Electrochemical surface-enhanced Raman spectroscopic study of redox processes of solution species at electrode modified with the redox dye Meldola blue

• Redox state of Meldola blue layer at electrode can be estimated by Raman spectroscopy.
• Electrooxidation of ascorbate at Meldola blue modified electrode occurs via redox mediation.
• Formation of reaction product benzoquinone can be detected by Raman spectroscopy during electrooxidation of hydroquinone.

Gold electrodes modified with adsorbed or electropolymerized layers of the redox dye Meldola blue have been prepared and studied by Surface enhanced Raman spectroscopy (SERS) at 785 nm laser excitation. The intensity of SERS spectra obtained differ essentially for electrochemically oxidized and reduced layers of MB, both in pH 1.0 and pH 7.0 solutions studied. Electrooxidation of ascorbate at MB modified electrodes in pH 7.0 solution was studied, and it has been shown with in situ SERS spectroscopy that the relative content of oxidized and reduced forms of MB within adsorbed or electropolymerized layer depends on electrode potential and ascorbate concentration. Also, electrooxidation of hydroquinone at MB modified electrodes in pH 1.0 solution has been studied, and the formation of reaction product benzoquinone has been demonstrated with SERS spectroscopy. This process occurs faster at electrode modified with electropolymerized MB, and at higher concentration of hydroquinone.