How to fit a response current-concentration curve? A semi-empirical investigation of non-enzymatic glucose sensor based on PANI-modified nickel foam

Abstract Linear relationships between current response and glucose concentration have long been preferred in studying non-enzymatic glucose electrochemical sensors. The relationships, however, are usually not linear in a wide concentration range. Under given conditions, solution diffusion coefficient is an important factor leading to the nonlinearity. Herein we analyzed the effect of glucose concentration ( c ) on solution diffusion coefficient and proposed a new simple sensing current response ( i ) equation for expressing the relationship between i and c derived from the Cottrell formula and the diffusion coefficient formula. The semi-empirical equation enables the relationship to be represented accurately over a wide glucose concentration range instead of having to be divided into two or more linear segments. For verifying its applicability, we fabricated a non-enzyme glucose sensing electrode with polyaniline-modified nickel foam (PANI/NF) by oxidant-induced in situ polymerization. An i-c curve of the electrodes has been investigated and the simple semi-empirical equation can exactly match the measurement within a c range from 1.0 μM to 20 mM, the total mean squared error for glucose solution is 0.000. In addition, the experiments of sensitivity, limit of detection, reproducibility and stability in 0.1 M NaOH all present satisfactory results, due to the 3D structure and plentiful surface active sites of NF, as well as the promotion of PANI for electrocatalytic glucose oxidation. Further, we prepared a PANI-hydroxyapatite-modified NF sensing electrode, and research results suggest that the semi-empirical equation is also appropriate for the three-component electrode system.