ，Ｃｒ和Ｍｏ讨论了混合酸及消化时间等因素对不同样品的影响，将此法用于标准物质大米粉（Ｇ ＢＷ０８５０２），猪肝（ＧＢＷ０８５５１），甘蓝（ＧＢＷ０８５０４）和河流沉积物（ＧＢＷ０８３０１）的分析，得到了满意的结果。     

Fabrication of a visible-light response mesoporous TiO2 membrane with superior water permeability via a weak alkaline sol-gel process

A visible-light response TiO(2) ultrafiltration membrane was fabricated via a weakly alkaline sol-gel method for the first time, and exhibited a cut-off molecular weight of 7500 Da and high pure water flux of 170 L m(-1) h(-1) bar(-1).     

DNA cycle amplification device on magnetic microbeads for determination of thrombin based on graphene oxide enhancing signal-on electrochemiluminescence

A novel and sensitive strategy which integrated a DNA cycle device onto magnetic microbeads (MB), amplifying the signal with graphene oxide (GO) and enhancing electrochemiluminescence (ECL) intensity, was developed and was further successfully applied to thrombin detection.     

Stochastic incompleteness for graphs and weak Omori-Yau maximum principle

We prove an analogue of the weak Omori-Yau maximum principle and Khas?minskii?s criterion for graphs in the general setting of Keller and Lenz. Our approach naturally gives the stability of stochastic incompleteness under certain surgeries of graphs. It allows to develop a unified approach to all known criteria of stochastic completeness/incompleteness, as well as to obtain new criteria.     

考虑借款企业决策行为的供应链CVaR利率决策模型

贷款利率是银行和其他金融机构用于权衡风险和收益的重要指标之一.考虑借款企业的决策行为,采用CVaR的风险度量准则作为决策标准,建立了基于条件风险价值最小的银行贷款利率决策模型,得到了权衡风险和收益条件下的最优利率.通过模型求解和数值分析发现:决策者的风险容忍水平直接对利率决策产生影响,CVaR风险度量准则可以帮助银行权衡收益和风险:借款企业利润率和自有资金是银行规避风险时需要着重考虑的关键因素.     

非负整数对称阵可实现性问题的算法

1引 言 设P是有p个元素,oj,j＝1,…,p,的有限集,{Si｝,I=1,…,n,为P的子集族.记A=(aij)为{Si｝的关联矩阵,其中,当Oj∈Si时aij=1,否则aij=0.若AAT＝B＝(bij),即bij=|Si ∩ Sj|,则B是对称的且bii≥Bij≥0.反过来,已知n阶非负整数对称阵B,是否存在一个n×m的0-1矩阵A使B=AAT,以及如何计算使B=AAT成立的最小的m(即容度),这即是John B Kelly于1968年在文献[1]中讨论的非负整数对称阵的可实现性问题.     

Enhanced photo-induced hydrophilicity of the sol-gel-derived ZnO thin films by Na-doping

Na-doped ZnO thin films with different Na/Zn ratio were prepared by sol-gel method. The microstructure, chemical composition, surface morphology, and wettability of the thin films were investigated by X-ray diffraction, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy, and water contact angle apparatus. The relation of wettability and Na/Zn ratio has been studied in detail. The wetting behavior of the thin films can be reversibly switched from hydrophobic to hydrophilic, through alternation of UV illumination and dark storage (or thermal treatment). Photo-induced hydrophilicity of the thin films increases with increasing Na/Zn ratio up to 0.08 and then decreases. The mechanism can be attributed to surface nanostructure and the concentration of Na doping.     

Tunable surface wettability of ZnO nanorods prepared by two-step method

Zinc oxide (ZnO) nanorods were deposited on silicon substrate by two-step method. The crystal structure, surface morphology and water contact angle (WCA) were measured by X-ray diffractometer (XRD), field emission scanning electron microscopy (FESEM), and water contact angle apparatus. It is demonstrated that the WCA of the as-grown ZnO nanorods varies between 136° and 43° and the contact angle reduction rate of ZnO nanorods changes rapidly with increasing growth time. The variation of contact angle in the as-grown samples and contact angle reduction rate has been attributed to the combined effects of the proportion of nonpolar planes in the outermost surface, the area fraction of vapor on the surface and the increase of surface energy of ZnO nanorods.     

不同配比基质对桂花生长的影响

用不同基质按照一定比例进行混合,采用盆栽方法栽培桂花,研究了不同基质对桂花生长的影响。结果表明,不同配比基质对桂花生长,包括叶绿素含量、质膜透性、脯氨酸含量,过氧化物酶活性和丙二醛含量等均有不同程度的影响,其中田园土、煤渣、河沙、珍珠岩、鸡粪、食用菌下脚料和花生壳按1.0、0.5、0.5、1.0、1.5、1.5和1.0比例混合的营养基质对桂花生长综合效果最好。