A "super-off" photoelectrochemical biosensor based on Cu-BTC nanozyme quenching strategy for the detection of dibutyl...

Ultrasensitive detection of phthalic acid (PAEs) is an extremely critical mission in environmental monitoring. We designed a "super-off" photoelectrochemical (PEC) biosensor by using MoO₃/Bi₂MoO₆ as photoanode and copper(II) benzene-1,3,5-tricarboxylate (Cu-BTC) nanozyme as highly efficient signal quencher. It was found that the PEC signal of MoO₃/Bi₂MoO₆ photoelectric material is very sensitive to the concentration of co-reactor H₂O₂. Therefore, a target-triggered endonuclease-assisted recycle was employed to convert the target DBP into amount of output DNA, which can trigger the assembly of DNA nanonet for the immobilization of Cu-BTC nanozyme. Thanks to the peroxidase-like activity of Cu-BTC, a "super off" photocurrent was observed due to the consumption of electron donor H₂O₂ in the electrolyte. Compared with the traditional quenching strategies such as steric hindrance and light energy competition, this enzymatic reaction on the electrode interfaces is more effective to induce the distinct decrease of photocurrent for analysis. Ultimately, the constructed PEC sensor exhibited a broad linear range from 1 fM to 100 nM and a detection threshold of 0.3 fM. This work highlights the significance of using peroxide-mimic enzyme as a signal amplifier in PEC sensing platform for environmental monitoring.