Characterization of Nanopipet-Supported ITIES Tips for Scanning Electrochemical Microscopy of Single Solid-State Nanopores

Author(s)

Chen, Ran ^[1] ; Balla, Ryan J. ^[1] ; Lima, Alex ^{[2, 1]} ; Amemiya, Shigeru ^[1]

Affiliation

^[1] Univ Pittsburgh, Dept Chem, 219 Parkman Ave, Pittsburgh, PA 15260 - USA

^[2] Univ Sao Paulo, Inst Chem, Dept Fundamental Chem, Av Prof Lineu Prestes 748, BR-05508000 Sao Paulo, SP - Brazil

• Document type: Journal article
• Source: Analytical Chemistry; v. 89, n. 18, p. 9946-9952, SEP 19 2017.
• Web of Science Citations: 8

Abstract

Nanoscale scanning electrochemical microscopy (SECM) is a powerful scanning probe technique that enables high-resolution imaging of chemical processes at single nanometer-sized objects. However, it has been a challenging task to quantitatively understand nanoscale SECM images, which requires accurate characterization of the size and geometry of nanoelectrode tips. Herein, we address this challenge through transmission electron microscopy (TEM) of quartz nanopipets for SECM imaging of single solid-state nanopores by using nanopipet-supported interfaces between two immiscible electrolyte solutions (ITIES) as tips. We take advantage of the high resolution of TEM to demonstrate that laser-pulled quartz nanopipets reproducibly yield not only an extremely small tip diameter of similar to 30 nm, but also a substantial tip roughness of nm. The size and roughness of a nanopipet can be reliably determined by optimizing the intensity of the electron beam not to melt or deform the quartz nanotip without a metal coating. Electrochemically, the nanoscale ITIES supported by a rough nanotip gives higher amperometric responses to tetrabutylammonium than expected for a 30 nm diameter disc tip. The finite element simulation of sphere-cap ITIES tips accounts for the high current responses and also reveals that the SECM images of 100 nm diameter Si3N4 nanopores are enlarged along the direction of the tip scan. Nevertheless, spatial resolution is not significantly compromised by a sphere-cap tip, which can be scanned in closer proximity to the substrate. This finding augments the utility of a protruded tip, which can be fabricated and miniaturized more readily to facilitate nanoscale SECM imaging. (AU)

• FAPESP's process: 13/16799-8 - High-resolution scanning electrochemical microscopy: construction of nanopipets tips and applications
• Grantee: Alex da Silva Lima
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate