A label-free photoelectrochemical aptasensing platform base on plasmon Au coupling with MOF-derived In2O3@g-C3N4 nanoarchitectures for tetracycline detection

A label-free photoelectrochemical (PEC) aptasensor for tetracycline (Tc) detection was successfully fabricated, and plasmon Au coupling with MOF-derived In2O3@g-C3N4 nanoarchitectures (AuInCN) with excellent PEC performance was employed as matrix for the first time. The homogeneous In2O3 nanoparticles (In2O3 NPs) derived from MIL-68(In) precursor were synthesized via calcination in air. The g-C3N4 nanosheets provided a favorable substrate for the fine distribution of In2O3 NPs. The In2O3@g-C3N4 (InCN) heterojunction with compact interface and matching band structure, facilitated the separation and transfer of electron-hole pairs. The surface plasmon resonance (SPR) of gold nanoparticles (Au NPs) could improve the light absorption and the photoelectron transfer of the modified electrode. Meanwhile, the decorated cysteamine stabilized Au NPs were also adequate to immobilize the SH-terminated aptamer as a biorecognition unit, and Tc molecules could be trapped through the specific interaction with the immobilized aptamer. An enhanced PEC photocurrent was realized under visible light illumination, due to the oxidation of captured Tc by photo-generated holes. Thereby, the concentration of Tc could be detected by observing the changes of photocurrent signals. Under optimized conditions, the PEC aptasensor exhibited the linear range from 0.01 nmol L−1 to 500 nmol L−1, with a detection limit (S/N = 3) of 3.3 pmol L−1. The prepared PEC aptasensor demonstrated acceptable stability, specificity and reproducibility, indicating the potential applications for the detection of Tc.