Novel Pt-Ag₃PO₄/CdS/Chitosan Nanocomposite with Enhanced Photocatalytic and Biological Activities

Decorating photocatalysts with noble metal nanoparticles (e.g., Pt) often increases the catalysts' photocatalytic activity and biomedical properties. Here, a simple and inexpensive method has been developed to prepare a Pt-Ag₃PO₄/CdS/chitosan composite, which was characterized and used for the visible light-induced photocatalytic and antibacterial studies. This synthesized composite showed superior photocatalytic activity for methylene blue degradation as a hazardous pollutant (the maximum dye degradation was observed in 90 min of treatment) and killing of Gram positive bacterial (Staphylococcus aureus and Bacillus cereus) as well as Gram negative bacteria (Klebsiella pneumoniae, Salmonella typhimurium, Escherichia coli, and Pseudomonas aeruginosa) under visible light irradiation. The antibacterial activity of CdS, CdS/Ag₃PO₄, and Pt-Ag₃PO₄/CdS/chitosan against E. coli, Pseudomonas aeruginosa, Salmonella typhimurium, Klebsiella pneumoniae, Staphylococcus aureus, and Bacillus cereus showed the zone of inhibition (mm) under visible light and under dark conditions at a concentration of 20 µg mL^-1. Furthermore, the cell viability of the CdS/chitosan, Ag₃PO₄, Ag₃PO₄/CdS/chitosan, and Pt-Ag₃PO₄/CdS/chitosan were investigated on the human embryonic kidney 293 cells (HEK-293), Henrietta Lacks (HeLa), human liver cancer cell line (HepG2), and pheochromocytoma (PC12) cell lines. In addition, the results indicated that the photodegradation rate for Pt-Ag₃PO₄/CdS/chitosan is 3.53 times higher than that of CdS and 1.73 times higher than that of the CdS/Ag₃PO₄ composite. Moreover, Pt-Ag₃PO₄/CdS/chitosan with an optimal amount of CdS killed large areas of different bacteria and different cells separately in a shorter time period under visible-light irradiation, which shows significantly higher efficiency than pure CdS and other CdS/Ag₃PO₄ composites. The superb performances of this composite are attributed to its privileged properties, such as retarded recombination of photoinduced electron/hole pairs and a large specific surface area, making Pt-Ag₃PO₄/CdS/chitosan a valuable composite that can be deployed for a range of important applications, such as visible light-induced photocatalysis and antibacterial activity.