Influence of ammonium nitrate concentration on structural evolution and optical properties tuning of CdS nanoparticles synthesized by precipitation method

Cadmium sulfide (CdS) shows vital applications in many fields, such as electronic devices, catalysis, and solar cell. In this study, CdS nanoparticles have been synthesized by a simple chemical precipitation method using cadmium chloride as Cd source, thiourea as S source and ammonium nitrate (NH4NO3) as a complexing agent. The effect of NH4NO3 concentration on the structural, optical and thermal properties of the CdS nanoparticles annealed at 160 °C were extensively studied using X-ray Diffractometer (XRD), Fourier transform infrared (FTIR), UV–visible spectrophotometer, scanning electron microscope (SEM), thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The FTIR result shows that the Cd-S stretching vibration band occurred in the range of 400 to 700 cm−1. The XRD patterns reveal a phase transformation from cubic to hexagonal with crystallinity improvement as the NH4NO3 concentration increases. The average nanocrystallite size estimated by the Scherrer method lying in the 2–11 nm range, and the size is tunable by varying the NH4NO3 concentration. The SEM images exhibit the formation of spherical nanoparticles. Blue shift of the absorption edge is observed on the UV–visible absorption spectra due to the presence of quantum confinement effects. The calculated optical band gap from the Tauc plot is higher than bulk CdS and becomes wider as the crystallite size decreases. Moreover, the TGA and DSC results reveal that the obtained CdS with smaller crystallite size exhibits improved thermal stability. The properties obtained in this study show that the ammonium nitrate is versatile to be used for generating and tuning the desired structural and optical properties of the CdS nanoparticles. [Display omitted]