Light-induced self-assembly of AgNPs for dual-range colorimetric detection of ethanol

Rapid and accurate ethanol determination is crucial for quality control in the alcoholic beverage industry. We report a facile, green colorimetric sensor based on ethanol-modulated self-assembly of AgNPs (Nano silver) under light irradiation. Using food-grade dextran and trisodium citrate as synergistic reducing and stabilizing agents, the photoreduction process yields AgNPs with distinct, ethanol-dependent morphologies, producing gray color in aqueous solution and yellow-brown color in ethanol solutions. This morphology-dependent optical response enables wide-range quantitative detection: 0.5-75% (v/v, R² = 0.9976) and 80-94% (v/v, R² = 0.9961). Mechanistic studies through reactive oxygen species (ROS) quenching identified superoxide anion (O₂˙^-) and singlet oxygen (¹O₂) as predominant species driving photoreduction. The sensor exhibits excellent selectivity against common beverage interferents and was successfully validated with commercial spirits (e.g., Fenjiu: 53.94% measured vs. 53% labeled; Erguotou: 41.77% vs. 42%). This method, characterized by rapidity (15 min), cost-effectiveness, and instrument-free operation, presents a practical platform for on-site alcohol monitoring and beverage authentication.