Single-walled carbon nanotubes covalently functionalized with cysteine: A new alternative for the highly sensitive and selective Cd(II) quantification

Abstract

This work is focused on the development of an electrochemical sensor for the quantification of Cd(II) based on the use of glassy carbon electrodes (GCE) modified with a dispersion of single-walled carbon nanotubes (SWCNTs) covalently functionalized with cysteine (Cys). Cd(II) is preconcentrated at the electrode surface by complex formation at open circuit potential, followed by the reduction at ∧0.900V and the final anodic voltammetric stripping in a 0.020M acetate buffer solution pH 5.00. The functionalization of SWCNTs was performed through the reaction between the carboxylic groups of oxidized SWCNT and amino groups of S-triphenylmethyl cysteine using a coupling chemistry agent based on benzotriazol for the activation of carboxylic residues.There was a linear relationship between Cd oxidation signal and Cd(II) concentration between 1.0 and 300.0α/4gL∧1 Cd(II), with a sensitivity of (49±2)í10∧3α/4Aα/4g∧1L and a detection limit of 0.3α/4gL∧1. The reproducibility was 1.7% using the same dispersion and 3.8% using 3 different dispersions. The sensor was challenged with groundwater samples enriched with Cd(II) showing excellent recovery percentages and excellent agreement with the values obtained by ICP-MS.