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  4. Site-selective surface enhanced Raman scattering study of ligand exchange reactions on aggregated Ag nanocubes
 
research article

Site-selective surface enhanced Raman scattering study of ligand exchange reactions on aggregated Ag nanocubes

Lapresta-Fernandez, Alejandro
•
Athanasopoulou, Evangelia Nefeli  
•
Silva, Paulo Jacob  
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June 15, 2022
Journal Of Colloid And Interface Science

Surface modification of ligand protected nanoparticles (NPs) can be driven by ligand exchange reactions (LER). Little is known about the mechanism of this reaction, especially when the particles are not spherical. Here, we use the intrinsic hot spots generated on the corners/edges of 40 nm silver nanocubes (AgNCs) and the extrinsic hot spots generated by the aggregation of AgNCs to obtain strong enhancements in surface enhanced Raman scattering (SERS) to monitor the displacement of poly(vinylpyrrolidone) with either a hydrophilic (sodium 11-mercapto-1-undecanesulfonate, MUS) or a hydrophobic ligand (1-octanethiol, OT). By focusing on the ratio (R) between the trans and gauche bands of the alkyl backbones of the ligands as an indicator of local order, we find that the LER proceeds in two different ways, particularly regarding the arrangement of the incoming ligands. In the case of OT, R becomes large almost immediately and stays high throughout the reaction, while in the case of MUS, R starts low and increases only towards the end of the reaction. We interpret the first behaviour as a LER that proceeds via the formation of densely packed and ordered OT islands, practically from the beginning of the reaction, that gradually grow over time. In the case of MUS, our interpretation is that molecules randomly deposit on the surface and form denser monolayer regions as the LER proceeds. Both monolayers evolved towards a homogeneous topography that corresponds to an ordered state (near all-trans) in the later stages (R >> 1). Such mechanisms may be extended to the cube faces (as planar scaffolds) since clear differences in the topographic profile were found by Atomic Force Microscopy (AFM). (c) 2022 Elsevier Inc. All rights reserved.

  • Details
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Type
research article
DOI
10.1016/j.jcis.2022.02.051
Web of Science ID

WOS:000791711000003

Author(s)
Lapresta-Fernandez, Alejandro
Athanasopoulou, Evangelia Nefeli  
Silva, Paulo Jacob  
Guven, Zekiye Pelin  
Stellacci, Francesco  
Date Issued

2022-06-15

Publisher

ACADEMIC PRESS INC ELSEVIER SCIENCE

Published in
Journal Of Colloid And Interface Science
Volume

616

Start page

110

End page

120

Subjects

Chemistry, Physical

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Chemistry

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ligand exchange mechanism

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silver nanocubes

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sers

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aggregated nps

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pvp

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self-assembled monolayers

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gold nanoparticles

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shell morphology

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facile synthesis

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spectroscopy

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nucleation

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reactivity

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reduction

Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
SUNMIL  
Available on Infoscience
May 23, 2022
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/188003
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