Enhanced cathodic photocurrent derived from N-type S doped-Bi2WO6 nanoparticles through an antenna-like strategy for photoelectrochemical biosensor

The sensitivity of cathodic photoelectrochemical (PEC) biosensor is mainly limited by the weak photocurrent response of p-type semiconductors due to the intrinsic weak hole conduction and severe charge recombination. Herein, we developed an antenna-like strategy that can amplify 10-fold of the cathodic photocurrent without using of p-type semiconductor. Specifically, poly (3,4-ethyl-enedioxythiophene) (PEDOT) was used as photocathode to improve the migration of photo-generated electrons (e-) from the n-type S doped-Bi2WO6 (Bi2WO6-xSx) photoanode through the external circuit and therefore an amplified cathodic photocurrent can be obtained toward such an antenna-like strategy. We further demonstrated that the antenna-like effect is originated from the super electrical conductivity of PEDOT photocathode and the facilitated charge separation of Bi2WO6-xSx photoanode by S doping. As a proof of concept, a self-powered dual-photoelectrode cathodic PEC biosensor driven by visible light was fabricated for microRNA-141 detection. Importantly, the biological recognition occurred at the photocathode could advance the anti-interference capability of the biosensor and show outstanding performance for microRNA-141 detection with a low limit of detection (LOD) of 0.3 fM. The antenna-like strategy offers a new method to amplify the cathodic photocurrent for sensitively PEC analysis.