Fabrication of hierarchical MIL-68(In)-NH2/MWCNT/CdS composites for constructing label-free photoelectrochemical tetracycline aptasensor platform.

It is essential to develop a highly efficient detection platform for tetracycline (Tc). Herein, based on well-designed hierarchical MIL-68(In)-NH2/MWCNT/CdS composites as a highly efficient transducer, a label-free visible light driven photoelectrochemical (PEC) aptasensor was systematically fabricated. Characterization results indicate that the forming of MIL-68(In)-NH2/CdS heterojunction remarkable facilitated the transfer and inhibited the recombination of charge carriers. Moreover, the transfer properties of multiwalled carbon nanotubes (MWCNTs) further improved the photoelectric conversion efficiency by adjusting electron transport routes. The aptamer as a biorecognition unit was grafted on the modified electrode by chemical bonding effect, and Tc molecules could be captured through the specific interaction of aptamer and Tc in solution. The concentration of Tc was detected by observing the fluctuation of photocurrent signals. Under optimized conditions, the proposed aptasensor showed the broad linear range from 0.1 nmol L-1 to 1 μmol L-1 with a low detection limit (LOD) of 0.015 nmol L-1. Furthermore, the high sensitivity, excellent reproducibility and favorable stability of the PEC sensing platform indicated the potential applications for antibiotic residues detecting in environmental media.