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Xu X, Valavanis D, Ciocci P, Confederat S, Marcuccio F, Lemineur JF, Actis P, Kanoufi F, Unwin PR. The New Era of High-Throughput Nanoelectrochemistry. Anal Chem 2023; 95:319-356. [PMID: 36625121 PMCID: PMC9835065 DOI: 10.1021/acs.analchem.2c05105] [Citation(s) in RCA: 34] [Impact Index Per Article: 34.0] [Reference Citation Analysis] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Indexed: 01/11/2023]
Affiliation(s)
- Xiangdong Xu
- Department
of Chemistry, University of Warwick, Coventry CV4 7AL, U.K.
| | | | - Paolo Ciocci
- Université
Paris Cité, ITODYS, CNRS, F-75013 Paris, France
| | - Samuel Confederat
- School
of Electronic and Electrical Engineering and Pollard Institute, University of Leeds, Leeds LS2 9JT, U.K.
- Bragg
Centre for Materials Research, University
of Leeds, Leeds LS2 9JT, U.K.
| | - Fabio Marcuccio
- School
of Electronic and Electrical Engineering and Pollard Institute, University of Leeds, Leeds LS2 9JT, U.K.
- Bragg
Centre for Materials Research, University
of Leeds, Leeds LS2 9JT, U.K.
- Faculty
of Medicine, Imperial College London, London SW7 2AZ, United Kingdom
| | | | - Paolo Actis
- School
of Electronic and Electrical Engineering and Pollard Institute, University of Leeds, Leeds LS2 9JT, U.K.
- Bragg
Centre for Materials Research, University
of Leeds, Leeds LS2 9JT, U.K.
| | | | - Patrick R. Unwin
- Department
of Chemistry, University of Warwick, Coventry CV4 7AL, U.K.
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King M, Avaro JT, Peter C, Hauser K, Gebauer D. Solvent-mediated isotope effects strongly influence the early stages of calcium carbonate formation: exploring D 2O vs. H 2O in a combined computational and experimental approach. Faraday Discuss 2022; 235:36-55. [PMID: 35388817 DOI: 10.1039/d1fd00078k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In experimental studies, heavy water (D2O) is employed, e.g., so as to shift the spectroscopic solvent background, but any potential effects of this solvent exchange on reaction pathways are often neglected. While the important role of light water (H2O) during the early stages of calcium carbonate formation has been realized, studies into the actual effects of aqueous solvent exchanges are scarce. Here, we present a combined computational and experimental approach to start to fill this gap. We extended a suitable force field for molecular dynamics (MD) simulations. Experimentally, we utilised advanced titration assays and time-resolved attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. We find distinct effects in various mixtures of the two aqueous solvents, and in pure H2O or D2O. Disagreements between the computational results and experimental data regarding the stabilities of ion associates might be due to the unexplored role of HDO, or an unprobed complex phase behaviour of the solvent mixtures in the simulations. Altogether, however, our data suggest that calcium carbonate formation might proceed "more classically" in D2O. Also, there are indications for the formation of new structures in amorphous and crystalline calcium carbonates. There is huge potential towards further improving the understanding of mineralization mechanisms by studying solvent-mediated isotope effects, also beyond calcium carbonate. Last, it must be appreciated that H2O and D2O have significant, distinct effects on mineralization mechanisms, and that care has to be taken when experimental data from D2O studies are used, e.g., for the development of H2O-based computer models.
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Affiliation(s)
- Michael King
- Department of Chemistry, University of Konstanz, Universitätsstr. 10, 78457 Konstanz, Germany
| | - Jonathan T Avaro
- Department of Chemistry, University of Konstanz, Universitätsstr. 10, 78457 Konstanz, Germany.,Empa, Lerchenfeldstrasse 5, 9014 St. Gallen, Switzerland
| | - Christine Peter
- Department of Chemistry, University of Konstanz, Universitätsstr. 10, 78457 Konstanz, Germany
| | - Karin Hauser
- Department of Chemistry, University of Konstanz, Universitätsstr. 10, 78457 Konstanz, Germany
| | - Denis Gebauer
- Institute of Inorganic Chemistry, Leibniz University of Hannover, Callinstr. 9, 30167 Hannover, Germany.
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Valavanis D, Ciocci P, Meloni GN, Morris P, Lemineur JF, McPherson IJ, Kanoufi F, Unwin PR. Hybrid scanning electrochemical cell microscopy-interference reflection microscopy (SECCM-IRM): tracking phase formation on surfaces in small volumes. Faraday Discuss 2021; 233:122-148. [PMID: 34909815 DOI: 10.1039/d1fd00063b] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
We describe the combination of scanning electrochemical cell microscopy (SECCM) and interference reflection microscopy (IRM) to produce a compelling technique for the study of interfacial processes and to track the SECCM meniscus status in real-time. SECCM allows reactions to be confined to well defined nm-to-μm-sized regions of a surface, and for experiments to be repeated quickly and easily at multiple locations. IRM is a highly surface-sensitive technique which reveals processes happening (very) close to a substrate with temporal and spatial resolution commensurate with typical electrochemical techniques. By using thin transparent conductive layers on glass as substrates, IRM can be coupled to SECCM, to allow real-time in situ optical monitoring of the SECCM meniscus and of processes that occur within it at the electrode/electrolyte interface. We first use the technique to assess the stability of the SECCM meniscus during voltammetry at an indium tin oxide (ITO) electrode at close to neutral pH, demonstrating that the meniscus contact area is rather stable over a large potential window and reproducible, varying by only ca. 5% over different SECCM approaches. At high cathodic potentials, subtle electrowetting is easily detected and quantified. We also look inside the meniscus to reveal surface changes at extreme cathodic potentials, assigned to the possible formation of indium nanoparticles. Finally, we examine the effect of meniscus size and driving potential on CaCO3 precipitation at the ITO electrode as a result of electrochemically-generated pH swings. We are able to track the number, spatial distribution and morphology of material with high spatiotemporal resolution and rationalise some of the observed deposition patterns with finite element method modelling of reactive-transport. Growth of solid phases on surfaces from solution is an important pathway to functional materials and SECCM-IRM provides a means for in situ or in operando visualisation and tracking of these processes with improved fidelity. We anticipate that this technique will be particularly powerful for the study of phase formation processes, especially as the high throughput nature of SECCM-IRM (where each spot is a separate experiment) will allow for the creation of large datasets, exploring a wide experimental parameter landscape.
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Affiliation(s)
| | - Paolo Ciocci
- Université de Paris, ITODYS, CNRS, F-75006 Paris, France.
| | - Gabriel N Meloni
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, UK.
| | - Peter Morris
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, UK.
| | | | - Ian J McPherson
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, UK.
| | | | - Patrick R Unwin
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, UK.
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McPherson IJ, Brown P, Meloni GN, Unwin PR. Visualization of Ion Fluxes in Nanopipettes: Detection and Analysis of Electro-osmosis of the Second Kind. Anal Chem 2021; 93:16302-16307. [PMID: 34846865 DOI: 10.1021/acs.analchem.1c02371] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Nanopipettes are finding increasing use as nano "test tubes", with reactions triggered through application of an electrochemical potential between electrodes in the nanopipette and a bathing solution (bath). Key to this application is an understanding of how the applied potential induces mixing of the reagents from the nanopipette and the bath. Here, we demonstrate a laser scanning confocal microscope (LSCM) approach to tracking the ingress of dye into a nanopipette (20-50 nm diameter end opening). We examine the case of dianionic fluorescein under alkaline conditions (pH 11) and large applied tip potentials (±10 V), with respect to the bath, and surprisingly find that dye ingress from the bath into the nanopipette is not observed under either sign of potential. Finite element method (FEM) simulations indicate this is due to the dominance of electro-osmosis in mass transport, with electro-osmotic flow in the conventional direction at +10 V and electro-osmosis of the second kind acting in the same direction at -10 V, caused by the formation of significant space charge in the center of the orifice. The results highlight the significant deviation in mass transport behavior that emerges at the nanoscale and the utility of the combined LSCM and FEM approach in deepening understanding, which in turn should promote new applications of nanopipettes.
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Affiliation(s)
- Ian J McPherson
- Department of Chemistry, University of Warwick, Gibbet Hill, Coventry CV4 7AL, United Kingdom
| | - Peter Brown
- Department of Chemistry, University of Warwick, Gibbet Hill, Coventry CV4 7AL, United Kingdom
| | - Gabriel N Meloni
- Department of Chemistry, University of Warwick, Gibbet Hill, Coventry CV4 7AL, United Kingdom
| | - Patrick R Unwin
- Department of Chemistry, University of Warwick, Gibbet Hill, Coventry CV4 7AL, United Kingdom
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Teahan J, Perry D, Chen B, McPherson IJ, Meloni GN, Unwin PR. Scanning Ion Conductance Microscopy: Surface Charge Effects on Electroosmotic Flow Delivery from a Nanopipette. Anal Chem 2021; 93:12281-12288. [PMID: 34460243 DOI: 10.1021/acs.analchem.1c01868] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Scanning ion conductance microscopy (SICM) is a powerful and versatile technique that allows an increasingly wide range of interfacial properties and processes to be studied. SICM employs a nanopipette tip that contains electrolyte solution and a quasi-reference counter electrode (QRCE), to which a potential is applied with respect to a QRCE in a bathing solution, in which the tip is placed. The work herein considers the potential-controlled delivery of uncharged electroactive molecules (solute) from an SICM tip to a working electrode substrate to determine the effect of the substrate on electroosmotic flow (EOF). Specifically, the local delivery of hydroquinone from the tip to a carbon fiber ultramicroelectrode (CF UME) provides a means of quantifying the rate of mass transport from the nanopipette and mapping electroactivity via the CF UME current response for hydroquinone oxidation to benzoquinone. EOF, and therefore species delivery, has a particularly strong dependence on the charge of the substrate surface at close nanopipette-substrate surface separations, with implications for retaining neutral solute within the tip predelivery and for the delivery process itself, both controlled via the applied tip potential. Finite element method (FEM) simulations of mass transport and reactivity are used to explain the experimental observations and identify the nature of EOF, including unusual flow patterns under certain conditions. The combination of experimental results with FEM simulations provides new insights on mass transport in SICM that will enhance quantitative applications and enable new possibilities for the use of nanopipettes for local delivery.
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Affiliation(s)
- James Teahan
- MAS Centre for Doctoral Training, University of Warwick, Coventry CV4 7AL, United Kingdom.,Department of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - David Perry
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Baoping Chen
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Ian J McPherson
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Gabriel N Meloni
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Patrick R Unwin
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom
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Operando analysis of the electrosynthesis of Ag2O nanocubes by scanning electrochemical microscopy. Electrochem commun 2021. [DOI: 10.1016/j.elecom.2021.106950] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
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