Mapping Electrochemiluminescence as Generated at Double‐Band Microelectrodes by Confocal Microscopy under Steady State

Abstract

A confocal microspectrometer was used to collect spatially resolved electrochemiluminescence (ECL) spectra from the annihilation reaction between Ru(bpy)3+ and Ru(bpy)3(3+), each species being generated at a platinum band microelectrode and separated by a micrometric insulating gap. The use of a confocal microspectrometer allows in situ photon detection of the ECL reaction with micrometric spatial resolution and observes the concentration distribution of the photon source in the vicinity of the interelectrode gap.

Evaluation of the Chemical Reactions from Two Electrogenerated Species in Picoliter Volumes by Scanning Electrochemical Microscopy

“…[37] In this case, the annihilation reaction can be demonstrated because light emission is an indicator of chemical reactivity and because the distribution of such emission can be studied spatially, for example, at different distances between the generating electrodes, [37] or by optical sampling of the spatial emission profile. [38] The Irreversible Case…”

Confocal Microscopy Imaging of Electrochemiluminescence at Double Band Microelectrode Assemblies: Numerical Solution of the Inverse Optical Problem

“…However, the ECL intensity distributions recorded experimentally with a confocal microscope reveal significant distortions and specific features which disagree with the theoretical expectations (compare schematic in Figure 1 c with Figure 1 b), [5] even though the microscope optical resolution [9,10] was sufficient for not introducing severe distortions beyond a moderate enlargement of the real ECL peak width. [5] Furthermore, we did not notice significant changes in the signal shape upon decreasing the confocal volume below the size that was selected, except for the deterioration of the signal-tonoise ratio.…”

“…[5] Furthermore, we did not notice significant changes in the signal shape upon decreasing the confocal volume below the size that was selected, except for the deterioration of the signal-tonoise ratio.…”

“…For such devices, the possible asymmetry in the location of the emissive zone has been investigated, and there is a need for the development of original approaches to image in situ, the light field emitted. Recently, [5] we investigated the mapping of light generated in a two-band microelectrode assembly using a confocal microscope; the key idea was to take advantage of the true three-dimensional (3D) optical resolution provided by confocal microscopy obtained by actively suppressing any signal coming from out-of-focus planes using a pinhole in front of the detector. Using such a set-up allows light originating from an in-focus plane to be imaged by the microscope objective as it freely passes the pinhole, whereas the light coming from out-of-focus planes is largely blocked by the pinhole.…”

“…In the case of ECL [1][2][3][4][5][6][7][8] generated in a two-band microelectrode assembly [2,[4][5][6][7] probed with a confocal microscope (see Figure 1 a), one would expect a direct in situ monitoring of the distribution of light sources free from significant distortions owing to the high spatial resolution of such microscopes. According to theory, [2,[4][5][6][7] the ECL light intensity distribution should exhibit a Gaussian-type shape, with a maximum located over the middle of the interelectrode gap and decreasing rapidly and monotonically to the left and right from this central point so as to reach negligible values when-or even before-the scanning point passes above each inner electrode edge. The width of this ECL intensity peak is expected to in-A realistic theoretical model describing the outcome of confocal microscopic imaging of electrochemiluminescence (ECL) light emission is derived for a two parallel band microelectrodes assembly operated under steady state.…”