Abstract:
A hydrogen peroxide (H2O2) sensor and biosensor based on modified multi-walled carbon nanotubes (CNTs) with titanium dioxide (TiO2) nanostructures was designed and evaluated. The construction of the sensor was performed using a glassy carbon (GC) modified electrode with a TiO2-CNT film and Prussian blue (PB) as an electrocalatyzer. The same sensor was also employed as the basis for H2O2 biosensor construction through further modification with horseradish peroxidase (HRP) immobilized at the TiO2-fCNT film. Functionalized CNTs (fCNTs) and modified TiO2-fCNTs were characterized by Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR), and X-Ray DifFraction (XRD), confirming the presence of anatase over the fCNTs. Depending on the surface charge, a solvent which optimizes the CNT dispersion was selected: dimethyl formamide (DMF) for fCNTs and sodium dodecylsulfate (SDS) for TiO2-fCNTs. Calculated values for the electron transfer rate constant (ks) were 0.027 s-1 at the PB-fCNT/GC modified electrode and 4.7 × 10-4 s-1 at the PB-TiO2/fCNT/GC electrode, suggesting that, at the PB-TiO2/fCNT/GC modified electrode, the electronic transfer was improved. According to these results, the PB-fCNT/GC electrode exhibited better Detection Limit (LD) and Quantification Limit (LQ) than the PB-TiO2/fCNT/GC electrode for H2O2. However, the PB film was very unstable at the potentials used. Therefore, the PB-TiO2/fCNT/GC modified electrode was considered the best for H2O2 detection in terms of operability. Cyclic Voltammetry (CV) behaviors of the HRP-TiO2/fCNT/GC modified electrodes before and after the chronoamperometric test for H2O2, suggest the high stability of the enzymatic electrode. In comparison with other HRP/fCNT-based electrochemical biosensors previously described in the literature, the HRP-fCNTs/GC modified electrode did not show an electroanalytical response toward H2O2.