Highly stable and redox active nano copper species stabilized functionalized-multiwalled carbon nanotube/chitosan modified electrode for efficient hydrogen peroxide detection

A highly redox active and stable nano copper species immobilized functionalized-multiwalled carbon nanotube (f-MWCNT) + chitosan (CHIT) film coated glassy carbon electrode (Cu@f-MWCNT + CHIT/GCE) was fabricated using a new preparation procedure, different from the conventional Cu2+ + MWCNT + CHIT bulk electro-codeposition coupled glassy carbon surface activation method, for selective and sensitive amperometric estimation of H2O2 at -100 mV vs Ag/AgCl in physiological solution. Several copper modified film electrodes with nano copper species immobilized into films made of single component or different combinations of CNT and CHIT (i.e., Cu@f-MWCNT + CHIT/GCE, Cu@SWCNT + CHIT/GCE, Cu@f-MWCNT/GCE, Cu@MWCNT/GCE, Cu@CHIT/GCE and Cu/GCE) were characterized by cyclic voltammetry in a blank pH 7 phosphate buffer solution (PBS), and only the Cu@f-MWCNT + CHIT/GCE showed well-defined redox peak with an half-wave potential (E-1/2) of -85 mV vs Ag/AgCI for the matrix immobilized Cu2' /Cu+ redox species with very good film stability and pronounced leaching resistance to copper. Transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray analysis, X-ray photoelectron spectroscopy were used to give a complete characterization of the Cu@f-MWCNT + CHIT/GCE. Effect of potential scan rate and pH on the redox response of the Cu@f-MWCNT + CHIT/GCE was studied to probe the mechanism of Cu2+/Cu+ electron transfer process. The Cu@f-MWCNT + CHIT/GC electrode showed effective electrocatalytic reduction of H2O2 in pH 7 PBS. Amperometric i-t method of H2O2 detection yielded a calibration plot linear up to 125 mu M with a current sensitivity of 0.463 A M-1 cm(-2). The newly developed Cu@f-MWCNT + CHIT/GC electrode displayed remarkable tolerance to co-existing interferents, such as cysteine, ascorbic acid, uric acid and nitrite at the H2O2 detection potential in pH 7 PBS. The ability of the sensor electrode for routine analyses was demonstrated by the detection of H2O2 present in simulated milk samples with appreciable recovery values. (C) 2011 Elsevier B.V. All rights reserved.