Hydrothermal Preparation and Optical Properties of ZnS: Cu, Al Nanocrystals Excited by X-ray

ZuS: Cu, Al nanocrystals were hydrothermally prepared at 200 degrees C and their photoluminescence (PL) and X-ray excited luminescence(XEL) properties were investigated. The effect of further annealing was also studied in detail. The average gain size of the samples with n (Cu)/n (Zn) = 3 x 10(-4) and n(Cu)/n(Al) = 2, which was directly hydrothermal-treated at 200 degrees C for 12 h, is about 15 nm; the spherical-like nanocrystals with well dispersity and narrow gain size distribution show cubic structure. The PL and XEL spectra of all of the samples show a broad emission band. The maximum PL and XEL intensities are observed for sample with n(Cu)/n(Zn) =3 x 10(-4) and n(Cu)/n(Al) =0.5. The XEL peak center is at about 470 nm. In this condition, the XEL intensity of the sample which was hydrothermally treated at 200 degrees C for 3 h then annealed in Ar at 800 degrees C for 1 h is enhanced and the peak is located at 520 nm. In the meantime, the XEL intensity is about eight times by comparison with that of the samples without annealing. The particles' agglomerate size is about 200-500 nm and roughly spherical particles show pure hexagonal structure. The samples with highly luminescence efficiencies and the smaller size could enhance the resolution of imaging systems. By comparing the PL and XEL spectra, the luminescence mechanism and different excitation mechanism of PL and XEL and effect of annealing on XEL were also discussed.