Synthesis, characterization and optical applications of nanomaterials
Item
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Title
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Synthesis, characterization and optical applications of nanomaterials
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Identifier
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d_2009_2013:beca3e284321:10701
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identifier
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10923
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Creator
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Xu, Fen,
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Contributor
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Hiroshi Matsui
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Date
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2010
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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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Physical chemistry | Materials science | Nanotechnology | nanomaterial | synthesis
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Abstract
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Nanomaterials have been studied extensively due to their potential application in electronics, photonics and nanodevices. There are a wide variety of methods developed to create the nano-scale materials. Chemical colloidal synthesis is the way most used since it is reproducible and high efficiency.;Nanoparticles lie at the heart of nanoscience for their novel electronic, magnetic and optical properties. In this dissertation, there are two parts where researches have been performed based on the synthesis of metal and semiconductor nanoparticles.;In part I, Semiconductor type-II core-shell quantum dots (QDs) ZnO-CdS have been synthesized by chemical colloidal method which was carried out in a two-step process. We initially synthesized ZnO core nanoparticles and overcoat them with CdS shell. UV-Visible spectra, photoluminescence spectra (PL), high resolution TEM images and X-ray microanalysis for composition studies of the core-shell nanoparticles were characterized. PL lifetime measurements showed this type-II ZnO-CdS core-shell QDs presented extended exciton lifetime due to the spatial separation of electrons and holes between the core and the shell, which opens various useful applications in biosensors and photovoltaic devices.;In part II, normal Raman (NR) and surface enhanced Raman scattering (SERS) spectra of 3-hydroxyflavone (3-HF) have been measured. The SERS spectra were obtained both on a Ag electrode surface and on Ag colloidal nanoparticles. The experimental results support the DFT geometry calculations, which show that an adatom site at the vertex of Ag20 cluster binding with the 3-HF molecular plane tilted at an angle of about 53° to the surface is a low-energy structure. This is consistent with the enhancement of in-plane vibrational modes. Furthermore, the effect of fluence level on the discoloration of marble surfaces after the removal of the encrustation by 355 nm laser pulses was comparatively studied. Considering the thermochemical reaction possibly occurring in the encrustation during laser irradiation, the mechanism responsible for the discoloration of the cleaned marble surface was analyzed. The reduction of iron oxides by graphite plays a key role in determining the final color of the cleaned marble surface. The marble surfaces before and after laser irradiation were characterized in terms of the chemical components through surface enhanced Raman spectroscopy on Ag colloidal nanoparticles. To analyze the working mechanism of the liquid layer covering the marble encrustation, distilled water, ethanol and acetone were used in marble cleaning to compare the cleaning efficiency at different fluence levels. Surface-enhanced Raman spectroscopy (SERS) on silver colloidal nanoparticles was also used to identify the chemical constituents of the cleaned marble with these three different liquids.
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Type
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dissertation
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Source
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2009_2013.csv
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degree
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Ph.D.
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Program
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Chemistry
