A Restudy of Direct Chelatometric Titration of Vanadium(IV) with N-Benzoyl-N-phenylhydroxylamine as Indicator

This paper restudies the method of direct chelatometric titration of V(IV) with N-benzoyl-N-phenylhydroxylamine (BPHA) as indicator. The indicator functions entirely differently from indicators hitherto used in chelatometry. The solution contains two independent systems – the indicator and the titrand-titrant system – without any color changing species. The BPHA-V(V) chelate once formed as the result of aerial oxidation constitutes the indicator system and does not react with EDTA. Its color therefore remains unchanged throughout titration. It is not a metallochromic indicator. Its function is that of color-screening. The color of the titrant system deepens during titration, but does not change. The end-point is indicated by one color completely covering up the other. Hence, this method is of purely empirical nature.Received July 5, 2002; accepted February 11, 2003 Published online July 16, 2003     

Synthesis and Characterization of Poly-Ortho-Methylaniline With Different Degrees of Oxidation

Poly-ortho-methylanilines (POT) in three states fully oxidized, fully reduced and oxidized in varying degrees were synthesized by the reaction of common POT (C-POT) having nearly equal amounts of benzenediamine and quinonediimine units with iodine or phenylhydrazine, and the resulting polymers were characterized by IR,~(13)C-NMR, SEM and elemental analysis. The results showed that the quinonediimine unit in C-POT could be reduced by phenylhydrazine to the benzenediamine unit,forming the polymer with low OD (oxidation degree) or in a fully reduced state and that iodine-oxidation resulted in the increase of quinonediimine unit and decrease of benzenediamine unit. The solubility and flexibility of the formed polymers depend strongly on the amount of quinonediimine unit in it. It is necessary to reduce the content of quinonediimine structure unit in order to improve the solubility of aniline-class polymers.     

Photolithographic Patterning and Doping of Silica Xerogel Films

This study shows that conventional photolithography can be applied for patterning native or organic dye-doped silica films (0.5 m thick) obtained via a base-catalyzed sol-gel process. Photoresist was spin-coated onto high optical quality xerogel films, soft-baked, exposed to UV irradiation through a photomask, and developed with a commercial photoresist developing solution. Etching away of the photoresist-unprotected areas of the silica films was carried out with a dilute HF solution, while the remaining unexposed photoresist was removed with acetone. Interdigitated array patterns with features as small as 0.5 mm show a smooth surface and extremely sharp interfaces. Densification of the films at 550°C for 2 h decreases the film thickness by 11%, increases the refractive index from 1.420 to 1.456, and allows for well-defined patterning down to length scales of 10 m. Since the densification conditions are incompatible with organic dopants, it is demonstrated that sol-gel films can be doped after pattering (post-doping) by adsorption of cationic dyes from solution. Scanning electron microscopy reveals that the microstructure of patterned sol-gel films is similar to that of bulk monoliths, indicating that the photolithographic procedure is not harmful to the film quality. All patterned films demonstrate highly regular light diffraction patterns.     

Adsorption of benzene on the V2O5/γ-Al2O3 catalyst

Adsorption of benzene on the V₂O₅/-Al₂O₃ catalysts was studied in the temperature interval from 443 to 493 K and at partial pressures of the adsorbate ranging from 1 to 400 Pa. The adsorption isotherms were plotted. The isosteric heats and various entropy characteristics of adsorption were determined. Mobility of benzene in the adsorption layer is restricted compared to the model of ideal dimeric gas. The adsorbed amounts of benzene and chlorobenzene are compared.     

Use of solid electrolyte GeSe-GeI<Subscript>2</Subscript> for electrochemical doping with germanium

Lead tellurite is study to show that solid electrolyte GeSe-GeI₂, which has the optimum composition and contains 5 mol % of GeI₂, can in principle be used for electrochemical doping of semiconducting materials with germanium by the coulometric titration method. Some parameters of the coulometric titration are considered. The doping efficiency is monitored by determining variations in the concentration of charge carriers using the Hall method and by measuring the EMF of corresponding galvanic cells.     

Effects of Poly(ethylene glycol) Doping on the Behavior of Pyrene, Rhodamine 6G, and Acrylodan-Labeled Bovine Serum Albumin Sequestered within Tetramethylorthosilane-Derived Sol-Gel-Processed Composites

We investigate the effects of controlled poly(ethylene glycol) (PEG) doping on the behavior of pyrene, rhodamine 6G (R6G), and acrylodan-labeled bovine serum albumin (BSA-Ac) sequestered within tetramethylorthosilicate (TMOS)-derived sol-gel-processed materials. To probe the dipolarity of the local environment within the composite we performed static fluorescence measurements on pyrene as the composites aged. We found that small levels of PEG loading effected significant enhancements in the local dipolarity surrounding the average pyrene molecule. Time-resolved fluorescence anisotropy measurements were used to follow the rotational reorientation dynamics of R6G as the composites aged. As the PEG loading increased, the R6G reorientational mobility increased. Nitrogen adsorption techniques were used to quantify the effects of PEG doping level on the surface area and final xerogel pore features. A large reduction in surface area was observed with PEG doping, but no detectable change in pore size was noted. The effects of PEG doping on a biomolecule were probed by following the time-resolved fluorescence anisotropy decay of BSA-Ac. These results showed that PEG doping resulted in increased biomolecule dynamics relative to that found for a neat, undoped TMOS-derived composites. Together these results show that PEG doping can be used to tune the sol-gel-processed composite dipolarity, alter the mobility of dopants sequestered within the composite, control analyte acessibility to the sensing chemistry, and modulate the internal dynamics within a biodopant.     

纳米Ce1-xCoxO2-δ固溶体的水热合成及表征

采用水热方法, 在络合剂及氧化剂的辅助下合成出传统方法难以合成的Ce1-xCoxO2-δ固溶体. XRD结果表明, Ce1-xCoxO2-δ固溶体具有立方萤石结构; 产物的平均粒度约为4 nm. 小半径、低价态Co离子的掺杂导致晶格收缩. 结合XRD和Raman表征结果确定固溶体的固溶限约为x=0.06. 紫外光谱分析结果表明, Co离子以混合价态(+2, +3)存在于CeO2晶格中, 随着钴掺杂量的增大, 带隙逐渐蓝移. 低于固溶限样品的室温体相电导率随着钴含量增大而提高.     

Ni(phen)(H2O)(V2O6)的水热合成和晶体结构（英）

A novel compound Ni(phen)(H₂O)(V₂O₆) has been hydrothermally synthesized and structurally determined to be a two-dimensional compound, which contains {V₂O₆}_n^2n- chains interconnected by nickel(Ⅱ) complexes via oxygen atoms. The crystallographic data measured by single-crystal X-ray diffraction analysis are as follows: C₁₂H₁₀N₂NiO₇V₂, M_r=454.81, monoclinic, space group P2₁/c, a=0.784 6(3), b=2.103 6(8), c=0.942 3(4) nm, β=112.872(5)°, V=1.433 0(10) nm³, Z=4, D_c=2.104 Mg·m^-3, μ(Mo Kα)=2.615 mm^-1, F(000)=904, T=298(2) K, 4 480 reflections collected, 2 470 independent (R_int=0.032 2), the final R=0.058 4 and wR₂=0.145 7 for 2 303 observed reflections with I>2σ(I). CCDC: 192520.     

Sol-Gel Fabrication and Properties of Silica Cores of Optical Fibers Doped with Yb3+, Er3+, Al2 O3 or TiO2

Optical cores of preforms for drawing optical fibers doped with Er3+ and Yb3+ were fabricated by the sol-gel method with the aim of increasing the thickness of glass layers coated in a single coating cycle and to determine the relation between the preparation conditions and optical properties of the fibers. Al2O3-P2O5-SiO2 and TiO2-P2O5-SiO2 glasses have been studied as matrices for entrapping the rare-earth elements. Input sols have been prepared from silicon and titanium alkoxides, AlCl3, ErCl3, YbCl3, POCl3, water and a modifier under acidic catalysis of HCl. The sols were coated on the inner wall of a silica substrate tube and the gel layers were sintered at high temperatures up to 2000°C after which the tube was collapsed into the preform. Continuous and homogenous glass films with the maximum thickness of about 8 m were fabricated. The influence of high-temperature heat treatment of the layers on their composition and optical attenuation was observed. The amplified stimulated emission of Er3+ around 1.55 m was measured under the excitation of the fibers by an Nd : YAG laser at 1.064 m.