Carbon-doped bimetallic oxide nanoflakes for simultaneous electrochemical analysis of ascorbic acid, uric acid, and acetaminophen in sweat

Abstract

Non-invasive continuous detection using tears or sweat as substitutes for blood samples has become an emerging method for real-time monitoring of human health. However, its development is limited by the low sample volume and low level of analytes. The simultaneous determination of multi-analytes with highly sensitive electrochemical sensing platforms has undoubtedly resulted in breakthrough innovations. Furthermore, the determination mode of multi-analyte combinations can accurately characterize the course of certain diseases. In particular, the simultaneous determination of ascorbic acid (AA), uric acid (UA), and acetaminophen (AC) in sweat will provide a one-stop detection system for cardiovascular and degenerative diseases for the entire course analysis. A sacrificial template strategy was adopted in this work using graphene oxide (GO) to guide the growth of two-dimensional Fe–Co composite nanoflakes with large specific surface areas. Defects were introduced via doping carbon through the incomplete pyrolysis of GO. The synthesized C-Fe_1.33Co_1.67O₄ exhibited massive redox sites and was highly reactive, which met the requirements for multi-substance analysis. The electrochemical sensor based on C-Fe_1.33Co_1.67O₄ accurately and sensitively demonstrated simultaneous detection of AA, UA, and AC in sweat, with a wide detection range for AA (4.0–11500 μM) and high sensitivity for UA and AC (304.5 μA mM⁻¹ and 404.1 μA mM⁻¹, respectively), along with low detection limit (1.69 μM for AA, 0.23 μM for UA, and 0.07 μM for AC). The sensor also possessed adequate mechanical flexibility, making it suitable for body surface detection, and its performance was maintained above 80% after high-intensity bending 350 times.