Unveiling the potential of polymer cholesteric liquid crystal interpenetrating networks as a label-free alcohol biochemical sensor†

In this study, an optical sensor is developed, incorporating hydrogen-bonded photonic array dots containing poly(acrylic acid) (PAA) within a polymer cholesteric liquid crystal interpenetrating polymer network (PCLC_IPN) framework, thereby effectively controlling porosity. This methodology involves the fabrication of a porous photonic film, subsequent infusion with a hydrogel (PAA), and precise UV-curing to generate patterned array dots. The sensor exhibits exceptional discriminatory capability between methanol and ethanol, accurately discerning their varying concentrations within alcohol solutions. The optical sensing performance of the film is rigorously evaluated through continuous monitoring of wavelength shifts in the transmission spectrum across various alcohol concentrations. Notably, the observed wavelength shifts demonstrate a linear correlation with the concentration of alcohol, thereby enabling precise quantitative analysis of the alcohol solutions. The sensor exhibits a sensitivity of 0.44 nm/% for ethanol concentrations ranging from 5% to 60%, increasing to 2.1 nm/% for concentrations between 60% and 80%. Similarly, for methanol, sensitivities of 0.68 nm/% (5–60%) and 2.2 nm/% (60–80%) are recorded. Remarkably, this sensitivity trend extends seamlessly to 1 : 1 ethanol/methanol ratios, with values of 0.49 nm/% (5–60%) and 2.25 nm/% (60–80%). Furthermore, these sensors demonstrate colorimetric response to different alcohols, rendering them accessible and cost-effective biosensors for visual detection, thus obviating the necessity for complex analytical instruments.