中文摘要：

采用改进的均匀沉淀法结合固-气硫化工艺制备了一系列Y2O2S：Yb，Ho上转换粒子．利用X射线晶体衍射（XRD）和透射电子显微镜（TEM）对粒子的结构和形貌进行了表征，并通过上转换发光光谱（UCL）和红外光谱（FTIR）研究了粒子的上转换发光性质．XRD和TEM结果表明，所制备的样品均为单一的六方相结构，且所有粒子均呈单分散和尺寸均一的球形，其尺寸分别为40，80和200nm．根据发光强度和激发功率问的对数关系曲线发现，随着粒子尺寸的降低，蓝光发射由三光子吸收过程转变为双光子吸收过程；而绿光和红光发射虽然一直保持双光子吸收过程，但其对数曲线斜率均随粒子尺寸的降低而逐渐增大．对该材料的粒子尺寸与上转换发光机制的关系进行了讨论．

英文摘要：

A series of Y2O2S： Yb, Ho upeonversion particles were prepared using an improved homogeneous precipitation method combined with a solid-gas sulfuration technology. The structure and morphology of particles were characterized by X-ray diffraction（XRD） and transmission electron microscope（ TEM）, and the upconversion luminescence （UCL） properties and mechanisms were studied by UCL spectra and FT-infrared spectra（FTIR）. The results of XRD indicated that the prepared samples were pure hexagonal structure. TEM images showed the prepared particles were mono-dispersed with regular sphere shape and exhibited the narrow size distribution with average size of 40, 80 and 200 nm, respectively. According to the ln-ln plots of emission intensity as a function of excitation power, it was found that the blue emissions varied from three-photon absorption process to two-photon absorption process with decreasing particle size. For the green and red emissions, only the two-photon absorption process was observed, but the slope values of the lnIP-lnIUCL plot increased with decreasing particle size. The mechanism of the effects of particle size on the UCL properties was discussed.