Bismuth sulphides prepared by thermal and hydrothermal decomposition of a single source precursor: the effect of reaction parameters on morphology, microstructure and catalytic activity.

Bismuth sulphides were prepared by thermal and hydrothermal decomposition of a precursor, bismuth tris-diethyldithiocarbamate, at different temperatures and times. The obtained results showed that the thermal decomposition of the precursor in a tube furnace was not very appropriate to control particle size and morphology. XRD results showed that at 310 °C the precursor was not fully decomposed but at 500 °C besides the orthorhombic bismuth sulphide, the metallic bismuth also started to be formed. At the highest temperature 1D crystals were formed with an apparent mean crystal size of 138 nm. However, hydrothermal decomposition was shown to be a very suitable method to control particle size and morphology just by varying some parameters such as temperature and time. For 6 hours reaction time, as temperature increased, the apparent mean crystal size decreased. The particle morphology was also very affected by this parameter, at 180 °C only 1D particles (nanorods) with lengths varying from 25 to 4700 nm were formed but at 200 °C not only 1D particles but also 2D particles were (nanosheets) obtained. Bismuth sulphide particles obtained at 180 °C and 24 hours reaction time were shown to be formed mostly by 2D particles compared to those obtained at 6 hours. It was clearly seen that the increase in reaction time and temperature led to the formation of bi-dimensional particles. The presence of 1D crystals in the samples obtained by hydrothermal decomposition at 180 °C/6 h and 180 °C/24 h is responsible for their high catalytic efficiency towards methylene blue dye degradation.

Temperature and time dependence on ZnS microstructure and phases obtained through hydrothermal decomposition of diethyldithiocarbamate complexes.

Zinc sulphide was obtained through hydrothermal decomposition of [Zn(S2CNEt2)] under different experimental conditions such as temperatures and reaction times. Hydrothermal reactions were carried out in a stainless steel autoclave at 160, 180 and 200 °C for 3, 6 and 24 hours. The obtained products were characterized using X-ray diffraction, scanning and high resolution transmission electron microscopies. Particle size and microstrain were determined by Rietveld refinement of experimental X-ray diffraction patterns. The obtained crystal size values were in the range of 6.1 to 30 nm and as the temperature and reaction times increase the particle size also increases. Band gap values are in the range of 3.34 to 3.60 eV and are highly dependent on the crystal microstrain. The catalyst activities were studied through the degradation of methylene blue dye solutions under ultraviolet radiation.