A hydrogel optical fibre sensor for rapid on-site ethanol determination

Ethanol plays a critical role in the modern chemical industry, food production, and medical research. Given its wide applications, the detection of ethanol concentration is very necessary. In this paper, a fibre device for rapid ethanol detection is proposed. The sensing head was fabricated with multimode fibre. The hydrogel was photo-cured on the fibre tip from polyethylene glycol diacrylate (PEGDA). In the hydrogel, rhodamine 6G (R6G) was immobilized as the fluorescent indicator. The sensor was designed based on the swelling behaviour of the hydrogel in liquid. The transparency of the hydrogel was modulated by the component of the water–ethanol mixture, thus, the fluorescence intensity of R6G was monitored for the determination of ethanol. Within the range of 0–62.2 vol%, the detection limit (LOD) was 0.4 vol%. A detailed comparison with other detection methods showed that the proposed sensor has the advantages of being single-ended, low LOD, cost-effective, and easy to prepare. It has great potential for on-site ethanol detection applications.