FTO supported Co3O4 thin film biosensor for detection of fructose
Electrochemical and non-enzymatic fructose detection has evoked keen interest in the scientific literature. Several authors have reported on different methods of electrode preparation for fructose sensors. However, little systematic study has been conducted to design a cheap, efficient method of depositing metal oxides to detect fructose. To address the challenge, a Co3O4 thin film was fabricated using a simple solution step deposition on Fluorine doped Tin oxide (FTO) glass electrode. In this study, a report on the selective oxidation of fructose on Co3O4 thin film electrode surface is presented. Electrode characterization was done using X-ray diffraction (XRD), High Resolution Transmission Electron Microscopy (HR-TEM), Scanning Electron Microscope (SEM), Atomic Fluorescence Microscopy (AFM), and Electrochemical Impedance Spectroscopy (EIS). All cyclic voltammetry (CVs) and chronoamperometry tests were carried out by the use of an AUTOLAB POTENTIOSTAT 302 N, controlled by Nova 2.0 software instrumentation using a customized 50 cm3 electrochemical cell. The cell consisted of a graphite rod as the counter electrode (CE), 3 M Ag/AgCl reference electrode (RE) and the fabricated Co3O4/FTO as the working electrode (WE). All experiments were carried out at 25±2 ⁰C. From the results, the constructed sensor exhibited two distinctive linear ranges in the ranges of 0.021 – 1.74 mM and from 1.74 - ~15 mM, covering a wide linear range of up to ~15 mM at an applied potential of +0.6V vs. Ag/AgCl in 0.1M NaOH solution. The sensor demonstrated a high, reproducible and repeatable sensitivity of 495 (lower concentration range) & 53 (higher concentration range) μA cm-2 mM-1 for a low R.S.D of 5 %. The Co3O4 thin film produced a low detection limit of ~1.7 μM for a signal to noise ratio of 3 (S/N = 3); a fast response time of 6s and long term stability. The repeatability and stability of the electrode resulted from the chemical stability of Co3O4 thin film. The study showed that the sensor was highly selective towards fructose compared to the presence of other key interferences i.e. AA, AC, and UA. Because of such a favourable electrocatalysis of the Co3O4 sensor towards fructose, the ease of the electrode fabrication and reproducibility makes it a future candidate for commercial applications in the food and beverages sector.