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Nanoparticles-loaded bio-based polymers have emerged as a sustainable substitute to traditional oil-based packaging materials, addressing the challenges of limited recyclability and significant environmental impact. However, the functionality and efficiency of nanoparticles have a significant impact on the application of bio-based composite films. Herein, graphitic carbon nitride (g-C 3 N 4) and titanium dioxide (TiO 2) coupled photocatalyst (g-C 3 N 4 -TiO 2) was prepared by one-step calcination and introduced into chitosan (CS) and polyvinyl alcohol (PVA) solution to fabricate g-C 3 N 4 -TiO 2 /CS/PVA green renewable composite film via solution casting method. The results demonstrated the successful preparation of a Z-scheme heterojunction g-C 3 N 4 -TiO 2 with exceptional photocatalytic activity. Furthermore, the incorporation of heterojunction enhanced mechanical properties, water barrier, and ultraviolet (UV) resistance properties of the fresh-keeping film. The g-C 3 N 4 -TiO 2 /CS/PVA composite film exhibited superior photocatalytic antibacterial preservation efficacy on strawberries under LED light, with a prolonged preservation time of up to 120 h, when compared to other films such as polyethylene (PE), CS/PVA, g-C 3 N 4 /CS/PVA, and TiO 2 /CS/PVA. In addition, the composite film has good recyclability and renewability. This work is expected to have great potential for low-cost fruit preservation and sustainable packaging, which also contributes to environmental protection. [Display omitted] • g-C 3 N 4 -TiO 2 Z -scheme heterojunction was prepared by a one-step calcination method. • The addition of g-C 3 N 4 -TiO 2 improved the mechanical, UV-barrier properties and water-blocking ability of CS/PVA film. • The g-C 3 N 4 -TiO 2 /CS/PVA composite film has excellent photocatalytic antibacterial and preservation properties. • The g-C 3 N 4 -TiO 2 /CS/PVA composite film is also green renewable and environmentally friendly. [ABSTRACT FROM AUTHOR]

Chitosan (CS) is an excellent raw material for the preparation of food packaging films due to its good film-forming properties, non-toxicity, and biodegradability. However, pure chitosan films have drawbacks such as weak mechanical properties and limited antimicrobial activity. In this work, novel food packaging films containing chitosan, polyvinyl alcohol (PVA) and porous graphitic carbon nitride (g-C 3 N 4) were successfully prepared. The PVA served to improve the mechanical properties of the chitosan-based films, whilst the porous g-C 3 N 4 acted as a photocatalytically-active antibacterial agent. The tensile strength (TS) and elongation at break (EAB) of the g-C 3 N 4 /CS/PVA films both increased by ~4 times compared to the pristine CS/PVA films at the optimum g-C 3 N 4 loading of ~10 wt%. The addition of g-C 3 N 4 increase the water contact angle (WCA) of the films from 38° to 50°, whilst decreasing the water vapor permeability (WVP) from 160 × 10−12 to 135 × 10−12 g∙Pa−1 s−1 m−1. The shelf life of strawberries covered with g-C 3 N 4 /CS/PVA films at room temperature could be extended up to 96 h, compared to 48 h and 72 h for strawberries covered with polyethylene (PE) films or CS/PVA films, respectively. The g-C 3 N 4 /CS/PVA films offered good antibacterial properties against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Further, the composite films could be easily recycled with the regenerated films offering almost identical mechanical properties and activities as the original films. The prepared g-C 3 N 4 /CS/PVA films thus offer promise for low-cost antimicrobial packaging applications. [Display omitted] • g-C 3 N 4 /CS/PVA photocatalytic packaging film was successfully prepared. • g-C 3 N 4 enhanced the barrier ability and antibacterial activity of the film. • PVA enhanced the mechanical properties and flexibility of the film. • The composite film showed better strawberries packaging properties. • The composite film can be easily recycled to prepare renewable film. [ABSTRACT FROM AUTHOR]