Noncovalent Modification of Carbon Nanotubes with Ferrocene−Amino Acid Conjugates for Electrochemical Sensing of Chemical Warfare Agent Mimics

Abstract

The electrochemical detection of chemical warfare agent (CWA) mimics was explored using multiwalled carbon nanotubes (MWCNTs) on indium tin oxide (ITO) surfaces in connection with ferrocene-amino acid conjugates. Various ferrocene-amino acid conjugates were synthesized and utilized as the recognition layer for the detection of CWA mimics. The ferrocene-amino acid conjugates were noncovalently attached to the pretreated MWCNTs on the ITO surface and reacted with CWA mimics, upon which the electrical properties of the MWCNTs and the Fc group were affected significantly. Alternating current voltammetry and capacitance-based detection offered large dynamic ranges for the detection of methylphosphonic acid, diethyl cyanophosphonate, ethylmethylphosphonate, and pinacolyl methylphosphonate in water. Electrochemical measurements showed dramatic changes upon the electrostatic interaction between the CWA mimics and the ferrocene-amino acid conjugates immobilized on MWCNTs on ITO surfaces. Electrochemical sensing in connection with MWCNTs is shown to be a promising analytical tool for the trace-level detection of CWA mimics in aqueous solutions.