Colorimetric sensors for discriminatory detection of arsenite ions: Application in milk, honey and water samples and molecular logic gates

Abstract

Millions of people are exposed to dangerous arsenic levels in drinking water, highlighting the urgent need for affordable, continuous on-site arsenic monitoring methods. It is crucial to specifically detect arsenite among inorganic arsenic anions because it is more poisonous than arsenate. Addressing these concerns, the present study developed 5-(4-nitrophenyl)-2-furaldehyde based two colorimetric chemosensors, N5R3 and N5R4, with different signaling groups for the selective detection of arsenite anions over arsenate in DMSO/H2O (6:4, v/v). The red-shift in the UV–Vis absorption spectra supported the distinct color changes of sensors N5R3 and N5R4 displayed upon binding with arsenite. Sensors demonstrated stability over a pH range of 6 to 12 and exhibited stability over a considerable time period. Among the chemosensors, N5R3 exhibited the lowest detection limit of 7.41 ppb with a high binding constant of 2.9976 × 106 M−1 for arsenite. The 1:1 binding interactions between the chemosensors and arsenite were confirmed using B-H plot and Job’s plot analysis. The intramolecular charge transfer (ICT) mechanism for detecting arsenite was proposed through UV and 1H NMR titrations, electrochemical studies, mass spectral analysis and DFT calculations. The interactions between the sensor and arsenite anions were further analyzed using global reactivity parameters (GRPs). Practical applications were demonstrated through the utilization of test strips and molecular logic gates. Both chemosensors efficiently recognized arsenite in real water, honey, and milk samples.