g-C3N4/Porphyrin-based graphdiyne (PDY) 2D/2D heterojunction for the ultrasensitive photoelectrochemical detection of microRNA-21

As an n-type semiconductor material with a wide band gap, g-C3N4 has been applied in the photoelectrochemical (PEC) sensing field, while the narrow absorption light range and tendency of electron-hole recombination significantly limit its practical applications. In this study, we developed a new g-C3N4/porphyrin-based graphdiyne (PDY) 2D/2D heterojunction photoelectric nanocomposites via in-situ growth of PDY on the g-C3N4 nanosheets. The introduction of PDY significantly enhances the light capture ability of g-C3N4 in terms of absorbance and the absorption range throughout the entire UV-Vis region. More importantly, the well-matched band structure between PDY and g-C3N4 inhibits the electron-hole recombination to improve the charge separation efficiency. In addition, such 2D/2D heterojunction has a short charge transfer distance and a large contact area, further promoting the interfacial charge transfer. As a result, the PEC response of g-C3N4/PDY is 2.54 times higher compared with that of g-C3N4, enabling the ‘turn on’ PEC determination of miRNA-21 according to the sandwich-type sensing strategy, and the linear range of 0.01 fM-100 pM with a limit of detection (LOD) of 0.005 fM was achieved. Due to the diversity of graphdiyne monomers, we envision that the g-C3N4/PDY 2D/2D heterojunction carrying different graphdiyne-based materials may exhibit great potential in PEC sensing, photocatalysis, and solar cells.