Potentiometric sensing is a relatively inexpensive and passive approach to evaluate the overall redox state of complex biological and environmental solutions. In this work, we report on potentiometric redox measurements in complex solutions containing one or more of the following biomolecules (ascorbic acid, uric acid, cysteine, NADH, or hydrogen peroxide) using platinum decorated nanoporous gold (NPG-Pt) electrodes. These electrodes have been shown to increase rates of electron transfer and reduce biofouling compared to traditional electrodes. This work focuses on the fabrication of platinum decorated nanoporous gold (NPG-Pt) electrodes by electrodeposition from solution containing potassium tetrachloroplatinate (II), 46-47% Pt at different times to optimize the percent platinum incorporated into the nanoporous gold framework (NPG).These electrodes were then used for the potentiometric sensing of a single redox molecule in a multicomponent complex mixture containing different redox molecules at different concentrations. The NPG surface area was reduced by ~10 %, ~30%, ~55% & ~70% by electrodepositing at a set potential for different periods. Scanning electron microscopy was used to observe the nanoporous framework of NPG & NPG-Pt. X-ray photoelectron spectroscopy (XPS) was used to determine the % Au, Pt and Ag in NPG as well as NPG-Pt electrodes. A linear dependence of open circuit potential (OCP) and the logarithmic concentration (e.g., Nernst-like behavior) was obtained for the single molecules in the complex mixture of three components avoiding the interference of the other two. We observe that NPG-Pt electrodes containing the highest amount of Pt showed the best response. This information is significant for measuring redox potentials in complex biological solutions.

Potentiometric sensing of a single biological redox molecule in a complex mixture of ascorbic acid, uric acid and biomolecules in microliter volumes using platinum_(Pt-) decorated nanoporous gold (NPG) electrodes

ACS Fall 2021

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