Hetero structured palladium-platinum core-shell nanocubes for use in a nonenzymatic amperometric glucose sensor

Hetero structured Pd-Pt core-shell nanocubes (NCs) are shown to display catalytic activity in the glucose oxidation reaction (GOR), and were employed as non-enzymatic glucose sensors in 0.1 M NaOH(aq) solution. High-angle annular dark-field transmission electron microscopy and line-scanned energy-dispersive X-ray spectroscopy analyses show that the growth of the Pt shell initially occurs via a layer-by-layer mode, but then switches to the island mode. The voids formed between Pt islands contribute to an increase in the electrochemically active surface area. Based on the same catalyst loading mass, the results of Tafel measurements and cyclic voltammetry indicate that the hetero structured Pd-Pt core-shell NCs (typically 32.7 nm in size) display an exchange current density of 1.81 × 10⁻² mA cm⁻² for chemisorption and dehydrogenation of glucose at the onset of the GOR, and an activity of 0.322 mA in the subsequent reaction that causes the formation gluconolactone on the Pt-OH surface. These values are larger than those observed for 7.5-nm Pt nanoparticles (1.51 × 10⁻² mA cm⁻² and 0.187 mA cm^-2, respectively). Additionally, the core-shell NCs exhibit a sensitivity of 170 μA∙mM⁻¹∙cm⁻² under GOR catalysis conditions, require a potential as low as −0.05 V (vs. Ag/AgCl) which favors selectivity, and have a linear response range that extends from 0.3 to 6.8 mM. The potential of these NCs for use in non-enzymatic sensing of glucose is further exemplified by a successful analysis of spiked calf serum. In our perception, this sensor also has a large potential in glucose fuel cells. (author)