The Role of pH on Infrared Spectral, Structural and Morphological Properties of Room-temperature Precipitated CdS Nanoparticles

In this work, room-temperature treated CdS nanoparticles were prepared in KOH solution via precipitation at different pH values by varying the ammonium nitrate (NH4NO3) concentration. The crystallite phase and size, surface morphology and infrared frequencies of functional groups were characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy, respectively. The SEM images show that the CdS nanoparticles are spherical in shape. Meanwhile, the FTIR result reveals that a broad band occurred in the range of 400-700 cm − 1 could be attributed to the molecular bonding structure of CdS. The XRD patterns exhibit four well-resolved crystalline peaks that represents the diffraction planes of a cubic CdS phase. Nevertheless, a minor decrement in the intensity for both infrared and crystalline bands denotes a slight reduction in structure crystallinity and further indicates that a higher purity of finer CdS nanoparticles is obtained as the pH value decreases. Also, the diffraction peak becomes slightly widen that implies a decrease in the mean crystallite size as validated by Debye-Scherrer method. Owing to their unique nanostructural and morphological features, the CdS nanoparticles obtained in this study have potential applications in photonic devices, optoelectronics, photocatalysis and solar cells.