Tuning selectivity of electrochemical sensors with polymer coatings

Electrochemical sensors are promising for health monitoring due to their repeatability and sensitivity, particularly when nanostructured. Yet, their translation into real applications is hindered by limited selectivity in the absence of specific binding receptors: many biomarkers exhibit similar oxidation potentials, producing overlapping voltammetric signals that impede molecular discrimination. Here, we demonstrate that the oxidation potential of several small-molecule biomarkers can be controlled through polymeric coatings, specifically poly(4-vinylpyridine), deposited onto glassy carbon electrodes. The polymer coating alters diffusion and adsorption characteristics, which ultimately lead to oxidation potential shifts of ascorbic acid and serotonin, enabling their separation of otherwise overlapping signals. These findings are supported by Chronocoulometry and Fourier-transform infrared spectroscopy analysis that reveal changes in diffusion coefficient, adsorbed charge, and hydrogen bonding that are likely responsible for the altered sensor performance. Moreover, this approach can be expanded to further polymers and biomarkers, including estradiol and melatonin. Finally, we demonstrate that the same selectivity trends persist on nanostructured, stretchable carbon-flower electrodes, where the high surface area further enhances sensitivity. Collectively, these findings reveal polymer-controlled peak-potential tuning as a powerful and broadly applicable route toward highly selective electrochemical sensors, enabling molecular discrimination in complex mixtures and opening new avenues for sensor-array-based detection.