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Quantitative imaging of ion transport through single nanopores by high-resolution scanning electrochemical microscopy.

Journal of the American Chemical Society (2012-06-05)
Mei Shen, Ryoichi Ishimatsu, Jiyeon Kim, Shigeru Amemiya
ABSTRACT

Here we report on the unprecedentedly high resolution imaging of ion transport through single nanopores by scanning electrochemical microscopy (SECM). The quantitative SECM image of single nanopores allows for the determination of their structural properties, including their density, shape, and size, which are essential for understanding the permeability of the entire nanoporous membrane. Nanoscale spatial resolution was achieved by scanning a 17 nm radius pipet tip at a distance as low as 1.3 nm from a highly porous nanocrystalline silicon membrane in order to obtain the peak current response controlled by the nanopore-mediated diffusional transport of tetrabutylammonium ions to the nanopipet-supported liquid-liquid interface. A 280 nm × 500 nm image resolved 13 nanopores, which corresponds to a high density of 93 nanopores/μm(2). A finite element simulation of the SECM image was performed to assess quantitatively the spatial resolution limited by the tip diameter in resolving two adjacent pores and to determine the actual size of a nanopore, which was approximated as an elliptical cylinder with a depth of 30 nm and major and minor axes of 53 and 41 nm, respectively. These structural parameters were consistent with those determined by transmission electron microscopy, thereby confirming the reliability of quantitative SECM imaging at the nanoscale level.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Tetrabutylammonium hydroxide solution, 1.0 M in methanol
Sigma-Aldrich
Tetrabutylammonium hydroxide solution, 40 wt. % in H2O
Sigma-Aldrich
Tetrabutylammonium hydrogensulfate, 97%
Sigma-Aldrich
Tetrabutylammonium phosphate monobasic solution, 1.0 M in H2O
Sigma-Aldrich
Tetrabutylammonium cyanide, 95%
Supelco
Tetrabutylammonium phosphate monobasic solution, suitable for ion pair chromatography, LiChropur, concentrate, ampule
Sigma-Aldrich
Tetrabutylammonium hydroxide solution, technical, ~40% in H2O (~1.5 M)
Sigma-Aldrich
Tetrabutylammonium perchlorate, ≥95.0% (T)
Supelco
Tetrabutylammonium hydroxide solution, ~40% in water, suitable for ion chromatography
Sigma-Aldrich
Tetrabutylammonium hydroxide solution, 54.0-56.0% in H2O
Supelco
Tetrabutylammonium perchlorate, for electrochemical analysis, ≥99.0%
Sigma-Aldrich
Tetrabutylammonium cyanide, technical, ≥80%
Sigma-Aldrich
Tetrabutylammonium bromide solution, 50 wt. % in H2O
Sigma-Aldrich
Tetrabutylammonium iodide, reagent grade, 98%
Sigma-Aldrich
Tetrabutylammonium fluoride solution, 1.0 M in THF
Sigma-Aldrich
Tetrabutylammonium bromide, ACS reagent, ≥98.0%
Sigma-Aldrich
Tetrabutylammonium fluoride solution, 75 wt. % in H2O
Sigma-Aldrich
Tetrabutylammonium nitrate, 97%
Supelco
Tetrabutylammonium iodide, suitable for ion pair chromatography, LiChropur, ≥99.0%
Supelco
Tetrabutylammonium bisulfate solution, suitable for ion pair chromatography, LiChropur, concentrate, ampule
Sigma-Aldrich
Tetrabutylammonium phosphate monobasic, puriss., ≥99.0% (T)
Sigma-Aldrich
Tetrabutylammonium iodide, ≥99.0% (AT)
Supelco
Tetrabutylammonium bromide, suitable for ion pair chromatography, LiChropur, ≥99.0%
Supelco
Tetrabutylammonium chloride, suitable for ion pair chromatography, LiChropur, ≥99.0%
Supelco
Tetrabutylammonium bisulfate, suitable for ion pair chromatography, LiChropur, ≥99.0%
Sigma-Aldrich
Tetrabutylammonium chloride, ≥97.0% (NT)
Sigma-Aldrich
Tetrabutylammonium bisulfate, puriss., ≥99.0% (T)
Sigma-Aldrich
Tetrabutylammonium bisulfate solution, ~55% in H2O
Sigma-Aldrich
Tetrabutylammonium azide