Sensitive photoelectrochemical detection of Hg2+with low background noise

Herein, a sensitive photoelectrochemical (PEC) biosensor with low background noise for the detection of the potential heavy metal pollutant mercury ion (Hg2+) was developed based on the Nb.BtsI-assisted Hg2+ cycle strategy as the signal amplification channel and the methylene blue (MB)-double stranded DNA (dsDNA) intercalation complex as the PEC signal indicator. When a trace of target Hg2+ was present, a multitude of output DNA (S2) were released from the preformed reaction platform Au@Fe3O4-H1 through the process of Nb.BtsI-assisted Hg2+ cycling, which greatly amplified the input signal of Hg2+ and thus significantly improved the detection sensitivity of this PEC biosensor. The released S2 could be captured by the 1-hexanethiol (HT)/S1/gold nanoparticles (Au NPs)-engineered biosensing interface to generate steady dsDNA (S1/S2) for embedding numerous photoactive substance MB by pi-pi stacking, giving rise to the formation of the MB-dsDNA intercalation complex. As a unique PEC signal indicator, the MB-dsDNA intercalation complex could produce significant PEC signals for quantitative determination of Hg2+ from 100 fM to 100 nM. Notably, the introduction of photoelectric signal indicator made the PEC biosensor embrace low background noise and negligible false positive signal, thereby producing the highly enhanced of sensitivity and accuracy. With the assistant of the Nb.BtsI-assisted Hg2+ cycle strategy and the MB-dsDNA intercalation complex, the developed biosensor possessed high sensitivity and excellent accuracy for Hg2+ with a low detection limit of 33.3 fM, demonstrating that the proposed sensing platform was provided with a great application prospect in the field of monitoring and control of environmental pollution concerning Hg2+.