A sensitive label-free photoelectrochemical aptasensor based on a novel PTB7-Th/H2O2 system with unexpected photoelectric performance for C-reactive protein analysis

Herein, a sensitive label-free photoelectrochemical (PEC) aptasensor was constructed for C-reactive protein (CRP) analysis based on a novel and efficient poly{4,8-bis[5-(2-ethylhexyl) thiophen-2-yl]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl-alt-3-fluoro-2-[(2-ethylhexyl)carbonyl] thieno[3,4-b]-thiophene-4,6-diyl} (PTB7-Th)/H2O2 system with unexpected photoelectric performance. The proposed PTB7-Th/H2O2 system without any sensitizer could surmount defect of the poor photoelectric conversion efficiency of PTB7-Th, leading to the unexpected 10-fold photocurrent enhancement compared to the common PTB7-Th/PBS system. The strong enhancement effect might originate from the special function of hydrogen peroxide (H2O2) towards PTB7-Th. On the one hand, H2O2 as electron acceptor could continuously capture photogenerated electrons located at acceptor part of PTB7-Th, which would visibly improve the charge separation efficiency of PTB7-Th and the electron-receiving property of electrolyte solution, thus leading to the obviously enhanced photoelectric conversion efficiency (PCE). More importantly, H2O2 as oxidant could oxidize PTB7-Th to obtain oxidation product of PTB7-Th (OPP) with carbonyl group and carboxyl group, and the electron cloud density in donor part of the OPP was higher than that of PTB7-Th, therefrom producing the stronger electron-donating property and higher photoelectrochemical (PEC) reaction efficiency. As a proof of concept, the proposed PTB7-Th/H2O2 system was successfully applied in the construction of a label-free PEC aptasensor for sensitive analysis of CRP, which performed a wide detection range from 1 pM to 1000 nM with a low detection limit of 0.33 pM. This study demonstrated a novel approach to the rational design of photoelectric conversion system with high PEC performance and provided an inspired tack for the construction of high-efficiency photoelectric devices.