Highly Reflective Organic/Inorganic Hybrid 1D Photonic Crystals Based on Silane-Functionalized TiO Nanoparticles for Colorimetric Humidity and Alcohol Vapor Sensing.

One-dimensional photonic crystals (1DPCs) have been extensively studied as colorimetric sensors responsive to various external stimuli. Herein, we report a simple spin-coating method to fabricate highly reflective, humidity- and alcohol-responsive organic/inorganic hybrid 1DPCs using silane-functionalized TiO nanoparticles and a DMA-based hydrophilic copolymer. The resulting 1DPCs, composed of a small number of alternating layers (≤8), exhibit distinct color changes and high reflectance (∼50%) in response to humidity and alcohol vapor, addressing the limitations of all-polymeric 1DPCs that require many layers or display low reflectivity. This approach offers a practical and scalable strategy for developing stimuli-responsive photonic crystal films, demonstrating strong potential for high-performance colorimetric sensing applications.