二安替比林基-4-羟基苯基甲烷及其与铬(Ⅵ)显色反应的研究

合成了二安替比林基-4-羟基苯基甲烷(DApHM),研究了它与铬(Ⅵ)的显色反应,建立了两个测定铬(Ⅵ)的新体系.在Mn(Ⅱ)和磷酸存在下,DApHM与 Cr(Ⅵ)反应生成橙红色产物,λ_max为435nm.CTMAB和Tween-80对该体系有明显增敏效果,其中CTMAB-DApHM-Cr(Ⅵ)体系ε为1.0 ×10~6;Tween-80-DApHM-Cr(Ⅵ)体系ε为6.9×10~5.Cr(Ⅵ)量在0.1～0.7μg/25mL间符合比尔定律.用于电镀废液和自来水中Cr(Ⅵ)的测定,结果满意.     

Adsorption enthalpy and desorption enthalpy during displacement of adsorbate to solvent in a liquid-solid system

The adsorption heat of the stoichiometric displacement process for the adsorption of a solute in a liquid-solid system was investigated. On the basis of the SDM-A and the rule of the additivity of energy, an expression which describes the dependence of the adsorption enthalpy on the nature and concentration of the solute, and on the solvent and adsorbent, was derived. The adsorption heat determined for the solute with the traditional method can be divided into two independent fractions, relating to the adsorption of the solute and to the desorption of the solvent. Experimental data on both isotherms from the literatures and precise calorimetry were used to test the adsorption heat and its fractions computed quantitatively via the equations presented in this study, and a satisfactory degree of conformity between them was obtained. Supported by the Natural Science Foundation of Shaanxi Province in China.     

Evolution of the geometrical and electronic structures of Gan(n=2-26) clusters: a density-functional theory study

Density-functional theory with generalized gradient approximation for the exchange-correlation potential has been used to calculate the lowest-energy geometries and electronic structure of neutral gallium clusters containing up to 26 atoms. Harmonic vibrational frequency analysis is undertaken to assure that the lowest-energy geometries are real local minima. With increasing cluster size, we find that the gallium clusters tend to adopt compact structures. The structures comprise triangular units that connect each other with different dihedral angles. The lowest-energy structure can be obtained by capping an atom on the structure of smaller one. The capping site occurs at a site where interactions with more atoms are available. The binding energy evolves monotonically with size, but Ga(8), Ga(14), and Ga(20) exhibit particularly higher stability. Except Ga(2) and Ga(4), all even-numbered gallium clusters we studied are closed-shell singlet states with a substantial highest occupied and lowest unoccupied molecular orbitals gap. The odd-numbered clusters are open shell with a small gap. The size dependence of cluster's ionization potentials and electron affinities is discussed and compared with available experiment.     

Measuring trihalomethane concentrations in water using supported capillary membrane sampling-gas chromatography

The objective of this study was to develop and evaluate a supported capillary membrane sampling-gas chromatography method for the analysis of trihalomethanes (THMs) in drinking water. The effects of experimental parameters, such as flow rate of carrier gas, water temperature, ionic strengths of solutions and transfer line temperature on the system performance were investigated. The results of method detection limit and accuracy and precision studies are reported.     

Isolation, characterization, and theoretical study of La2@C78

A new metallofullerene, La2@C78, has been synthesized by DC arc discharge method, isolated by high-performance liquid chromatography, and characterized by laser desorption time-of-flight mass spectrometry, UV-vis-NIR absorption, differential pulse voltammetry, 13C NMR spectroscopy, and theoretical calculations. The La2@C78/CS2 solution is dark violet and presents several characteristic absorption features at 647, 561, 533, and 386 nm, with an onset around 1000 nm. With respect to empty D3-C78, the capability of La2@C78 as an electron acceptor or donor is stronger. Addition of 1,1,2,2-tetrakis(2,4,6-trimethylphenyl)-1,2-disirane to La2@C78 photochemically, as well as thermally, affords bis- and mono-adducts. Theoretical studies and 13C NMR spectroscopic analysis of La2@C78 indicate that it possesses a D3h-C78 cage (78:5).     

检测易爆气体的催化发光传感器研究

报道了一种用于定量分析易爆气体混合物丙烷和异丁烷的基于碳酸锶纳米材料的催化发光传感器。基于该传感器在不同温度下对两种气体的灵敏度不同，在320℃和342℃两个工作温度下，两种气体的浓度范围均为1000mL／m^3～10000mL／m^3时，分别建立了混合组分浓度相对催化发光强度的两个线性回归方程。在342℃时，丙烷和异丁烷的检出限（3σ）分别为50mL／m^3和20mL/m^3。可通过解上述两个联立方程式求得未知混合物中两组分的浓度。外来物质甲烷、乙烷、CO、氨气通过传感器时，甲烷和乙烷分别引起5．6％和17．2％的干扰，其它气体不干扰测定。20000mL／m^3的水蒸气不干扰2000mL／m^3丙烷和异丁烷气体的测定。用该法分析了人工合成样品中两种气体的浓度。     

乙烯基聚硅氧烷共聚反应竞聚率的测定及其对复合粒子形态的影响

用Ｆｉｍｅｍａｎ－Ｒｏｓｓ法处理数据，测定了乙烯基聚硅氧烷（ＳＶ）与苯乙烯（ＳＴ）、甲基丙烯酸甲酯（ＭＭＡ）和甲基丙烯酸正丁酯（ｎ－ＢＭＡ）的共聚反应的竞聚率，结果为ｒＳＴ＝１．４５和ｒＳＶ＝１．０８，ｒＭＭＡ＝０．７８和ｒＳＶ＝２．０１，ｒｎ－ＢＭＡ＝０．４６和ｒＳＶ＝３．４９．以含ＳＶ的乳液作为种子进行烯类单体的乳液聚合，单体和ＳＶ共聚反应对复合粒子的形态有很大影响。     

聚苯乙烯稀溶液的小角激光弹性和准弹性光散射

随着激光技术的发展,近年来出现了与散射光频加宽相应的光子相干光谱即准弹性光散射。于是,利用光散射(也称弹性光散射)法不仅能获得高聚物的各种物性参数如分子量(?),第二维利系数A_2和均方旋转半径(),而且还能得到大分子在溶液中的动态参数,即扩散系数D_0。由D_0求得流体力学半径R_H。本文只涉及小角度准弹性光散射(1°<θ<7°)对稀溶液范围的平动扩散系数的测定。与文献比较,表明方法是成功的。     

钇对2618合金组织及性能的影响

采用X射线，光学显微镜及扫描电镜等手段研究了2618合金中的组织与相结构，并研究了元素钆在2618合金中的存在形式及其对合金力学性能的影响。结果表明，微量钆元素在铝合金中是以化合物形式存在的；钆对合金中的铸态组织及Al9FeNi仃形态没有影响。由于微量钆的加入，降低了铜与镁在2618合金中的固溶量，减少了时效析出相A2CuMg数量，从而降低2618合金的室温强度帮在250℃的高温瞬时强度；但由于微量钆减少了铜与镁在2618合金中的扩散速度，延缓了时效机的粗化，并由于第二相数量的增多，因此提高了2618合金在250℃经100h高温热暴露后的高温瞬时强度。     

C1/Ag(111)体系研究 Ⅳ.氯吸附对甲醇吸附氧化的影响

运用HREELS技术对甲醇在预吸附氯的Ag(111)表面上的吸附氧化行为进行了较细致的研究.结果证明Cl对甲醇氧化的影响缘于它在Ag(111)上的吸附所引起的表面结构的改变进而改变表面氧吸附物种,从而使得甲醇氧化的中间产物发生变化.实验结果说明甲醇在Ag(111)和低暴露量氯吸附的Ag(111)表面上的氧化行为是相似的,检测到了中间产物Ⅰ和Ⅲ;在高暴露量氯吸附的Ag(111)上甲醇氧化时则产生中间产物Ⅰ、Ⅳ和甲醛物种.对上述不同的甲醇氧化行为作了分析,并指出了以前人们在考察甲醇氧化机理时只考虑原子氧作用的片面性.