[Ru(dcbpy)2dppz]2+/Fullerene Cosensitized PTB7‐Th for Ultrasensitive Photoelectrochemical MicroRNA Assay

A new cosensitization photoelectrochemical (PEC) strategy was established by using a donor–acceptor‐type photoactive material, 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), as a signal indicator, which was cosensitized with bis(4,4′dicarboxyl‐2,2′‐bipyridyl)(4,5,9,14‐tetraazabenzo[b]triphenylene)ruthenium(II) ([Ru(dcbpy)2dppz]2+) embedded in the grooves of the DNA duplex and fullerene (nano‐C60) immobilized on the surface of DNA nanoflowers for microRNA assay. [Ru(dcbpy)2dppz]2+ and nano‐C60 could effectively enhance the photoelectric conversion efficiency (PCE) of PTB7‐Th as a result of well‐matched energy levels among nano‐C60, [Ru(dcbpy)2dppz]2+ and PTB7‐Th, leading to a clearly enhanced photocurrent signal. Meanwhile, a target recycling magnification technique based on duplex‐specific nuclease was applied in this work to obtain higher detection sensitivity. The proposed biosensor demonstrated excellent analytical properties within a linear detection range of 2.5 fm to 2.5 nm and a limit of detection down to 0.83 fm. Impressively, this cosensitization PEC strategy offers an effective and convenient avenue to significantly improve the PCE of a photoactive material, resulting in a remarkably improved photocurrent signal for ultrasensitive and highly accurate detection of various targets. Into the groove: A cosensitization photoelectrochemical (PEC) strategy was established by using a donor–acceptor‐type photoactive material with a ruthenium complex and fullerene (see figure). The ruthenium complex is embedded in the grooves of the DNA duplex and fullerene is immobilized on the surface of DNA nanoflowers for microRNA assay.