ABSTRACT
We investigated sputtered nanocarbon films with respect to the effect of suppressing surface oxygen on their electrochemical properties. The nanocarbon film consisted of nanocrystallites with mixed sp2 and sp3 bonds formed by unbalanced magnetron sputtering. Ultraviolet/ozone (UV/O3) irradiation and electrochemical pretreatment (ECP) were conducted to change the surface oxygen concentration of nanocarbon film. X-ray photoelectron spectroscopy (XPS) measurements revealed that nanocarbon films with different amounts of surface oxygen could be prepared. In addition, we observed no significant increase of the surface roughness (Ra) at the angstrom level after treatments, owing to a stable structure containing 40% of sp3 bonds. The electrode characteristics, including the potential window and electrochemical properties for some redox species, such as Ru(NH3)63+/2+, were investigated. Some electrochemical measurements of zinc ions (Zn2+) and hydrogen peroxide (H2O2) showed that the electrochemical reaction was improved by suppressing the surface oxygen. These results clearly indicated that the low surface oxygen concentration plays an important role in these electrochemical reactions.
ABSTRACT
Bicontinuous microemulsion (BME)-based hydrogel films were integrated with screen-printed electrodes (SPEs) comprising working, counter, and reference electrodes to form stand-alone, semi-solid-state electrochemical systems that do not require an outer electrolyte solution. The gel network of the BME hydrogel only exists in the microaqueous phase and retains the structure of the entire BME gel. Following gelation, a microaqueous phase with sufficient ionic strength ensured effective ionic conductivity, even in thin gel films. This enabled the electrochemical reaction to proceed using a thin gel film as an electrolyte solution. However, an intact micro-oil phase with no gel network enabled efficient extraction from an external oil solution and exhibited rapid electrochemistry that was comparable to that of a BME solution. Cyclic voltammograms of lipophilic redox species in oil using the gel-integrated SPE system demonstrated successfully in the oil itself and in the air with dropped oil onto the system.
ABSTRACT
A nanocarbon film consisting of nanocrystallites with mixed sp2 and sp3 bonds formed by unbalanced magnetron sputtering, was studied with respect to changes in the characteristics caused by the surface oxygen concentration. An electrochemical pretreatment (ECP) was conducted to change the surface oxygen concentration of the nanocarbon film. X-ray photoelectron spectroscopy (XPS) measurements revealed that nanocarbon films with different amounts of surface oxygen could be prepared. In addition, we observed no significant increase of surface roughness (Ra) at the angstrom level after ECP, owing to a stable structure containing 40% of sp3 bonds. The electrode characteristics, including the potential window, and electrochemical properties for some redox species, such as Ru(NH3)63+/2+, Fe(CN)63-/4- and some biomolecules, were investigated. The anodic potential limit became wider and ΔEp of Fe(CN)63-/4- became smaller at the treated nanocarbon film electrode than those of the as-deposited nanocarbon film electrode. Based on these results, we realized to measure uridylic acid (UMP) and inosine triphosphate (ITP) with a high oxidation potential by direct oxidation, which was difficult to measure at the as-deposited nanocarbon film electrode.
