A Flexible Highly Sensitive Non-Enzymatic Electrochemical Urea Sensor Based on Nonwoven Fabric That Uses Ag-Doped NiO

Transition metals, one of the many modifiers used in enzyme-free sensors, have received impressive attention among the various modification materials for urea electrochemical sensors with low cost. Textiles represent a flexible material for collecting sweat samples for non-invasive urea detection. In our study, we developed a nonwoven fabric-based modified carbon paste electrode using Ag-doped NiO (Ag/NiO) as a sensitive non-enzymatic electrochemical urea sensor. A variety of techniques were used to characterize synthesized Ag/NiO, including scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), electrochemical impedance spectroscopy (EIS), diffuse reflectance spectroscopy (DRS), and X-ray diffraction (XRD). The electrochemical properties of the Ag/NiO nanocomposite modified carbon paste on a textile electrode were studied using electrochemical impedance spectroscopy, cyclic voltammetry, and amperometry. The electrode was able to oxidize urea in alkaline solutions with high sensitivity, a wide linear range (2.5 × 10^–3 to 5 mM), a low detection limit (8 µM), long-term stability, and good selectivity. Finally, urea concentrations in human sweat samples and plasma were determined by the sensor.