Heterocyclic-based optical responsive chemosensors for the detection of arsenite and phosphate in semi-aqueous medium: Application in logic gate operations, RGB tool, and DFT studies

Abstract

Highly selective and sensitive organic chemosensors S2R1-S2R3 were synthesized using thienyl-substituted pyridine derivative and characterized by various spectroscopic techniques. The effect of substituents on selectivity is observed in the chemosensors S2R1 through S2R3, with the rate of reactivity toward ions following the trend as -NO<inf>2</inf> > -CN > –OCH<inf>3</inf> group. The chemosensor S2R1 exhibited selectivity towards arsenite and phosphate, achieving a Limit of Detection (LOD) of 0.2672 ppm and 0.5042 ppm, respectively, in 30% aq. (CH<inf>3</inf>)<inf>2</inf>SO solution. It was also observed that S2R2 was selective for PO<inf>4</inf>3? ions in 100% (CH<inf>3</inf>)<inf>2</inf>SO solution with an LOD of 0.521 ppm. The spectral redshifts observed in the organo-aqueous media potentializes the sensor to be colorimetrically active. The probe S2R1 showed the lowest LOD and high binding constant with AsO<inf>2</inf>? and PO<inf>4</inf>3? ions. Other characterization techniques, such as electrochemical studies, 1H NMR titration, UV–visible titration, and DFT experiments, demonstrated the sensing mechanism of arsenite and phosphate ions with the chemosensors through an intermolecular hydrogen bonding and intermolecular charge transfer (ICT) process followed by its practical applicability for real world-sensing. © 2024 Elsevier B.V.