A nitrobenzodioxazole-based water-soluble chemosensor for colorimetric quantification of aqueous hypochlorite

A nitrobenzoxadiazole (NBD)-based colorimetric chemosensor CNA (N,N,N-trimethyl-2-(2-(7-nitrobenzo[c][1,2,5]oxadiazol-4-yl)hydrazineyl)-2-oxoethan-1-aminium chloride) was synthesised. The sensor CNA can detect hypochlorite (ClO-) via colour variation of yellow to colourless. The detection limit for ClO- by CNA was analysed to be 0.36 mu M. Moreover, the naked-eye test strip was successfully applied for ClO- detection. The probing mechanism of CNA to ClO- was proposed to be a hydrolytic cleavage reaction of CNA by ClO- and was demonstrated by electrospray ionisation mass spectrometry (ESI-MS), Fourier-transform infrared (FTIR), proton nuclear magnetic resonance (1H NMR) analysis and density functional theory (DFT) calculations.