The equilibrium geometries, relative stabilities, and electronic properties of Ca2Sin （n = 1-11） clusters have been systematically investigated by using the density function theory at the 6-311G （d） level The opti...The equilibrium geometries, relative stabilities, and electronic properties of Ca2Sin （n = 1-11） clusters have been systematically investigated by using the density function theory at the 6-311G （d） level The optimized geometries indicate that the most stable isomers have three-dimensional structures for n = 3-11. The electronic properties of Ca2 Sin （n = 1-11） dusters axe obtained through the analysis of the natural charge population, natural electron configuration, vertical ionization potential, and vertical electron affinity. The results show that the charges in corresponding Ca2Sin clusters transfer from the Ca atoms to the Sin host. Based on the obtained lowest-energy geometries, the size dependence of cluster properties, such as averaged binding energies, fragmentation energies, second-order energy differences, HOMO- LUMO gaps and chemical hardness, are deeply discussed.展开更多
This work was aimed at improving the water-resistance stability of CaS：Eu2＋,Sm2＋ phosphor. An organic-inorganic com- posite coating method was adopted in order to obtain ideal phosphor. The phosphor was coated with...This work was aimed at improving the water-resistance stability of CaS：Eu2＋,Sm2＋ phosphor. An organic-inorganic com- posite coating method was adopted in order to obtain ideal phosphor. The phosphor was coated with SiO2 via sol-gel technique and it was also covered by polymethyl methacrylate （PMMA） via dissolution-cohesion technique. Powder X-ray diffraction （XRD） patterns, fluorescence spectroscopy and transmission electron microscopy （TEM） were employed to characterize the phase structures, emission spectrum and surface morphologies, respectively. In addition, the water-resistance stability of the phosphor was tested by soaking the phosphor into deionized water. The results showed that the phase structures remained the same as the uncoated phosphor and the po- sition of the fluorescence peak did not shift after surface treatment. Results showed that the water-resistance stability of the phosphor was improved to some degree. Moreover, the photoluminescence （PL） intensity of the coated phosphors reduced less than 10% of the original phosphors. Though being soaked into deionized water for 50 h, the phosphor coated with 10 wt.%SiO2-10 wt.%PMMA retained 85.9% PL intensity compared to that of the uncoated phosphor. Therefore, it could be concluded that the 10 wt.%SiO2-10 wt.%PMMA composite coating effectively improved the phosphor water resistance and retained its good optical properties.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos.11304167 and 51374132Postdoctoral Science Foundation of China under Grant No.20110491317Natural Science Foundation of Henan Province under Grant Nos.2011B140015,132300410209,and 132300410290
文摘The equilibrium geometries, relative stabilities, and electronic properties of Ca2Sin （n = 1-11） clusters have been systematically investigated by using the density function theory at the 6-311G （d） level The optimized geometries indicate that the most stable isomers have three-dimensional structures for n = 3-11. The electronic properties of Ca2 Sin （n = 1-11） dusters axe obtained through the analysis of the natural charge population, natural electron configuration, vertical ionization potential, and vertical electron affinity. The results show that the charges in corresponding Ca2Sin clusters transfer from the Ca atoms to the Sin host. Based on the obtained lowest-energy geometries, the size dependence of cluster properties, such as averaged binding energies, fragmentation energies, second-order energy differences, HOMO- LUMO gaps and chemical hardness, are deeply discussed.
基金supported by National Natural Science Foundation of China(11305260)
文摘This work was aimed at improving the water-resistance stability of CaS：Eu2＋,Sm2＋ phosphor. An organic-inorganic com- posite coating method was adopted in order to obtain ideal phosphor. The phosphor was coated with SiO2 via sol-gel technique and it was also covered by polymethyl methacrylate （PMMA） via dissolution-cohesion technique. Powder X-ray diffraction （XRD） patterns, fluorescence spectroscopy and transmission electron microscopy （TEM） were employed to characterize the phase structures, emission spectrum and surface morphologies, respectively. In addition, the water-resistance stability of the phosphor was tested by soaking the phosphor into deionized water. The results showed that the phase structures remained the same as the uncoated phosphor and the po- sition of the fluorescence peak did not shift after surface treatment. Results showed that the water-resistance stability of the phosphor was improved to some degree. Moreover, the photoluminescence （PL） intensity of the coated phosphors reduced less than 10% of the original phosphors. Though being soaked into deionized water for 50 h, the phosphor coated with 10 wt.%SiO2-10 wt.%PMMA retained 85.9% PL intensity compared to that of the uncoated phosphor. Therefore, it could be concluded that the 10 wt.%SiO2-10 wt.%PMMA composite coating effectively improved the phosphor water resistance and retained its good optical properties.
