Sensitive and selective photoelectrochemical immunosensing platform based on potential-induced photocurrent-direction switching strategy and a direct Z-scheme CdS//hemin photocurrent-direction switching system

Abstract

Herein, we develop a novel ultrasensitive and selective photoelectrochemical (PEC) immunosensor based on a potential-induced photocurrent-direction switching of the CdS-chitosan nanoparticles (CdS-CS NPs) and a direct Z-scheme CdS/hemin photocurrent-direction switching system. Taking the detection of Prion (PrPC) as example, the CdS-CS NPs served as photoactive materials showed a cathodic photocurrent by the potential-stimulated switching of the photocurrent direction strategy, after immobilization of the captured antibody of PrPC (Ab1) onto the surface of CdS-CS NPs, nitrogen-doped porous carbon (NPC)-hemin polyhedra labelled with secondary antibody of PrPC (Ab2) were subsequently introduced onto the immunosensing interface due to the antigen−antibody specific recognition, and could act as a photocurrent-direction converter of CdS-CS NPs to produce a big anodic photocurrent which was opposite to that of CdS-CS NPs, owe to the well-matched energy levels between CdS and hemin to form a direct Z-scheme CdS/hemin system. By coupling the potential-stimulated switching of the photocurrent direction strategy and direct Z-scheme photocurrent-direction switching system, PrPC was detected sensitively with a wide linear response range from 4 to 1000 aM and a low detection limit of 0.53 aM. Also, the developed PEC immunosensing platform showed excellent selectivity. Going beyond the conventional “signal-off” or “signal-on” driven immunosensor, this strategy may has promising applications in bioanalysis, disease diagnostics, and clinical biomedicine.