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Self-assembly of ZnS-encapsulated SiO_2 nanospheres for enhanced photoluminescence

机译：ZnS包裹的SiO_2纳米球的自组装增强了光致发光

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摘要

ZnS-encapsulated spherical SiO_2 nanostructures were prepared by a one-step solvothermal method. The samples were characterized by x-ray diffraction, transmission electron microscopy, selected-area electron diffraction, infrared spectra, UV-visible spectra, and photoluminescence. It is found that 27 nm ZnS in a wurtzite phase was encapsulated by a low-porosity SiO_2 layer, which compares to a particle size of 8.5 nm for bare ZnS as prepared under similar conditions. Contrary to the theoretical predictions of the quantum size effect, the encapsulated ZnS showed a band gap energy surprisingly larger than that for the bare one. Moreover, the encapsulated ZnS/SiO_2 nanostructures exhibited 'self-activated centers', as characterized by a blue photoluminescence emission band at 430 nm, while the bare ZnS nanoparticles gave a surface sulfur species-mediated green emission at 520 nm. These observations are explained in terms of the encapsulated nanostructure and the relevant defect nature in which the SiO_2 layer reduces the nonradiative recombination centers and enhances the photoluminescence intensity.
机译：通过一步溶剂热法制备了ZnS包裹的球形SiO_2纳米结构。通过X射线衍射，透射电子显微镜，选择区域电子衍射，红外光谱，UV-可见光谱和光致发光来表征样品。发现纤锌矿相中的27 nm ZnS被低孔隙率的SiO_2层包裹，相比之下，在相似条件下制备的裸露ZnS的粒径为8.5 nm。与量子尺寸效应的理论预测相反，封装的ZnS显示出的带隙能量惊人地大于裸露的带隙能量。此外，封装的ZnS / SiO_2纳米结构表现出“自激活中心”，其特征是在430 nm处有蓝色光致发光发射带，而裸露的ZnS纳米颗粒在520 nm处具有表面硫物种介导的绿色发射。这些观察是根据包封的纳米结构和相关的缺陷性质来解释的，其中SiO 2层减少了非辐射复合中心并增强了光致发光强度。

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