Controlled electrodeposition of brookite TiO₂ for photoelectroanalysis at printed carbon electrodes

TiO₂-based photoelectrochemical (PEC) (bio)sensors have high photoactivity, chemical stability, and biocompatibility. However, their performance depends on multiple factors, including deposition method, morphology, and interaction with the target analyte. Herein, we describe a PEC platform based on TiO₂ electrodeposition directly onto printed carbon electrodes (without heat treatment), designed for point-of-care (POC) applications. Brookite TiO₂ nanocrystals were synthesized via electrodeposition in an acidic solution containing TiCl₃, and parameters such as pH and temperature were optimized to improve photoelectrocatalytic activity. Photoelectrooxidation of ascorbic acid (AA) with electrodes prepared under optimal conditions (pH 2.5, 80 °C) had 10.5 times higher photocurrents than electrodes modified with commercial TiO₂ nanoparticles via drop casting. The resulting sensor was highly sensitive and selective for AA, with a linear range from 10 to 1000 µM and a limit of detection of 3.25 µM (S/N = 3). Since brookite TiO₂ electrodeposition does not require thermal treatment, printed carbon electrodes on polymer substrates can be used in producing miniaturized devices for sensitive, selective PEC (bio)sensors.