Photochromic biodegradable film based on polyvinyl alcohol modified with silver chloride nanoparticles and spirulina; investigation of physicochemical, antimicrobial and optical properties

•Biodegradable polyvinyl alcohol film was modified with silver chloride nanoparticles and spirulina.•PVA/AgCl/Sp film showed excellent antimicrobial and antioxidant properties and was suitable for active food packaging.•PVA/AgCl film showed good photochromic property in the exposure of sunlight and UV light.•Photochromic PVA/AgCl films can be used in the packaging of food products sensitive to light oxidation. In this study, biodegradable film was prepared from polyvinyl alcohol (PVA), Silver chloride (AgCl) and spirulina (Sp). Surface morphology, mechanical properties, antioxidant, antimicrobial, optical properties, etc. were investigated. The FTIR results confirmed the effect of AgCl and Sp on PVA structure. Sp increased the moisture content and solubility in water. The XRD results showed the semi-crystalline structure of PVA. AgCl nanoparticles activated the antibacterial property of the film against Escherichia coli and Staphylococcus aureus bacteria and Sp caused a strong increase in the antioxidant property of the film. Examining the light transmittance of films containing AgCl nanoparticles showed that the transmittance of films containing nanoparticles decreased with exposure to sunlight and ultraviolet light with increasing treatment time, which indicates the activation of the photochromic property of films containing AgCl in the presence of light. The results showed the suitable photochromic property of the PVA/AgCl films.