Observation of Desorption and Direct Electron Transfer Reaction of Cytochrome on Bare ITO Electrode with Electrochemical Slab Optical Waveguide Spectroscopy.

Cyclic voltammograms (CVs) of cytochrome (cytc) on the bare ITO were measured with every 10 times of the continuous the solution exchange (SE) processes at the same time of slab optical waveguide (SOWG) spectral observation, and it was proved that direct electron transfer (DET) reaction functionality of cytc adsorbed on the bare ITO electrode was kept after 100 times SE processes. The existence of three kinds of cytc molecules which were weakly adsorbed, strongly adsorbed and immobilized on the bare ITO electrode below a monolayer coverage was indicated from the change in the Soret band absorbance at 408 nm due to the desorption reaction of cytc with observation by electrochemically controlled SOWG spectroscopy. As the actual procedure, 100 times of the SE process in the SOWG cell by hands induced the gradual decrease of the absorbance due to cytc desorption, and with every 10 times of the SE process SOWG absorption spectra were obtained. The SOWG absorbance decay curve was well fitted with two components exponential equation depending on the SE process numbers showing that around 31.6% of the cytc molecules adsorbed on bare ITO electrode were finally immobilized.