ASU Electronic Theses and Dissertations
This collection includes most of the ASU Theses and Dissertations from 2011 to present. ASU Theses and Dissertations are available in downloadable PDF format; however, a small percentage of items are under embargo. Information about the dissertations/theses includes degree information, committee members, an abstract, supporting data or media.
In addition to the electronic theses found in the ASU Digital Repository, ASU Theses and Dissertations can be found in the ASU Library Catalog.
Dissertations and Theses granted by Arizona State University are archived and made available through a joint effort of the ASU Graduate College and the ASU Libraries. For more information or questions about this collection contact or visit the Digital Repository ETD Library Guide or contact the ASU Graduate College at gradformat@asu.edu.
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The size detection limit of single particle inductively coupled plasma spectrometry (spICP-MS) was determined for 40 elements, demonstrating the feasibility of spICP-MS to different NP species in water. The K-means Clustering Algorithm was used to process the spICP-MS signals, and achieved precise particle-noise differentiation and quantitative particle size resolution. A dry powder assay based on NP-catalyzed methylene blue (MB) reduction was developed to rapidly and sensitively detect metallic NPs in water by measuring their catalytic reactivity.
Four different wet-chemical-based NP surface reactivity assays were demonstrated: “borohydride reducing methylene blue (BHMB)”, “ferric reducing ability of nanoparticles (FRAN)”, “electron paramagnetic resonance detection of hydroxyl radical (EPR)”, and “UV-illuminated methylene blue degradation (UVMB)”. They gave different reactivity ranking among five NP species, because they targeted for different surface reactivity types (catalytic, redox and photo reactivity) via different reaction mechanisms. Kinetic modeling frameworks on the assay outcomes revealed two surface electron transfer schemes, namely the “sacrificial reducing” and the “electrode discharging”, and separated interfering side reactions from the intended surface reaction.
The application of NPs in chemical mechanical polishing (CMP) was investigated as an industrial case to understand NP surface transformation via adsorbing ions in water. Simulation of wastewater treatment showed CMP NPs were effectively removed (>90%) by lime softening at high pH and high calcium dosage, but 20-40% of them remained in water after biomass adsorption process. III/V ions (InIII, GaIII, and AsIII/V) derived from semiconductor materials showed adsorption potentials to common CMP NPs (SiO2, CeO2 and Al2O3), and a surface complexation model was developed to determine their intrinsic complexation constants for different NP species. The adsorption of AsIII and AsV ions onto CeO2 NPs mitigated the surface reactivity of CeO2 NPs suggested by the FRAN and EPR assays. The impact of the ion adsorption on the surface reactivity of CeO2 NPs was related to the redox state of Ce and As on the surface, but varied with ion species and surface reaction mechanisms.
Intense supersonic molecular beams of these transient molecules were generated via laser ablation and spectroscopically characterized using a novel medium-resolution two-dimensional (2D) spectroscopic approach, as well as high-resolution laser induced fluorescence (LIF). The 2D medium resolution approach, which was used in the studies SrOH, ThF, ThCl and YbOH, uses a multiplexing method that simultaneously records dispersed fluorescence and excitation spectra. A significant advantage of 2D-LIF imaging is that all the electronics states can be targeted to determine the electronics states and associated vibrational spacing individually. Consequently, in the 2D spectra of ThF, ThCl and YbOH, several previously unobserved band systems have been detected in one single scan. For the DF spectra of SrOH and YbOH, the determined branching ratios show that the transitions of these molecules are diagonal (i.e. Δv=0), which is essential for the proposed potential for laser cooling. In the high-resolution of YbF, ThF, ThCl and SrOH optical spectra were recorded to an accuracy of ±30 MHz, which represents an unprecedented precision of 1:10+8.
In addition to field free spectra, optical Stark and Zeeman studies were performed to determine the most fundamental magneto-and electro-static properties. Effective Hamiltonian operators were employed to analyze the recorded spectra and determine the spectroscopic parameters. This data set also establishes a contribution toward developing new computational methodologies for treating relativistic effects and electron correlation.
Additionally, a theoretical formalism is presented to show that when preferential orientations of water dipoles exist at the interface, electrophoretic charges can be produced without free charge carriers, i.e., neutral solutes can move in a constant electric field due to the divergence of polarization at the interface. Furthermore, the concept of interface susceptibility is introduced. It involves the fluctuations of the surface charge density caused by thermal motion and its correlation over the characteristic correlation length with the fluctuations of the solvent charge density. Solvation free energy and interface dielectric constant are formulated accordingly. Unlike previous approaches, the solvation free energy scales quite well in a broad range of ion sizes, namely in the range of 2-14 A° . Interface dielectric constant is defined such that the boundary conditions in the Laplace equation describing a micro- or mesoscopic interface are satisfied. The effective dielectric constant of interfacial water is found to be significantly lower than its bulk value. Molecular dynamics simulation results show that the interface dielectric constant for a TIP3P water model changes from nine to four when the effective solute radius is increased from 5 A° to 18 A° . The small value of the interface dielectric constant of water has potentially dramatic consequences for hydration.
Temperature and polarizability effects on electron transfer in biology and artificial photosynthesis
(ET) and then provide modifications to the model. A confirmation of the inverted energy
gap law, which is the cleanest verification so far, is presented for donor-acceptor complexes.
In addition to the macroscopic properties of the solvent, the physical properties of the solvent
are incorporated in the model via the microscopic solvation model. For the molecules
studied in this dissertation, the rate constant first increases with cooling, in contrast to the
prediction of the Arrhenius law, and then decreases at lower temperatures. Additionally,
the polarizability of solute, which was not considered in the original Marcus theory, is included
by the Q-model of ET. Through accounting for the polarizability of the reactants, the
Q-model offers an important design principle for achieving high performance solar energy
conversion materials. By means of the analytical Q-model of ET, it is shown that including
molecular polarizability of C60 affects the reorganization energy and the activation barrier
of ET reaction.
The theory and Electrochemistry of Ferredoxin and Cytochrome c are also investigated.
By providing a new formulation for reaction reorganization energy, a long-standing disconnect
between the results of atomistic simulations and cyclic voltametery experiments is
resolved. The significant role of polarizability of enzymes in reducing the activation energy
of ET is discussed. The binding/unbinding of waters to the active site of Ferredoxin leads
to non-Gaussian statistics of energy gap and result in a smaller activation energy of ET.
Furthermore, the dielectric constant of water at the interface of neutral and charged
C60 is studied. The dielectric constant is found to be in the range of 10 to 22 which is
remarkably smaller compared to bulk water( 80). Moreover, the interfacial structural
crossover and hydration thermodynamic of charged C60 in water is studied. Increasing the
charge of the C60 molecule result in a dramatic structural transition in the hydration shell,
which lead to increase in the population of dangling O-H bonds at the interface.
that arises in the response of a molecule to an external electric field. To illustrate
the plausibility of the idea, we used Simmons' tunneling model, which describes image
charge and dielectric effects on electron transport through a barrier. In such a
model, the barrier height depends on the dielectric constant of the electrode-molecule-electrode junction, which in turn can be approximately expressed in terms of the
molecular polarizability via the classical Clausius-Mossotti relation. In addition to
using the tunneling model, the validity of the relationships between the molecular
polarizability and the molecular conductance was tested by comparing calculated
and experimentally measured conductance of different chemical structures ranging
from covalent bonded to non-covalent bonded systems. We found that either using
the tunneling model or the first-principle calculated quantities or experimental data,
the conductance decreases as the molecular polarizability increases. In contrast to
this strong correlation, our results showed that in some cases there was a weaker or
none correlation between the conductance and other molecular electronic properties
including HOMO-LUMO gap, chemical geometries, and interactions energies. All
these results together suggest that using the molecular polarizability as a molecular
descriptor for conductance can offer some advantages compared to using other
molecular electronic properties and can give additional insight about the electronic
transport property of a junction.
These results also show the validity of the physically intuitive picture that to a first
approximation a molecule in a junction behaves as a dielectric that is polarized in the
opposite sense of the applied bias, thereby creating an interfacial barrier that hampers
tunneling. The use of the polarizability as a descriptor of molecular conductance offers
signicant conceptual and practical advantages over a picture based in molecular
orbitals. Despite the simplicity of our model, it sheds light on a hitherto neglected
connection between molecular polarizability and conductance and paves the way for
further conceptual and theoretical developments.
The results of this work was sent to two publications. One of them was accepted
in the International Journal of Nanotechnology (IJNT) and the other is still under
review in the Journal of Physical Chemistry C.