Steady-state luminescence spectroelectrochemistry

Luminescence spectroscopy (fluorescence or phosphorescence) is one of the relatively under explored areas of spectroelectrochemistry. This is surprising given the high sensitivity and selectivity of this technique, but may be due to the experimental difficulties in achieving 90° orientation between excitation and detector. Reports employing this spectroelectrochemical method have been inaeasing. 

Such an arrangement is analogous to the OTTLE experiment described for electronic spectroscopy. The working electrode is frequently a wire mesh such as gold, platinum, or a 

Nemst plots analogous to those in UV-vis spectroelectrochemistry are achievable using luminescence spectroelectrochemistry in which the concentrations of oxidized and reduced species are obtained by using the luminescence quantum yields of the analyte according to 

In the simplest spectroscopic description of the Nemst equation, the two redox states should not emit in the same spectral region. Since it is unusual for a single species to emit in two different oxidation states, this requirement is usually fulfilled in emission measurements and is a distinct advantage over absorbance measurements. In many instances, however, the oxidized or reduced form of the analyte can quench the luminescent precursor leading to lower intensity values. This can lead to serious errors in the apparent concentrations of the oxidized and reduced species and therefore the values derived from the Nemst plots. 

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An example which highlights both the steady-state and time-resolved aspects of luminescence spectroelectrochemistry is shown in Figure 14.18. This study reported a dinuclear ruthenium (II) complex bridged by dianionic bridge shown in the inset of the figure (49). 

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