Fabrication and optical properties of core/shell CdS/LaPO₄:Eunanorods

Abstract

We report the preparation of CdS/LaPO₄:Eu nanorods via a three-step chemical route involving solvothermal preparation of CdS nanorods. Then, the surface functionalisation of CdS nanorods by citric acid is done. Finally, the formation of the LaPO₄ shell is achieved. The core/shell nanostructure is confirmed by X-ray diffraction studies and transmission electron microscopy (TEM) analysis. The crystal phase of LaPO₄ (shell) changes with changing the temperature of heating. It is interesting to note that the lattice strain of CdS (core) increases from 0.27% to 1.09% for pure CdS nanorods and core CdS nanorods, respectively. The lattice strain can be modified from tensile to compressive by changing the crystal phase of the LaPO₄ (shell). It is found that the photoluminescence properties are sensitive to the crystal phase of the LaPO₄ shell, which can be tuned by temperature of heating. From the decay time measurements, it is evident that the energy transfer occurs from core CdS nanorods to Eu³⁺ ions in the LaPO₄ shell and the calculated energy transfer efficiency from CdS nanorods to Eu³⁺ ions is 50.9% for the 600 °C heated core/shell nanostructure. The experimental quantum efficiency is 47% for CdS/LaPO₄:Eu samples and this efficiency increases due to energy transfer from CdS to Eu³⁺ ions in the LaPO₄ shell.