Nanometer-Sized Electrochemical Sensors

Abstract

Nanometer-sized glass-sealed metal ultramicroelectrodes (UMEs) have been prepared using a laser-based micropipet puller. The tip was exposed to solution either by etching away a small portion of glass insulator or by micropolishing. The characterization of the UMEs was carried out by a combination of steady-state voltammetry, scanning electron microscopy (SEM), and scanning electrochemical microscopy (SECM). The cyclic voltammograms obtained have a regular shape with very small capacitive and resistive background. The effective electrode radii obtained from voltammetry were between 2 and 500 nm. From the SEM micrographs, the shape of polished tips appears to be close to a microdisk, while the geometry of etched electrodes is closer to conical. Accordingly, the SECM current-distance curves (i T -d) obtained with polished electrodes fit well the theory for a disk-shaped tip, while a 20-nm-radius etched electrode was shown to be a fairly sharp cone with a height-to-radius ratio of about 2.5. The experimental data were compared to the theory developed for disk-shaped, conical, and recessed tips to demonstrate suitability of the produced electrodes for quantitative electrochemical experiments. The prospects of steady-state measurements of the rates of fast heterogeneous reactions are discussed. Submicrometer-sized ion selective electrodes (ISEs) were prepared by coating etched Ag tips with silver iodide. The concentration response of such ISEs remained stable and linear after coating of the ISEs with protective Nafion film.

Topographical and electrochemical nanoscale imaging of living cells using voltage-switching mode scanning electrochemical microscopy

“…The reliable fabrication of nanoelectrodes with a small ratio of electrodeinsulation to active electrode (RG) is of particular importance to improve SECM spatial resolution (2). In particular, a variety of different approaches have been adopted to create small electrodes with thin insulating coats such as photolithography (3), chemical vapor deposition (4), electrodeposited paint methods (5,6), laser pulling techniques (7)(8)(9)(10)(11), and pyrolytic carbon deposition (12)(13)(14)(15). Photolithography and chemical vapor deposition can be used to make thin insulation layers, but pinholes are often a problem.…”

Métodos para fabricação de microeletrodos visando a detecção em microambientes

“…Estes instrumentos funcionam à base de aquecimento do capilar de vidro com resistências elétricas ou por laser [31][32][33] . Este último método possui vantagens, pois permite um controle mais apurado do aquecimento.…”

Peer Reviewed: Atomic Force Microscopy Probes Go Electrochemical

“…An ultramicroelectrode (UME) with micrometer dimensions usually serves as the imaging tip, but nanometer-sized electrodes are becoming more widespread (15)(16)(17). SECM is a solution-based technique, and the tip functions as either the working electrode in a dynamic electrochemistry circuit or as the indicator electrode in a potentiometric arrangement.…”