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Dipole-dipole interactions in spin-labeled Au nanoparticles as a measure of interspin distances

Ionita, P., Caragheorgheopol, A., Gilbert, B.C. and Chechik, V. (2005) Dipole-dipole interactions in spin-labeled Au nanoparticles as a measure of interspin distances. Journal of Physical Chemistry B, 109 (9). pp. 3734-3742. ISSN 1520-6106

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Abstract

A series of Au nanoparticles modified with a nitroxide-functionalized ligand was prepared with a range of spin-label coverage. The X-band EPR spectra of frozen solutions of these nanoparticles showed coverage-dependent line-broadening due to dipole−dipole interactions between spin labels. We developed a methodology to analyze such spectra in terms of geometrical features of the nanoparticles (e.g., Au core size and the length of the spin-labeled ligand). Our method is based on the assumption that the spectral line shape is determined by the average distance between nearest-neighboring spin labels adsorbed on the Au particle. Geometrical and statistical analysis then relates this distance to the line shape parameter d1/d, which was calibrated using a model system. Application of this methodology to the experimental spectra provided information about the conformation of ligands on the Au surface. We found that, if the spin-labeled ligand is substantially longer than the surrounding protecting layer, it does not adopt a fully stretched conformation but wraps around the particle immediately above the layer of surrounding ligand. Our results also show that the ligands do not adsorb cooperatively on the Au surface.

Item Type: Article
Academic Units: The University of York > Chemistry (York)
Depositing User: York RAE Import
Date Deposited: 20 Apr 2009 11:45
Last Modified: 20 Apr 2009 11:45
Published Version: http://dx.doi.org/10.1021/jp045696n
Status: Published
Publisher: American Chemical Society
Identification Number: 10.1021/jp045696n
URI: http://eprints.whiterose.ac.uk/id/eprint/6847

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