Film-Based Fluorescent Sensor for Monitoring Ethanol-Water-Mixture Composition via Vapor Sampling

In situ, on line, noncontact, and fast monitoring of the compositions of ethanol-water mixtures via vapor-phase sampling has remained a challenge for years. In this work, we report for the first time a film-based fluorescent sensor showing unprecedented ability to discriminate the compositions of ethanol-water mixtures. Importantly, ethanol contents in the mixtures can vary from 0 to 100% (v/v), the response time is less than 2 s, and the sensing is fully reversible. More importantly, the monitoring was performed via vapor-phase sampling, avoiding sample contamination. The principle behind it is ascribed to the big difference in the fluorescent quantum yield of the sensing unit, a newly designed and synthesized monosubstituted fluorescent o-carborane derivative (ZPCarb), in the two solvents. In addition, the sensor as developed was successfully used for the determination of ethanol contents in four commercial liquors, suggesting its potential application in the quality control of beverages, in monitoring fermentation processes, and in other processes.