Construction of a In2O3/ultrathin g-C3N4 S-scheme heterojunction for sensitive photoelectrochemical aptasensing of diazinon

Abstract

A single semiconductor-based photoelectrochemical (PEC) aptasensor usually faces a challenge of low sensitivity due to poor solar energy utilization and a high photogenerated carrier recombination rate. Herein, an ultra-thin carbon nitride nanosheet-coated In₂O₃ (In₂O₃/CNS) S-type heterojunction-based PEC aptasensor has been established to achieve highly sensitive detection of diazinon (DZN) pesticide in water environment. Construction of S-type heterojunction induces a band shift and an electric field effect, enhancing light utilization and accelerating directional transmission of carriers, leading to outstanding PEC performance. The creation of internal electric field at interface ensures stable carrier transport. Additionally, ultrathin CNS structure can effectively shorten the transport path of carriers. The close coating of In₂O₃ and CNS promotes the transfer of charge. The synergistic effects amplify the sensor's response, ultimately enabling the effective detection of DZN residue over a wide detection range (0.98 ∼ 980.0 pg mL^-1), a low detection limit (0.33 pg mL^-1, S/N = 3) and excellent accuracy in practical application (RSD < 5 %). This work provides a reference for the construction of a new S-type heterojunction-based PEC sensor.

Keywords: Carbon nitride; Diazinon; In(2)O(3); Photoelectrochemical aptasensor; S-type heterojunction.