The Effect of Chemical Composition and Electrolyte Temperature on the Size and Structure of Cadmium Sulfide Nanocrystals Obtained by the Electrolytic Method

Cadmium sulfide (CdS) nanocrystals were produced by the electrolytic method in a glass electrolyzer with cadmium electrodes. Solutions of sodium thiosulfate (Na2S2O3), sodium sulfite (Na2SO3) and sodium sulfide (Na2S) in distilled water were used as electrolytes. It was determined that the composition of the obtained phases depends on the electrolyte and the synthesis temperature. Cadmium sulfide as a single-phase reaction product was obtained from Na2S2O3 and Na2S solutions at T = 371 K. The use of other electrolytes and temperatures yields additional phases CdCO3 and Cd, besides CdS. The size of the synthesized nanoparticles and their crystal structure were evaluated from XRD data using Debye-Scherrer and Williamson-Hall formulae. The size of CdS nanoparticles decreases as the temperature of sodium thiosulfate solution lowers from T = 371 K to T  292 K. The values of mechanical stress were calculated for the cubic and hexagonal modifications of CdS nanocrystals. Raman spectra of cadmium sulfide nanocrystals obtained from sodium thiosulfate solution were investigated. Scattering bands at frequency positions 302 cm – 1, 603 cm – 1, and 900 cm – 1, with monotonously decreasing intensity, were recorded. Detailed analysis of produced experimental results and reported literature data was undertaken. It was established that the phase transition from the cubic sphalerite to hexagonal wurtzite takes place during the annealing of nanocrystals at T = 773 K. The phase transition results in increased size and lower mechanical stress in cadmium sulfide nanocrystals.