Non-enzymatic glucose sensing based on hierarchical platinum micro-/nanostructures

Abstract

Non-enzymatic glucose monitoring for biomedical applications asks for long-term stable and selective sensors at neutral pH. A hierarchical platinum micro-/nanostructured electrode along with a novel measurement scheme leads to increased sensitivity, selectivity and stability compared to state-of-the-art. The hierarchical electrode coating was applied by a scalable two-step process, which combined electrochemical deposition and colloidal synthesis to obtain a hierarchical structure with high surface roughness. This three-dimensional structure consists of a cauliflower-like platinum deposition, which is coated by a platinum nanowire network. Amperometric glucose measurements showed a 10,000-fold increase in sensitivity (473 μA cm−2 mM−1) compared to unmodified electrodes and linear behavior in the physiological range. The obtained sensitivities are among the highest values reported for non-enzymatic glucose sensors in neutral pH media. The hierarchical morphology provides a selectivity mechanism depending on the reaction kinetics, improving the selectivity for glucose in the presence of the interferent ascorbic acid 2000-fold. Selectivity was further enhanced by low-frequency electrochemical impedance spectroscopy (EIS). Chronoamperometric protocols were developed to achieve long-term stability and overcome the loss of sensitivity due to electrode poisoning. Using chronoamperometric protocols for both the amperometry and the EIS measurements improved stability significantly. The presented results make hierarchical platinum micro-/nanostructured electrodes a promising candidate for continuous glucose monitoring.