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Abstract Electrochemical experiments at individual nanoparticles (NPs) can provide new insights into their structure–activity relationships. By using small nanoelectrodes as tips in a scanning electrochemical microscope (SECM), we recently imaged individual surface‐bound 10–50 nm metal NPs. Herein, we introduce a new mode of SECM operation based on tunneling between the tip and a nanoparticle immobilized on the insulating surface. The obtained current vs. distance curves show the transition from the conventional feedback response to electron tunneling between the tip and the NP at separation distances of less than about 3 nm. In addition to high‐resolution imaging of the NP topography, the tunneling mode enables measurement of the heterogeneous kinetics at a single NP without making an ohmic contact with it. The developed method should be useful for studying the effects of nanoparticle size and geometry on electrocatalytic activity in real‐world applications.
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Electrochemistry at a single nanoparticle: from bipolar regime to tunnelling
This paper is concerned with long-distance interactions between an unbiased metal nanoparticle (NP) and a nanoelectrode employed as a tip in the scanning electrochemical microscope (SECM). A NP immobilized on the inert substrate acts as a bipolar electrode, producing positive SECM feedback. The tip current magnitude depends strongly on the ratio of the particle and tip radii and the heterogeneous charge-transfer kinetics. The onset of electron tunneling was observed at very short separation distances (<2–3 nm) at which the NP behaves as a part of the tip electrode. The rate constant of the electron-transfer (ET) or electrocatalytic reaction at the NP can be extracted from either feedback or tunneling current. The tunneling mode of SECM can be used to investigate heterogeneous reactions occurring at a single NP without making an ohmic contact with it. This technique can also help elucidate nanoparticle/electrode interactions in various electrochemical systems ranging from NPs immobilized on the electrode surface to nanoimpact collision events.
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- Award ID(s):
- 1763337
- PAR ID:
- 10091538
- Date Published:
- Journal Name:
- Faraday Discussions
- Volume:
- 210
- ISSN:
- 1359-6640
- Page Range / eLocation ID:
- 173 to 188
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/c8fd00041g
