[Preparation and spectrum properties of ZnS : Ag nanocrystals]

In the present paper, ZnS : Ag nanoparticles were prepared with simple chemicals by hydrothermal method. XRD patterns indicated that the products have cubic zinc blende crystal structure. The particle diameters were calculated using the Scherer's formula, and the particle size showed a nonlinear increase with the rise of reaction temperature. TEM images demonstrated the approximate sphere shapes of products, and the crystal sizes approached the estimated ones respectively. The luminescence properties were investigated with PL and PLE spectra. Emission peaks were at about 450 nm. This emission was ascribed to the recombination between the sulfur vacancy-related electron trap donor having an energy level just below the conduction band and the Ag-related hole trap acceptor above the valence band. Excitation peaks were at about 333 nm, and the excitation was attributed to the near-band-edge absorption of ZnS matrix. The luminescence intensity was strongly influenced by the reaction temperatures and time. It increased, decreased, and then increased again with the rise of reaction temperature, and increased then decreased with the increase in reaction time. ZnS : Ag nanoparticles synthesized at 200 degrees C for 6 hours have a well luminescence intensity.