Selectivity enhancement of amperometric nitric oxide detection via shape-controlled electrodeposition of platinum nanostructures
Nitric oxide (NO) is a biologically multifunctional gaseous signaling molecule. For electrochemical NO detections, complex membranes are commonly adopted to acquire the selectivity for NO over other oxidizable biological species. In this study, we demonstrate the improved selectivity in amperometric NO measurements at nanostructured Pt. The Pt layers were electrodeposited on Au substrate electrodes at a constant potential (−0.2 V vs. Ag/AgCl) with a constant deposition charge (0.08 C). The various distinctive nanostructures of Pt deposits were obtained via either changing the precursor concentrations (from 5 to 75 mM K2PtCl4) or using a different precursor (75 mM H2PtCl6). With a higher K2PtCl4 concentration, the Pt deposition became less sharp and the smoothest Pt was deposited with 75 mM H2PtCl6. The most greatly sharp-pointed nanostructures were generated with the lowest precursor concentration (5 mM K2PtCl4) and exhibited the highest sensitivity, which was attributed to the hydrophobic property of sharply nanostructured Pt. A hydrophobic neutral gas molecule, NO, possibly has a more favorable access to the inner surface of more hydrophobic Pt deposition and eventually increases the oxidation current. NO current sensitivity was enhanced at the more hydrophobic Pt surface, whereas the oxidation currents of acetaminophen, L-ascorbic acid, nitrite and hydrogen peroxide, four oxidizable biological interfering species, were independent of the Pt nanostructure. Conclusively, the enhanced amperometric selectivity to NO was achieved by the simple electrodeposition method without any additional membranes.