Bimetallic PtM (M = Pd, Ir) nanoparticle decorated multi-walled carbon nanotube enzyme-free, mediator-less amperometric sensor for H2O2

A new highly catalytic and intensely sensitive amperometric sensor based on PtM (where M = Pd, Ir) bimetallic nanoparticles (NPs) for the rapid and accurate estimation of hydrogen peroxide (H2O2) by electrooxidation in physiological conditions is reported. PtPd and PtIr NPs-decorated multiwalled carbon nanotube nanocatalysts (PtM/MWCNTs) were prepared by a modified Watanabe method, and were characterized by XRD, TEM, ICP, and XAS. The sensors were constructed by immobilizing PtM/MWCNTs nanocatalysts in a Nafion film on a glassy carbon electrode. Both PtPd/MWCNTs and PtIr/MWCNTs assemblies catalyzed the electrochemical oxidation of H2O2. Cyclic voltammetry characterization measurements revealed that both the PtM (M = Pd, Ir)/MWCNTs/GCE possessed similar electrochemical surface areas (similar to 0.55 cm(2)), and electron transfer rate constants (similar to 1.23 x 10(-3) cm s(-1)); however, the PtPd sensor showed a better performance in H2O2 sensing than did the Ptlr counterpart. Explanations were sought from XAS measurements to explain the reasons for differences in sensor activity. When applied to the electrochemical detection of H2O2, the PtPd/MWCNTs/GC electrode exhibited a low detection limit of 1.2 mu M with a wide linear range of 2.5-125 mu M (R-2 = 0.9996). A low working potential (0 V (SCE)), fast amperometric response (<5 s), and high sensitivity (414.8 mu A mM(-1) cm(-2)) were achieved at the PtPd/MWCNTs/GC electrode. In addition, the PtPd/MWCNTs nanocatalyst sensor electrode also exhibited excellent reproducibility and stability. Along with these attractive features, the sensor electrode also displayed very high specificity to H2O2 with complete elimination of interference from UA, AA, AAP and glucose. (C) 2012 Published by Elsevier B.V.