Simultaneous Noncontact Topography and Electrochemical Imaging by SECM/SICM Featuring Ion Current Feedback Regulation

Abstract

We described a hybrid system of scanning electrochemical microscopy (SECM) and scanning ion conductance microscopy (SICM) with ion current feedback nanopositioning control for simultaneous imaging of noncontact topography and spatial distribution of electrochemical species. A nanopipette/nanoring electrode probe provided submicrometer resolution of the electrochemical measurement on surfaces with complex topology. The SECM/SICM probe had an aperture radius of 220 nm. The inner and outer radii of the SECM Au nanoring electrode were 330 and 550 nm, respectively. Characterization of the probe was performed with scanning electron microscopy (SEM), cyclic voltammetry (CV), and approach curve measurements. SECM/SICM was applied to simultaneous imaging of topography and electrochemical responses of enzymes (horse radish peroxidase (HRP) and glucose oxidase (GOD)) and single live cells (A6 cells, superior cervical ganglion (SCG) cells, and cardiac myocytes). The measurements revealed the distribution of activity of the enzyme spots on uneven surfaces with submicrometer resolution. SECM/SICM acquired high resolution topographic images of cells together with the map of electrochemical signals. This combined technique was also applied to the evaluation of the permeation property of electroactive species through cellular membranes.

Characterization of Nanopipettes

“…2,3 While the simplest nanopipettes contain just a single channel, multichannel devices are also possible, which increases the versatility of nanopipettes for nanoscience applications. 4,5 The channels can be open 5,6 (filled with electrolyte and a control electrode) or functionalized with deposited carbon, for example, to produce ultramicroelectrodes (UMEs) 7,8 that can also be further functionalized [9][10][11] to tune the sensory properties. Nanoelectrodes can also be fabricated by electrochemically plating nanopipettes with a variety of different metals.…”

Fabrication and Characterization of Dual Function Nanoscale pH-Scanning Ion Conductance Microscopy (SICM) Probes for High Resolution pH Mapping

“…Various SICM based positioning strategies have been developed over the years, to expand the range of substrates open to study. Moreover, the technique has been combined with complementary techniques including SECM [29][30][31][32] and near field scanning optical microscopy to enhance the information content. 33 Herein, we present an extremely quick and simple method to fabricate a hybrid pH-SICM probe, with an iridium oxide-coated electrode for pH sensing and an SICM barrel for distance control.…”

Simultaneous Interfacial Reactivity and Topography Mapping with Scanning Ion Conductance Microscopy

“…[8][9][10][11][12][13] In essence, the operation of SICM is based on the detection of changes of the conductance current, flowing between two quasi-reference counter electrodes (QRCEs), one in a nanopipette filled with electrolyte and one in the bulk solution. The current magnitude is a measure of resistance of the pipette probe and the tip-to-substrate gap.…”