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.