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Galyamova A, Crooks RM. Effect of Intermediate Semiconducting TiOx Thin Films on Nanoparticle-Mediated Electron Transfer: Electrooxidation of CO. NANOMATERIALS 2022; 12:nano12050855. [PMID: 35269345 PMCID: PMC8912720 DOI: 10.3390/nano12050855] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/18/2021] [Revised: 02/27/2022] [Accepted: 03/01/2022] [Indexed: 12/26/2022]
Abstract
The concept of nanoparticle-mediated electron transfer (eT) across insulating thin films was elucidated theoretically by Allongue and Chazalviel in 2011. In their model, metal nanoparticles (NPs) are immobilized atop passivating, self-assembled monolayers (SAMs). They found that under certain conditions, related to the thickness of the SAM and the size of the NPs, efficient faradaic oxidation and reduction reactions could proceed at the NP surface. In the absence of NPs, however, eT was suppressed by the insulating SAM thin films. Allongue and Chazalviel concluded that, within certain bounds, eT is mediated by fast tunneling between the conductive electrode and the metal NPs, while the kinetics of the redox reaction are controlled by the NPs. This understanding has been confirmed using a variety of experimental models. The theory is based on electron tunneling; therefore, the nature of the intervening medium (the insulator in prior studies) should not affect the eT rate. In the present manuscript, however, we show that the theory breaks down under certain electrochemical conditions when the medium between conductors is an n-type semiconductor. Specifically, we find that in the presence of either Au or Pt NPs immobilized on a thin film of TiOx, CO electrooxidation does not proceed. In contrast, the exact same systems lead to the efficient reduction of oxygen. At present, we are unable to explain this finding within the context of the model of Allongue and Chazalviel.
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Abadie T, Sella C, Perrodin P, Thouin L. Electrochemical Generation and Detection of Transient Concentration Gradients in Microfluidic Channels. Theoretical and Experimental Investigations. Front Chem 2019; 7:704. [PMID: 31709233 PMCID: PMC6822297 DOI: 10.3389/fchem.2019.00704] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Accepted: 10/08/2019] [Indexed: 12/21/2022] Open
Abstract
Transient concentration gradients generated and detected electrochemically in continuous flow microchannels were investigated by numerical simulations and amperometric measurements. Operating conditions including device geometry and hydrodynamic regime were theoretically delineated for producing gradients of various profiles with tunable characteristics. Experiments were carried out with microfluidic devices incorporating a dual-channel-electrode configuration. Under these conditions, high electrochemical performance was achieved both to generate concentration gradients and to monitor their dynamics along linear microchannels. Good agreement was observed between simulated and experimental data validating predictions between gradient properties and generation conditions. These results demonstrated the capability of electrochemical microdevices to produce in situ tunable concentration gradients with real-time monitoring. This approach is versatile for the active control in microfluidics of microenvironments or chemical gradients with high spatiotemporal resolution.
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Affiliation(s)
| | | | | | - Laurent Thouin
- PASTEUR, Département de chimie, École normale supérieure, PSL University, Sorbonne Université, CNRS, Paris, France
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Ostojic N, Duan Z, Galyamova A, Henkelman G, Crooks RM. Electrocatalytic Study of the Oxygen Reduction Reaction at Gold Nanoparticles in the Absence and Presence of Interactions with SnOx Supports. J Am Chem Soc 2018; 140:13775-13785. [DOI: 10.1021/jacs.8b08036] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Nevena Ostojic
- Department of Chemistry, Center for Electrochemistry, and Texas Materials Institute, The University of Texas at Austin, 105 East 24th Street, Stop A5300, Austin, Texas 78712-1224, United States
| | - Zhiyao Duan
- Department of Chemistry, Center for Electrochemistry, and Texas Materials Institute, The University of Texas at Austin, 105 East 24th Street, Stop A5300, Austin, Texas 78712-1224, United States
| | - Aigerim Galyamova
- Department of Chemistry, Center for Electrochemistry, and Texas Materials Institute, The University of Texas at Austin, 105 East 24th Street, Stop A5300, Austin, Texas 78712-1224, United States
| | - Graeme Henkelman
- Department of Chemistry, Center for Electrochemistry, and Texas Materials Institute, The University of Texas at Austin, 105 East 24th Street, Stop A5300, Austin, Texas 78712-1224, United States
| | - Richard M. Crooks
- Department of Chemistry, Center for Electrochemistry, and Texas Materials Institute, The University of Texas at Austin, 105 East 24th Street, Stop A5300, Austin, Texas 78712-1224, United States
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Ustarroz J, Ornelas IM, Zhang G, Perry D, Kang M, Bentley CL, Walker M, Unwin PR. Mobility and Poisoning of Mass-Selected Platinum Nanoclusters during the Oxygen Reduction Reaction. ACS Catal 2018. [DOI: 10.1021/acscatal.8b00553] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Affiliation(s)
- Jon Ustarroz
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, U.K
- Research Group Electrochemical and Surface Engineering (SURF), Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
| | - Isabel M. Ornelas
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, U.K
- Nanoscale Physics, Chemistry and Engineering Research Laboratory, University of Birmingham, Birmingham B15 2TT, U.K
| | - Guohui Zhang
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, U.K
| | - David Perry
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, U.K
| | - Minkyung Kang
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, U.K
| | | | - Marc Walker
- Department of Physics, University of Warwick, Coventry CV4 7AL, U.K
| | - Patrick R. Unwin
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, U.K
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