Light induced antibacterial activity and photocatalytic properties of Ag/Ag3PO4 -based material of marine origin

Fish bones were converted into materials consisting of silver phosphate (Ag₃PO₄), β-calcium phosphate (β-Ca₃(PO₄)₂, β-TCP) and hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂, HAp), as well as of metallic silver (Ag⁰), with a simple treatment in solution and calcination (650 or 1000°C). The antibacterial activity of the material was measured in the dark and under UV and white light irradiation; this is the first time that an Ag₃PO₄-based material was tested under these conditions. Results showed light-enhanced antibacterial properties toward Gram-positive and Gram-negative strains (Methicillin-resistant Staphylococcus aureus - MRSA, Escherichia coli, Pseudomonas aeruginosa), with inactivation rates of up to 99.999% under UV light, and 99% for E. coli under white light (artificial indoor lighting). The photocatalytic activity was also tested, and the degradation of methylene blue dye was observed under both UV and white light. Even if the MB degradation was to a smaller extent under white light, it was approximately twice that of the commercial photocatalyst P25. This work demonstrates the valorisation of a food industry by-product such as fish bones to form a potentially valuable material, with important applications in self sterilizing surfaces and environmental remediation.