人工活性膜模板制备铅钡铬酸盐纳米棒及其光学性能

利用胶棉人工活性膜模板与乙二胺的协同作用，成功制备了铬酸铅、铬酸钡纳米棒.前者直径范围为28～55 nm，最大长径比为25，结构为单斜单晶；后者直径范围为24～38 nm，最大长径比为28，结构为正交单晶.产物相对于其体材料而言，红外光谱峰值仅有少量蓝移，而紫外-可见光谱最大吸收峰则分别蓝移了30 nm和35 nm，荧光发射峰也分别蓝移了9 nm和15 nm，这均是纳米材料量子尺寸效应的体现.还对产物的形成机理作了初步探讨.     

Applying the Taguchi Robust Design to Optimization of the Experimental Conditions for Synthesis of Lead Chromate Nanorods

Orthogonal array design was employed as statistical method for controllable, simple, and fast synthesis of highly uniform PbCrO₄ nanorods by precipitation method. Lead chromate nanorods were synthesized by addition of lead solution to chromate reagent. Effect of reaction conditions on the width of lead chromate rods were quantitavely evaluated by analysis of variance. Finally, optimum conditions for synthesis of lead chromate nanorods by this simple and fast method were proposed. The results of analysis of variance showed that 0.001 mol/L lead and chromate ion concentrations are optimum conditions for producing lead chromate nanorods with 87 ± 15 nm width.     

PHYSICO-MECHANICAL,OPTICAL, AND WAXS STUDIES ON CHAIN EXTENDED POLYURETHANE

Thermoset polyurethane (PU) elastomers were prepared using castor oil, 4,4′-methylenebis(phenyl isocyanate) (MDI), and tol-uene-2,4-diisocyanate (TDI). The effect of aromatic diamines on the physico-mechanical and optical properties of chain extended polyurethane prepared using castor oil has been investigated. Tensile strength and percent elongation lies in the range 13–24 MPa and 76–32, respectively. Higher tensile strength was observed for 4,4′-diaminodiphenylsulphone (DDS) than the 4,4′-diaminodiphenylmethane (DDM) chain extender. The properties imparted by the extenders are explained on the basis of the groups present in the diamines. These changes have been interpreted quantitatively in terms of microcrystalline parameters computed using wide-angle X-ray scattering data.     

2, 2, 4, 13, 13, 15, —六甲基—1, 5, 12, 16—四氮杂环二十二烷—N′, N″′—二乙酸及其镧系配合物的合成和表征

本文合成了题头所示大环配体,并制备了它的十四种镧系元素(La～Lu,Pm除外)固体配合物.用元素分析,DTA-TG,红外光谱以及电导测定等手段研究了这些化合物的组成和性质.基于这些分析结果可建议配合物化学式为Ln(H₂L)(NO₃)₃·nH₂O.     

New method of automatic photometric determination of proteins in whole milk. II. Linearity, selectivity, and specificity

A new procedure for the preconcentration of p.p.b. concentrations of chromate from aqueous solutions has been developed. Water samples containing chromate are acidified to pH 5 and passed through an anion-exchange resin bed (AG1-X4, 100–200 mesh. Cl^? form) in ascending flow, so that the chromate is adsorbed in a narrow zone at the lower end of the resin bed. The chromate is eluted rapidly with small volumes of an acidic reductant solution which reacts with chromate on the column to form chromium(III) during the actual elution step, thus producing very high concentration factors.     

Tin (II) chloride in glycerol as a titrimetric reagent in carbonate media

Tin(II) chloride solutions in glycerol are much more stable to light and atmospheric oxidation than the usual hydrochloric acid solutions, although the general reducing properties of the solutions are similar. In bicarbonate media, ferricyanide and chromate can be readily determined; some possible applications are outlined.     

Synthesis,Characterization, and Applications of Copper Nanoparticles

Copper nanoparticles with different structural properties and effective biological effects may be fabricated using new green protocols. The control over particle size and in turn size-dependent properties of copper nanoparticles is expected to provide additional applications. Various methods for the synthesis of copper nanoparticles have been reported including chemical methods, physical methods, biological methods, and green synthesis. Biological methods involve the use of plant extracts, bacteria, and fungi. Commendable work has been done regarding the synthesis and stability of copper nanoparticles. There is a need to summarize the behavior of copper nanoparticles in different media under various conditions. Here, a complete list of the literature on the synthesis of copper nanoparticles, their properties, stabilizing agents, factors affecting the morphology, and their applications is presented. The importance of copper nanoparticles compared to other metal nanoparticles are due to high conductivity. Methods for the synthesis of copper nanoparticles, including green protocols using plants and micro-organisms compared chemical methods, have also been reviewed.     

The Young's modulus of a microcrystalline cellulose

This research is concerned with an investigation into the determination of the micromechanical properties of particulate form of cellulose; namel microcr stalline cellulose. Using the technique of Raman spectroscop the shift in the 1095cm^–1 Raman band, characteristic of cellulose, with strain is monitored and compared to the deformation of natural cellulose fibres (flax and hemp). From the values of the shift rate of the 1095cm^–1 band for flax and hemp and the experimentally-determined value for microcrystalline cellulose the value for the Young's modulus of microcrystalline cellulose was estimated to be 25±4GPa. It has been shown that this value is consistent with the measured degree of crystallinity of microcrystalline cellulose. Theoretical modelling has also enabled the Young's modulus for compacted microcrystalline cellulose to be determined for fibres in either 2-D in-plane and 3-D arrangements. These values have been show to be consistent with recent direct measurements of the modulus of compacted material.     

Immobilization of Oospora lactis lipase

A number of new sorbents for the immobilization of lipases have been synthesized from Silokhrom and Porokhrom, and also from microcrystalline cellulose. The conditions for the immobilization of lipases have been selected and some of their properties have been studied.Institute of Microbiology, Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 729–732, September–October, 1988.     

Thermal decomposition of ammonium copper chromate: effect of the addition of barium

The influence of the addition of barium (as barium chromate) to ammonium copper chromate on its thermal decomposition has been investigated by TG, DTG and DTA in the temperature range 303–1273 K. The solid products formed in the decomposition at different temperatures were characterised by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and also by measuring their specific surface area. The addition of BaCrO₄ at different concentrations (0–19.8%) was found not to change the general trend in the decomposition of ammonium copper chromate (which occurs in four distinct steps), except small changes in the temperature corresponding to DTG and DTA peaks. However, the sintering (or crystal growth) of the solid product is largely reduced by the presence of BaCrO₄.     

Synthesis,characterization, and curing of hyperbranched allyl ether–maleate functional ester resins

A model two-step synthesis of a saturated hyperbranched hydroxyl-terminated ester has been developed to show a synthesis route. Three different series of hyperbranched esters with different terminations have been synthesized to relate some of their properties to their structures. This route has then been used to synthesize three different allyl ethermaleate functional hyperbranched ester resins in a two-step procedure. The resins have been characterized with respect to rheology, structure, and properties, and the differences are discussed. The allyl ether-maleate functional resins have also been studied with respect to curing performance and final film properties. © 1993 John Wiley & Sons, Inc.     

A comparative study on the thermal decomposition of lanthanide biscitrato chromate(III) hydrates, Ln[CrC6(H5O7)2]·nH2O

The thermal decomposition of lanthanide biscitrato chromate (III) hydrates, [Ln(Cr(C₆H₅O₇)₂] nH₂O whereLn=Pr, Nd, Dy and Ho have been carried out in static air and flowing argon atmospheres and thereby compared the decomposition nature with that of the lanthanum biscitrato chromate(III) dihydrate reported earlier. The precursor complexes decompose in four major steps. Stable oxycarbonates and chromates(V) have been isolated as intermediates. It has been found that for heavier lanthanide complexes all the decomposition steps are pushed to higher temperature ranges. Moreover, the thermal stability range of chromates(V) is much lesser compared to that of LaCrO₄. Based on the observed experimental results a general scheme for the decomposition of lanthanide biscitrato chromate(III) hydrates is proposed.     

香豆素衍生物在数种薄层基质上的室温磷光发射特性

考查了二十多种香豆素衍生物在国产ＭＮ－Ｐ型和ＭＮ－Ｃ型微晶纤维素膜，ＤＥＡＥ离子交换膜上的室温磷光发射特性，并与用滤纸作基质时的结果作了比较。在这些基质上，多数衍生物都能发射不同强度的ＲＴＰ信号，且在其ＲＴＰ特性间呈现，某些取代基效应。从发光稳定性和信背比考虑，ＭＮ－Ｃ型比ＭＮ－Ｐ型膜更适合于这些衍生物的ＲＴＰ发射。     

The effect of pressure on neutron irradiated ammonium chromates

The effect of pressure on neutron irradiated ammonium chromate and ammonium dichromate has been studied. Compression was found to have no effect on the retention and on the M and DP yields in both salts. Pressure applied before heating was found to retard annealing in ammonium chromate, while it appeared to have no influence on the annealing of ammonium dichromate.     

双(三苯基甲硅烷)铬酸酯催化剂及其配制过程中表面化学反应的研究

本文采用红外光谱分析等方法,研究了双(三苯基甲硅烷)铬酸酯的加热、光照和水解反应的一些性质;探讨了双(三苯基甲硅烷)铬酸酯催化剂配制过程的化学变化。当其沉淀在硅胶上时,与硅胶表面羟基反应,生成表面有机铬化合物,铬的价态不变。加入烷基铝后,表面铬化合物还原生成含有Cr-C或Cr-O键的低价表面化合物,其对乙烯聚合具有催化活性。并指出了本催化剂活性组份可能的负载机理。     

Microanalysis of sulphide, sulphite, sulphate and thiosulphate by thin-layer chromatography and ring-colorimetry

Clean and rapid analytical separations of microgram quantities of S(2-), SO(3)(2-), SO(4)(2-) and S(2)O(3)(2-) ions have been accomplished by ascending thin-layer chromatography on microcrystalline cellulose with n-propanol-1M ammonia-acetone (30: 20: 2) as the solvent system. The separated species have been determined by ring-colorimetry.     

Surface-mediated chromate-resistant mechanism of Enterobacter cloacae bacteria investigated by atomic force microscopy

The Enterobacter cloacae CYS-25 strain isolated from a chromate plant shows a strong capability for chromate resistance instead of chromate reduction in aerobic conditions. In this study, atomic force microscopy (AFM) was used for studying the morphology characteristics of bacterial properties during the chromate resistance process. The average length of E. cloacae bacteria in the stationary phase is about 2.3 +/- 0.6 microm, while under the stimulation of 400 mg/L CrO42-, the length of bacteria increases to 3.2 +/- 0.7 microm. Height and phase images showed that, with the addition of CrO42-, the smooth surface of bacteria changed into one with discontinuous features with characteristic dimension of 40-200 nm. Analysis reveals that these compact convex patches are organic components stimulated by CrO42-. A chromate resistance mechanism relating to the overexpression of extracellular biologic components for preventing the permeability of CrO42- into the cell is proposed as the survival strategy of E. cloacae in chromate situation.     

Complex lanthanide chromate(VI)-phosphates K2R(CrO4)(PO4) (R = Dy-Lu, Y)

The conditions of formation of complex lanthanide chromate(VI)-phosphates K₂R(CrO₄)(PO₄) were found and these compounds were synthesized by solid-state synthesis with variation of the starting compounds, the temperature of synthesis (500–800 °C), and the annealing time (6–200 h). These salts are typical of late lanthanides, R = Dy-Lu, Y. Using lutetium derivatives as examples, it was shown that no similar compounds with lithium or sodium are formed. All the complex chromate(VI)-phosphates obtained decompose under static conditions at temperatures above 550 °C. They are isostructural and crystallize in the monoclinic system. The unit cell parameters for thulium, ytterbium, and lutetium compounds were calculated. It is shown by IR spectroscopy that PO₄ tetrahedra in the crystal lattice of potassium lanthanide chromate(VI)-phosphates are substantially distorted, whereas the CrO₄ tetrahedra retain the regular tetrahedron symmetry (T _d ). Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 622–626, April, 2006.     

Interaction between Se and Cr and distribution of Zn,Rb, Co,and Fe in mice given chromate ions and selenium compounds

Male SAS/4 mice injected intraperitoneally with chromate ions and Se-compounds (i.e. selenodiglutathione, selenocystine, selenomethionine and SeO₂). The distribution of Se, Cr, Zn, Rb, Co and Fe in liver, kidneys, spleen, heart, lungs, blood, small intestine and eyes has been studied by instrumental neutron activation analysis. Cr was incorporated in all investigated organs and the efficiency of the Cr-accumulation was affected upon the Se-injection. It was found that the mutual and indirect interaction occurs between injected Se-compounds and chromate ions. On the other hand, the interaction of Cr with Zn has been competitive. Injection with chromate ions affects the contents of Rb, Co and Fe in mice organs.     

Condition of lead iodide in the medium of lyophilic sols

The condition of lead chromate in gelatin and agar agar medium has been studied. In presence of agar agar medium the colloid formed is stabilised by lead ions and coagulated by the excess of chromate ions. Lead chromate forms a very stable colloid in the presence of gelatin sol which could not be precipitated by excess of lead ions or chromate ions. Due to the formation of a very stable colloid in gelatin medium, well defined rings of lead chromate are not obtained in gelatin gel.