Bipolar simultaneously quenching in polarity-switchable photoelectrochemical biosensor for sensing lead ion

The development of sensitive and accurate analysis method for lead ions (Pb²⁺) detection is crucial and desirable for controlling environmental pollution. In this work, a photoactive CNCBO based polarity-switchable photoelectrochemical (PEC) biosensor with bipolar simultaneously quenching induced by Rhodamine B (RhB) decorated DNA tree has been proposed for sensing Pb²⁺. Specifically, the g-C₃N₄ sensitized by CuBi₂O₄ was designed to form the desiring photoactive material CNCBO that can generate a high initial cathodic photocurrent, accompanying by the reversed anodic photocurrent occurring with L-Cysteine (L-cys) as a polarity regulator. Afterwards, the incursion of target Pb²⁺ realized the cleavage on the Y-bracket DNA containing two hairpins with specific cleavage site, thereby leading to the in-situ generation of DNA trees for immobilizing massive of signal quenching molecules RhB. Interestingly, the DNA tree with a large spatial resistance caused obstacles to the electron flow while the quencher RhB absorbed photogenerated electrons, which can synergistical action on the photocurrent and thus obtained bipolar simultaneously quenching model with significantly enhanced sensitivity and accuracy, reflecting ultra-low detection limit of 0.05 fM toward Pb²⁺ and superior anti-interference ability in the detection of natural water samples. The present work focuses on environmental monitoring and intended to improve effectiveness and precision of the platform in environmental pollutants sensing via polarity-switchable detection method.