Phase Modulation of Ti₃O/R-TiO₂ Nanocomposites for the Self-Powered Photoelectrochemical Sensing of Tetracycline

A self-powered photoelectrochemical (PEC) sensor based on a Ti 3 O/rutile TiO 2 (Ti 3 O/ R -TiO 2 ) heterophase junction nanocomposite is constructed for a highly sensitive and specific detection of tetracycline (TC). The Ti 3 O/ R -TiO 2 heterophase junction is successfully grown in situ on a Ti substrate via a one-step calcination method. XRD and Rietveld refinement results confirm that the contents of Ti 3 O and R -TiO 2 can be tuned by the adjustment of the calcination temperature. Benefiting from the improved generation and separation of photogenerated electron–hole pairs as a result of the introduction of metallic phase Ti 3 O and heterophase junction, the Ti 3 O/ R -TiO 2 photoelectrode prepared at 700 °C (Ti 3 O/ R -TiO 2 -700) and beyond presents much higher photocurrent density than the photoelectrode with pure R -TiO 2 under light irradiation. More importantly, a self-powered PEC sensor with good performance was constructed for TC detection by using Ti 3 O/ R -TiO 2 -700 as a photoelectrode. This PEC sensor displays a wide working range (3–300 μM) and a low detecting limit (0.039 μM) as well as good sensitivity. Additionally, a possible charge separation mechanism over the Ti 3 O/ R -TiO 2 heterophase junction is also proposed. This work provides valuable insight into the design and development of high-performance photoelectrodes through the modulation of crystal phases in nanocomposites for highly effective chemical sensors.