Development of Solution‐ and Film‐Based Economical Sensors for Reversible Sensing of Fluoride and Cyanide Ions

Abstract

AbstractThree Bisphenol based economical sensors were developed from readily available reagents with single synthetic step. The bisphenols were obtained from reaction of 2,6‐dimethylphenol with 4‐hydroxybenzaldehyde (BP‐1), 4‐bromobenzaldehyde (BP‐2) and 4‐nitrobenzaldehyde (BP‐3). The cyanide and fluoride ions induce visual colour changes which enabled their naked eye detection and distinguished them as well. All the three sensors were able to detect these anions upto a nano molar range. Selective detection of these two anions with paper strips experiments were demonstrate by taking the BP‐1 as representative case. Again, among the sensors BP‐1 was chosen to immobilize into the cellulose based hydrogel matrix. Resulting composite efficiently detect cyanide and fluoride ions in 100 % aqueous system which otherwise was not feasible owing to water insolubility of BP‐1. The 1 cm2 film containing 0.01 mmol of BP‐1 can absorb 2 ppm of fluoride ion from standard aqueous solution of KF. The morphology study reveals a smooth and miscible distribution of BP‐1 into the polymer matrix. Surface morphology of the composite changes upon treatment with cyanide solution. Both the solution and film based sensing of these anions were found to be reversible in nature. The substituent effect on anion binding ability of respective sensors were demonstrated experimentally and validated theoretically.