Ag or Au Nanoparticles Decorated Multiwalled Carbon Nanotubes Coated Carbon Paste Electrodes for Amperometric Determination of H 2 O 2

Composite materials made of multiwalled carbon nanotubes and silver (Ag-MWCNT) or gold particles (Au-MWCNT) were synthesized and characterized by XRD and SEM/EDS techniques. The composites and the MWCNTs were applied as surface modifiers of carbon paste electrodes (CPEs). The mediator based electrocatalytic activity of the modified electrodes was investigated for H 2 O 2 oxidation/reduction by electrochemical measurements. All voltammetric working electrodes (Ag-MWCNT/CPE, Au-MWCNT/CPE, MWCNT/CPE and the bare CPE) were characterized by cyclic voltammetry (CV) in acetate and phosphate supporting electrolytes (0.1 mol L −1 , pH 4.50 and 7.50, respectively) in the absence and presence of the H 2 O 2 analyte. Amperometric experiments were performed in stirred solutions at selected constant working potentials, in accordance with the CV responses, for developing new analytical methods for the determination of H 2 O 2 . In the case of the Ag-MWCNT/CPE the most promising working potentials in the acetate buffer solution were − 0.40 V and + 0.80 versus SCE; in phosphate buffer solution these values were between − 0.20 and − 0.30 V and from + 0.60 to + 1.0 V. The Au-MWCNT/CPE is applicable in acetate buffer supporting electrolyte in the working potential close to − 0.30 V versus SCE and from + 0.70 to + 1.0 V; in the phosphate buffer solution only from + 0.60 V versus SCE and higher values. Due to the presence of the signal enhancement effect of Au and Ag nanoparticles, the sensitivity of the obtained methods is significantly higher in comparison to the results obtained by the MWCNT/CPE and bare CPE. The relative standard deviation of the measurements was lower than 10%. The practical application using the Ag-MWCNT/CPE was shown for the determination of H 2 O 2 in real nursing product sample. It was proven that the developed mediator based (electro)catalytic platform exhibits low detection limit, high selectivity, reproducibility and stability.