Preparation of boron-doped diamond electrodes modified with copper-gold nanoparticles (CuAuNP) as oxygen sensors

Boron-doped diamond (BDD) electrodes are promising because they offer a wide electrochemical potential window, low background current, and good physical and chemical stability. In this study, to make them sensitive to dissolved oxygen, BDD electrodes were modified with copper-gold nanoparticles (CuAuNPs). A one-pot chemical reduction method was used to synthesize the CuAuNPs. Transmission electron microscopy revealed that the average diameter of the CuAuNPs was around 11 nm. The electrochemical behavior during oxygen reduction was characterized by cyclic voltammetry in a potential range from -1.0 to -1.5 V in a pH 7 phosphate-buffered saline solution containing various concentrations of the dissolved oxygen. The cyclic voltammograms showed that peaks corresponding to oxygen reduction occurred at -0.13 V. An approximately linear calibration curve was derived to correlate the peak current to the concentration of dissolved oxygen, indicating that the CuAuNP-BDD electrodes are promising for use as oxygen sensors. These electrodes can be readily applied to environmental monitoring, industrial safety, fuel cells, and automotive applications.