A portable smartphone platform based on a fluorescent–colorimetric sensor for visual detection of trace water in edible vegetable oils

Abstract

Accurate monitoring of water content in organic solvents and food sources is essential for safety considerations as it adversely affects chemical processes and food safety. Although many water-sensitive fluorescent materials have been developed, the preparation of simple and low-cost sensors for rapid real-time water analysis remains a valuable research hotspot. In this study, a simple Schiff base-derived fluorescent sensor (NSP) was easily converted into its deprotonated form (NSP·F) in the presence of F⁻, which exhibited a remarkable fluorescent–colorimetric effect, high sensitivity and fast response to moisture in organic solvents. The sensitivity of the NSP·F sensor towards water in acetonitrile, N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) could reach as low as 0.013%, 0.0038% and 0.0017% (v/v), respectively. The NSP·F sensor also showed a good response to relative humidity in its surroundings in a short period of time. Based on its sensitivity, NSP·F was successfully used for the accurate, reliable and convenient monitoring of water content in organic solvents and edible vegetable oils. NSP·F-absorbed easy-to-prepare filter paper strips were used in an inkless writing fluorescent display device with reversibility. Furthermore, owing to the drastic change in the emission color of the NSP·F solution, the portable monitoring of water content can be realized with the help of a smartphone-assisted color analysis application, providing the possibility for real-time water content analysis using the sensor.