Cosensitization Strategy with Cascade Energy Level Arrangement for Ultrasensitive Photoelectrochemical Protein Detection.

Here, a photoelectrochemical (PEC) biosensor was established by a cosensitization strategy with cascade energy level arrangement for ultrasensitive detection of prostate-specific antigen (PSA). The proposed cosensitization strategy was based on the well-matched energy level arrangement of four kinds of organic photoactive materials, in which 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) was used as the photoactive material and perylenetetracarboxyl diimide (PDI), fullerene (nano-C60), and polyaniline (PANI) were employed as the sensitizers. The resulting PTB7-Th/PDI/nano-C60/PANI cascade cosensitization structure with narrow energy level gradient (<0.54 eV) could effectively improve electron transfer capability, obviously raise light energy utilization and significantly enhance photoelectric conversion efficiency, leading to dramatically enhanced photocurrent response. Using PSA as a target model, the proposed PEC biosensor exhibited high sensitivity and excellent stability with a wide detection range from 1 fg/mL to 0.1 ng/mL and a detection limit of 0.43 fg/mL. Moreover, the proposed PEC biosensor provides a cascade cosensitization strategy that could significantly improve PEC performances and open up a promising platform to establish high selectivity, stability, and ultrasensitive analytical techniques.