Nanostructured Photonic Hydrogels for Real-Time Alcohol Detection

Rapid, reliable, and reusable sensors with a low limit of detection can play a vital role in alcohol detection, which is vital in a myriad of industries. Herein, hydrogel-based fiber optic probes were developed for alcohol sensing by a simple, rapid, and facile process. Aztec microstructures with a periodicity of 3 μm were imprinted onto alcohol-sensitive hydrogels for fabricating stand-alone and fiber optic sensors. The hydrogel matrix undergoes swelling in response to alcohol solutions, altering its diffraction efficiency. The real-time sensing capability of the developed sensors was demonstrated in response to various concentrations of ethanol, isopropanol, methanol, and dimethyl sulfoxide in the concentration range of 0 to 50 vol %. For the stand-alone sensors, sensitivities of 23, 21, and 15 μW/vol % were recorded for dimethyl sulfoxide (DMSO), isopropanol, and ethanol, respectively. For the optical fiber probes, sensitivities of 2.3, 2.2, 1.94, and 1.14 μW/vol % were recorded for DMSO, isopropanol, ethanol, and methanol, respectively. A fast response time of 20 s was recorded for both stand-alone and optical fiber sensors. Higher sensitivity toward DMSO was observed, with a low limit of detection of 0.5 vol %. The developed optical fiber sensors may have applications in remote and real-time alcohol sensing in forensics, medicine, food, and beverage manufacturing industries.