A novel cyanide-selective colorimetric and fluorescent chemosensor: First molecular security keypad lock based on phosphotungstic acid and CN− inputs

Abstract

Rhodamine B (RhB) an available dye has been developed as novel and efficient colorimetric and fluorometric chemosensor for cyanide ions in an absolutely aqueous media. The UV–vis absorption and fluorescent emission titrations experiments have been employed to study the sensing process. RhB could act as an efficient “ON–OFF” fluorescent response for phosphotungstic acid (H3PW12O40 or PTA) based on an ion associate process. Also (RhB+)3·PTA3− could operate as an “OFF–ON” fluorescent sensor for cyanide anions based on a ligand substitution process. It has been identified as highly sensitive probe for CN− which responds at 0.3 and 0.04μmolL−1 concentration levels by absorption and fluorescent method respectively. Depending upon the sequence of addition of PTA and CN− ions into the solution, RhB could be as a molecular security keypad lock with PTA and CN− inputs. The ionic inputs to new fluorophore have been mimicked as a superimposed electronic molecular keypad lock. The results were compared successfully (>96%) with the data of a spectrophotometry approved method (EPA 9014-1) for cyanide ions.