Spectroscopic and microscopic studies of aggregated molecules coated onto nanomaterials.
Item
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Title
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Spectroscopic and microscopic studies of aggregated molecules coated onto nanomaterials.
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Identifier
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AAI3231995
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identifier
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3231995
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Creator
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Jean-Mary, Fleumingue.
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Contributor
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Adviser: Daniel L. Akins
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Date
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2006
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Language
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English
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Publisher
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City University of New York.
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Subject
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Chemistry, Physical | Chemistry, Analytical
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Abstract
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Small self-assembled groupings of molecules (in particular, the so-called J-type molecular aggregates) can possess remarkable linear and nonlinear optical responses to radiation. Such inherent responses coupled with the enhanced efficiencies of some optical processes when noble metal nanostructures are present may engender composite systems with useful functionalities. This dissertation, hence, focuses on three principal missions. The first centered on the synthesis of stable, reproducible, monodisperse nanometric noble-metal spheres and nanoshells, the second on the fabrication of well-organized molecular assemblies on the nanoparticles surface, and the third on developing or implementing nanofabrication strategies to orient and pattern these nanostructures onto two-dimensional substrates.;Nanosize, spherical silver and gold particles and gold nanoshells are formed by chemical reduction, occasionally, in the presence of protective agents. The synthesized nanoparticles have one or more peaks in the absorption spectrum in the visible range, depending on the particles' sizes and shapes. The resulting metal nanoparticles having sizes between 5-100 nm and spherical morphology have their structures evaluated qualitatively evaluated from their surface plasmon band and quantitatively measured using dynamic light scattering (DLS), atomic force microscopy (AFM) and transmission electron microscopy (TEM).;The present dissertation reports, among other things, on the adsorption and aggregate formation of four related cyanine dyes on nanoparticle surfaces in solution and cast films. By using a combination of UV-Visible absorption, fluorescence and Raman spectroscopy, AFM, near-field scanning optical microscopy (NSOM), and quantum chemical calculations, insight has been gained in the relationship between chemical structure, aggregate structure and optical properties. The observations confirm aggregation by the characteristic narrow J-absorption and J-emission bands. J-aggregation was found to depend strongly on the nanoenvironement, with the presence of nanoparticles greatly improving the stability of the J-aggregates.;Tailoring the optical properties of metal nanoparticles by organizing chromophores of specific properties on them can yield photoresponsive nanohybrid materials with exciting opportunities for the design of novel, photon-based devices for sensing and optical switching. Applications of nanoparticle-based materials, in which collective nanoparticle optical properties are exploited, are currently emerging for surface-enhanced Raman (SERS), metal-enhanced fluorescence (MEF), surface plasmon resonance (SPR) and colorimetric assays.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
