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Title: Evolution of the alkyl-chain dynamics in monolayer-protected gold clusters

Abstract

Alkyl-chain dynamics in monolayer protected metal cluster systems of gold have been studied by the quasielastic neutron scattering technique. Measurements have been carried out with 6, 12, and 18 carbon-long thiolate protected gold clusters of 4 nm core diameter. Dynamics of the monolayers in these systems, as indicated by the quasielastic broadening, were found to evolve continuously with increase in temperature from 270 to 400 K. Analysis of the elastic incoherent structure factor showed that while only a small portion of each chain is dynamically active at low temperature, the dynamics extend to almost the whole chain at 400 K. Although an improved model compared to our earlier reports, involving precessional motion of the chains on a cone is found to explain the observed data, a further improvement with reorientation of the chain around its axis with additional body axis fluctuation was most consistent with the experiment. The studies revealed the existence of complex dynamical motions of alkyl chains on the clusters. The studies suggest that repeated washings provide more space for the monolayer chains as a result of the removal of the phase transfer catalysts between the alkyl chains on the cluster surface. This provides space for greater orientationalmore » freedom, resulting in the observed dynamics even at lower temperatures.« less

Authors:
;  [1];  [2]; ;  [3]
  1. Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India)
  2. Institute Lau-Langevin, BP156, F-38042, Grenoble, Cedex 9 (France)
  3. DST Unit on Nanoscience, Department of Chemistry and Sophisticated Analytical Instrument Facility, Indian Institute of Technology Madras, Chennai 600 036 (India)
Publication Date:
OSTI Identifier:
20976702
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. B, Condensed Matter and Materials Physics; Journal Volume: 75; Journal Issue: 7; Other Information: DOI: 10.1103/PhysRevB.75.075414; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 36 MATERIALS SCIENCE; CARBON 18; CATALYSTS; CHAINS; CRYSTAL STRUCTURE; GOLD; NEUTRON DIFFRACTION; NEUTRON REACTIONS; ORGANIC COMPOUNDS; QUASI-ELASTIC SCATTERING; STRUCTURE FACTORS; SURFACE TREATMENTS; SURFACES; TEMPERATURE RANGE 0065-0273 K

Citation Formats

Mukhopadhyay, R., Mitra, S., Johnson, M., Rajeev Kumar, V. R., and Pradeep, T. Evolution of the alkyl-chain dynamics in monolayer-protected gold clusters. United States: N. p., 2007. Web. doi:10.1103/PHYSREVB.75.075414.
Mukhopadhyay, R., Mitra, S., Johnson, M., Rajeev Kumar, V. R., & Pradeep, T. Evolution of the alkyl-chain dynamics in monolayer-protected gold clusters. United States. doi:10.1103/PHYSREVB.75.075414.
Mukhopadhyay, R., Mitra, S., Johnson, M., Rajeev Kumar, V. R., and Pradeep, T. Thu . "Evolution of the alkyl-chain dynamics in monolayer-protected gold clusters". United States. doi:10.1103/PHYSREVB.75.075414.
@article{osti_20976702,
title = {Evolution of the alkyl-chain dynamics in monolayer-protected gold clusters},
author = {Mukhopadhyay, R. and Mitra, S. and Johnson, M. and Rajeev Kumar, V. R. and Pradeep, T.},
abstractNote = {Alkyl-chain dynamics in monolayer protected metal cluster systems of gold have been studied by the quasielastic neutron scattering technique. Measurements have been carried out with 6, 12, and 18 carbon-long thiolate protected gold clusters of 4 nm core diameter. Dynamics of the monolayers in these systems, as indicated by the quasielastic broadening, were found to evolve continuously with increase in temperature from 270 to 400 K. Analysis of the elastic incoherent structure factor showed that while only a small portion of each chain is dynamically active at low temperature, the dynamics extend to almost the whole chain at 400 K. Although an improved model compared to our earlier reports, involving precessional motion of the chains on a cone is found to explain the observed data, a further improvement with reorientation of the chain around its axis with additional body axis fluctuation was most consistent with the experiment. The studies revealed the existence of complex dynamical motions of alkyl chains on the clusters. The studies suggest that repeated washings provide more space for the monolayer chains as a result of the removal of the phase transfer catalysts between the alkyl chains on the cluster surface. This provides space for greater orientational freedom, resulting in the observed dynamics even at lower temperatures.},
doi = {10.1103/PHYSREVB.75.075414},
journal = {Physical Review. B, Condensed Matter and Materials Physics},
number = 7,
volume = 75,
place = {United States},
year = {Thu Feb 15 00:00:00 EST 2007},
month = {Thu Feb 15 00:00:00 EST 2007}
}