Morphology-Dependent Photocatalytic Degradation of Organic Pollutant and Antibacterial Activity with CdS Nanostructures

Abstract

Efficient removal of organic pollutants from waste water by nanostructured photocatalysts has become an emerging research due to its importance in environmental remediation. Herein, CdS nanostructures with different morphologies i.e., spherical, nanopetal and rose-like have been synthesized by wet chemical method using TEA as a structure directing agent. The morphology, crystal structure, composition, surface area and optical properties of the nanostructures are investigated by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), Brunauer-Emment-Teller (BET) analyser, Ultraviolet-Visible (UV-Vis) absorption spectroscopy and Photoluminescence (PL) spectroscopy. XRD patterns indicate the existence of hexagonal phase of CdS in all the three morphologies. The SEM images confirm the morphological transformation of spherical CdS nanoparticles (NPs) to nanopetal and rose-like morphology with the increase in concentration of TEA in the synthesis process. UV-visible absorption spectra show that rose-like CdS nanostructure exhibits red-shift of absorption wavelength compared to spherical and nanopetal CdS nanostructures. The increase in intensity of PL peak of rose-like CdS at 576.6 nm compared to that of spherical and nanopetal CdS, confirms the presence of more S vacancies or defect states. The BET specific surface areas of spherical, nanopetal and rose-like CdS nanostructures are determined to be 4.18, 6.64 and 8.93 m2/g, respectively. The EIS Nyquist plot confirms the higher electron transfer efficiency of rose-like CdS than that of spherical and nanopetal CdS. The photocatalytic activity of these three nanostructures are evaluated for the degradation of methylene blue (MB) dye in water solution under sunlight irradiation. Among the three structures, rose-like CdS nanostructure shows highest photocatalytic efficiency (96.5%) under sunlight irradiation within 120 min of sunlight irradiation. Antibacterial activity of the synthesized CdS nanostructures is performed against two Gram-positive and Gram-negative bacteria and rose-like CdS shows more activity against both types of bacteria than that of spherical and nanopetal CdS.