Synthesis and fluorescence properties of CdTe:Eu3+ nanocrystals and core-shell SiO2-coated CdTe:Eu3+ nanospheres

Eu3+ doped-CdTe (CdTe:Eu3+) nanocrystals were prepared via a facile hydrothermal method, and Eu3+ was successfully incorporated into the crystal lattice of CdTe and measured by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible (UV-Vis) absorption spectroscopy and fluorescence emission. The CdTe:Eu3+ nanocrystals still have a cubic crystal structure, and the corresponding XRD peaks of CdTe:Eu3+ nanocrystals shift to larger angles compared with those of pure CdTe. The CdTe:Eu3+ nanocrystals are monodisperse and the particles size is about 2-4 nm. Compared with pure CdTe, the CdTe:Eu3+ nanocrystals have larger band gap and thus exhibit blueshift in the emission spectra, which could be accounted for by the energy transfer between Eu3+ and CdTe. To enhance the stability and functionality of CdTe:Eu3+ nanocrystals, the CdTe:Eu3+ nanocrystals were coated with SiO2 and the core-shell SiO2-coated CdTe:Eu3+ nanocrystals (CdTe:Eu3+@SiO2) were prepared via micro-emulsion method. TEM results show that CdTe:Eu3+ nanocrystals are uniformly dispersed in the shell, and CdTe:Eu3+@SiO2 nanospheres are uniformly spherical with an average diameter of about 75 nm. The fluorescence emission of CdTe:Eu3+@SiO2 (567 nm) shows a blueshift compared with that of CdTe:Eu3+ nanocrystals (632 nm), possibly because of altered surface properties after SiO2 coating. CdTe:Eu3+ and CdTe:Eu3+@SiO2 with tunable photoluminescence are potentially useful in fabricating optical and bioimaging devices.