Sulfur-doped zinc oxide nanoparticles for enhanced degradation of 2,4-DCP under natural sunlight

The present research focuses on synthesizing and characterizing sulfur-doped Zinc oxide (S-ZnO) nanoparticles (NPs) utilizing an economical, simple, cost-effective, and solution-free thermo-mechanical technique. The antibacterial activity of these nanoparticles against Klebsiella pneumoniae and their efficiency in the photocatalytic degradation of the pollutant 2,4-dichlorophenol are assessed. Powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to investigate the crystallite size and morphological features, respectively. XRD results for S-ZnO NPs with concentrations of 3 wt%, 5 wt%, and 7 wt% showed crystallite sizes of 14.51 nm, 11.33 nm, and 10.14 nm, respectively. FE-SEM shows the morphology of pristine ZnO as rod-shaped and when sulfur is doped in ZnO, it shows tube-shaped morphology. The band gap values for pristine ZnO and 5 wt% S-ZnO NPs were 3.02 eV and 2.82 eV, respectively, highlighting the enhanced photocatalytic potential of the doped nanoparticles. Pristine ZnO and 5 wt% S-ZnO NPs have surface areas of 30.86 m²/g and 39.77 m²/g, respectively. Photocatalytic studies demonstrated that 5 wt% S-ZnO NPs exhibit superior photocatalytic activity, achieving 92% degradation of 2,4-dichlorophenol in an aqueous medium within 60 min at a concentration of 0.8 mg/mL under natural sunlight. Scavenger tests using histidine and ascorbic acid confirmed that hydroxyl radicals (⋅OH) played a key role in pollutant breakdown. The reusability of S-ZnO NPs revealed stability over three cycles. Antibacterial tests using the disc diffusion method against Klebsiella pneumoniae indicated that 5 wt% S-ZnO had stronger antibacterial effects than pristine ZnO, making it promising for environmental remediation and biomedical applications.