Improved sensitivity of photoelectrochemical sensors based on field-effect transistors with variable extending gate electrodes

It is an innovative research field to develop highly sensitive photoelectrochemical (PEC) sensors by introducing transistors. Herein, we proposed extended gate field effect transistors-based PEC sensors (EGFET-based PEC sensors) to improve the sensitivity of PEC sensors in comparison to the traditional three-electrode system-based PEC sensors (TES-based PEC sensors) mostly reported in current publications. The 3D TiO 2 nanotube arrays, g-C 3 N 4 /TiO 2 and Ti 3 O/TiO 2 heterojunctions were fabricated as the sensing electrodes in both kinds of PEC sensors, respectively. Three sets of parallel experiments were conducted using these three photoactive materials with different structures to comprehensively study the effects of two kinds of sensors on the important sensing performance indicators. Interestingly, these two kinds of sensors have similar linear ranges, but the sensitivity of the EGFET-based PEC sensor is more than four times that of the TES-based PEC sensor, indicating that the former is more suitable for detecting analytes with trace concentration than the latter. Additionally, these PEC sensors all have great reproducibility and stability. Therefore, we suggest that EGFET-based PEC sensors show promising potential in the practical applications. With the special geometric advantage, EGFET-based PEC sensors may stimulate current research of PEC sensors on the trend for miniaturized, integrated and highly sensitive sensors.