Transparent Poly(vinyl alcohol) Films Incorporating Cu₂O Nanospheres: Tunable Colors with Enhanced Antibacterial Performance

Structural coloration presents an eco-friendly alternative to chemical pigments but suffers from mechanical fragility and limited antimicrobial functionality. Herein, a strategy is proposed to prepare transparent poly(vinyl alcohol) (PVA) films with vibrant colors by incorporating submicrometer single-crystalline Cu2O spheres as Mie scattering agents, aiming to overcome these limitations. At 0.7 wt % loading, the Cu2O/PVA film exhibited vivid and tunable structural colors across the visible spectrum via sphere diameter modulation, while maintaining substantial transparency. Notably, the short-wavelength-absorbing property of the composite films is crucial for decorative films, which can protect our eyes from harmful short-wavelength lights such as blue bands. Enhanced mechanical robustness is achieved with a tensile strength of 20.6 MPa and an elongation at break of 360% surpassing the pure PVA film. Moreover, their excellent antibacterial properties (≥69%), biocompatibility, low migration of copper ions, and good barrier performances make them suitable for food packaging to extend the food shelf life. Cu2O/PVA films can be prepared in large areas, rendering them practically valuable in the packaging industry. This design provides a promising strategy for enhancing the functionality and aesthetic appeal in both the decoration and food packaging fields.