Hybrid SPR/Fabry–Pérot Cavity-Based Films with Versatile Color Tunability and Sensitive Environmental Sensing

Plasmonic nanostructures enable vivid structural coloration through resonant light-matter interactions. However, their utility is often hampered by the inherently limited spectral tunability of standalone surface plasmon resonance (SPR), which restricts practical applications in adaptive optical systems. Here, we present hybrid SPR/Fabry-Pérot (F-P) cavity-based Au-Al-colloidal photonic crystal (Au-Al-CPC) films that overcome this limitation by synergizing SPR with F-P cavity resonances. The hybrid films are fabricated through magnetron sputtering of Au nanoparticles onto Al nanoisland arrays, enabling versatile structural color tunability across the full visible spectrum through precise F-P cavity periodicity modulation. Notably, they achieve sensitive environmental response and exhibit rapid solvent- and glucose-triggered spectral shifts with a refractive index sensitivity of 425 nm/RIU. Customized shadow masks further allow single-step creation of intricate multicolor patterns for decorative optics and anticounterfeiting labels. This work establishes a versatile SPR/F-P hybrid platform, showing great prospects in adaptive photonics, optical anticounterfeiting, and environmental sensing.