In this work we have synthesized and characterized cadmium oxide (CdO) working electrodes for electrochemical studies of native biomolecules in aqueous systems. Electrodeposited CdO films were generated through application of a constant current (4.5 mA/cm2) to an indium-doped tin oxide (ITO) working electrode immersed in a 0.1 M cadmium chloride (CdCl2) solution and subsequently annealed at 450 ˚C for 1.5 h. X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy methods were employed to characterize deposited material. As proof of concept, cyclic voltammetry of redox dyes with CdO working electrodes was performed to determine their redox potentials. Azurin, a copper blue protein from Pseudomonas aerunginosa,and cytochrome c, a small heme protein purified from bovine heart, were among the metalloproteins investigated. A novel small volume (50 and 750 µL) cyclic voltammetry cell was employed that facilitates sample recovery. Cyclic voltammograms were recorded at 10 mV/s for each sample with a CdO working electrode, a saturated Ag/AgCl reference electrode (–0.044 V vs. SCE), and a platinum counter electrode in aqueous solutions containing 100 mM Tris buffer and 200 mM KCl.
References
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Figure 1. Small volume CV designed and used for metalloprotein analysis.