A colorimetric probe for real-time naked-eye detection of cyanide and hydroxide ions in tap water: Experimental and Theoretical Studies

A naphthyl derivative colorimetric sensor (L) bearing hydrazone receptors was synthesized via a one-step reaction process, and its recognition properties towards biologically important anions in acetonitrile-water mixture were investigated by naked eye observation and spectroscopic methods of UV-Vis and 1H NMR analysis. The molar addition of anions such as TBAF-, TBAOH-, TBACN- and TBAAcO- induced a marked red shift of the charge transfer band (∆λ = 73 nm, from 337 nm to 410 nm) concomitant with a visible “naked eye” detectable colorimetric activities. In addition, soaked-in-L paper strips prepared could significantly discriminate cyanide (KCN) and hydroxide (NaOH) ions dissolved in tap water, via litmus test method. The study was complimented by density functional theory computations to have more insight in the interaction between L and the anions.