Orange-peel-derived carbon dots embedded in polyvinyl alcohol films for transparent and flexible UV-blocking applications

Abstract

The development of sustainable UV-shielding materials with balanced optical transparency is crucial for advanced packaging and surface protection applications. In this work, we report a green and cost-effective approach for preparing flexible poly(vinyl alcohol) (PVA) composite films embedded with carbon dots derived from waste-orange peels (OP-CDs). The OP-CDs synthesized via a simple pyrolysis route exhibited strong UV absorption and bright blue fluorescence originating from π–π* and n–π* transitions associated with surface carbonyl and amine groups. When incorporated into the PVA matrix, the resulting PVA@OP-CDs-9 (OP-CDs: 9 mg/mL) composite films effectively blocked 100% of the UV-C (230–280 nm) and UV-B (280–315 nm) radiation and more than 90% of the UV-A (315–400 nm) light while maintaining moderate visible-light transparency with 25–30% transmittance at 550 nm. The films also displayed good mechanical flexibility, thermal stability, and antioxidant activity, significantly reducing fruit browning under UV light exposure. Furthermore, the films were recyclable and reusable with minimal performance loss. This study provides a sustainable route for the transformation of biomass waste into efficient, flexible, and biodegradable UV-blocking films suitable for food packaging and protective coatings.