Nontoxic Cross-Linked Graphitic Carbon Nitride-Alginate-Based Biodegradable Transparent Films for UV and High-Energy Blue Light Shielding

Flexible, transparent, and biodegradable films that can shield dangerous UV and high-energy blue light (HEBL) are high in demand to satisfy the ever-increasing expectations for environmental sustainability. To achieve this goal, biopolymer alginate is an excellent choice that has an outstanding film-forming ability. However, alginate has the limitation of poor UV and HEBL blocking ability. Thus, in this study, UV and HEBL blocker graphitic carbon nitride (g-C3N4) was incorporated in alginate films to enhance the compatibility, applicability, and durability. The ATR-FTIR, TGA, DTG, and FE-SEM results indicated that the composite film formation was due to hydrogen bonding, and the composite films revealed synergistic properties of alginate and g-C3N4. Though the incorporation of g-C3N4in films enhanced the mechanical and thermal stabilities of the films, the films were still flexible. The UV–visible transmittance characterization confirmed that the prepared films could block both UV and HEBL radiation while maintaining transparency in visible regions. In experiments involving only 2 wt % g-C3N4, nearly 90% of UV (200–400 nm) and 95% of HEBL (400–450 nm) irradiation were blocked. Additionally, the inclusion of g-C3N4also facilitated the biodegradation process of composite films. Moreover, after 6 months, the composite films exhibited excellent UV and HEBL shielding with excellent mechanical durability.