Preparation of quasi-monodispersed CdxZn1−xS nanocrystals and their optical properties

Quasi-monodispersed CdxZn1−xS nanocrystals were prepared in a solvothermal process and characterized with X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersion X-ray analysis (EDX), UV–vis diffuse reflectance absorption spectra and photoluminescence spectra. The results showed that the uniform CdxZn1−xS nanocrystals with narrow size distribution could be obtained using laurylamine as solvent; and the mean diameter was 2.8 nm. Meanwhile, it was also found that the band gap energies and the fluorescence emission peaks of as-prepared CdxZn1−xS nanocrystals systematically shifted to shorter wavelength with increasing Zn content. The Cd0.5Zn0.5S nanocrystals can exhibit obviously upconversion emission due to two-photon excitation. In addition, the preparation and properties of CdxZn1−xS nanocrystals were studied as functions of reaction time and reaction temperature, respectively.