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Metal Nanoparticle Aerogel CompositesWe have fabricated sol-gels containing gold and silver nanoparticles. Formation of an aerogel produces a blue shift in the surface plasmon resonance as a result of the decrease in the dielectric constant of the matrix upon supercritical extraction of the solvent. However, as a result of chemical interface damping this blue shift does not obey effective medium theories. Annealing the samples in a reducing atmosphere at 400 C eliminates this discrepancy and results in narrowing and further blue shifting of the plasmon resonance. Metal particle aggregation also results in a deviation from the predictions of effective medium theories, but can be controlled through careful handling and by avoiding the use of alcohol. By applying effective medium theories to the heterogeneous interlayer surrounding each metal particle, we extend the technique of immersion spectroscopy to inhomogeneous materials characterized by spatially dependent dielectric constants, such as aerogels. We demonstrate that the shift in the surface plasmon wavelength provides the average fractional composition of each component (air and silica) in this inhomogeneous layer, i.e. the porosity of the aerogel or equivalently, for these materials, the catalytic dispersion. Additionally, the kinetics suggest that collective particle interactions in coagulated metal clusters are perturbed during silica gelation resulting in a change in the aggregate geometry.
Document ID
20010021265
Acquisition Source
Marshall Space Flight Center
Document Type
Preprint (Draft being sent to journal)
Authors
Smith, David D.
(NASA Marshall Space Flight Center Huntsville, AL United States)
Sibille, Laurent
(NASA Marshall Space Flight Center Huntsville, AL United States)
Ignont, Erica
(NASA Marshall Space Flight Center Huntsville, AL United States)
Snow, Lanee
(NASA Marshall Space Flight Center Huntsville, AL United States)
Rose, M. Franklin
Date Acquired
August 20, 2013
Publication Date
January 1, 2000
Subject Category
Composite Materials
Meeting Information
Meeting: Aerogels
Location: Albuquerque, NM
Country: United States
Start Date: October 9, 2000
Distribution Limits
Public
Copyright
Other

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