Abstract
The diversity of materials proposed for non-enzymatic glucose detection and the lack of standardized protocols for assessing sensor performance have caused considerable confusion in the field. Therefore, methods for pre-evaluation of working electrodes, which will enable their conscious design, are currently intensively sought. Our approach involved comprehensive morphologic and structural characterization of copper sulfides as well as drop-casted suspensions based on three different polymers—cationic chitosan, anionic Nafion, and nonionic polyvinylpyrrolidone (PVP). For this purpose, scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy were applied. Subsequently, comparative studies of electrochemical properties of bare glassy carbon electrode (GCE), polymer- and copper sulfides/polymer-modified GCEs were performed using electrochemical impedance spectroscopy (EIS) and voltammetry. The results from EIS provided an explanation for the enhanced analytical performance of Cu-PVP/GCE over chitosan- and Nafion-based electrodes. Moreover, it was found that the pH of the electrolyte significantly affects the electrocatalytic behavior of copper sulfides, indicating the importance of OHads in the detection mechanism. Additionally, diffusion was denoted as a limiting step in the irreversible electrooxidation process that occurs in the proposed system.
Highlights
The most practical and commercialized methods for the self-monitoring of diabetes are based on the electrochemical measurement of glucose levels
The calculated average diameter of 91 nm suggests significant surface development since the microflower size observed on the scanning electron microscopy (SEM) images was around 2.5 μm
Analysis of the results indicated that the highest electrochemically active surface area (EASA) of 50.98 mm2 possessed chitosan-modified glassy carbon electrode (GCE) (Figure S4a)
Summary
The most practical and commercialized methods for the self-monitoring of diabetes are based on the electrochemical measurement of glucose levels. A real breakthrough in point-of-care diagnosis was the proposal of direct electron transfer implemented by connecting electrically active enzyme sites with the electrode [1,2]. It triggered the emergence of a new path in bioactive molecule detection, which acquired the status of the fourth sensor generation. In this case, enzymes are substituted by nanomaterials, which are directly involved in glucose oxidation [3,4]. This approach offers the possibility to bypass some intrinsic limitations of enzymes, such as vulnerability to detergents and sterilization, demanding immobilization procedures, and activity changes due to temperature, pH, and humidity variations [1]
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