Perry, David, Al Botros, Rehab, Momotenko, Dmitry, Kinnear, Sophie L. and Unwin, Patrick R. (2015) Simultaneous nanoscale surface charge and topographical mapping. ACS Nano, 9 (7). pp. 7266-7276. doi:10.1021/acsnano.5b02095 ISSN 1936-0851.

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Abstract

Nanopipettes are playing an increasingly prominent role in nanoscience, for sizing, sequencing, delivery, detection, and mapping interfacial properties. Herein, the question of how to best resolve topography and surface charge effects when using a nanopipette as a probe for mapping in scanning ion conductance microscopy (SICM) is addressed. It is shown that, when a bias modulated (BM) SICM scheme is used, it is possible to map the topography faithfully, while also allowing surface charge to be estimated. This is achieved by applying zero net bias between the electrode in the SICM tip and the one in bulk solution for topographical mapping, with just a small harmonic perturbation of the potential to create an AC current for tip positioning. Then, a net bias is applied, whereupon the ion conductance current becomes sensitive to surface charge. Practically this is optimally implemented in a hopping-cyclic voltammetry mode where the probe is approached at zero net bias at a series of pixels across the surface to reach a defined separation, and then a triangular potential waveform is applied and the current response is recorded. Underpinned with theoretical analysis, including finite element modeling of the DC and AC components of the ionic current flowing through the nanopipette tip, the powerful capabilities of this approach are demonstrated with the probing of interfacial acid–base equilibria and high resolution imaging of surface charge heterogeneities, simultaneously with topography, on modified substrates.

Item Type:	Journal Article
Subjects:	Q Science > QC Physics Q Science > QD Chemistry
Divisions:	Faculty of Science, Engineering and Medicine > Science > Chemistry
Library of Congress Subject Headings (LCSH):	Nanochemistry, Finite element method, Impedance (Electricity), Surface energy
Journal or Publication Title:	ACS Nano
Publisher:	American Chemical Society
ISSN:	1936-0851
Official Date:	28 July 2015
Dates:	Date Event 28 July 2015 Published 14 July 2015 Available 1 July 2015 Accepted 8 April 2015 Submitted
Volume:	9
Number:	7
Number of Pages:	11
Page Range:	pp. 7266-7276
DOI:	10.1021/acsnano.5b02095
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
Date of first compliant deposit:	31 December 2015
Date of first compliant Open Access:	28 July 2016
Funder:	European Research Council (ERC), Engineering and Physical Sciences Research Council (EPSRC), Marie Curie Intra-European Fellowship (IEF)
Grant number:	ERC-2009 AdG 247143-QUANTIF (ERC), EP/F500378/1 (EPSRC), 626158 FUNICIS (IEF)
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