Zhao G, Giolando D M, Kirchhoff J R
Department of Chemistry, University of Toledo, Ohio 43606-3394, USA.
Anal Chem. 1995 Apr 15;67(8):1491-5. doi: 10.1021/ac00104a031.
Novel ring-disk ultramicroelectrodes (RD-UMEs) with analytical tip diameters as small as 25-30 microns were fabricated. Carbon RD-UMEs were reproducibly prepared by the chemical vapor deposition of alternating concentric layers of silica and carbon on resistively heated 10 microns carbon fibers. High-quality films with excellent adhesion at the interfaces between the carbon and silica layers were shown by electrochemical and scanning electron microscopy measurements. Electrochemical measurements of a solution of 1.0 mM ferrocene with 200 mM LiClO4 in CH3CN were used to characterize the single- and dual-electrode response lf the RD-UME. The electrochemical responses of the ring and the disk are sigmoidal in shape and indicated that radial diffusion is the primary mode of mass transport at each electrode at slow scan rates. Diffusion-controlled generation-collection experiments showed that the concentric dual-electrode configuration exhibits high collection efficiencies at the ring electrode with a 2-5 microns separation between electrodes and a 2-4 microns ring thickness. Close proximity of the ring and disk electrodes led to enhanced detection sensitivity due to back diffusion of regenerated molecules of a reversible redox couple from the collector to the generator electrode.
制备了尖端分析直径小至25 - 30微米的新型环形圆盘超微电极（RD - UMEs）。通过在电阻加热的10微米碳纤维上化学气相沉积交替的同心二氧化硅层和碳层，可重复地制备碳RD - UMEs。通过电化学和扫描电子显微镜测量表明，在碳层和二氧化硅层之间的界面处具有优异附着力的高质量薄膜。使用在乙腈中含有1.0 mM二茂铁和200 mM高氯酸锂的溶液进行电化学测量，以表征RD - UME的单电极和双电极响应。环形和圆盘的电化学响应呈S形，表明在慢扫描速率下，径向扩散是每个电极处质量传输的主要模式。扩散控制的生成 - 收集实验表明，同心双电极配置在电极间距为2 - 5微米且环厚度为2 - 4微米的环形电极处表现出高收集效率。由于可逆氧化还原对的再生分子从收集电极向发生电极的反向扩散，环形和圆盘电极的紧密接近导致检测灵敏度提高。
