Improvement of laccase biosensor characteristics using sulfur-doped TiO₂ nanoparticles

The search for new nanoscale materials with predictable properties to target the timely and fast detection of toxic components in wastewater is one of the most promising directions of modern biosensorics. We have shown that TiO₂ nanoparticles modified with sulfur significantly improve the main operational parameters of laccase-based electrodes when compared with controls. The nanoparticle samples were labeled as TiO₂S(0.75), TiO₂S(1.5), and TiO₂S(3.0), in which the numbers in parentheses refer to the quantity of H₂SO₄ (mL) used in the synthesis. The nanoparticles and enzyme were immobilized by means of Nafion film formed on a carbon rod electrode. It was shown that the modification of Nafion film by TiO₂ or TiO₂S(1.5) nanoparticles does not affect the size of the nanocavities and defect structure of the main polymer matrix as revealed by positron annihilation spectroscopy. It testifies that the structural-morphological difference between the film samples is rather small, and the improving of the sensor operational parameters for TiO₂S(1.5)-based laccase electrodes is connected only with the impact of sulfur doping, but not the difference in membrane properties. The developed bioelectrodes were tested for phenol analysis in real communal wastewater samples spiked with these analytes, demonstrating the high accuracy of the assay.