CdSe:Nd纳米晶及CdSe:Nd@SiO2核壳结构的合成及发光性能

利用有机相法合成Nd³⁺掺杂CdSe纳米晶（CdSe∶Nd），通过X射线粉末衍射（XRD）、透射电镜（TEM）、紫外吸收光光谱及荧光光谱表征，证明Nd³⁺已经成功掺入到CdSe的晶格中。与纯CdSe纳米晶相比，CdSe∶Nd纳米晶的结构仍为立方晶型，且形貌近似球形，均匀分散，粒径约为2~4 nm。紫外吸收峰和荧光发射峰都发生红移，而且掺杂后的CdSe∶Nd纳米晶量子产率也提高，这可能是由于掺杂Nd³⁺引入了新的杂质能级，带隙减小。为了实现CdSe∶Nd纳米晶的可加工性和功能性，通过微乳法合成SiO₂壳包覆的CdSe∶Nd纳米球（CdSe∶Nd@SiO₂纳米球），CdSe∶Nd@SiO₂纳米球呈均匀球形，直径约为100~115 nm，并且包壳后的CdSe∶Nd@SiO₂纳米球发射峰（581 nm）与CdSe∶Nd纳米晶（598 nm）相比，发光强度提高且发射峰蓝移，蓝移约为17 nm，可能是因为SiO₂壳可以减少纳米晶表面的非辐射跃迁以及改善表面缺陷导致的。

Synthesis and Fluorescence Properties of CdSe: Nd and CdSe: Nd@SiO2 Core-Shell Structures

CdSe:Nd nanocrystals (CdSe:Nd NCs) were synthesized via organic phase method. The objective of this research was to investigate structure, microstructure, optical properties and possible luminescence mechanism of CdSe:Nd and CdSe:Nd@SiO₂. It is confirmed that Nd³⁺ is successfully incorporated into the crystal lattice of CdSe through XRD, TEM, UV-visible absorption spectroscopy and fluorescence emission. Compared with pure CdSe NCs, CdSe:Nd NCs still have a cubic crystal structure, the lattice constant of CdSe and CdSe:Nd NCs is 0.605 and 0.609 nm, respectively. The lattice of CdSe:Nd constant increases, it may be due to the ionic radius of Nd³⁺ is larger than Cd²⁺. When Nd³⁺ is incorporated into the crystal lattice of CdSe:Nd NCs, which results in dilation of crystal lattice. CdSe:Nd NCs are monodisperse and spherical particles with an average diameter of 2-4 nm. Both absorption spectrum and emission spectrum red-shift, and the quantum yields of the CdSe:Nd NCs also increase, which may be due to the introduction of new impurity levels and the decrease of the band gap. To enhance the stability and functionality of CdSe:Nd NCs, CdSe:Nd NCs were coated with SiO₂ (CdSe:Nd@SiO₂ spheres) and the core-shell SiO₂ -coated CdSe:Nd NCs (CdSe:Nd@SiO₂) were prepared via the micro-emulsion method. XRD patterns show that the patterns of CdSe:Nd@SiO₂ contain the characteristic peak of CdSe:Nd NCs, which proves that CdSe:Nd has entered in the SiO₂ shell successfully. CdSe:Nd NCs are uniform spherical with an average diameter of 100-115 nm, and CdSe:Nd NCs can be clearly seen in the SiO₂ shell. The fluorescence emission of CdSe:Nd@SiO₂ (581 nm) shows a blue-shift compared with CdSe:Nd NCs(598 nm), possibly because of altered surface properties and reduction of nonradiative transitions.