A naphthoquinone based colorimetric probe for real-time naked eye detection of biologically important anions including cyanide ions in tap water: experimental and theoretical studies

A naphthoquinone based colorimetric sensor (N) bearing hydrazone receptors in aqueous media was developed and its recognition properties towards biologically important anions in DMSO–water mixture (9 : 1) were investigated using spectroscopic methods. The hydrazone based receptors showed selectivity towards anions (F(−), OH(−), CN(−) and AcO(−)), through naked eye observable colour changes, from green to light blue (F(−), CN(−) and AcO(−)) and violet (OH(−)). The colour changes were concomitant with spectral changes. The sensor could also detect the presence of fluoride ions in commercially available toothpastes, through remarkable colour and spectral changes. In addition, test paper strips prepared from N were able to detect the presence of cyanide (KCN) and hydroxide (NaOH) in tap water. The study was complimented by density functional theory computations to have more insight in the interaction between N and the anions.