Electrochemically Active Mercury Nanodroplets Trapped in a Carbon Nanoparticle–Chitosan Matrix

Abstract

A thin composite film of carbon nanoparticles (ca. 8 nm diameter) and chitosan biopolymer (poly-d-glucosamine, from chitin, 75 -85% deacetylated) was prepared by evaporation from aqueous dispersion onto glassy carbon electrode surfaces. The amine groups in the chitosan biopolymer were used to effectively bind Hg(II) ions from an aqueous pH 5 KCl solution. During redox cycling voltammetric responses for bound mercury are readily observed and mercury nanodroplets (ca. 5.4 (AE 1.0) nm diameter based on SAXS measurements) are formed in the film by applying a negative potential. The binding of Hg(II) ions to the chitosan -carbon nanoparticle film occurs with an approximate Langmuirian constant of 2.7 Â 10 4 mol À1 dm 3 and the process is dependent on (i) the chitosan content in the film, (ii) the Hg 2þ concentration, and (iii) the immobilization time. The immobilized mercury nanodroplets within the carbon nanoparticle -chitosan film are electrochemically active and allow the co-deposition of other metals in the form of amalgams. Preliminary experiments for the anodic stripping voltammetry for Pb 2þ and for Cu 2þ are demonstrated. Mercury nanodroplet modified chitosan -carbon nanoparticle film electrodes represent a novel electroanalytical tool.

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