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 (E1/2) of −85 mV vs Ag/AgCl 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 μM 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.