Oxygen vacancies enhanced photoelectrochemical aptasensing of 2, 3', 5, 5'-tetrachlorobiphenyl amplified with Ag3VO4 nanoparticle-TiO2 nanotube array heterostructure

This work proposed an enhancing mechanism of both oxygen vacancies (OVs) and the heterostructure for amplifying the photoelectrochemical (PEC) aptasensing signal. The OVs were formed by in situ electrochemical reduction of TiO2 nanotube arrays (TNTAs), and well-separated Ag3VO4 nanoparticles (NPs) were then deposited on the TNTAs. The band gaps and positions of these nanomaterials were evaluated by Tauc equation and Mott-Schottky plots to verify the formation of the heterojunction. The OVs and heterojunction greatly enhanced the visible light absorption and improved the charge separation of TNTAs. The amplified PEC signal could be quenched by the resonance energy transfer between Ag3VO4 NPs and gold nanorods (Au NRs), which were labeled on the complementary DNA (cDNA) to the aptamer immobilized on the heterojunction. Upon the recognition of the aptamer to target analyte, the Au NR-cDNA was detached from the sensor, leading to a “signal-on” aptasensing strategy. Under optimal conditions, the PEC aptasensor displayed a detection limit of 0.015 pg mL−1 and a linear range from 0.02 to 300 ng mL−1 for 2,3',5,5'-tetrachlorobiphenyl.