A two-component polymeric optode membrane based on a multifunctional ionic liquid

Abstract

This work details the use of a 2-component optode membrane which is capable of generating three distinct colours in the presence of Cu²⁺ and Co²⁺ ions. It has been found that the ionic liquid (IL) trihexyltetradecylphosphonium dicyanamide [P_6,6,6,14][DCA] can act as plasticizer, ligand and transducer dye when used in poly(vinyl chloride) (PVC) membranes, which significantly simplifies the optode membrane cocktail. Upon exposure to an aqueous Cu²⁺ solution, a yellow colour is generated within the membrane, while exposure to an aqueous Co²⁺ solution generates a blue colour. Exposure to a solution containing both ions produces a green colour. Vibrational spectroscopy has been used to investigate the molecular basis of the IL–metal ion the binding mechanism. Analytical characteristics of the membranes including the effect of interfering ions, binding constants and the limit of detection for both ions have been estimated. Finally the case of simultaneous dual-analyte recognition is presented based on two distinct absorption maxima.