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Title: Fluorescence Off-On Sensors for F-, K+, Fe3+, and Ca2+ Ions.
Creator: Sui, Binglin, Belfield, Kevin, Miles, Delbert, Zou, Shengli, Frazer, Andrew, Bhattacharya, Aniket, University of Central Florida
Abstract / Description: Fluorescence spectroscopy has been considered to be one of the most important research techniques in modern analytical chemistry, biochemistry, and biophysics. At present, fluorescence is a dominant methodology widely used in a great number of research domains, including biotechnology, medical diagnostics, genetic analysis, DNA sequencing, flow cytometry, and forensic analysis, to name just a few. In the past decade, with the rapid development of fluorescence microscopy, there has been a...
Show moreFluorescence spectroscopy has been considered to be one of the most important research techniques in modern analytical chemistry, biochemistry, and biophysics. At present, fluorescence is a dominant methodology widely used in a great number of research domains, including biotechnology, medical diagnostics, genetic analysis, DNA sequencing, flow cytometry, and forensic analysis, to name just a few. In the past decade, with the rapid development of fluorescence microscopy, there has been a considerable growth in applying fluorescence technique to cellular imaging. The distinguished merits of fluorescence techniques, such as high sensitivity, non-invasiveness, low cytotoxicity, low cost, and convenience, make it a promising tool to replace radioactive tracers for most biochemical measurements, avoiding the high expense and difficulties of handling radioactive tracers.Among the wide range of applications of fluorescence technique, fluorescent sensing of various cations and anions is one of the most important and active areas. This dissertation is all about developing fluorescent sensors for physiologically significant ions, including F-, K+, Fe3+, and Ca2+. All of these sensors demonstrate fluorescence (")turn-on(") response upon interacting with their respective ions, which makes them much more appealing than those based on fluorescence quenching mechanisms.In Chapter II, a novel highly selective fluorescence turn-on F- sensor (FS), comprised of a fluorene platform serving as the chromophore, and two 1,2,3-triazolium groups functioning as the signaling moieties, is described. The function of FS is established on the basis of deprotonation of the C-H bonds of 1,2,3-triazolium groups, which makes FS the first reported anion sensor based on the deprotonation of a C-H bond. Easy-to-prepare test strips were prepared for determining F- in aqueous media, providing an inexpensive and convenient approach to estimate whether the concentration of F- contained in drinking water is at a safe level.Chapter III contains an optimized synthesis of a reported K+-selective group (TAC), and the development of two TAC-based fluorescence turn-on K+ sensors (KS1 and KS2). The synthetic route of TAC is shortened and its overall yield is enhanced from 3.6% to 19.5%. Both KS1 and KS2 exhibited excellent selectivity toward K+ over other physiological metal cations, high sensitivity for K+ sensing, and pH insensitivity in the physiological pH range. Confocal fluorescence microscopy experiments demonstrate that they are capable of sensing K+ within living cells. 2PA determination reveals that KS2 has a desirable 2PA cross section of 500 GM at 940 nm, which makes it a two-photon red-emitting fluorescent sensor for K+.Chapter IV describes the development of a novel BODIPY-based fluorescence turn-on Fe3+ sensor (FeS). FeS is a conjugate of two moieties, a BODIPY platform serving as the fluorophore and a 1,10-diaza-18-crown-6 based cryptand acting as the Fe3+ recognition moiety. FeS displays good selectivity, high sensitivity, reversibility, and pH insensitivity toward Fe3+ sensing. Based on its excellent performance in determining Fe3+ and very low cytotoxicity, FeS was effectively applied to sensing Fe3+ in living cells.In Chapter V, a new BODIPY-based fluorescence turn-on sensor (CaS) was designed and synthesized for selectively and sensitively determining Ca2+. CaS is comprised of two moieties, a BODIPY fluorophore and a Ca2+ complexing unit. CaS demonstrated selective fluorescence turn-on response towards Ca2+ over other biological metal cations. Moreover, CaS exhibited desirable sensitivity for Ca2+ detection, which makes it more suitable for extracellular Ca2+ determination. In addition, CaS was insensitive to the pH of the physiological environment, especially in the pH range of blood and serum. Therefore, CaS has potential to be applied to sensing Ca2+ ions in extracellular environments.Chapter VI discusses potential future work of KS2 and CaS, following the results achieved in this dissertation. Based on the desirable performances of both sensors in sensing their respective ions, future work could largely be focused on their applications in cellular imaging.
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Date Issued: 2014
Identifier: CFE0005888, ucf:50883
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005888

Title: Electrical, Optical and Chemical Properties of Organic Photo Sensitve Materials.
Creator: Shi, Zheng, Liao, Yi, Kolpashchikov, Dmitry, Ye, Jingdong, Zou, Shengli, Su, Ming, University of Central Florida
Abstract / Description: Light as a (")green(") source of energy has become increasingly attractive throughout the past century and has shown versatility for the application of activating chemical reactions. Compared with traditional energy sources, it provides a more direct, selective and controllable method. My PhD study was focused on the study of photochemistry of organic materials in two different systems. The first system is regarding reversible photoacids which generate protons on irradiation. With the aim of...
Show moreLight as a (")green(") source of energy has become increasingly attractive throughout the past century and has shown versatility for the application of activating chemical reactions. Compared with traditional energy sources, it provides a more direct, selective and controllable method. My PhD study was focused on the study of photochemistry of organic materials in two different systems. The first system is regarding reversible photoacids which generate protons on irradiation. With the aim of systematically studying these novel types of long lived photoacids, a series of photoacids was designed, synthesized and whose chemical mechanism was thoroughly investigated. This type of photoacid changes from a weak acid to a strong acid with a pH change of several units, which achieves nearly complete proton dissociation upon visible light irradiation. The whole process is reversible and the half-life of the proton-dissociation state is long enough to be used in many applications. Besides fundamental studies, different applications based on this type of photoacids were also completed. An esterification reaction was catalyzed and the volume of a pH-sensitive polymer was altered due to the large amount of photo generated protons from this photoacid. A reversible electrical conductivity change of polyaniline (PANI) was also achieved by doping with this reversible photoacid. In order to induce a large conductivity increase, an irreversible photoacid generator (PAG) was embedded in a novel PANI/PAG/PVA novel composition. In this system, Poly (vinyl alcohol) (PVA) forms a hydrogen-bonding network to facilitate proton transfer between the PAG and PANI. A final electrical conductivity of 10-1 S cm-1 was successfully achieved after irradiation. The second system in which I explored photochemistry of organic molecules concerns Photo-retro-Diels-Alder (PrDA) reactions and a variety of Diels-Alder (DA) adducts were designed for these studies. UV light was used to trigger the retro-Diels-Alder reactions. Quantum yield of each DA adducts was investigated. This revealed that the photo-reactivity of this process depends on the electron-donating ability of the diene and the electron-withdrawing ability of the dienophile component. Mechanistic studies of this PrDA reaction reveal that a charge-separated intermediate is generated from a singlet excited state. This was applied to an unsaturated cyclic ?-diketones (DKs), which underwent PrDA reactions and generated anthracene derivatives and carbon monoxide (CO), which itself plays profound and important roles in biological systems. These unsaturated cyclic ?-diketones (DKs) encapsulated in micelles are effective CO-releasing molecules (CORMs) and are capable of carrying and releasing CO in cellular systems. This novel type of organic CORMs has potentially low toxicity and generates fluorescence, which provides a useful tool for the study of the biological functions of CO.
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Date Issued: 2013
Identifier: CFE0005114, ucf:50748
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005114

Title: Degradation of Hexachlorobenzene, Pentachlorophenol and Pentachloroanisole using Activated Magnesium in an Acidified Ethanol/Ethyl Lactate Cosolvent System.
Creator: Garbou, Amel, Yestrebsky, Cherie, Clausen, Christian, Zou, Shengli, Chumbimuni Torres, Karin, Randall, Andrew, University of Central Florida
Abstract / Description: For many centuries, chemists have dedicated many labor-intensive hours to improving the quality of life for mankind by developing synthetic methods for the production of compounds which fulfill the needs and meet the demands of society. However, the innovation of such compounds has frequently come at the cost of detrimental side-effects that do not always present themselves until many years, or even decades, following their initial application. Many compounds in this category come in the form...
Show moreFor many centuries, chemists have dedicated many labor-intensive hours to improving the quality of life for mankind by developing synthetic methods for the production of compounds which fulfill the needs and meet the demands of society. However, the innovation of such compounds has frequently come at the cost of detrimental side-effects that do not always present themselves until many years, or even decades, following their initial application. Many compounds in this category come in the form of globally-distributed halogenated molecules which are toxic to many living organisms, susceptible to bioaccumulation and resistant to biodegradation processes. Such compounds are classified as persistent organic pollutants (POPs), and require safe, sustainable and economically viable remediation techniques due to their destructive effects on organisms and the environment In the work done for this dissertation study, three particular POPs, which can be further classified as Polychlorinated Aromatic Hydrocarbons (PCAHs), were studied: pentachlorophenol (PCP), hexachlorobenzene (HCB) and pentachloroanisole (PCA).Chlorophenols are highly toxic compounds, usually found in soils, water, and effluents resulting from industrial activities. These environmentally-persistent compounds have been found to exhibit probable carcinogenic properties by the United States Environmental Protection Agency and the International Agency for Research on Cancer. The most toxic chlorophenol is PCP, which has a regulated maximum contaminant level (MCL) of 0.03 mg/L in water. Due to the high toxicity of PCP, it is necessary to treat water and soils that have tested positive for concentrations above the MCL. The aim of this work is to demonstrate the capabilities of using ball-milled zero-valent magnesium powder with various amendments, such as acetic acid (as an activator) and ethanol for the dechlorination of PCP. The dechlorination processes of these various combinations wereivcompared in an attempt to determine the most effective system for the degradation of PCP to phenol. Three systems with powerful capabilities of treatment were studied: ball-milled magnesium powder, ball-milled magnesium carbon (Mg/C), and mechanically alloyed magnesium with palladium. The results of these studies indicate that the most rapid and complete PCP dechlorination is achieved using mechanically alloyed Mg/Pd and a matrix consisting of at least 0.02 g Mg0/mL of ethanol and 10 ?L acetic acid/mL of ethanol, in which case 20 ng/?L of PCP was dechlorinated to phenol in approximately 15 min. with a carbon mass balance of 94.89%. Hexachlorobenzene (HCB), like many chlorinated organic compounds, has accumulated in the environment from agricultural and industrial activity. After its introduction as a fungicide in 1945, the extensive use of this toxic chemical has instigated its infiltration into all food types. Prohibition from commercial use was enforced in the United States in 1966 due to animal, and possible human, carcinogenic effects. Because of the health risks and the adverse impact on various ecosystems, remediation of this contaminant is of vital concern. The objective of this study is to evaluate the proficiency of activated-magnesium metal in a protic solvent system to enhance the reductive dechlorination of HCB. Experimental results were compared with those predicted by quantum chemical calculations based on Density Functional Theory (DFT). Multivariate analysis detected complete degradation of HCB within 30 minutes, having a rate constant of 0.222 min-1, at room temperature. Dechlorination was hypothesized to proceed via an ionic mechanism, and the main dechlorination pathways of HCB in 1:1 ethanol/ethyl lactate were HCB ? PCBz ? 1,2,4,5-TCB; 1,3,4,5-TCB ? 1,2,4-TriCB; 1,3,5-TriCB ? 1,4-DiCB; 1,3-DiCB. The direct relationship between the decreasing number of Cl substituents and dechlorination reaction kinetics agrees with the ?G values predicted by the computational model. Therefore, the lowest energy pathway for C-vCl bond dissociation predicted computationally agrees with the experimentally determined kinetic data. The experimental results from these studies have helped to improve our understanding of the dechlorination mechanisms, thereby offering insight into the most efficient pathways for remediation in the environment. This methodology shows promise for the development of an economic and sustainable field application for the treatment of other chlorinated aromatic compounds. In further work, developments will be made in the modification of the system to allow for the implemetation of field-scale applications.Chloroanisoles are compounds that have similar properties to chlorophenols, but have a higher tendency to bioaccumulate and resist degradation because of their lipophilicity. They are not manufactured for commercial use, but exist in equilibrium with chlorophenols in the environment through biological transformation. Due to the toxicity of both compounds, a strategy for remediation is highly sought after. This study has served to develop an approach to meet the needs for this treatment, based on the successful treatment of PCPs using zero-valent magnesium (ZVMg) discussed in Chapter 1. The results of the method, which makes use of ZVMg/C in acidified ethanol, are compared for both target analytes. Both substrates were degraded to less-chlorinated byproducts within the first four hours; however PCP vanished at a faster rate with no detection at seven minutes. The more heavily-chlorinated byproducts showed faster degradation rates for both compounds, which also had 2,4-dichlorinated congeners in common as major byproducts. The mole balances of PCA and PCP were 92.6% and 94.8%, respectively. Further studies were done to enhance degradation kinetics by re-spiking with acetic acid after two weeks. Although complete degradation was still not achieved, a slight improvement was observed for bothvicompounds, more so with respect to PCP. Kinetic data followed pseudo first-order trends for the degradation of both PCA and PCP.
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Date Issued: 2016
Identifier: CFE0006456, ucf:51433
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006456

Title: Theoretical-Experimental Study of the Two-Photon Circular Dichroism of Helicenes and Aromatic Amino Acids in the UV Region: From the Structure-Property Relationship to the Final Implementation.
Creator: Vesga Prada, Yuly Katherine, Hernandez, Florencio, Huo, Qun, Chumbimuni Torres, Karin, Zou, Shengli, Tatulian, Suren, University of Central Florida
Abstract / Description: Two-photon circular dichroism (TPCD) has been recognized for its exceptional spectroscopic ability for the structural and conformational analysis of chiral systems due to its high sensitivity to small peptide structural distortions. In 2008, Hernandez and co-workers demonstrated TPCD experimentally by the development of the Double L-scan technique. Since then, we have been working on a systematic theoretical-experimental study of chiral molecules using TPCD. In this dissertation, I present my...
Show moreTwo-photon circular dichroism (TPCD) has been recognized for its exceptional spectroscopic ability for the structural and conformational analysis of chiral systems due to its high sensitivity to small peptide structural distortions. In 2008, Hernandez and co-workers demonstrated TPCD experimentally by the development of the Double L-scan technique. Since then, we have been working on a systematic theoretical-experimental study of chiral molecules using TPCD. In this dissertation, I present my contribution to the continuation to the study of the structure-property relationship of TPCD in molecules with axial chirality in solution, as well as the implementation of the TPCD measurements in the near- and far-UV regions. Employing a theoretical-experimental approach I will discuss: 1) the effect of the pulse width of the excitation source on the TPCD spectra of biaryl derivatives, 2) the theoretical study of the TPCD signal in the far-UV on molecular structures simulating aromatic amino acid residues in proteins with secondary structures, and 3) the pros and cons of the implementation of the FUV-TPCD spectrometer. The outcomes of my research reveal the potential of TPCD for the conformational analysis of relatively complex molecular systems such as peptides in the far-UV region, an area never accessed before. Additionally, we exposed the applicability of TPCD as a complimentary method to standard electronic circular dichroism (ECD) for the study of complex structures. Finally, I demonstrate for the very first time experimental evidence of TPCD in the near- to Far-UV region.
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Date Issued: 2016
Identifier: CFE0006514, ucf:51375
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006514

Title: Analysis of Benzopyrenes and Benzopyrene Metabolites by Fluorescence Spectroscopy Techniques.
Creator: Al-Farhani, Bassam, Campiglia, Andres, Harper, James, Zou, Shengli, Frazer, Andrew, Lee, Woo Hyoung, University of Central Florida
Abstract / Description: Polycyclic aromatic hydrocarbons (PAHs) are some of the most common and toxic pollutants encountered worldwide. Presently, monitoring is restricted to sixteen PAHs, but it is well understood that this list omits many toxic PAHs. Among the (")forgotten(") PAHs, isomers with molecular weight 302 are of particular concern due to their high toxicological properties. The chromatographic analysis of PAHs with MW 302 is challenged by similar retention times and virtually identical mass fragmentation...
Show morePolycyclic aromatic hydrocarbons (PAHs) are some of the most common and toxic pollutants encountered worldwide. Presently, monitoring is restricted to sixteen PAHs, but it is well understood that this list omits many toxic PAHs. Among the (")forgotten(") PAHs, isomers with molecular weight 302 are of particular concern due to their high toxicological properties. The chromatographic analysis of PAHs with MW 302 is challenged by similar retention times and virtually identical mass fragmentation patterns.The first original component of this dissertation evolves from a high-resolution spectroscopic approach specifically developed to fulfil this gap. Herein, 4.2 K Laser-Excited Time-Resolved Shpol'skii Spectroscopy (4.2K LETRSS) is applied to the analysis of HMW-PAHs in a complex coal tar standard reference material (SRM 1597a). The spectral and lifetime information obtained with LETRSS provide the required selectivity for the unambiguous determination of PAH isomers in the high-performance liquid chromatography (HPLC) fractions. Complete LETRSS analysis is possible with microliters of HPLC fractions and organic solvent. The excellent analytical figures of merit associated to its non-destructive nature, which provides ample opportunity for further analysis with other instrumental methods, makes this approach a unique alternative for the analysis of isomers of HMW-PAHs in complex environmental samples.The second original component of this dissertation focuses on the development of screening methodology for the routine analysis of PAH metabolites in urine samples. It explores the room-temperature fluorescence (RTF) properties of 3-hydroxy-benzo[a]pyrene, benzo[a]pyrene-trans-9,10-dihydrodiol, benzo[a]pyrene-r-7,t-8,c-9-tetrahydrotriol and benzo[a]pyrene-r-7,t-8,c-9,c-10-tetrahydrotetrol previously extracted with octadecyl-silica membranes. RTF measurements from extraction membranes are carried out with the aid of fiber optic probe that eliminates the need for manual optimization of signal intensities. Relative standard deviations varying from 2.07% (benzo[a]pyrene-r-7,t-8,c-9-tetrahydrotriol) to 8.55% (3-hydroxy-benzo[a]pyrene) were obtained with a straightforward procedure. Analytical recoveries from human urine samples varied from 87.54 (&)#177; 3.11% (3-hydroxy-benzo[a]pyrene) to 99.77 (&)#177; 2.48% (benzo[a]pyrene-r-7,t-8,c-9,c-10-tetrahydrotetrol). The excellent analytical figures of merit and the simplicity of the experimental procedure demonstrate the potential of Solid phase extraction-RTF for screening biomarkers of PAH exposure in numerous urine samples.
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Date Issued: 2016
Identifier: CFE0006520, ucf:51363
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006520

Title: Development of a nano-sensing approach and a portable prototype for real-time detection and quantification of free mercury in stream-flow: combining science and engineering in pro of the environment.
Creator: Chemnasiri, Warinya, Hernandez, Florencio, Kuebler, Stephen, Zou, Shengli, Uribe Romo, Fernando, Huo, Qun, University of Central Florida
Abstract / Description: Mercury (Hg) is a well-known hazardous environmental contaminant existing in several forms, but all are toxic to human in one way or the others. Since Hg usually settles into water polluting the environment and accumulating in living organisms, it is crucial to monitor Hg levels in the aquatic ecosystem. Although there are many well established techniques currently used to detect Hg, most of them require elaborate and time-consuming sample preparation and pre-concentration procedures, as well...
Show moreMercury (Hg) is a well-known hazardous environmental contaminant existing in several forms, but all are toxic to human in one way or the others. Since Hg usually settles into water polluting the environment and accumulating in living organisms, it is crucial to monitor Hg levels in the aquatic ecosystem. Although there are many well established techniques currently used to detect Hg, most of them require elaborate and time-consuming sample preparation and pre-concentration procedures, as well as costly and bulky equipment that limit their practical application in the field. In order to overcome the existent limitations in Hg determination methods, Hernandez and co-workers proposed the first surface Plasmon resonance (SPR) (-) based Hg sensor using gold nanorods (AuNRs) that offers high sensitivity and selectivity, attributed to the strong affinity between Au and Hg. In this dissertation, I first present my contribution to the understanding of the effect of size and aspect ratio of AuNRs on the limit of detection (LOD) and the dynamic range (DR) of the SPR-based Hg sensor using the qualitative model. In this part I demonstrate how both sensitivity and DR can be improved simultaneously via a modified wet chemistry procedure. Then, I show our approach towards the immobilization of AuNRs silane coated glass slides to expand the application of the SPR-based Hg sensor to stream-flow. Finally, I present the design and fabrication of the first real prototype of the SPR-based Hg sensor, and its application in stream-flow detection and speciation of mercury in the environment. The outcomes of my research have resulted in an innovative real-time portable Hg sensor apparatus with the desired high sensitivity, selectivity and DR to be used in stream-flow applications in Oak Ridge National Labs sites.
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Date Issued: 2015
Identifier: CFE0006283, ucf:51589
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006283

Title: Study of Polychlorinated Biphenyl Dechlorination by Zero Valent Magnesium With and Without Activated Carbon in Acidified Ethanol-Ethyl Lactate System.
Creator: Zullo, Fiona, Yestrebsky, Cherie, Clausen, Christian, Campiglia, Andres, Zou, Shengli, Duranceau, Steven, University of Central Florida
Abstract / Description: Polychlorinated biphenyls (PCBs) are synthetic organic chemicals that ca de detected in the environment worldwide. PCBs were banned in the U.S in 1979 owing to their toxicity and persistence in the environment. Today PCBs are classified as human carcinogens and are among the top ten of the U.S Environmental Protection Agency's (EPA) most toxic chemicals. Many researchers have shown soil to be contaminated with PCBs at concentrations as high as 750 ppm. Given the toxicity of PCBs, there is an...
Show morePolychlorinated biphenyls (PCBs) are synthetic organic chemicals that ca de detected in the environment worldwide. PCBs were banned in the U.S in 1979 owing to their toxicity and persistence in the environment. Today PCBs are classified as human carcinogens and are among the top ten of the U.S Environmental Protection Agency's (EPA) most toxic chemicals. Many researchers have shown soil to be contaminated with PCBs at concentrations as high as 750 ppm. Given the toxicity of PCBs, there is an urgent need to extract and degrade such chemicals from contaminated soil in a cost effective way. Prior work revealed a novel method of degradation of PCBs via hydrodehalogenation with zero-valent magnesium in acidified ethanol and ethyl lactate as a solvent system. Even though this degradation method gave satisfactory results for PCB degradation, this system cannot tolerate more than 3% water in order to degrade PCBs, limiting its application to wet soil field samples. In the present work a new system of acidified ethanol and ethyl lactate with ZVMg over activated carbon was developed which shows promising results on the degradation process of PCBs even with water present in the system. A detailed study of the byproducts formed in the dechlorination process and a degradation pathway, along with the activity of the system over time, are presented in this research.Also, a study of the mechanism involved in this reaction was done via computational methods to elucidate a mechanism pathway. It was demonstrated that these reactions are exothermic and involved two transition states, the formation of the first transition state being the limiting step of this reaction.The torsion angle of the PCB congeners was also shown to be an extremely important factor in order to be able to use activated carbon as part of the remediation process. These findings allow a greater understanding of the reductive dechlorination assisted by ZVMg and will help to improve the remediation process in field samples.
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Date Issued: 2016
Identifier: CFE0006205, ucf:51105
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006205

Title: Fabrication and Study of Graphene-Based Nanocomposites for Sensing and Energy Applications.
Creator: McInnis, Matthew, Zhai, Lei, Yestrebsky, Cherie, Zou, Shengli, Blair, Richard, Chen, Quanfang, University of Central Florida
Abstract / Description: Graphite is an allotrope of carbon made up of atomically thin sheets, each covalently bound together, forming a ?-conjugated network. An individual layer, called graphene, has extraordinary electrical, thermal and physical properties that provide the opportunity for innovating new functional composites. Graphene can be produced directly on a metallic substrate by chemical vapor deposition or by chemical oxidation of graphite, forming a stable aqueous suspension of graphene oxide (GO), which...
Show moreGraphite is an allotrope of carbon made up of atomically thin sheets, each covalently bound together, forming a ?-conjugated network. An individual layer, called graphene, has extraordinary electrical, thermal and physical properties that provide the opportunity for innovating new functional composites. Graphene can be produced directly on a metallic substrate by chemical vapor deposition or by chemical oxidation of graphite, forming a stable aqueous suspension of graphene oxide (GO), which allows for convenient solution processing techniques. For the latter, after thermal or chemical reduction, much of the properties of the starting graphene re-emerge due to the reestablishment of ?-conjugation. The ?-conjugated basal plane of graphene has been shown to influence the crystallization of ?-conjugated polymers, providing thermodynamically strong nucleation sites through the relatively strong ?-? interactions. These polymers can homocrystallize into 1-D filaments, but when nucleated from graphene, the orientation and geometry can be controlled producing hierarchical structures containing an electrical conductor decorated with wires of semi-conducting polymer. The resulting structures and crystallization kinetics of the conjugated polymer, poly(3-hexylthiophene-2,5-diyl) (P3HT) nucleated by graphene was studied. Further, field-effect transistors were developed using graphene as both the electrodes and the polymer crystallization surface to directly grow P3HT nanowires as the active material. This direct crystallization technique lead to higher charge mobility and higher on-off ratios, and this result was interpreted in terms of the morphology and polymer-graphene interface.Besides these thin-film technologies, neat GO suspensions can be lyophilized to produce monolithic, free-standing aerogels and then reduced to produce an electrically conductive porous material with a surface area greater than 1000 m2/g. The present research focuses on functionalizing the aerogel surfaces with metal nanoparticles to increase electrical conductivity and to impart functionality. Functionalization was carried out by adding a metal salt as a precursor and a chelating agent to inhibit GO flocculation. The GO and metal salt were simultaneously reduced to form rGO aerogels homogeneously loaded with metal nanoparticles. The size and distribution of these nanoparticles was controlled by concentration and chelating agent identity and abundance. Optimum aerogel formulations were used as a functioning and reversible conductometric hydrogen gas sensor and as an anode in an asymmetric supercapacitor with excellent properties.
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Date Issued: 2015
Identifier: CFE0006227, ucf:51066
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006227

Title: Detection of Inorganic Phosphate in Environmental Water Samples using a Terbium and Gold Nanoparticle-based FRET Chemosensor.
Creator: Johnson, Madeleine, Campiglia, Andres, Zou, Shengli, Harper, James, Frazer, Andrew, Khondaker, Saiful, University of Central Florida
Abstract / Description: A novel chemosensor for the detection of inorganic phosphate (Pi) in environmental water samples is outlined. The sensing solution is comprised of a luminescent lanthanide, terbium (Tb3+), chelated to ethylenediaminetetraacetic acid (EDTA) acid in solution with cetyltrimethylammonium bromide (CTAB)- capped gold nanoparticles (AuNPs). The Tb-EDTA and AuNPs undergo a Fluorescence resonance energy transfer (FRET) mechanism in which the Tb3+ luminescence is quenched. Upon the addition of...
Show moreA novel chemosensor for the detection of inorganic phosphate (Pi) in environmental water samples is outlined. The sensing solution is comprised of a luminescent lanthanide, terbium (Tb3+), chelated to ethylenediaminetetraacetic acid (EDTA) acid in solution with cetyltrimethylammonium bromide (CTAB)- capped gold nanoparticles (AuNPs). The Tb-EDTA and AuNPs undergo a Fluorescence resonance energy transfer (FRET) mechanism in which the Tb3+ luminescence is quenched. Upon the addition of inorganic phosphate (Pi), the AuNPs begin to aggregate and precipitate out of solution. The aggregation of AuNPs results in the restoration of the Tb-EDTA signal which can then be correlated to Pi concentration in the matrix of analysis. The developed sensor has the potential for on-site monitoring of Pi in environmental waters at the sampling location; this would be advantageous for the prevention and understanding of eutrophication events caused by anthropogenic release of nutrients such as Pi. The limit of detection (LOD) of the luminescence sensor (83 ppb-Pi) is within the range of LODs previously reported for on-site monitoring of Pi. Quantitative analysis carried out via the multiple standard additions method provided accurate determination of Pi concentrations in heavily contaminated environmental waters. Additional studies include the synthesis of an organic antenna for the sensitization of the lanthanide ion and further improvement of detection levels.
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Date Issued: 2017
Identifier: CFE0006747, ucf:51874
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006747

Title: An Adhesive Vinyl-Acrylic Electrolyte and Electrode Binder for Lithium Batteries.
Creator: Tran, Binh, Zhai, Lei, Zou, Shengli, Kuebler, Stephen, Hernandez, Florencio, Gesquiere, Andre, University of Central Florida
Abstract / Description: This dissertation describes a new vinyl-acrylic copolymer that displays great potential for applications in lithium ion batteries by enabling novel, faster, safer and cost-effective processes. Understanding the chemistry of materials and processes related to battery manufacturing allows the design of techniques and methods that can ultimately improve the performance of existing batteries while reducing the cost. The first and second parts of this dissertation focuses on the free radical...
Show moreThis dissertation describes a new vinyl-acrylic copolymer that displays great potential for applications in lithium ion batteries by enabling novel, faster, safer and cost-effective processes. Understanding the chemistry of materials and processes related to battery manufacturing allows the design of techniques and methods that can ultimately improve the performance of existing batteries while reducing the cost. The first and second parts of this dissertation focuses on the free radical polymerization of poly(ethylene glycol) methyl ether methacrylate (PEGMA), methyl methacrylate (MMA), and isobutyl vinyl ether (IBVE) monomers to afford a vinyl-acrylic poly(PEGMA-co-MME-co-IBVE) random copolymer and the investigation of its properties as a soluble, amorphous, and adhesive electrolyte that is able to permanently hold 800 times its own weight. Such material properties envision a printable battery manufacturing procedure, since existing electrolytes lack adhesion at a single macromolecular level. Electrolytes can also be used as an electrode binder so long as it has structural integrity and allows ion transfer to and from the active electrode material during insertion/extraction processes. In the third section, the use of this electrolyte as a water-soluble binder for the aqueous fabrication of LiCoO2 cathodes is presented. Results of this study demonstrated the first aqueous process fabrication of thick, flexible, and fully compressed lithium ion battery electrodes by using commercial nickel foam as a supporting current collector. This feat is rather impressive because these properties are far superior to other aqueous binders in terms of material loading per electrode, specific area capacity, durability, and cell resistance. Finally, the fourth section expands on this concept by using the poly(PEGMA-co-MMA-co-IBVE) copolymer for the aqueous fabrication of a low voltage Li4Ti5O12 anode type electrode. Altogether, results demonstrate as a proof of concept that switching the current toxic manufacturing of lithium-ion batteries to an aqueous process is highly feasible. Furthermore, new electrode manufacturing techniques are also deemed possible.
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Date Issued: 2013
Identifier: CFE0004761, ucf:49780
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004761

Title: Novel optical properties of metal nanostructures based on surface plasmons.
Creator: Wang, Haining, Zou, Shengli, Liao, Yi, Kolpashchikov, Dmitry, Gesquiere, Andre, Su, Ming, University of Central Florida
Abstract / Description: Surface plasmons have been attracted extensive interests in recent decades due to the novel properties in nanometer sized dimensions. My work focused on the novel optical properties of metal nanostructures based on surface plasmons using theoretical simulation methods. In the first part, we investigated metal nanofilms and nanorods and demonstrated that extremely low scattering efficiency, high absorption efficiency and propagation with long distance could be obtained by different metal...
Show moreSurface plasmons have been attracted extensive interests in recent decades due to the novel properties in nanometer sized dimensions. My work focused on the novel optical properties of metal nanostructures based on surface plasmons using theoretical simulation methods. In the first part, we investigated metal nanofilms and nanorods and demonstrated that extremely low scattering efficiency, high absorption efficiency and propagation with long distance could be obtained by different metal nanostructures. With a perforated silver film, we demonstrated that an extremely low scattering cross section with an efficiency of less than 1% can be achieved at tunable wavelengths with tunable widths. The resonance wavelength, width, and intensity are influenced by the shape, size and arrangement pattern of the holes, as well as the distance separating the holes along the polarization direction. The extremely low scattering could be used to obtain high absorption efficiency of a two-layer silver nanofilm. Using the discrete dipole approximation method, we achieved enhanced absorption efficiencies, which are close to 100%, at tunable wavelengths in a two-layer silver thin film. The film is composed of a 100 nm thick perforated layer facing the incident light and a 100 nm thick solid layer. Resonance wavelengths are determined by the distances between perforated holes in the first layer as well as the separation between two layers. The resonance wavelengths shift to red with increasing separation distance between two layers or the periodic distance of the hole arrays. Geometries of conical frustum shaped holes in the first layer are critical for the improved absorption efficiencies. When the hole bottom diameter equals the periodic distance and the upper diameter is about one-third of the bottom diameter, close to unit absorption efficiency can be obtained. We examined the electromagnetic wave propagation along a hollow silver nanorod with subwavelength dimensions. The calculations show that light may propagate along the hollow nanorod with growing intensities. The influences of the shape, dimension, and length of the rod on the resonance wavelength and the enhanced local electric field, |E|2, along the rod were investigated. In the second part, a generalized electrodynamics model is proposed to describe the enhancement and quenching of fluorescence signal of a dye molecule placed near a metal nanoparticle (NP). Both the size of the Au NPs and quantum yield of the dye molecule are crucial in determining the emission intensity of the molecule. Changing the size of the metal NP will alter the ratio of the scattering and absorption efficiencies of the metal NP and consequently result in different enhancement or quenching effect to the dye molecule. A dye molecule with a reduced quantum yield indicates that the non-radiative channel is dominant in the decay of the excited dye molecules and the amplification of the radiative decay rate will be easier. In general, the emission intensity will be quenched when the size of metal NP is small and the quantum yield of dye molecule is about unity. A significant enhancement factor will be obtained when the quantum yield of the molecule is small and the particle size is large. When the quantum yield of the dye molecule is less than 10-5, the model is simplified to the surface enhanced Raman scattering equation.
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Date Issued: 2013
Identifier: CFE0004769, ucf:49786
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004769

Title: Synthesis of Fluorene-based derivatives, Characterization of Optical properties and their Applications in Two-photon Fluorescence Imaging and Photocatalysis.
Creator: Githaiga, Grace, Belfield, Kevin, Patino Marin, Pedro, Chumbimuni Torres, Karin, Zou, Shengli, Cheng, Zixi, University of Central Florida
Abstract / Description: The two-photon absorption (2PA) phenomenon has attracted attention from various fields ranging from chemistry and biology to optics and engineering. Two of the common NLO applications in which organic materials have been used are three-dimensional (3D) fluorescence imaging and optical power limiting. Two-photon absorbing materials are, therefore, in great demand to meet the needs of emerging technologies. Organic molecules show great promise to meet this need as they can be customized through...
Show moreThe two-photon absorption (2PA) phenomenon has attracted attention from various fields ranging from chemistry and biology to optics and engineering. Two of the common NLO applications in which organic materials have been used are three-dimensional (3D) fluorescence imaging and optical power limiting. Two-photon absorbing materials are, therefore, in great demand to meet the needs of emerging technologies. Organic molecules show great promise to meet this need as they can be customized through molecular engineering, and as the development of two-photon materials that suit practical application intensifies, so does research to meet this need. However, there remains some uncertainty in the particulars of design criteria for molecules with large 2PA cross sections at desired wavelengths, as such research to understand structure-property relationships is matter of significant importance. As a result, the full potential of 2PA materials has not been fully exploited. Several strategies to enhance the magnitude and tune the wavelength of 2PA have been reported for ?-conjugated organic molecules. On this account, we have designed novel fluorophores using the fluorene moiety and modified it to tune the properties of the compounds.Chapter 2 of this dissertation reports the successful application of fluorene-based compounds in photocatalysis; a process that involves the decomposition of organic compounds into environmentally friendly carbon dioxide and water attesting to the photostability of the fluorene moiety. A facile organic nanoparticle preparation method is reported in chapter 3 using the reprecipitation method, whose surface was then modified using a naturally occurring surfactant, Lecithin, and were then successfully used in fluorescence cell imaging. Chapter 4 reports the design and synthesis of a fluorene-based compound using an acceptor, s-indacene-1, 3, 5, 7(2H, 6H)-tetra one, or Janus Dione, a moiety that is relatively new and that has not been fully exploited despite its very attractive features. Owing to the hydrophobicity of this compound, notwithstanding its unprecedented 2PA cross section, it was not applicable in fluorescence cell imaging but provided the tenets for the design of related derivative. This limitation was circumvented in the concluding chapter by tuning the compound's hydrophilicity. The hydrophilic Janus dione probe was then used as envisioned for cell imaging as the dual prerequisites for fluorescence imaging probes; large 2PA cross sections and high fluorescence quantum yields were met.
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Date Issued: 2015
Identifier: CFE0005620, ucf:50207
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005620

Title: Enhanced Two-Photon Absorption in a Squaraine-Fluorene-Squaraine Dye: Design, Synthesis, Photophysical Properties, and Solvatochromic Behavior.
Creator: Moreshead, William, Belfield, Kevin, Campiglia, Andres, Zou, Shengli, Frazer, Andrew, Beiler, Rosalind, University of Central Florida
Abstract / Description: The discovery of any new technology is usually accompanied by a need for new or improved materials which make that technology useful in practical applications. In the case of two-photon absorption (2PA) this has truly been the case. Since its first demonstration in 1961, there has been an ever increasing quest to understand the relationships between two-photon absorption and the structure of two-photon absorbing materials. This quest has been motivated by the many applications for 2PA which...
Show moreThe discovery of any new technology is usually accompanied by a need for new or improved materials which make that technology useful in practical applications. In the case of two-photon absorption (2PA) this has truly been the case. Since its first demonstration in 1961, there has been an ever increasing quest to understand the relationships between two-photon absorption and the structure of two-photon absorbing materials. This quest has been motivated by the many applications for 2PA which have been reported, including fluorescence bioimaging, 3D microfabrication, 3D optical data storage, upconverted lasing, and photodynamic therapy.The work presented in this dissertation represents another step in the effort to better understand the structure/property relationships of 2PA. In this work a new, squaraine-fluorene-squaraine molecule, proposed through a joint effort of quantum and synthetic chemists, was synthesized and its photophysical properties were measured. The measurements included linear and two-photon photophysical properties, as well as solvatochromic behavior. Quantum calculations were done to aid in understanding those photophysical and solvatochromic properties. A single squaraine dye was also synthesized and used as a model compound to assist in understanding this new structure.In Chapter 1 an introduction to 2PA and several of its applications is given. Chapter 2 gives a background of 2PA structure/property relationships that have been reported to date, based on work done with polymethine dyes. Chapter 3 gives a full account of the synthesis, characterization, and detailed quantum chemical analyses of this new squaraine-fluorene-squaraine molecule and the corresponding model compound squaraine dye. Chapter 4 gives some additional work and suggested future directions.
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Date Issued: 2013
Identifier: CFE0005384, ucf:50450
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005384

Title: Light-Matter Interactions of Plasmonic Nanostructures.
Creator: Reed, Jennifer, Zou, Shengli, Belfield, Kevin, Zhai, Lei, Hernandez, Eloy, Vanstryland, Eric, University of Central Florida
Abstract / Description: Light interaction with matter has long been an area of interest throughout history, spanning many fields of study. In recent decades, the investigation of light-matter interactions with nanostructures has become an intense area of research in the field of photonics. Metallic nanostructures, in particular, are of interest due to the interesting properties that arise when interacting with light. The properties are a result of the excitation of surface plasmons which are the collective...
Show moreLight interaction with matter has long been an area of interest throughout history, spanning many fields of study. In recent decades, the investigation of light-matter interactions with nanostructures has become an intense area of research in the field of photonics. Metallic nanostructures, in particular, are of interest due to the interesting properties that arise when interacting with light. The properties are a result of the excitation of surface plasmons which are the collective oscillation of the conduction electrons in the metal. Since the conduction electrons can be thought of as harmonic oscillators, they are quantized in a similar fashion. Just as a photon is a quantum of oscillations of an electromagnetic field, the plasmon is a quantum of electron oscillations of a metal. There are three types of plasmons:1. Bulk plasmons, also called volume plasmons, are longitudinal density fluctuations which propagate through a bulk metal with an eigenfrequency of ?_p called the plasma frequency.2. Localized surface plasmons are non-propagating excitations of the conduction electrons of a metallic nanoparticle coupled to an electromagnetic field. 3. Surface plasmon polaritons are evanescent, dispersive propagating electromagnetic waves formed by a coupled state between a photon and the excitation of the surface plasmons. They propagate along the surface of a metal-dielectric interface with a broad spectrum of eigenfrequencies from ?=0 to ?= ?_p??2. Plasmonics is a subfield of photonics which focuses on the study of surface plasmons and the optical properties that result from light interacting with metal films and nanostructures on the deep subwavelength scale. In this thesis, plasmonic nanostructures are investigated for optical waveguides and other nanophotonic applications through computational simulations primarily base on electrodynamic theory. The theory was formulated by several key figures and established by James Clerk Maxwell after he published a set of relations which describe all classical electromagnetic phenomena, known as Maxwell's equations. Using methods based on Maxwell's equations, the optical properties of metallic nanostructures utilizing surface plasmons is explored. In Chapter 3, light propagation of bright and dark modes of a partially and fully illuminated silver nanorod is investigated for waveguide applications. Then, the origin of the Fano resonance line shape in the scattering spectra of a silver nanorod is investigated. Next, in Chapter 4, the reflection and transmission of a multilayer silver film is simulated to observe the effects of varying the dielectric media between the layers on light propagation. Building on the multilayer film work, metal-insulator-metal waveguides are explored by perforating holes in the bottom layer of a two layer a silver film to investigate the limits of subwavelength light trapping, confinement, and propagation. Lastly, in Chapter 5, the effect of surface plasmons on the propagation direction of electromagnetic wave around a spherical silver nanoparticle which shows an effective negative index of refraction is examined. In addition, light manipulation using a film of silver prisms with an effective negative index of refraction is also investigated. The silver prisms demonstrate polarization selective propagation for waveguide and optical filter applications. These studies provide insight into plasmonic mechanisms utilized to overcome the diffraction limit of light. Through better understanding of how to manipulating light with plasmonic nanostructures, further advancements in nanophotonic technologies for applications such as extremely subwavelength waveguides, sensitive optical detection, optical filters, polarizers, beam splitters, optical data storage devices, high speed data transmission, and integrated subwavelength photonic circuits can be achieved.
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Date Issued: 2013
Identifier: CFE0005049, ucf:49964
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005049

Title: Synthesis and Study of Chemo-Hydrothermally Derived Water-Soluble Chitosan and Chiosan-Metal Oxide Composites.
Creator: Basumallick, Srijita, Santra, Swadeshmukul, Kolpashchikov, Dmitry, Zou, Shengli, Ye, Jingdong, Seal, Sudipta, University of Central Florida
Abstract / Description: Chitosan (CS) is a man-made sugar based biopolymer derived from chitin, the second most abundant natural polymer after cellulose. Chitin is sourced from crustacean species such as shrimps and crabs. The chemical structure of chitin contains N-Acetyl D-glucosamine monomer units which forms CS upon deacetylation. In CS, ?-(1-4) linked D-glucosamine units are randomly distributed. Approximately 75% - 80% sugar units contains primary amine groups in commercially available low molecular weight CS....
Show moreChitosan (CS) is a man-made sugar based biopolymer derived from chitin, the second most abundant natural polymer after cellulose. Chitin is sourced from crustacean species such as shrimps and crabs. The chemical structure of chitin contains N-Acetyl D-glucosamine monomer units which forms CS upon deacetylation. In CS, ?-(1-4) linked D-glucosamine units are randomly distributed. Approximately 75% - 80% sugar units contains primary amine groups in commercially available low molecular weight CS. Biodegradability, low toxicity, mucoadhesive and transfecting properties of CS polymer are attractive for applications as oral and nasal drug delivery systems. Chitosan polymer is water insoluble at neutral pH. To solubilize CS, dilute mineral acid (such as hydrochloric acid and nitric acid) or organic acid (such as acetic acid) is often used. CS contains both hydroxyl and primary amine groups in its structure. In acidic solution, the amine functional groups become protonated (positively charged). Positively charged CS remains stable only in low pH condition due to electrostatic repulsion of charged polymer segments. Therefore, by using a suitable anionic (negatively charged) cross-linker, stable CS particles (such as nanoparticles and microspheres) can be prepared. This is popularly known as ionic gelation method. Extensive studies have been done on the synthesis of drug loaded CS particles where particle integrity is maintained by ionic gelation using tripolyphosphate (TPP, an anionic cross-linker). Drug encapsulated CS-TPP composite particles are shown to maintain biodegradability and biocompatibility. The CS-TPP composite particles exhibits very limited dispersibility at neutral pH conditions specifically in neutral buffered conditions. A number of biomedical applications (including systemic drug formulations) however demands buffer-stable CS composite particles for achieving optimal therapeutic outcome.To overcome the above dispersibility issues, CS polymer and CS particles units have been chemically modified using water soluble motifs (such as water soluble polymer or ligands). This approach is very cumbersome and usually involves multiple purification steps. Chemical modification of natural CS chain introduces risks of compromising biodegradability and biocompatibility. Therefore, there is a strong need for developing a straightforward method of making water soluble CS and CS particles.Chapter 1 of this dissertation presents an overview of the CS polymer, various applications of CS polymers, methods of making CS polymers and CS particles, current limitations of synthesis methods for preparing stable chitosan particles at neutral pH conditions and finally delineates the scope of the proposed research work.Chapter 2 describes development of chemo-hydrothermal synthesis method for producing water soluble CS polymer and water dispersible CS composite particles. In this method, a chemical (depolymerizing agent) is used to treat CS polymer in a hydrothermal (high temperature and high pressure) condition. Two types of depolymerizing agents have been used, an inorganic acid (e.g. hydrochloric acid, HCl) and a bicarboxylic organic acid (e.g. tartaric acid, TA). In both cases, 100% depolymerized CS polymer was obtained. Chemical characteristics of the depolymerized CS were comparable to acid solubilized CS. CS polymer exhibits weak fluorescence. Interestingly, hydrothermally depolymerized CS shows strong fluorescence properties irrespective of the nature of depolymerizing agent used. TA not only depolymerized CS but also formed CS-TA composite particulate structures in solution via self-assembly. The CS-TA composite particles are stable in a wide pH range from 5 to 11. Detailed spectroscopic and microscopic studies have been done to understand the basic mechanism of particle formation and increase in fluorescence properties (i.e. structure-property relationship). Usefulness of CS-TA in solubilizing water-insoluble cargos (such as fluorescein isothiocyanate, FITC) has been demonstrated.Chapter 3 is focused on hydrothermal synthesis of mixed-valence copper (Cu) oxide loaded CS-TA composite particles and their characterization. Crystalline Cu oxide nanoparticles were coated with the CS-TA layer. Water dispersibility of Cu oxide greatly improved upon coating with CS-TA material. To demonstrate catalytic activity of Cu-oxide loaded CS-TA film in sequestering carbon dioxide (CO2), an electrochemical setup was used. Electrochemical reduction of CO2 was successfully demonstrated. It was observed that CS-TA environment not only maintained catalytic properties of Cu oxide but also allowed solution processing of Cu-oxide film onto the electrode surface.Chapter 4 discusses a convenient method of making monodispersed water dispersible Cu loaded chitosan nanoparticles (Cu-CS) using HCl depolymerized CS polymer. The purpose of this study was to investigate if there was any improvement in antibacterial properties of Cu-CS nanoparticles prepared using hydrothermally treated CS polymer. Interestingly, it was observed that the antibacterial efficacy of Cu was not compromised in Cu-CS nanoparticles. Moreover, the materials exhibited improvement in antibacterial efficacy against both Gram-negative and Gram-positive bacteria species. A plausible mechanism has been proposed to explain antibacterial results.Chapter 5 summarizes major findings of this dissertation research and presents future research directions.
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Date Issued: 2014
Identifier: CFE0005461, ucf:50395
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005461

Title: Squaraine dyes, design and synthesis for various functional materials applications.
Creator: Zhang, Yuanwei, Belfield, Kevin, Campiglia, Andres, Zou, Shengli, Frazer, Andrew, Cheng, Zixi, University of Central Florida
Abstract / Description: This dissertation contains the synthesis and characterization of squaraine based new functional materials. In the first part of this thesis work, a water soluble benzothiazolium squaraine dye was synthesized with pyridium pendents, and controlled aggregation properties were achieved. After formation of partially reversible J-aggregation on a polyelectrolyte (poly(acryl acid) sodium salt) template, the nonlinear, two-photon absorption cross section per repeat unit was found to be above 30-fold...
Show moreThis dissertation contains the synthesis and characterization of squaraine based new functional materials. In the first part of this thesis work, a water soluble benzothiazolium squaraine dye was synthesized with pyridium pendents, and controlled aggregation properties were achieved. After formation of partially reversible J-aggregation on a polyelectrolyte (poly(acryl acid) sodium salt) template, the nonlinear, two-photon absorption cross section per repeat unit was found to be above 30-fold enhanced compared with nonaggregate and/or low aggregates. Using a similar strategy, sulfonate anions were introduced into the squaraine structure, and the resulting compounds exhibited good water solubilities. A 'turn on' fluorescence was discovered when these squaraine dyes interacted with bovine serum albumin (BSA), titration studies by BSA site selective reagents show these squaraine dyes can bind to both site I and II of BSA, with a preference of site II. Introduction of these squaraine dyes to BSA nanoparticles generated near-IR protein nano fabricates, and cell images were collected. Metal sensing properties were also studied using the sulfonates containing a benzoindolium squaraine dye, and the linear response of the absorption of the squaraine dye to the concentration of Hg2+ makes it a good heavy metal-selective sensing material that can be carried out in aqueous solution. Later, a squaraine scaffold was attached to deoxyribonucleosides by Sonogashira coupling reactions, in which the reaction conditions were modified. Iodo-deoxyuridine and bromo-deoxyadenosine were used as the deoxyribonucleosides building blocks, and the resulting squaraine dye-modified deoxyribonucleosides exhibited near-IR absorption and emission properties due to the squaraine chromophore. Interestingly, these non-natural deoxyribonucleosdies showed viscosity dependent photophysical properties, which make them nice candidates for fluorescence viscosity sensors at the cellular level. After incubation with cells, these viscosity sensors were readily uptaken by cell, and images were obtained showing regions of high viscosity in cells.
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Date Issued: 2013
Identifier: CFE0005451, ucf:50369
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005451

Title: 1, 2, and 3 Dimension Carbon/Silicon Carbon Nitride Ceramic Composites.
Creator: Calderon Flores, Jean, Zhai, Lei, Campiglia, Andres, Yestrebsky, Cherie, Zou, Shengli, Khondaker, Saiful, University of Central Florida
Abstract / Description: Polymer-derived ceramics (PDCs) are exceptional ultra-high temperature and stable multifunctional class of materials that can be synthesized from a polymer precursor through thermal decomposition. The presented research focuses on 1-D nanofibers, 2-D films and 3-D bulk, carbon-rich silicon carbon nitride (SiCN) ceramics. 1-D nanofibers were prepared via electrospinning for light weight, flame retardant and conductive applications. The commercially available CerasetTM VL20, a liquid...
Show morePolymer-derived ceramics (PDCs) are exceptional ultra-high temperature and stable multifunctional class of materials that can be synthesized from a polymer precursor through thermal decomposition. The presented research focuses on 1-D nanofibers, 2-D films and 3-D bulk, carbon-rich silicon carbon nitride (SiCN) ceramics. 1-D nanofibers were prepared via electrospinning for light weight, flame retardant and conductive applications. The commercially available CerasetTM VL20, a liquid cyclosilazane pre-ceramic precursor, was mixed with polyacrylonitrile (PAN) in order to make the cyclosilazane electrospinnable. Carbon-rich PDC nano?bers were fabricated by electrospinning various ratios of PAN/cyclosilazane solutions followed by pyrolysis. Surface morphology of the electro spun nanofibers characterized by SEM show PDC nano?bers with diameters ranging from 100-300 nm. Also, thermal stability towards oxidation showed a 10% mass loss at 623oC. 2-D carbon/SiCN films were produced by drop-casting a mixture of PAN/cyclosilazane onto a glass slide followed by pyrolysis of the film. Samples ranging from 10:1 to 1:10 PAN:cyclosilazane were made by dissolving the solutes into DMF to produce solutions ranging from 1% to 12% by weight. Green, heat-stabilized, and pyrolyzed 8% films were examined with FTIR to monitor the change in chemical structure at each step of the ceramization. SEM shows that high PAN samples produced films with ceramic embedded spheroid components in a carbon matrix, while high cyclosilazane samples produced carbon embedded spheroid.Finally, this research focuses on the challenge of making fully dense, 3-D bulk PDCs materials. Here we present a composite of SiCN with reduced graphene oxide (rGO) aerogels as a route for fully dense bulk PDCs. Incorporation of the rGO aerogel matrix into the SiCN has its pros and cons. While it lowers the strength of the composite, it allows for fabrication of large bulk samples and an increase in the electrical conductivity of the PDC. The morphology, mechanical, electrical properties and thermal conductivity of graphene-SiCN composite with varying rGO aerogel loading (0.3-2.4%) is presented. The high temperature stability, high electrical conductivity and low thermal conductivity of these composites make them excellent candidates for thermoelectric applications. Generally, carbon-rich SiCN composites with improved thermal and electrical properties are of great importance to the aerospace and electronics industries due to their expected harsh operating environments.
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Date Issued: 2015
Identifier: CFE0005768, ucf:50095
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005768

Title: Chemistry and(&)nbsp;Structure of Ru/SiO2(&)nbsp;and Ru/Al2O3 Interfaces.
Creator: Ezzat, Sameer, Campiglia, Andres, Coffey, Kevin, Zou, Shengli, Frazer, Andrew, Harper, James, Coffey, Kevin, University of Central Florida
Abstract / Description: The resistivity size effect in nanoscale metals is of both scientific and technological interest, the latter due to its importance to interconnects between transistors in integrated circuits. In this work we report the variation of resistivity associated with surface scattering of ex-situ annealed single crystal Ru thin films grown on sapphire substrates by sputter deposition. A set of samples were overcoated with dielectric and subjected to a variety of reducing and oxidizing anneals. The...
Show moreThe resistivity size effect in nanoscale metals is of both scientific and technological interest, the latter due to its importance to interconnects between transistors in integrated circuits. In this work we report the variation of resistivity associated with surface scattering of ex-situ annealed single crystal Ru thin films grown on sapphire substrates by sputter deposition. A set of samples were overcoated with dielectric and subjected to a variety of reducing and oxidizing anneals. The changes in the chemistry and structure of the dielectric interface induced by the anneals, as determined by x-ray reflectivity and x-ray photoelectron spectroscopy measurements, are related to the changes in the specularity of the surface for electron scattering in the context of the Fuchs-Sondheimer semi-classical model of the resistivity size effect.
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Date Issued: 2019
Identifier: CFE0007454, ucf:52727
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007454

Title: Quantum Chemical Studies for the Engineering of Metal Organic Materials.
Creator: Rivera Jacquez, Hector, Masunov, Artem, Balaeff, Alexander, Harper, James, Heider, Emily, Zou, Shengli, Kaden, William, University of Central Florida
Abstract / Description: Metal Organic Materials (MOM) are composed of transition metal ions as connectors and organic ligands as linkers. MOMs have been found to have high porosity, catalytic, and optical properties. Here we study the gas adsorption, color change, and non-linear optical properties of MOMs. These properties can be predicted using theoretical methods, and the results may provide experimentalists with guidance for rational design and engineering of novel MOMs. The theory levels used include semi...
Show moreMetal Organic Materials (MOM) are composed of transition metal ions as connectors and organic ligands as linkers. MOMs have been found to have high porosity, catalytic, and optical properties. Here we study the gas adsorption, color change, and non-linear optical properties of MOMs. These properties can be predicted using theoretical methods, and the results may provide experimentalists with guidance for rational design and engineering of novel MOMs. The theory levels used include semi-empirical quantum mechanical calculations with the PM7 Hamiltonian and, Density Functional Theory (DFT) to predict the geometry and electronic structure of the ground state, and Time Dependent DFT (TD-DFT) to predict the excited states and the optical properties.The molecular absorption capacity of aldoxime coordinated Zn(II) based MOMs (previously measured experimentally) is predicted by using PM7 Theory level. The 3D structures were optimized with and without host molecules inside the pores. The absorption capacity of these crystals was predicted to be 8H2 or 3N2 per unit cell. When going beyond this limit, the structural integrity of the bulk material becomes fractured and microcrystals are observed both experimentally and theoretically.The linear absorption properties of Co(II) based complexes are known to change color when the coordination number is altered. In order to understand the mechanism of this color change TD-DFT methods are employed. The chromic behavior of the Co(II) based complexes studied was confirmed to be due to a chain in coordination number that resulted in lower metal to ligand distances. These distances destabilize the occupied metal d orbitals, and as a consequence of this, the metal to ligand transition energy is lowered enough to allow the crystals to absorb light at longer wavelengths.Covalent organic frameworks (COFs) present an extension of MOM principles to the main group elements. The synthesis of ordered COFs is possible by using predesigned structures andcarefully selecting the building blocks and their conditions for assembly. The crystals formed by these systems often possess non-linear optical (NLO) properties. Second Harmonic Generation (SHG) is one of the most used optical processes. Currently, there is a great demand for materials with NLO optical properties to be used for optoelectronic, imaging, sensing, among other applications. DFT calculations can predict the second order hyperpolarizability ?2 and tensor components necessary to estimate NLO. These calculations for the ?2 were done with the use of the Berry's finite field approach. An efficient material with high ?2 was designed and the resulting material was predicted to be nearly fivefold higher than the urea standard.Two-photon absorption (2PA) is another NLO effect. Unlike SHG, it is not limited to acentric material and can be used development of in vivo bio-imaging agents for the brain. Pt(II) complexes with porphyrin derivatives are theoretically studied for that purpose. The mechanism of 2PA enhancement was identified. For the most efficient porphyrin, the large 2PA cross-section was found to be caused by a HOMO-LUMO+2 transition. This transition is strongly coupled to 1PA allowed Q-band HOMO-LUMO states by large transition dipoles. Alkyl carboxyl substituents delocalize the LUMO+2 orbital due to their strong ?-acceptor effect, enhancing transition dipoles and lowering the 2PA transition to the desirable wavelengths range.The mechanism 2PA cross-section enhancement of aminoxime and aldoxime ligands upon metal addition of is studied with TD-DFT methods. This mechanism of enhancement is found to be caused by the polarization of the ligand orbitals by the metal cation. After polarization an increase in ligand to ligand transition dipole moment. This enhancement of dipole moment is related to the increase in 2PA cross-sections.
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Date Issued: 2015
Identifier: CFE0005990, ucf:50777
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005990

Two-Photon Absorption (3)	+ -
Computational Chemistry (2)	+ -
DFT (2)	+ -
Discrete Dipole Approximation (2)	+ -
Photoacid (2)	+ -

Two-photon absorption (2)	+ -
nanoparticle (2)	+ -
two-photon absorption (2)	+ -
waveguides (2)	+ -
2D Materials (1)	+ -
3 (1)	+ -
5 (1)	+ -
6-trichloro-2-pyridinol (1)	+ -
Activated carbon (1)	+ -
Amyloid fibril (1)	+ -
Azulene (1)	+ -
BODIPY (1)	+ -
Ball-milled zero-valent magnesium (1)	+ -
Beta sheet inhibitor (1)	+ -
Bioimaging (1)	+ -
Biosensors (1)	+ -
Catalysis (1)	+ -
Ceramic nanofibers (1)	+ -
Chemo Hydrothermally Treated (1)	+ -
Chitin (1)	+ -
Chitosan (1)	+ -
Computational chemistry (1)	+ -
Conductive Ceramics (1)	+ -
Continuous metal film (1)	+ -
Copper-Chitosan (1)	+ -

ETD Collection (38)	+ -
Honors Collection (1)	+ -

University of Central Florida (39)	+ -
Zou, Shengli (39)	+ -
Campiglia, Andres (11)	+ -
Harper, James (9)	+ -
Belfield, Kevin (8)	+ -

Frazer, Andrew (8)	+ -
Zhai, Lei (8)	+ -
Yestrebsky, Cherie (6)	+ -
Gesquiere, Andre (5)	+ -
Kolpashchikov, Dmitry (5)	+ -
Beazley, Melanie (4)	+ -
Cheng, Zixi (4)	+ -
Chumbimuni Torres, Karin (4)	+ -
Huo, Qun (4)	+ -
Kuebler, Stephen (4)	+ -
Chen, Gang (3)	+ -
Heider, Emily (3)	+ -
Hernandez, Florencio (3)	+ -
Liao, Yi (3)	+ -
Miles, Delbert (3)	+ -
Randall, Andrew (3)	+ -
Su, Ming (3)	+ -
Ye, Jingdong (3)	+ -
Bhattacharya, Aniket (2)	+ -
Blair, Richard (2)	+ -
Clausen, Christian (2)	+ -
Coffey, Kevin (2)	+ -
Khondaker, Saiful (2)	+ -
Legron-Rodriguez, Tamra (2)	+ -
Masunov, Artem (2)	+ -

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