Studies on a glutathione coated hollow ZnO modified glassy carbon electrode; a novel Pb(ii) selective electrochemical sensor

Herein, we report the electrochemical detection of heavy metal ions such as Pb(ii), Cd(ii) and Hg(ii) ions while using glutathione coated hollow ZnO modified glassy carbon electrode (Glu-h-ZnO/GCE). An excellent voltammetric response of the modified electrode towards these metal ions was observed by different voltammetric techniques. Among the different target metal ions, a selective electrochemical response (sensitivity = 4.57 mu A mu M-1) for the detection of Pb(ii) ions was obtained with differential pulse voltammetric (DPV) measurements. Besides, under optimal experimental conditions and in the linear concentration range of 2-18 mu M, a very low detection limit of 0.42 mu M was obtained for Pb(ii) ion. The observed electrochemical behaviour of Glu-h-ZnO/GCE towards these metal ions is in conformity with the band gap of the composite in the presence of various test metal ions. The band gap studies of the composite and various "Composite-Metal Ion" systems were obtained by reflectance as well as by computational methods where results are in close agreement, justifying the observed electrochemical behaviour of the systems. The lowest band gap value of the "Composite-Pb" system may be the reason for the excellent electrochemical response of the Glu-h-ZnO modified GCE towards the detection of Pb(ii) ion.