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981.
对半导体材料进行表面化学修饰或改性,是提高其光催化活性、有效利用光能的一种重要措施.本文结合水热化学法、化学池沉积和后续热处理等,分别制备了未修饰α-Fe2O3和钒修饰的α-Fe2O3光电极材料.利用X射线粉末衍射(XRD)谱和紫外-可见漫反射光谱(UV-Vis-DRS)技术分析表征了材料的晶相结构、化学组成和光谱吸收等固体物理化学性能;利用光电流测量和电化学交流阻抗谱(EIS)实验技术,并基于1 mol·L-1NaOH (pH 13.6)中的光电化学水分解反应,研究了钒修饰对α-Fe2O3材料光电化学性能的增强作用.结果表明,与未修饰的Fe2O3材料相比,钒修饰α-Fe2O3样品出现FeVO4的XRD特征峰,但临界光吸收波长未发生红移;钒修饰使Fe2O3材料的光电流增大4-5倍、光生载流子在电极表面的复合几率降低了3/4-4/5、电极表面电荷传递速率(表观一级速率常数)明显提高.结合Fe2O3/溶液界面半导体能带模型和有关研究结果,分析了研究体系的界面电荷动力学传输过程以及钒修饰使α-Fe2O3材料光电化学性能增强的原因. 相似文献
982.
自制了一种进样毛细管可替换的常规同心雾化器,由雾化器器体、石英毛细管(外径0.37 mm,内径0.25mm)和雾化器适配器在环氧树脂胶的黏合作用下组装而成.将雾化器浸入沸水中,环氧树脂胶即软化,从而实现雾化器各组件的拆卸分离及破损或堵塞的进样毛细管的更换.自制同心雾化器在雾化气流量为0.87L.min-1、样品提升量在1.09mL.min-1左右达到最佳灵敏度.在最佳实验条件下,比较了自制的毛细管同心雾化器和Mein-hard同心雾化器的性能,前者在灵敏度、检出限、准确度、长期稳定性和多原子离子产率方面均优于或相当于后者.自制的可替换毛细管同心雾化器相比同类的商品同心雾化器,具有制作简单、使用方便、维护经济等优点. 相似文献
983.
采用电感耦合等离子体发射光谱法对土壤勘查地球化学样品中的钼进行测定,并对测量结果进行不确定度评定. 分析了影响测量不确定度的主要来源,对测定全过程的重复性、样品称量、拟合曲线、标准溶液、玻璃量具及仪器等影响不确定度的因素进行分析,按JJF l059—1999《测量不确定度评定与表示》的规定进行评定,并计算出扩展不确定度,使结果的表达更加客观和真实. 相似文献
984.
建立了一个简单、快速、有效的适用于质谱或液相色谱-质谱联用的在线固相萃取(SPE)高通量除盐方法。方法分为单柱和双柱模式,借助于包含双梯度泵(上样泵/分析泵)、自动进样器和配有十通切换阀的柱温箱的高效液相色谱系统,完成样品的自动化在线除盐。单柱模式通过上样泵实现在SPE柱上进样和除盐,被分析物则保留在SPE柱上;除盐完成后,通过阀切换利用分析泵洗脱富集在SPE柱上的被分析物。双柱模式则在单柱模式基础上增加了1根SPE柱,在色谱管理软件控制下2根SPE柱轮流工作,高效率完成样品的在线除盐。该方法在结合质谱分析蛋白质、多肽等领域具有较好的应用前景。 相似文献
985.
Using the pseudomode method, we theoretically analyze the creation of quantum correlations between two two-level dipole-dipole interacting atoms coupled with a common structured reservoir with different coupling strengths. Considering certain classes of initial separable-mixed states, we demonstrate that the sudden birth of atomic entanglement as well as the generation of stationary quantum correlations occur. Our results also suggest a possible way to control the occurrence time of entanglement sudden birth and the stationary value of quantum correlations by modifying the initial conditions of states, the dipole-dipole interaction, and the relative coupling strength. These results are helpful for the experimental engineering of entanglement and quantum correlations. 相似文献
986.
LU Wei-da QIU Jie ZHAO Gai-xia QIE Liang-yi WEI Xin-bing GAO Hai-qing 《高等学校化学研究》2012,28(6):1035-1040
Cardiac ischemia/reperfusion(I/R) injury is a critical condition, often associated with high morbidity and mortality. The cardioprotective effect of grape seed proanthocyanidin extracts(GSPE) against oxidant injury during I/R has been described in previous studies. However, the underlying molecular mechanisms have not been fully elucidated. This study investigated the effect of GSPE on reperfusion arrhythmias especially ventricular tachycardia(VT) and ventricular fibrillation(VF), the lactic acid accumulation and the ultrastructure of ischemic cardiomyocytes as well as the global changes of mitochondria proteins in in vivo rat heart model against I/R injury. GSPE significantly reduced the incidence of VF and VT, lessened the lactic acid accumulation and attenuated the ultrastructure damage. Twenty differential proteins related to cardiac protection were revealed by isobaric tag for relative and absolute quantitation(iTRAQ) profiling. These proteins were mainly involved in energy metabolism. Besides, monoamine oxidase A(MAOA) was also identified. The differential expression of several proteins was validated by Western blot. Our study offered important information on the mechanism of GSPE treatment in ischemic heart disease. 相似文献
987.
The effect of topography on generation of the solitary Rossby waves is researched.Here,the topography,as a forcing for waves generation,is taken as a function of longitude variable x and time variable t,which is called unstable topography.With the help of a perturbation expansion method,a forced mKdv equation governing the evolution of amplitude of the solitary Rossby waves is derived from quasi-geostrophic vorticity equation and is solved by the pseudospectral method.Basing on the waterfall plots,the generational features of the solitary Rossby waves under the influence of unstable topography and stable topography are compared and some conclusions are obtained. 相似文献
988.
《Tetrahedron: Asymmetry》2004,15(20):3257-3261
The crystalline inclusion complexes of azobenzene 1 with cholic CA and deoxycholic DCA acid were prepared and their solid state CD spectra measured. The positive Cotton effect sign, corresponding to the lowest energy n–π* transition, was correlated with the M,M helicity of the twisted guest molecule. The absolute sense of twist of the enclathrated guest molecule 1 was deduced from the X-ray structure of the 1·CA complex. In addition, the solid state CD spectrum of the enantiomorphous crystals of methyl yellow 2 was measured. The source of the optical activity is a slight twisting of the constituent molecules and their helical arrangement in the crystal. 相似文献
989.
《Solid State Sciences》2004,6(9):907-913
The total electrical conductivity of strontium ferrites, including intergrowth Sr4Fe6O13+δ, Sr3Fe2O6+δ with a Ruddlesden–Popper structure, and SrFeO2.5+δ where the cubic perovskite lattice transforms into vacancy-ordered brownmillerite at p(O2)<10 Pa and T<850 °C, was measured at 650–1000 °C in the oxygen partial pressure range 10−15 Pa to 50 kPa. The data were used in order to determine partial ion, p- and n-type electron contributions in the vicinity of electron–hole equilibrium point. The ferrites with brownmillerite and Ruddlesden–Popper structures exhibit substantial ion transport due to thermally-activated disordering of oxygen vacancies and oxygen ions in the perovskite structural slabs, whereas the ion conductivity of Sr4Fe6O13+δ remains below 0.01 S cm−1 in the studied conditions. The bonding energy of oxygen ions, evaluated from the formation enthalpy of n-type charge carriers, increases in the sequence Sr4Fe6O13+δ<SrFeO3+δ<Sr3Fe2O6+δ. These values correlate with thermodynamic stability of strontium ferrites at low p(O2). The transition of SrFeO2.5+δ brownmillerite into disordered cubic phase above 850 °C leads to higher stability in reducing atmospheres. The level of p-type conductivity is mainly governed by the concentration of electron holes, which was calculated from the oxygen content determined by coulometric titration technique. The hole mobility, which is quite similar for all strontium ferrites and has a temperature-activated character, varies in the range 0.005–0.05 cm2 V−1 s−1 indicative of small-polaron conduction mechanism. 相似文献
990.
《Solid State Sciences》2003,5(8):1177-1186
Three new one-dimensional coordination polymers have been prepared using Hg(II), Ag(I) and Zn(II) inorganic salts in combination with 2,5-bis(3-pyridyl)-1,3,4-oxadiazole (L6). The compounds were characterized by single crystal X-ray diffraction, IR spectroscopy, and elemental analysis. In the solid state, compounds 1 and 3 (1: monoclinic, P21/n, a=5.5373(3) Å, b=16.7839(9) Å, c=16.8120(9) Å, β=92.8610(10)°, V=1560.52(15) Å3, Z=4; 3: monoclinic, P21/n, a=7.2958(4) Å, b=11.7214(6) Å, c=16.3979(9) Å, β=101.1150(10)°, V=1375.99(13) Å3, Z=4) feature novel one-dimensional helical chain motif. Compound 2, however, (2: monoclinic, P21/c, a=5.5506(4) Å, b=16.5895(12) Å, c=16.6871(11) Å, β=95.424(2)°, V=1529.70(19) Å3, Z=4) exhibits one-dimensional zigzag chain motif, which result from the different conformations adopted by the L6 ligand and also the different metal coordination geometry. The luminescent properties of three new compounds were investigated in the solid state. 相似文献