The effect of structural and optical properties on the photocatalytic efficiency of Zinc Sulphide nanoparticles obtained by hydro/solvothermal decomposition of Zinc N,N-diethyldithiocarbamate

Cubic and hexagonal zinc sulphide nanoparticles were prepared by hydro/solvothermal decomposition of Zinc N,N-diethyldithiocarbamate by using different experimental conditions such as pH values, solvents and the presence of a particle stabilizer, sodium polyacrylate. The effect of these different experimental conditions on the microstructure and photocatalytical efficiency of ZnS was investigated in this work. Microstructural parameters, such as, apparent mean crystal size, microstrain and crystal size distribution were determined by analysis of experimental X-ray diffraction. Apparent mean crystal sizes were in the range of 6.5-44 nm and the lattice microstrain varied from 0.24% to 0%. Dimethylformamide showed to be more suitable than water to form small particles with a very narrow size distribution. The obtained optical band gaps and Urbach energies were in range of 3.32-3.60 eV and 0.09-0.15 eV, respectively. Photoluminescence spectra showed strong visible light emissions (green, blue and white) associated to the electronic levels introduced by the presence of superficial defects. The photocatalytic efficiency of these samples was investigated towards methylene blue degradation and a correlation between this efficiency and the PL intensity was observed. This correlation was associated to the formation of surface active centres at catalyst surfaces and the local potential fluctuations of valence and conduction bands.