Peroxide Electrochemical Sensor and Biosensor Based on Nanocomposite of TiO₂ Nanoparticle/Multi-Walled Carbon...

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.