Direct imaging of electrochemical reactions at the single-molecule level is of potential interest in materials, diagnostic, and catalysis applications. Electrochemiluminescence (ECL) offers the opportunity to convert redox events into photons. However, it is challenging to capture single photons emitted from a single-molecule ECL reaction at a specific location, thus limiting high-quality imaging applications. We developed the nanoreactors based on Ru(bpy)32+-doped nanoporous zeolite nanoparticles (Ru@zeolite) for direct visualization of nanoconfinement-enhanced ECL reactions. Each nanoreactor not only acts as a matrix to host Ru(bpy)32+ molecules but also provides a nanoconfined environment for the collision reactions of Ru(bpy)32+ and co-reactant radicals to realize efficient in situ ECL reactions. The nanoscale confinement resulted in enhanced ECL. Using such nanoreactors as ECL probes, a dual-signal sensing protocol for visual tracking of a single biomolecule was performed. High-resolution imaging of single membrane proteins on heterogeneous cells was effectively addressed with near-zero backgrounds. This could provide a more sensitive tool for imaging individual biomolecules and significantly advance ECL imaging in biological applications.
Keywords: dual-signal imaging mode; electrochemiluminescence; nanoconfinement-enhanced emission; nanoreactor; single-molecule imaging.