Robust and efficient UV-reflecting one-dimensional photonic crystals enabled by organic/inorganic nanocomposite thin films for photoprotection of transparent polymers

Abstract

Using a one-dimensional photonic crystal (1DPhC) film is a promising photoprotection technique for transparent polymer products, since it can be designed to selectively reflect UV light and allow the transmittance of visible light. Cracking and low adhesion caused by mechanical mismatching of 1DPhCs with polymer substrates remain a grand challenge. Herein, a facile and cost-effective approach is developed by combining sol–gel derived organic/inorganic (O/I) nanocomposites with layer-by-layer (LBL) spin-coating to produce 1DPhC films with well-controlled alternating layered structures. With modification using an organosilane, the dispersibility of SiO₂ and TiO₂ nanoparticles and the interfacial interaction between neighboring layers were improved, which resulted in a defect-free and robust 1DPhC multilayer film tightly bonded onto a polycarbonate (PC) surface. The developed 1DPhC film exhibits enhanced compatibility with the PC substrate and possesses preeminent anti-failure performance in harsh environments. The optical properties of the O/I nanocomposite 1DPhC film were tuned by changing the spin-coating speed. An intense UV reflectance of 70% at 340 nm was achieved by the 1DPhC film, while it still maintained high transmittance of over 86% to visible light. Theoretical and experimental studies verified that the high reflectance of UV light contributed to the efficient decaying of normal incident UV light across the developed 1DPhC film, leading to enhanced photoprotection for the polycarbonate. Therefore, this study provides insights into the design and fabrication of highly compatible and mechanically robust 1DPhC films with defined reflection properties suitable for polymer and flexible substrates.