Naked eye sensing of anions using thiourea based chemosensors with real time application

Novel chromogenic sensors with thiourea moiety as receptor unit were synthesized and characterized using IR and NMR spectroscopic techniques. The receptors 1 and 2 bearing hydrogen bonding site demonstrate visually striking color change, UV–vis, and fluorescence responses for F−, AcO−, and OH− over other anions such as Cl−, Br−, H2PO4− and HSO4−. Both the receptors 1 and 2 demonstrate detection limit at micro molar level. Further insight to the nature of interaction between receptors and anions was studied using 1H NMR titration experiment. In particular, the fluoride of tooth paste and mouthwash in water phase can be detected by receptor 2.