A versatile photoelectrochemical biosensor based on in-situ grown 2D COFs film for sensitive detection of Hg2+ and aflatoxin B1

A versatile photoelectrochemical (PEC) biosensor was constructed based on two-dimensional covalent organic frameworks (COFs) film composed of tris(4-aminophenyl)amine and 1,4-phthalaldehyde connected through imine bonds (TA-P COFs) was grown in situ on the electrode surface under mild conditions for detecting mercury ion (Hg2+) and aflatoxin B1 (AFB1). This strategy easily conquers the main predicaments of traditional PEC biosensor stability and detection accuracy: limited the photoelectric material easy to fall off the electrode surface and the low photoelectric conversion efficiency. [Display omitted] •The method of synthesizing COFs at room temperature not only had mild reaction conditions, but also greatly shortened the reaction time.•The COFs film obtained by in-situ growth was easier to adhere to the electrode surface, resulting in accelerating the charge transfer between the electrode and the material interface.•The enzyme-assisted amplification and chain replacement strategies triggered by targets increased Hg2+ and AFB1 conversion efficiency.•The “ON-OFF-ON” PEC biosensor realized the sensitive detection of Hg2+ and AFB1. Herein, a highly stable and low-toxic photoelectrochemical (PEC) biosensor was constructed based on two-dimensional covalent organic frameworks (COFs) film composed of tris(4-aminophenyl)amine and 1,4-phthalaldehyde connected through imine bonds (TA-P COFs) was grown in situ on the electrode surface under mild conditions for detecting mercury ion (Hg2+) and aflatoxin B1 (AFB1). Impressively, the TA-P COF film adhered to the electrode surface through in-situ growth not only accelerated the charge transfer between the interfaces, but also improved the stability of the biosensor, further improving the accuracy of detection. Accordingly, when the cyclic amplification process was triggered in the presence Hg2+ to generate a large amount of output DNA, the signal probe with abundant quencher porous carbon hollow spheres s (PCHS) was modified on the electrode surface through the output DNA for the signal “OFF” detection of Hg2+. Meanwhile, due to the specific binding of the target to the aptamer, the released hairpin DNA 2 (H2) signal probe was modified on the electrode surface through base complementary pairing to achieve the signal “ON” detection of AFB1. The suggested multifunction biosensor achieved sensitive detection of Hg2+ in the range of 10 fM–100 nM and AFB1 in the range of 10 fg mL−1–10 ng mL−1, which showed great practical a