Influence of pH on particle size, band-gap and activation energy of CdS nanoparticles synthesized at constant frequency ultrasonic wave irradiation

Cadmium sulfide (CdS) nanoparticles are prepared through different potential of hydrogen (pH) ranging from 8 to 12 at constant frequency ultrasonic wave irradiation. Sodium hydroxide (NaOH) was preferred as the pH modifier. The effect of pH variation on the structural, optical and electrical properties of CdS particles was studied. The particle sizes from X-Ray diffraction (XRD) analysis were found in the range 29-39 nm. The results of the optical absorption showed that the band gap energy values of the CdS nanoparticles decreased from 2.48 to 2.38 eV with increasing pH values which was measured in diffused reflectance spectra (DRS). Photoluminescence spectra were recorded to investigate the presence of electronic transitions as well as interstitial position of cadmium. A High Resolution Scanning electron microscopy (HRSEM) and transmission electron microscopy (TEM) study revealed the particle size and morphology of the mixed spherical shaped and rod shaped nanoparticles. Electrical conductivity measurements were carried out on CdS nanoparticles and the Activation energy of the samples were calculated by dc conductivity studies.