Universal Hydrogen-Treated TiO₂ Nanorod Array/Ti₂CO MXene PEC Aptamer Sensor Modulated by the Transport...

A semiconductor photoelectrochemical (PEC) aptamer sensor has been widely researched in recent years because of its broad application prospects. However, a universal PEC sensor has not been achieved, and its sensing mechanism based on a photogenerated carrier transfer process has yet to be elucidated. Herein, a novel hydrogen-treated TiO₂ nanorod array one-dimensional (1D)/Ti₂CO MXene two-dimensional (2D) (H-TiO₂/Ti₂CO) PEC aptamer sensor is presented, which achieved a record detection range of 10^-9-10³ μg/L and a limit of detection (LOD) of 1 fg/L for microcystic toxins-LR detection. Besides, the PEC sensor can also test serotonin (5-HT), aflatoxin-B1, and prostate-specific antigen (PSA) with high performance by changing the aptamers, exhibiting favorable application universality. Furthermore, a new phenomenon of a switchable enhanced/suppressed photocurrent detection signal was discovered from H-TiO₂/Ti₂CO PEC aptamer sensors through the variation of the length of the TiO₂ nanorod. Meanwhile, it reveals that the steric hindrance effect determines the photogenerated hole transfer and depolarization processes, which is proposed for the first time as the predominant mechanism of the switchable enhanced/suppressed photocurrent signal for PEC sensors, giving possibilities to develop PEC sensors with higher efficiency.