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51.
本文报道了不同组成的YPxV1-xO4(0≤x≤1):Dy^3+的合成和结构。YPxV1-xO4(0≤x≤1)为四方晶系,晶胞参数随x的增大呈线性减小。基质的Stokes位移随x的增大逐渐变大,而激发光谱峰值则向短波方向移动。在YPxV1-xO4:0.006Dy^3+体系中,x>0.4时出现的基质发射是由PO^3-4引起的。基质及Dy^3+的发光效率和Dy^3+的发光强度的黄蓝比均与x有关。同时探 相似文献
52.
本文研究并探讨了NK-ELN型离子交换树脂在再生贮氢合金材料包覆液过程中,温度、流速、溶液中离子浓度等条件对树脂交换容量和再生效率的影响,为树脂法再生贮氢合金材料包覆液工艺的制定,提供了一系列重要参数。 相似文献
53.
采用UVVis光谱法研究了茜素红S(ARS)与5′鸟苷酸(5′GMP)在pH4.80的弱酸性缓冲溶液中生成络合物的结合反应。与试剂比较,络合物的最大吸收峰红移92nm,测得络合物和表观摩尔吸光系数为ε=1.3×104L·mol-1·cm-1;最大结合数n=10;浓度线性范围0.2~16mg/L;检出限为6.1×10-8mol/L。研究了ARS与5′GMP是分子间作用力的结合反应,并对时间、温度、离子强度对结合反应的影响,以及无机物、生物物质对反应体系的干扰情况进行了初步研究。 相似文献
54.
55.
光谱实验室的建设和管理 总被引:1,自引:0,他引:1
阐述冶金、铸造等行业用于金属成分分析的直读发射光谱仪实验室的建设和管理。从仪器的调研、选型,实验室选址,基础设施设备的准备,仪器的安装、调试、验收、日常分析,实验室管理等几个方面,分别作了介绍。 相似文献
56.
Lisheng Chi Ian Swainson Jae-Hyuk Her Osvald Knop 《Journal of solid state chemistry》2005,178(5):1376-1385
The perovskite-structured compound methylammonium lead chloride orders into a low-temperature phase of space group Pnma, in which at 80 K each of the orthorhombic axes , and is doubled with respect to the room temperature disordered cubic phase (). The structure was solved by ab initio methods using the programs EXPO and FOX. This unusual cell basis for space group Pnma is not that of a standard tilt system. This phase, in which the methylammonium ions, are ordered shows distorted octahedra. The octahedra possess a bond angle variance of 60.663°2 and a quadratic elongation of 1.018, and are more distorted than those in the ordered phase of methylammonium lead bromide. There is also an alternating long and short Pb-Cl bond along a, due to an off-center displacement of Pb within the octahedron. This suggests that the most rigid unit is actually the methylammonium cation, rather than the PbCl6 octahedra, in agreement with existing spectroscopic data. 相似文献
57.
Solid Phase Extraction Chemiluminescence Determination of Methamidaphos on Vegetables 总被引:3,自引:0,他引:3
IntroductionDuring recent years,organophosphorus pesticides(OPPs)have been widely used in agriculture becauseof their low environmental persistence and high effec-tiveness.However,they have a high acute toxicity.Trace amounts of OPPs may remain in foodstu… 相似文献
58.
SynthesisandCrystalStructureofMnSm_4(SiO_4)_3O¥ChiLi-Sheng;DengShui-Quan;ZhuangHong-Hui;HuangJin-Shun;(StateHeylaboratoryofStr?.. 相似文献
59.
Kwok WM Zhao C Guan X Li YL Du Y Phillips DL 《The Journal of chemical physics》2004,120(19):9017-9032
A combined experimental and theoretical study of the ultraviolet photolysis of CH2I2 in water is reported. Ultraviolet photolysis of low concentrations of CH2I2 in water was experimentally observed to lead to almost complete conversion into CH2(OH)2 and 2HI products. Picosecond time-resolved resonance Raman spectroscopy experiments in mixed water/acetonitrile solvents (25%-75% water) showed that appreciable amounts of isodiiodomethane (CH2I-I) were formed within several picoseconds and the decay of the CH2I-I species became substantially shorter with increasing water concentration, suggesting that CH2I-I may be reacting with water. Ab initio calculations demonstrate the CH2I-I species is able to react readily with water via a water-catalyzed O--H-insertion and HI-elimination reaction followed by its CH2I(OH) product undergoing a further water-catalyzed HI-elimination reaction to make a H2C=O product. These HI-elimination reactions produce the two HI leaving groups observed experimentally and the H2C=O product further reacts with water to produce the other final CH2(OH)2 product observed in the photochemistry experiments. These results suggest that CH2I-I is the species that reacts with water to produce the CH2(OH)2 and 2HI products seen in the photochemistry experiments. The present study demonstrates that ultraviolet photolysis of CH2I2 at low concentration leads to efficient dehalogenation and release of multiple strong acid (HI) leaving groups. Some possible ramifications for the decomposition of polyhalomethanes and halomethanols in aqueous environments as well as the photochemistry of polyhalomethanes in the natural environment are briefly discussed. 相似文献
60.
Rogers PH Michel E Bauer CA Vanderet S Hansen D Roberts BK Calvez A Crews JB Lau KO Wood A Pine DJ Schwartz PV 《Langmuir : the ACS journal of surfaces and colloids》2005,21(12):5562-5569
The directed three-dimensional self-assembly of microstructures and nanostructures through the selective hybridization of DNA is the focus of great interest toward the fabrication of new materials. Single-stranded DNA is covalently attached to polystyrene latex microspheres. Single-stranded DNA can function as a sequence-selective Velcro by only bonding to another strand of DNA that has a complementary sequence. The attachment of the DNA increases the charge stabilization of the microspheres and allows controllable aggregation of microspheres by hybridization of complementary DNA sequences. In a mixture of microspheres derivatized with different sequences of DNA, microspheres with complementary DNA form aggregates, while microspheres with noncomplementary sequences remain suspended. The process is reversible by heating, with a characteristic "aggregate dissociation temperature" that is predictably dependent on salt concentration, and the evolution of aggregate dissociation with temperature is observed with optical microscopy. 相似文献