控制电位滴定法的误差分析

研究了影响控制电位滴定法测定结果准确度的因素,得到的结论是:第一,电位的控制误差及滴定剂体积的测定误差是影响控制电位滴定法测定结果准确度的主要因素.计算模型中的比例系数越大,滴定曲线的变化率越大,这种影响越小.第二,多组分体系的测定误差,与组分在计算模型中比例系数的相对大小有关.比例系数越大,测定误差越小.第三,不同浓度(或不同浓度比)待测溶液滴定曲线的差异越大,对控制电位滴定法的测定越有利.     

A new luminol derivative as a fluorescent probe for trace analysis of copper(II)

Microchimica Acta - A new luminol derivative has been synthesized and its fluorescence has been studied. The luminol derivative emits at 460 nm in pH 10.0 phosphate buffer which is...     

A Preliminary experimental study of the boron concentration in vapor and the isotopic A preliminary experimental study of the boron concentrationin vapor and the isotopic fractionation of boron betweenseawater and vapor during evaporation of seawater

A laboratory experiment was undertaken to investigate the behaviour of boron at theseawater-air interface under air flow conditions. Dried air at 25 and 35℃ was passed over or bub-bled through seawater at the same temperature. A combination of ice-chilled condensers and KOHimpregnated cellulose fibre filters was used to collect boron from the reacted air. When air strippedof boron was passed over the seawater, boron was found in the reacted air, and its concentrationwas higher in the higher temperature test. In the tests where air was bubbled through seawater theconcentration of boron in the reacted air was directly proportional to the air flow rate. In this situa-tion the boron in the reacted air was mainly introduced as a spray of microdroplets. Isotopic analy-sis of the collected boron in the non-bubbled tests yields fractionation factors which demonstratethat the lighter isotope, 10B, is enriched in the reacted air. The size of the fractionation changeswith temperature, ruling out a purely kinetic effect.     

A simple approach toward low‐dielectric polyimide nanocomposites: Blending the polyimide precursor with a fluorinated polyhedral oligomeric silsesquioxane

This article describes a new and simple method for preparing polyimide nanocomposites that have very low dielectric constants and good thermal properties: simply through blending the polyimide precursor with a fluorinated polyhedral oligomeric silsesquioxane derivative, octakis(dimethylsiloxyhexafluoropropyl) silsesquioxane (OF). The low polarizability of OF is compatible with polyimide matrices, such that it can improve the dispersion and free volume of the resulting composites. Together, the higher free volume and lower polarizability of OF are responsible for the lower dielectric constants of the PI‐OF nanocomposites. This simple method for enhancing the properties of polyimides might have potential applicability in the electronics industry. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6296–6304, 2008     

Growth and characterization of MOMBE grown HfO2

HfO₂ dielectric layers were grown directly on the p-type Si (1 0 0) by metalorganic molecular beam epitaxy (MOMBE). Hafnium tetra-butoxide was used as a Hf precursor and pure oxygen was introduced to form an oxide layer. The properties of the layers with different thicknesses were evaluated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), and capacitance–voltage (C–V) and current–voltage (I–V) analyses. XRD and HRTEM results showed that the HfO₂ films thinner than 12 nm were amorphous while the films thicker than 12 nm began to crystallize in the tetragonal and the monoclinic phases. The XPS spectra of O 1s show that the O---Si binding energies shifted to the lower binding energy with increasing the HfO₂ layer thickness. Moreover, the snap back phenomenon is observed in accumulation capacitance. These changes are believed to be linked with the decomposition of SiO and the crystallization of HfO₂ layer during the film growth.     

A Series of Three‐Dimensional Rare Earth Coordination Polymers with Two Binary Carboxylate as Mixed‐Ligand: Syntheses,Structures, Properties of [LnIII(mal)(ox)0.5(H2O)2]·2H2O (Ln = Pr,Nd, and La)

A series of lanthanide coordination polymers, [Ln^III(mal)(ox)_0.5(H₂O)₂]·2H₂O (Ln = Pr ( 1 ), Nd ( 2 ), and La ( 3 ); H₂mal= maleic acid; H₂ox = oxalic acid), were synthesized firstly by the reaction of Ln^III nitrate salts with maleic anhydrid and oxalic acid under hydrothermal conditions and were characterized by elemental analysis, IR spectroscopy, and single‐crystal X‐ray diffraction. X‐ray diffraction analyses reveal that they are crystallized in orthorhombic space group Fddd. Lanthanide metal center atom (Ln) and its corresponding centrosymmtric atom link through two chelating/bridging bidentate carboxyl groups of maleic acid ligands to form an infinite inorganic rod‐shaped building unit. These rod‐shaped building units were linked to each other through the carbon atoms of the maleate anions on the [110] plane to form lanthanide‐maleic acid layers. The oxalic acid pillared lanthanide‐maleic acid layers with intersected channels by free water molecules consist of a 3D framework structure. The thermogravimetric analyses of 1 – 3 were discussed in detail. The courses of the thermal decomposition of complexes are similar.     

用Zn/F离子先后注入和热退火法实现ZnO量子点的可控生长

将Zn/F离子先后注入到非晶二氧化硅中并分别在400,600,700 ℃下进行了退火.用光学吸收谱、透射电子显微镜(TEM)、高分辨透射电子显微镜(HRTEM)对退火的样品进行分析,发现在600 ℃退火后ZnO量子点已经形成.二次离子质谱仪(SIMS)测试发现在溅射时间为2 s时Si,Zn元素同时出现,说明没有在衬底的表面形成ZnO薄膜.从原子力显微镜(AFM)图像看到有少量的颗粒被蒸发到衬底的表面,说明在衬底的内部形成了ZnO量子点.F离子注入的作用为在衬底的内部形成ZnO量子点提供了O2分子.