Polymer-infiltrated SiO₂ inverse opal photonic crystals for colorimetrically selective detection of xylene vapors

Xylenes are common aromatic volatile organic compounds, which can cause severe environmental pollution and healthy issues. The current instrumental detection methods are generally expensive, time-consuming, complex, and unable to be used for on-site detection. It is thus highly desirable to develop an efficient method for the detection of xylenes. In this study, we report the development of a polymer infiltrated SiO₂ inverse opal photonic crystal (IOPC) for selective detection of xylene vapors. Poly(4-vinylbenzyl chloride-co-methyl methacrylate) (P(VBC-co-MMA)), which shows strong affinity towards xylenes because of their similar solubility parameters, was synthesized and infiltrated into SiO₂ IOPC (P(VBC-co-MMA)-SiO₂ IOPC). The resulting P(VBC-co-MMA)-SiO₂ IOPC sensor shows color change from green to red upon exposure to xylene vapors as the diffusion and adsorption of gaseous xylenes increased the effective refractive index of the IOPC. It shows good sensitivity with a limit of detection of 0.51, 0.41 and 0.17 μg mL⁻¹ for o-xylene, m-xylene, and p-xylene, respectively. The sensor also shows excellent selectivity for xylenes over other organic vapors. In addition, the P(VBC-co-MMA)-SiO₂ IOPC sensor demonstrates quick response and good reversibility. This polymer infiltrated IOPC sensor provides a universal strategy for the detection of organic vapors through building a sensor using polymers with similar solubility parameters to targeting vapors.