Graphene oxide-enhanced polymer cholesteric photonic array dots for linear, reversible and selective alcohol identification

The selective detection of volatile organic compounds (VOCs) such as ethanol and methanol remains challenging due to their structural similarities and low reactivity, necessitating simple, real-time sensors for applications in health monitoring, environmental safety, and industrial processes. Herein, we report a graphene oxide (GO)-enhanced polymer cholesteric liquid crystal interpenetrating polymer network (PCLCIPN) photonic array dot sensor for discriminating ethanol, methanol, and their mixtures (ratios 1:1, 1:3, 3:1) in aqueous solutions. The sensor integrates a porous PCLC template with a poly(acrylic acid)/GO (0.05 wt%) hydrogel, functionalized by 0.60M NaOH to disrupt hydrogen bonds and enable reversible swelling/deswelling. GO incorporation facilitates π-π electron stacking, enhancing alcohol absorption and structural stability. UV-vis transmission spectroscopy reveals linear photonic bandgap wavelength shifts (ΔλPBG) from 5% to 70% alcohol concentrations, with sensitivities of -0.902 to -1.260 nm/% at 5 s for various compositions, outperforming prior systems limited to 5–60% or nonlinear responses. The distinct ethanol/methanol response is attributed to differences in their Hansen solubility parameters. The sensor exhibits rapid response, low limits of detection (LoD: -1.244 to -3.291%/15 µL), and reversibility over 80 cycles. This photonic platform advances label-free, visual VOC sensing for point-of-care and on-site applications.