High efficiency electrochemiluminescence of 3D porous g-CN with dissolved O as co-reactant and its sensing application for ultrasensitive detection of microRNA in tumor cells.

In this work, the electrochemiluminescence (ECL) phenomenon of three-dimensional graphitic carbon nitride (3D g-CN) was reported. Firstly, the proposed 3D g-CN possessed 3D porous interconnected open-framework which enabled faster charge transport and efficient penetration of co-reactants due to "pore confinement effect". Then, we found that the dissolved O could serve as an excellent co-reactant for cathodic ECL of 3D g-CN. And the high specific surface area was beneficial to better adsorbing and gathering of dissolved O and reactive oxygen species (ROSs), which made them full contact on the surface or inside of 3D g-CN, giving a more sufficient ECL reaction and higher ECL signal. Based on the proposed 3D g-CN-O ECL system, a sensitive biosensor was constructed for microRNA-21 (miRNA-21) detection with assistance of 3D spherical tracks assisted 3D DNA walking machine, which exhibited superior performance for miRNA-21 with detection limit of 0.22 fM. The proposed 3D g-CN-O ECL system with high ECL efficiency and the effective target conversion and amplification strategies were beneficial to construct ultra-sensitive ECL sensing platform, which would be better applied to clinical bioanalysis.