Colorimetric, fluorometric, and electrochemical sensing of cyanide ion in aqueous media using merocyanine-ferrocene conjugate

Abstract

Rapid detection of hazardous ions has received a considerable deal of attention in recent decades due to its usefulness in preserving a greener environment for humans. The severe toxicity of cyanide (CN–) ions is a major environmental problem. Therefore, a substituted merocyanine salt having a ferrocene segment was designed and synthesized with the expectation to yield a probe with colorimetric, and electrochemical properties. The merocyanine derivative was characterized by NMR, IR, and high-resolution mass spectrometric analysis. The merocyanine salt was screened for the colorimetric detection of toxic ions in aqueous media. Utilizing UV–vis, fluorescence spectroscopy, cyclic voltammetry, and digital image analysis, an acceptable limit of detection value was witnessed. A hypochromic and hypsochromic shift in the absorption spectra was observed in the presence of cyanide ions. The 1H NMR spectroscopy shows the interaction of CN– with the probe at the spiro-carbon of the merocyanine salt and metal center of the ferrocene segment. The electrochemical input during cyclic voltammetric studies resulted in the formation of C–C bonds on complexation with cyanide ions due to an increase in electron density on the nitrogen atom of the indoline segment. The limit of detection calculated using UV–visible spectroscopy was 2.28 µM, fluorescence spectroscopy provided 1.48 µM , and 0.61 µM was witnessed using cyclic voltammetry.