Diffusional depth profiling using electrochemiluminescence microscopy.

Introducing excess tris(2,2'-bipyridine)ruthenium(II) ([Ru(bpy)3]2+) enables electrochemiluminescence microscopy to access z-depth information as the emissive layer diffuses away from the electrode.

• Why it matters: Conventional ECL relies on coreactant in large excess, confining signal near the electrode and limiting z-resolution, which makes 3D imaging difficult.
• What they did: The authors tune the [Ru(bpy)3]2+ to tri-n-propylamine (TPrA) concentration ratio to control emission-layer diffusivity, using simulations and scanning electrochemical microscopy to capture diffusion profiles.
• The result: As TPrA depletes, the mechanism shifts from heterogeneous oxidation to chemiluminescence, producing a time-extended emissive layer that enables diffusional depth profiling of spirulina algae and spheroid cell models.

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