On-site colorimetric detection of adulterated gasoline using highly reflective 1D photonic crystal sensors based on photo-crosslinked polymer–titania hybrids

The adulteration and distribution of pure commercial gasoline remain a global problem because of the lack of a simple method for the rapid on-site detection of adulterated gasoline. Therefore, herein, we propose a simple method, based on highly reflective one-dimensional photonic crystals (1D PCs), for the on-site rapid colorimetric detection of adulterated gasoline by the naked eye. A photo-crosslinked copolymer–titania hybrid (Ti70) with a high refractive index and a photo-crosslinked methyl acrylate (MA)-based polymeric material containing 4-benzoylphenyl acrylate (BPA) (P(MA-co-BPA)) with a low refractive index were synthesized, characterized, and used in the fabrication of an 11-layered 1D PC sensor (Ti70/P(MA-co-BPA) PC). Ti70/P(MA-co-BPA) PC exhibited no color change in pure commercial gasoline. However, when Ti70/P(MA-co-BPA) PC was immersed in methanol, xylene, toluene, and benzene, it rapidly turned from bluish-purple to blue, sky-blue, greenish-yellow, and reddish-orange, respectively, and had high reflectivities. Additionally, when immersed in binary (gasoline/toluene and gasoline/methanol) and ternary (gasoline/toluene/methanol) mixtures, Ti70/P(MA-co-BPA) PC demonstrated significant color changes within short periods (~2 min). Ti70/P(MA-co-BPA) PC exhibited excellent recyclability, which was verified via repeated swelling/deswelling tests for 10 cycles. These results indicate the applicability of the proposed novel Ti70/P(MA-co-BPA) PC for the rapid on-site colorimetric detection of adulterated gasoline by the naked-eye. We believe that the findings of this study will provide considerable insight for developing simple and high-performance 1D PC sensors for practical use and will also serve as a basis for exploring their potential applications.