Ultrasensitive detection of doxycycline enabled by oxygen vacancy modulated TiO₂ nanotubes

TiO₂ nanotubes rich in oxygen vacancies (Ov), which were successfully fabricated on Ti foils, were used as the working electrode of a photoelectrochemical (PEC) sensor. The TiO₂ nanotube electrode optimized with abundant Ov demonstrated a remarkable photocurrent density of 1.03 mA/cm², which is approximately 2.9 times higher than that of the TiO₂ nanotube electrode. When applied to the detection of DOC, this electrode exhibited a wide linear detection range spanning from 0.1 to 100 μM and achieved an exceptionally low detection limit of 0.043 μM with a signal-to-noise ratio of 3. Furthermore, comparative experiments indicated that the Ov-enriched TiO₂ nanotube electrode exhibited excellent anti-interference capabilities and long-term stability, ensuring the accuracy and reliability of the detection outcomes. The superior detection performance is primarily attributed to two aspects: on one hand, Ov act as electron traps, facilitating the capture and transfer of photogenerated electrons, effectively prolonging the lifetime of these carriers; on the other hand, Ov also serves as active sites, enhancing the adsorption of DOC molecules and reaction kinetics, further amplifying the detection signal. This work offers a theoretical and experimental groundwork for the rapid monitoring of residual antibiotics.