Enhanced photoelectrocatalytic H2O2 detection in cell culture media via electrochemically induced oxygen vacancies and Ti3+ sites in fluoride-free anodic TiO2.

Accurate detection of hydrogen peroxide (H2O2), a key regulator in cellular signaling and disease progression, remains challenging due to its low concentration and high reactivity. In this study, a photoelectrochemical (PEC) sensor based on defect-engineered, fluoride-free anodic TiO2 nanotube arrays was developed for sensitive H2O2 detection. Ordered TiO2 nanotubes were prepared via electrochemical anodization and annealing, followed by electrochemical reduction to introduce oxygen vacancies and Ti3+ defects. Characterization confirmed that the nanotube structure and anatase phase were retained, while defect density increased with reduction time, leading to enhanced conductivity, charge separation, and PEC activity. The optimized sample (TiO2-600-r150) exhibited the highest photocurrent response, indicating an optimal defect concentration. It demonstrated a linear detection range up to 0.7 mM, with a sensitivity of 76.49 μA mM-1 cm-2 and a detection limit of 14.0 μM. Additionally, the sensor showed excellent selectivity and maintained stable performance in diluted cell culture media. These results highlight the critical role of defect engineering in improving PEC performance and demonstrate the potential of TiO2-based sensors for reliable H2O2 detection in biological systems.