Linked Life Data

19785139

Source:http://linkedlifedata.com/resource/pubmed/id/19785139

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
3
pubmed:dateCreated
2009-9-29
pubmed:abstractText
Characterizing the structure and dynamic properties of a single monolayer is a challenge due to the minute amount of material that is probed. Here, EPR spectroscopy is used for investigating the spatial and temporal organization of self-assembled monolayers of 5- and 16-doxyl stearic acid (5 DSA and 16 DSA, respectively) adsorbed on a GaAs substrate. The results are complemented with FTIR and ellipsometery measurements, which provide the evidence for the formation of monolayers. Moreover, a comparison with the FTIR spectrum of a monolayer of stearic acid shows that the monolayers of the spin labeled molecules are less packed due to the hindrance introduced by the labeling group. The EPR spectra provide a new insight on the ordering in the layer and more interestingly, it reveals the time dependence of the organization. For 5DSA, with the spin-label group situated close to the substrate, the EPR spectrum immediately after adsorption is poorly resolved and dominated by the spin-exchange interaction between neighboring molecules. As time increases (up to 1 week) the resolution of the 14N hyperfine coupling increases, revealing a better organized monolayer where the molecules are more homogenously spaced. Moreover, the spectrum of the layer, after reaching equilibrium, shows that there is no motional freedom near the GaAs surface. Orientation dependence measurements on the equilibrated sample show the presence of a preferred orientation of the molecules, although with a wide distribution. The spectrum of the 16DSA monolayer, where the nitroxide spin label is situated at the end of the chain, far from the surface, also showed a poorly resolved spectrum at short times, but unlike 5DSA, it did not exhibit any time dependence. Through EPR line-shape simulations and by comparison with FTIR results, the differences between 5DSA and 16DSA were attributed to difference in coverage caused by the bulky spin label near the surface in the case of 5DSA.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Feb
pubmed:issn
1463-9076
pubmed:author
pubmed:issnType
Print
pubmed:day
7
pubmed:volume
7
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
524-9
pubmed:meshHeading
pubmed:year
2005
pubmed:articleTitle
EPR studies on the organization of self-assembled spin-labeled organic monolayers adsorbed on GaAs.
pubmed:affiliation
Department of Chemical Physics, Weizmann Institute of Science, Rehovot, 76100, Israel.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't