Voltage-switchable detection of H2O2 and 4-nitrophenol with reduced graphene oxide titanium dioxide composite

Abstract

A facile eco-friendly, simple and cost-effective two-step approach for synthesizing rGO–TiO₂ nanocomposite was explored for the potential switched nonenzymatic detection of hydrogen peroxide (H₂O₂) and 4-nitrophenol. Morphological studies of the nanocomposite revealed the formation of uniform nanoflakes. Electrochemical measurements showed enhanced electrocatalytic performance with low barrier electron transfer between the redox centers of each analyte and the electrode surface. The sensor demonstrated a wide linear detection range from 2.7 nM to 27 nM (R² = 0.99) for H₂O₂ and 22 nM to 224 nM for 4-NP using cyclic voltammetry (CV). The detection limits were determined to be 2.7 nM for H₂O₂ and 20 nM for 4-NP. The rGO–TiO₂ nanocomposite electrode shows an increased sensitivity of 3.3632 A L mol⁻¹ cm⁻² and 21.97 A L mol⁻¹ cm⁻² for H₂O₂ and 4-NP, respectively. The rGO–TiO₂ hybrid electrode utilized different operational potentials for each analyte, which may lead to a voltage-switchable dual-analyte sensor with higher selectivity. rGO–TiO₂ also demonstrated good reproducibility, linear response range and limit of detection for both analytes. In addition, the clinical significance of the nanocomposite was tested for H₂O₂ in milk samples and 4-NP in water samples, which showed a percentage recovery close to 100. These results indicate that rGO–TiO₂-based hybrid nanocomposite is a promising choice for a nonenzymatic biosensor due to its enhanced electrocatalytic activities.