Photononic crystal-plasmonic synergy-driven ultrabright upconversion for high-efficiency near-infrared photocatalysis

Abstract

The limited penetration depth of ultraviolet/visible light and the low quantum yield of upconversion nanoparticles (UCNPs) have hindered their practical application in near-infrared (NIR)-driven photocatalysis. To address this, we propose a rational design combining plasmonic, upconversion, and photocatalytic components into a composite architecture: SiO₂ sphere array@Au film@UCNPs. The plasmonic SiO₂–Au interface concentrates excitation fields within nanoscale gaps, achieving optimal spectral coupling with UCNPs. This configuration suppresses radiative losses and enhances fluorescence intensity by 10.4-fold. The amplified emission efficiently excites the adjacent Au film, generating hot carriers that drive methylene blue degradation. Mechanistic studies reveal synergistic contributions from plasmon-enhanced luminescence, localized thermal activation, and radical generation (–OH/O₂⁻), underpinning the high catalytic performance. Theoretical modeling of optical and energy-transfer properties further supports the proposed mechanisms. This work demonstrates high-efficiency photocatalysis under 980 nm NIR light, offering promising potential for rapid dye degradation and advancing environmental and water-safety applications.