Visualization of diffusion within nanoarrays

Liu, Yang, Holzinger, Angelika, Knittel, Peter, Poltorak, Lukasz, Gamero-Quijano, Alonso, Rickard, William D.A., Walcarius, Alain, Herzog, Grégoire, Kranz, Christine, and Arrigan, Damien W.M. (2016) Visualization of diffusion within nanoarrays. Analytical Chemistry, 88 (13). pp. 6689-6695.

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Abstract

The direct experimental characterization of diffusion processes at nanoscale remains a challenge that could help elucidate processes in biology, medicine and technology. In this report, two experimental approaches were employed to visualize ion diffusion profiles at the orifices of nanopores (radius (ra) of 86 ± 6 nm) in array format: (1) electrochemically assisted formation of silica deposits based on surfactant ion transfer across nanointerfaces between two immiscible electrolyte solutions (nanoITIES); (2) combined atomic force - scanning electrochemical microscopy (AFM-SECM) imaging of topography and redox species diffusion through the nanopores. The nature of the diffusion zones formed around the pores is directly related to the interpore distance within the array. Nanopore arrays with different ratios of pore center-to-center separation (rc) to pore radius (ra) were fabricated by focused ion beam (FIB) milling of silicon nitride (SiN) membranes, with 100 pores in a hexagonal arrangement. The ion diffusion profiles determined by the two visualization methods indicated the formation of overlapped or independent diffusion profiles at nanopore arrays with rc/ra ratios of 21 ± 2 and 91 ± 7, respectively. In particular, the silica deposition method resulted in formation of a single deposit encompassing the complete array with closer nanopore arrangement, whereas individual silica deposits were formed around each nanopore within the more widely spaced array. The methods reveal direct experimental evidence of diffusion zones at nanopore arrays and provide practical illustration that the pore-pore separation within such arrays has a significant impact on diffusional transport as the pore size is reduced to the nanoscale. These approaches to nanoscale diffusion zone visualization open up possibilities for better understanding of molecular transport processes within miniaturized systems.

Item ID: 53222
Item Type: Article (Research - C1)
ISSN: 1520-6882
Additional Information:

This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes

Funders: Australian Research Council (ARC), Deutscher Akademischer Austausch Dienst (DAAD), Agence Nationale pour la Recherche (ANR), Australian Technology Network (ATN)
Projects and Grants: ARC DP130102040, DAAD 57060632, ANR-14-CE14-0002-01
Date Deposited: 19 Apr 2018 02:17
FoR Codes: 03 CHEMICAL SCIENCES > 0301 Analytical Chemistry > 030102 Electroanalytical Chemistry @ 50%
03 CHEMICAL SCIENCES > 0306 Physical Chemistry (incl Structural) > 030604 Electrochemistry @ 50%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970103 Expanding Knowledge in the Chemical Sciences @ 100%
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