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Ultrafast spectroscopy of novel mate...

Hardison, Lindsay M.

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Ultrafast spectroscopy of novel materials.

Record Type:	Language materials, printed : Monograph/item
Title/Author:	Ultrafast spectroscopy of novel materials./
Author:	Hardison, Lindsay M.
Description:	150 p.
Notes:	Adviser: Valeria D. Kleiman.
Contained By:	Dissertation Abstracts International69-02B.
Subject:	Chemistry, Physical. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3300744
ISBN:	9780549457664

Ultrafast spectroscopy of novel materials.
Hardison, Lindsay M.

Ultrafast spectroscopy of novel materials. - 150 p.

Adviser: Valeria D. Kleiman.

Thesis (Ph.D.)--University of Florida, 2007.

My research focused on steady state and time-resolved photophysical characterization of a series of semiconductor nanoparticles and water soluble conjugated polyelectrolytes. Several studies have shown that the electronic structure and relaxation dynamics in CdSe nanocrystals are not only size but are also shape and passivation dependent; however, there is no detailed comparison of the photophysical properties of ZnCdSe particles with different relative amounts of Zn. This dissertation presents data collected for colloidal CdSe, CdSe/ZnSe and ZnCdSe nanoparticles with rod-like architectures synthesized and investigated in our labs to determine how size, shape, passivation and composition affect the quantum confinement and dynamics. In addition, a series of different polymer repeat unit lengths of a linear conjugated polyelectrolyte (CPE) with a carboxylate ionic side chain have been synthesized and their photophysical properties have been explored.

ISBN: 9780549457664Subjects--Topical Terms:

560527
Chemistry, Physical.

Ultrafast spectroscopy of novel materials.
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020 $a 9780549457664
035 $a (UMI)AAI3300744
035 $a AAI3300744
040 $a UMI $c UMI
100 1 $a Hardison, Lindsay M. $3 1280790
245 1 0 $a Ultrafast spectroscopy of novel materials.
300 $a 150 p.
500 $a Adviser: Valeria D. Kleiman.
500 $a Source: Dissertation Abstracts International, Volume: 69-02, Section: B, page: 1029.
502 $a Thesis (Ph.D.)--University of Florida, 2007.
520 $a My research focused on steady state and time-resolved photophysical characterization of a series of semiconductor nanoparticles and water soluble conjugated polyelectrolytes. Several studies have shown that the electronic structure and relaxation dynamics in CdSe nanocrystals are not only size but are also shape and passivation dependent; however, there is no detailed comparison of the photophysical properties of ZnCdSe particles with different relative amounts of Zn. This dissertation presents data collected for colloidal CdSe, CdSe/ZnSe and ZnCdSe nanoparticles with rod-like architectures synthesized and investigated in our labs to determine how size, shape, passivation and composition affect the quantum confinement and dynamics. In addition, a series of different polymer repeat unit lengths of a linear conjugated polyelectrolyte (CPE) with a carboxylate ionic side chain have been synthesized and their photophysical properties have been explored.
520 $a Spectral shifts and line broadening exhibited within the Raman spectroscopy, UV-Vis spectroscopy and photoluminescence aided in determining the extent of alloying and compositional disorder created during the alloying process. The photoluminescence quantum yield of ZnCdSe nanorods is higher than that from pristine CdSe nanorods indicating a higher binding energy of the exciton. This effect is speculated to be due to increased localization of the exciton as a result of fluctuations in the composition, ultimately resulting in increases in luminescence efficiencies.
520 $a Moreover, time-resolved photoluminescence characterized lifetimes of nanoparticles with similar shape but different composition. Emission of an inhomogeneous population distribution (different sizes, shapes or composition) leads to the simultaneous probing of particles with different decaying rates. A stretched exponential function, I(t)= A*exp[-(t/tau) beta], can be used to describe these systems, where beta <1 corresponds to disperse populations. In the experiments presented here, the photoluminescence data yields small beta values, independent of the emitted photon energy. Photoluminescence decay lifetime, tau, of the samples increased with alloying time due to compositional disorder leading to exciton localization.
520 $a The dynamics of each nanorod was studied by absorption changes using ultrafast pump-probe spectroscopy. An excitation wavelength dependence study has been conducted to gain insight into the intraband/interband relaxation in core/shell nanorods with small valence band offsets. Determination of the dynamics and mechanisms of these systems will be useful for the study of fundamental physics and light emitting applications such as LED's, photovoltaic devices, lasing and fluorescence tagging.
520 $a CPEs are soluble in polar solvents and their conformational properties can be tuned to enhance their emissive behavior for sensing and device applications. It was found that polymer concentration, solvent, aggregation inducer and chain length, all affect the quenching efficiency; therefore, this dissertation examines energy transfer mechanism responsible for this behavior using ultrafast upconversion. Upon excitation of the aggregates from energetically higher lying isolated chains, the fluorescence lifetimes result in multi-exponential behavior due to the competition between the radiative and non-radiative decay.
590 $a School code: 0070.
650 4 $a Chemistry, Physical. $3 560527
650 4 $a Chemistry, Polymer. $3 1018428
650 4 $a Engineering, Materials Science. $3 1017759
690 $a 0494
690 $a 0495
690 $a 0794
710 2 $a University of Florida. $3 718949
773 0 $t Dissertation Abstracts International $g 69-02B.
790 $a 0070
790 1 0 $a Kleiman, Valeria D., $e advisor
791 $a Ph.D.
792 $a 2007
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3300744