View All Items

Title: SELF-ASSEMBLY OF SQUARAINE DYES.
Creator: Qaddoura, Maher, Belfield, Kevin, University of Central Florida
Abstract / Description: Squaraine dyes have been a subject of extensive investigations lately due to their wide applications in important technological fields such as bioimaging probes, bioconjucation, second generation photosensitizers for photodynamic therapy, second harmonic generating organic dyes, two-photon absorbing materials with large cross section values, and, finally, photoconducting materials in photovoltaic cells. While a large number of patents and papers has been produced regarding their applications...
Show moreSquaraine dyes have been a subject of extensive investigations lately due to their wide applications in important technological fields such as bioimaging probes, bioconjucation, second generation photosensitizers for photodynamic therapy, second harmonic generating organic dyes, two-photon absorbing materials with large cross section values, and, finally, photoconducting materials in photovoltaic cells. While a large number of patents and papers has been produced regarding their applications limited work has been done concerning their thermotropic behavior, including their liquid crystalline properties, or correlation of the crystalline structure to both the solid state aggregation and their photophysical properties. In the first chapter of this dissertation, a series of squaraine dyes, based on 2, 4-bis squaraine including ethyl, propyl, butyl, pentyl, hexyl, and heptyl derivatives, were synthesized by condensation of the corresponding 4-(N,N-di-n-alkylamino)-2-hydroxyphenol with squaric acid. The thermal behavior of the series was recorded using both thermogravemetic analysis (TGA) and differential scanning calorimetry (DSC) while their crystalline structures were elucidated via single crystal X-ray diffraction. The length of the alkyl chain proved to have a significant effect on both the thermotropic behavior and the crystalline structure of the squaraine series. Two derivatives, butyl and heptyl, revealed the presence of liquid crystalline mesophases, smectic and nematic, respectively, that were confirmed and characterized via polarized light microscopy (PLM) and X-ray diffraction. In the second chapter, J- and H- aggregates were investigated in thin films by UV-vis spectroscopy; several of the derivatives formed H- and/or J-aggregates upon thin film formation via spin coating before and after thermal annealing, as indicated by UV-vis spectroscopy. The molecular structure, crystal structure, aggregation, and thermal behavior provide insight into the supramolecular assembly of this important class of materials. Photophysical measurements revealed large molar absorptivity, reasonably high fluorescence quantum yields, and significant fluorescence anisotropy, making these derivatives suitable candidates for a number of electro-optic and photonics applications. The third chapter was devoted to investigate liquid crystal-directed supramolecular assembly of a squaraine dye. Thus, The squaraine (SQ) dye, 2, 4-bis squaraine was used to prepare a series of SQ dye/cholesteryl pelargonate mixtures with varying dye concentrations (1%, 3%, 7.5%, 10.8%, 15%, and 20% w/w). Their phase transitions were investigated using differential scanning calorimetry, polarized light microscopy and X-ray diffraction. The squaraine dye itself exhibits no liquid crystalline behavior. The concentration of the dye in the cholesteric compound proved to have a significant effect on the dye aggregation behavior and phase transitions in cholesteryl pelargonate manifested by the appearance of new mesophases and formation of J- and H- aggregates. The texture morphology, X-ray diffraction analyses, and UV-vis absorbance spectra provide compelling evidence of the viability of the self-assembly of squaraines in the liquid crystalline mesophase. In the last chapter we will discuss possible modifications that can improve the aggregation systems.
Show less
Date Issued: 2011
Identifier: CFE0003717, ucf:48773
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003717

Title: BLOCK COPOLYMER STABILIZED SELF-ASSEMBLED MAGNETIC NANOPARTICLES.
Creator: ZHANG, LI, BELFIELD, KEVIN, University of Central Florida
Abstract / Description: Magnetic materials are currently being developed in the areas of pharmacology and medicinal chemistry for use in applications such as drug delivery and magnetic resonance imaging. Magnetic fluids are being used in audio equipment and hard disk drives. Their suspension in a particular fluid is promoted by the adsorption or reaction of steric or electrostatic stabilizers, which are appropriate for the particular medium. Critical to the success of these magnetic fluids is the development of the...
Show moreMagnetic materials are currently being developed in the areas of pharmacology and medicinal chemistry for use in applications such as drug delivery and magnetic resonance imaging. Magnetic fluids are being used in audio equipment and hard disk drives. Their suspension in a particular fluid is promoted by the adsorption or reaction of steric or electrostatic stabilizers, which are appropriate for the particular medium. Critical to the success of these magnetic fluids is the development of the steric stabilizers, which must prevent the coagulation of the metal particles. Polymeric materials are one of the most suitable nonmagnetic media to disperse the magnetic nanoparticles, forming polymeric nanocomposites in ferrofluids. We have developed strategies in molecular nanoscience to design polymeric systems for stabilization of magnetic nanoparticles. Ring opening metathesis polymerization (ROMP) was used to prepare a series of novel, well-defined diblock copolymers of bicyclo[2.2.1]hept-5-ene 2-carboxylic acid 2-cyanoethyl ester and bicyclo[2.2.1]hept-2-ene, consisting of both anchoring and steric stabilizing blocks. Both ester and cyano groups were incorporated into the polymers to chelate and stabilize the iron oxide magnetic nanoparticles. These polynorbornene-based copolymers were characterized by GPC, along with 1H NMR, FTIR, DSC, and TGA. Using diblock copolymers as stabilizers, nanostructured maghemite (ã-Fe2O3) magnetic ferrofluids were prepared in toluene or cyclohexanone via thermal decomposition of Fe(CO)5 and then the oxidation of iron nanoparticles. Transmission electron microscopic (TEM) images showed a highly crystalline structure of the ã-Fe2O3 nanoparticles, with average particle size varying from 5 to 7 nm. Polymer films containing iron oxide nanoclusters were also prepared from the diblock copolymers. For comparison, a commercial triblock copolymer (BASF PluronicR F127) surfactant was used to prepare stabilized ferrofluids. In addition to ã-Fe2O3 nanoparticles, other types of magnetic nanoparticles, such as FePt, were investigated using this triblock copolymer as a stabilizer. The results indicated that the norbornene diblock copolymers could also be used for the preparation of FePt stabilized magnetic ferrofluids in the future research work.
Show less
Date Issued: 2004
Identifier: CFE0000230, ucf:46272
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000230

Title: SIMULATION STUDIES OF SELF-ASSEMBLY AND PHASE DIAGRAMOF AMPHIPHILIC MOLECULES.
Creator: Bourov, Geuorgui, Bhattacharya, Aniket, University of Central Florida
Abstract / Description: The aim of this dissertation is to investigate self-assembled structures and the phase diagram of amphiphilic molecules of diverse geometric shapes using a number of different computer simulation methods. The semi-realistic coarse-grained model, used extensively for simulation of polymers and surfactant molecules, is adopted in an off-lattice approach to study how the geometric structure of amphiphiles affects the aggregation properties. The results of simulations show that the model system...
Show moreThe aim of this dissertation is to investigate self-assembled structures and the phase diagram of amphiphilic molecules of diverse geometric shapes using a number of different computer simulation methods. The semi-realistic coarse-grained model, used extensively for simulation of polymers and surfactant molecules, is adopted in an off-lattice approach to study how the geometric structure of amphiphiles affects the aggregation properties. The results of simulations show that the model system behavior is consistent with theoretical predictions, experiments and lattice simulation models. We demonstrate that by modifying the geometry of the molecules, self-assembled aggregates are altered in a way close to theoretical predictions. In several two and three dimensional off-lattice Brownian Dynamics simulations, the influence of the shape of the amphiphilic molecules on the size and form of the aggregates is studied systematically. Model phospholipid molecules, with two hydrophobic chains connected to one hydrophilic head group, are simulated and the formation of stable bilayers is observed. In addition, (practically very important) mixtures of amphiphiles with diverse structures are studied under different mixing ratios and molecular structures. We find that in several systems, with Poisson distributed chain lengths, the effect on the aggregation distribution is negligible compared to that of the pure amphiphilic system with the mean length of the Poisson distribution. The phase diagrams of different amphiphilic molecular structures are investigated in separate simulations by employing the Gibbs Ensemble Monte Carlo method with an implemented configurational-bias technique. The computer simulations of the above mentioned amphiphilic systems are done in an area where physics, biology and chemistry are closely connected and advances in applications require the use of new theoretical, experimental and simulation methods for a better understanding of their self-assembling properties. Obtained simulation results demonstrate the connection between the structure of amphiphilic molecules and the properties of their thermodynamically stable aggregates and thus build a foundation for many applications of the remarkable phenomena of amphiphilic self-assembly in the area of nanotechnology.
Show less
Date Issued: 2005
Identifier: CFE0000695, ucf:46491
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000695

Title: INVESTIGATION OF AMINOGLYCOSIDE INDUCED NANOPARTICLE SELF-ASSEMBLIES.
Creator: Leong, Michael, Self, William, University of Central Florida
Abstract / Description: Aminoglycosides are a group of broad-spectrum antibiotics that, under neutral pH conditions, carry a positive charge. The net cationic charge arises from the high number of amino groups in the core structure of aminoglycosides. Previous studies performed have shown that negatively charged citrate ligand-capped gold nanoparticles (AuNPs) can interact with various biomolecules such as aminoglycosides. AuNPs bound to biomolecules have been used in conjugation with various assaying techniques to...
Show moreAminoglycosides are a group of broad-spectrum antibiotics that, under neutral pH conditions, carry a positive charge. The net cationic charge arises from the high number of amino groups in the core structure of aminoglycosides. Previous studies performed have shown that negatively charged citrate ligand-capped gold nanoparticles (AuNPs) can interact with various biomolecules such as aminoglycosides. AuNPs bound to biomolecules have been used in conjugation with various assaying techniques to detect and study compounds in vitro and in vivo. AuNPs also have strong light scattering properties that can be used with a wide variety of imaging and assaying techniques. Our laboratory has previously performed experiments on the aminoglycoside antibiotic ribostamycin sulfate. During this experiment, the concentration dependent rod-like assembly of ribostamycin sulfate was characterized. This experiment used three analytical techniques in conjunction with AuNPs: (1) dynamic light scattering (DLS), (2) UV-Vis absorption spectroscopy, and (3) dark field optical microscope imaging (DFM). This suite of techniques was used to analyze mixtures of ribostamycin sulfate at different concentration with different sized AuNPs. The primary objective of this research was to determine if the techniques used to characterize the self-assembly of ribostamycin sulfate could be generalized and applied to other aminoglycoside antibiotics. The secondary objective of this research was to determine if other aminoglycoside antibiotics formed rod-like assemblies. This study demonstrated that AuNPs can be used to detect self-assembled oligomers for different aminoglycoside antibiotics. In addition, this study also revealed that not all aminoglycoside antibiotics will self assemble into rod-like oligomers similar to ribostamycin. It was observed that the aminoglycoside antibiotic amikacin self assembled into rod-like aggregates similar to ribostamycin sulfate but the aminoglycoside antibiotics neomycin sulfate and streptomycin sulfate did not.
Show less
Date Issued: 2018
Identifier: CFH2000339, ucf:45911
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFH2000339

Title: BRANCHED AND SPIRAL ORGANIC NANOTUBES BASED ON THE SELF-ASSEMBLY OF BILE ACIDS.
Creator: Zhang, Xuejun, Fang, Jiyu, University of Central Florida
Abstract / Description: The self-assembly of chiral amphiphilic molecules in aqueous solutions is of particular interest because the chirality of individual molecules is often expressed in their supermolecular structures. Self-assembled tubes made of chiral amphiphilic molecules represent useful supramolecular architectures which hold promise as controlled release vehicles for drug delivery, encapsulates for functional molecules, and nanoreactors for chemical reactions. Lithocholic acid (LCA) is a secondary bile...
Show moreThe self-assembly of chiral amphiphilic molecules in aqueous solutions is of particular interest because the chirality of individual molecules is often expressed in their supermolecular structures. Self-assembled tubes made of chiral amphiphilic molecules represent useful supramolecular architectures which hold promise as controlled release vehicles for drug delivery, encapsulates for functional molecules, and nanoreactors for chemical reactions. Lithocholic acid (LCA) is a secondary bile acid with the concentration being identical to that of cholesterol in the hepatic bile and gallbladder. It has a rigid, nearly planar hydrophobic steroid nucleus, with four hydrogen atoms and one hydroxyl group directed toward the concave side, and the convex side with three methyl groups. The ionic head with a carboxyl group is linked to the steroid nucleus through a short alkyl chain. In this thesis work, I study the self-assembly behavior of LCA at the liquid-solid interface, in confined spaces, and bulk solution. We find that the initially formed LCA vesicles further assemble into fractal tubes on glass slides by diffusion-limited aggregation and pronglike tubes by the capillary flow generated in an evaporating vesicle solution confined by two parallel glass slides. While in bulk solution, the LCA vesicles linearly aggregate and fuse into spiral tubes at pH 12.0. The spiral tubes can transition into a straight shape as the pH of solution is reduced to 7.4. The shape transition of the tubes is reversible as the pH of solution is adjusted back to 12.0. The pH-switchable shape transition suggests that the self-assembled LCA tubes can act as a supramolecular chemical spring. Finally, the LCA tubes are endowed with optical functionality by embedding cadmium sulfide nanopaticles (CdS) in the tube walls by the co-assembling synthesis of cadmium sulfide (CdS) nanoparticles with lithocholic acid (LCA) molecules. The fluorescent composite tubes can undergo pH switchable spiral/straight, which are a promising system for a variety of materials and biological applications.
Show less
Date Issued: 2010
Identifier: CFE0003479, ucf:48959
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003479

Title: FORMATION OF LYOTROPIC LIQUID CRYSTALS THROUGH THE SELF-ASSEMBLY OF BILE ACID BUILDING BLOCKS.
Creator: Tamhane, Karan, Fang, Jiyu, University of Central Florida
Abstract / Description: Liquid crystalline materials (LCMs) have gained much popularity over the past century. The thermotropic forms of these materials have been extensively studied and employed in a range of innovative applications. The lyotropic liquid crystal systems that have been studied in the past have often been formed by the organization of natural and synthetic small molecules in solutions. In this study, we use self-assembled supramolecular structures as building blocks to fabricate lyotropic liquid...
Show moreLiquid crystalline materials (LCMs) have gained much popularity over the past century. The thermotropic forms of these materials have been extensively studied and employed in a range of innovative applications. The lyotropic liquid crystal systems that have been studied in the past have often been formed by the organization of natural and synthetic small molecules in solutions. In this study, we use self-assembled supramolecular structures as building blocks to fabricate lyotropic liquid crystals. We investigate the self-assembly of a naturally occurring bile acid called lithocholic acid (LCA), to form supramolecular fibrous and tubular structures in basic aqueous solutions. We control the morphology of the self-assembled structures by manipulating experimental parameters in order to gain comprehensive knowledge regarding the self-assembly process. We characterize these structures with respect to their morphology i.e. their length, diameter, flexibility and shape using atomic force microscopy, optical microscopy and infrared spectroscopy. We produce lyotropic liquid crystal phases using self-assembled LCA structures through modification of physical parameters such as concentration, temperature, shear and pH. The nature of the lyotropic liquid crystal phases depends upon the morphology of the fibers and tubes. We observe that the short, rigid fibers and tubes form nematic phases while long, flexible fibers and tubes form cholesteric phases. We also study the phase transitions of the liquid crystal (LC) phases by observing their patterns using a polarizing microscope. Observations show that LC phases form in samples with LCA concentration above 0.75%w/w. Since the process of self-assembly is time-dependent, so is the formation of liquid crystal phases. We note that the optimum LCA concentration for LC phase formation is 2%-4%w/w and that the liquid crystal transition temperature is about 70°C.
Show less
Date Issued: 2009
Identifier: CFE0002954, ucf:47972
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002954

Title: Self-Assembled Two-Component Organic Tubes: Structures and Applications.
Creator: Liang, Wenlang, Fang, Jiyu, Huo, Qun, Deng, Weiwei, University of Central Florida
Abstract / Description: Bile acids are physiologically important metabolites, which are synthesized in liver as the end products of cholesterol metabolism and then secreted into the intestines. They play a critical role in the digestion and absorption of fats and fat-soluble vitamins through emulsifications. The amphipathic and chiral nature of bile acids makes their unique building blocks for assembling supramolecular structures including vesicles, fibers, ribbons and hollow tubes. Lithocholic acid (LCA) is a...
Show moreBile acids are physiologically important metabolites, which are synthesized in liver as the end products of cholesterol metabolism and then secreted into the intestines. They play a critical role in the digestion and absorption of fats and fat-soluble vitamins through emulsifications. The amphipathic and chiral nature of bile acids makes their unique building blocks for assembling supramolecular structures including vesicles, fibers, ribbons and hollow tubes. Lithocholic acid (LCA) is a secondary bile acid. Our studies show LCA can self-assemble into helical tubes in aqueous solution by the linear aggregation and fusion of vesicles. The objective of this dissertation is to tune the structure of helical tubes and functionalize them by the co-assembly of ionic LCA and cationic cetyltrimethylammonium bromide (CTAB) and ionic LCA and cationic cyanine dye (CD), respectively. The first part of this dissertation focuses on the ionic-assembly of LCA and CTAB to synthesize the helical tubes with varied diameters and pitches. Our studies show that LCA and CTAB can self-assemble into helical tubes in NH4OH aqueous solution. The diameter of the helical tubes can be changed by adjusting the molar ratio of LCA and CTAB. The pitch of the helical tubes can be tuned by varying NH4OH concentrations. Differential scanning calorimetry studies indicate that there is a homogeneous composition distribution in the LCA/CTAB helical tubes. X-ray diffraction analysis studies show that the helical tubes have multibilayer walls with an average d-spacing of 4.11nm. We demonstrate that the helical tubes with varied diameters and pitches can be transformed into helical silica through the sol-gel transcription of tetraethoxysilane (TEOS). The second part of this dissertation is to use the ionic self-assembly of LCA and CD to design light-harvesting tubes by mimicking green sulfur bacteria that are known to be a highly efficient photosynthesizer. X-ray diffraction and optical spectra show that LCA and CD can co-assemble into J- or H-aggregate tubes, depending the condition under which the self-assembly occurs. We demonstrate the feasibility of using the J-aggregate nanotubes in the sensitive and selective detection of mercury (II) ions by the photoinduced electron transfer under sunlight. The presence of mercury (II) ions in aqueous solution could be detected for concentrations as low as 10 pM.
Show less
Date Issued: 2013
Identifier: CFE0005201, ucf:50635
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005201

Title: DEVELOPMENT AND APPLICATION STUDY OF NANOSCALE THIN FILM MATERIALS AND POLYMER NANOCOMPOSITES.
Creator: Chen, Hui, Huo, Qun, University of Central Florida
Abstract / Description: This dissertation demonstrated that the manipulation of substances at the molecular or nanometer level can lead to the discovery and development of new materials with interesting properties and important applications. Chapter 1 describes the development of a nanoscale molecular thin film material for corrosion protection. By using a self-assembled monolayer film with a thickness of only about 1 nanometer as a linkage, a covalent bonding was achieved between a polyurethane top coating and an...
Show moreThis dissertation demonstrated that the manipulation of substances at the molecular or nanometer level can lead to the discovery and development of new materials with interesting properties and important applications. Chapter 1 describes the development of a nanoscale molecular thin film material for corrosion protection. By using a self-assembled monolayer film with a thickness of only about 1 nanometer as a linkage, a covalent bonding was achieved between a polyurethane top coating and an aluminum alloy substrate. This covalent bonding between polymer top coating and the aluminum alloy substrate significantly improved the corrosion resistance of the substrate. Chapter 2 and Chapter 3 describe the development of a gold nanoparticle-polymer composite material in different forms with a number of applications. Gold nanoparticles are among one of the most extensively studied nanomaterials. When the size of gold is shrunk to the nanometer scale, many interesting and new physical properties start to appear from gold nanoparticles. The optical properties of gold nanoparticles, particularly the surface plasmon resonance absorption, have been investigated in this dissertation for the development of multifunctional nanocomposite materials. Chapter 2 presents the preparation of a gold nanoparticle/poly(methyl methacrylate) (PMMA) nanocomposite film and the application of such films for microstructure fabrication using a direct laser writing technique. Gold nanoparticles are excellent photon-thermal energy converters due to their large absorption cross section at the surface plasmon resonance region. Upon laser irradiation of the nanocomposite film, the thermal energy converted from the absorbed photon energy by gold nanopaticles induced a complete decomposition of PMMA, leading to the formation of various microstructures on the nanocomposite films. Chapter 3 reports the further development of a nanoparticle/polymer composite nanofiber material fabricated through an electrospinning process. The matrix of the nanofiber is made of two polyelectrolytes, poly(acrylic acid) (PAA) and poly(allylamine hydrochloride) (PAH). Three methods were developed to incorporate gold nanoparticles into the polymer matrix. The composite nanofiber materials developed in this study demonstrate multifunctional properties, including good electrical conductivity, photothermal response, and surface-enhanced IR absorption. This material may be used for many important applications including catalysis, chemical and biological sensors, and scaffold materials for tissue engineering. In Chapter 4, another most important nanomaterial, carbon naotubes (CNTs), were introduced as fillers to prepare polymer nanocomposites. A dispersion method for multi-walled carbon nanotubes (MWCNTs) using a conjugated conducting polymer, poly(3-hexylthiophene) (P3HT) as the third component and trifluoroacetic acid (TFA) as a co-solvent was developed. Due to the excellent dispersion of carbon nanotubes in PMMA and enhanced conductivity of the nanocomposites by the conjugated conducting polymers, the prepared composite materials has an extremely low percolation threshold of less than 0.006 wt% of MWCNT content. The potential use of MWCNT/conducting polymer composites for energy storage applications such as suppercapacitors was further investigated by Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS) and charging-discharging cycles. Compared to pure carbon nanotubes, the nanocomposite materials have significantly improved properties and are promising for supercapacitor applications.
Show less
Date Issued: 2008
Identifier: CFE0002265, ucf:47825
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002265

Title: APPLICATION OF ALKYLSILANE SELF-ASSEMBLED MONOLAYERS FOR CELLPATTERNING AND DEVELOPMENT OF BIOLOCIAL MICROELECTROMECHANICALSYSTEMS.
Creator: Wilson, Kerry, Hickman, James, University of Central Florida
Abstract / Description: Advances in microfabrication and surface chemistry techniques have provided a new paradigm for the creation of in vitro systems for studying problems in biology and medicine in ways that were previously not practical. The ability to create devices with micro- to nano-scale dimensions provides the opportunity to non-invasively interrogate and monitor biological cells and tissue in large arrays and in a high-throughput manner. These systems hold the potential to, in time, revolutionize the way...
Show moreAdvances in microfabrication and surface chemistry techniques have provided a new paradigm for the creation of in vitro systems for studying problems in biology and medicine in ways that were previously not practical. The ability to create devices with micro- to nano-scale dimensions provides the opportunity to non-invasively interrogate and monitor biological cells and tissue in large arrays and in a high-throughput manner. These systems hold the potential to, in time, revolutionize the way problems in biology and medicine are studied in the form of point-of-care devices, lab-on-chip devices, and biological microelectromechanical systems (BioMEMS). With new in vitro models, it will be possible to reduce the overall cost of medical and biological research by performing high-throughput experiments while maintaining control over a wide variety of experimental variables. A critical aspect of developing these sorts of systems, however, is controlling the device/tissue interface. The surface chemistry of cell-biomaterial and protein-biomaterial interactions is critical for long-term efficacy and function of such devices. The work presented here is focused on the application of surface and analytical chemistry techniques for better understanding the interface of biological elements with silica substrates and the development a novel Bio-MEMS device for studying muscle and neuromuscular biology. A novel surface patterning technique based on the use of a polyethylene glycol (PEG) silane self-assembled monolayer (SAM) as a cytophobic surface and the amine-terminated silane diethyeletriamine (DETA) as a cytophilic surface was developed for patterning a variety of cell types (e.g. skeletal muscle, and neural cells) over long periods of time (over 40 days) with high fidelity to the patterns. This method was then used to pattern embryonic rat skeletal muscle and motor neurons onto microfabricated silicon cantilevers creating a novel biological microelectromechanical system (BioMEMS) for studying muscle and the neuromuscular junction. This device was then used to study the effect of exogenously applied substances such as growth factors and toxins. Furthermore, a whispering-gallery mode (WGM) biosensor was developed for measuring the adsorption of various proteins onto glass microspheres coated with selected silane SAMS commonly used in BioMEMS system. With this biosensor it was possible to measure the kinetics of protein adsorption onto alkylsilane SAMS, in a real-time and label-free manner.
Show less
Date Issued: 2009
Identifier: CFE0002631, ucf:48210
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002631

Title: PROBING AND TUNING THE SIZE, MORPHOLOGY, CHEMISTRY AND STRUCTURE OF NANOSCALE CERIUM OXIDE.
Creator: Kuchibhatla, Satyanarayana, Seal, Sudipta, University of Central Florida
Abstract / Description: Cerium oxide (ceria)-based materials in the nanoscale regime are of significant fundamental and technological interest. Nanoceria in pure and doped forms has current and potential use in solid oxide fuel cells, catalysis, UV- screening, chemical mechanical planarization, oxygen sensors, and bio-medical applications. The characteristic feature of Ce to switch between the +3 and + 4 oxidation states renders oxygen buffering capability to ceria. The ease of this transformation was expected to be...
Show moreCerium oxide (ceria)-based materials in the nanoscale regime are of significant fundamental and technological interest. Nanoceria in pure and doped forms has current and potential use in solid oxide fuel cells, catalysis, UV- screening, chemical mechanical planarization, oxygen sensors, and bio-medical applications. The characteristic feature of Ce to switch between the +3 and + 4 oxidation states renders oxygen buffering capability to ceria. The ease of this transformation was expected to be enhanced in the nanoceria. In most the practical scenarios, it is necessary to have a stable suspension of ceria nanoparticles (CNPs) over longer periods of time. However, the existing literature is confined to short term studies pertaining to synthesis and property evaluation. Having understood the need for a comprehensive understanding of the CNP suspensions, this dissertation is primarily aimed at understanding the behavior of CNPs in various chemical and physical environments. We have synthesized CNPs in the absence of any surfactants at room temperature and studied the aging characteristics. After gaining some understanding about the behavior of this functional oxide, the synthesis environment and aging temperature were varied, and their affects were carefully analyzed using various materials analysis techniques such as high resolution transmission electron microscopy (HRTEM), UV-Visible spectroscopy (UV-Vis), and X-ray photoelectron spectroscopy (XPS). When the CNPs were aged at room temperature in as-synthesized condition, they were observed to spontaneously assemble and evolve as fractal superoctahedral structures. The reasons for this unique polycrystalline morphology were attributed to the symmetry driven assembly of the individual truncated octahedral and octahedral seed of the ceria. HRTEM and Fast Fourier Transform (FFT) analyses were used to explain the agglomeration behavior and evolution of the octahedral morphology. Some of the observations were supported by molecular dynamic simulations. Poly (ethylene glycol) (PEG) and ethylene glycol (EG) were used to control the kinetics of this morphology evolution. The ability to control the agglomeration of CNPs in these media stems from the lower dielectric constant and an increased viscosity of the EG and PEG based solvents. CNPs when synthesized and aged in frozen conditions, i.e. in ice, were found to form one dimensional, high aspect ratio structures. A careful analysis has provided some evidence that the CNPs use the porous channels in ice as a template and undergo oriented attachment to form nanorods. When the aging treatment was done near freezing temperature in solution, the nanorods were not observed, confirming the role of channels in ice. When synthesized in aqueous media such as DI water, PEG and EG; CNPs were observed to exhibit a reversible oxidation state switching between +3 and +4. Band gap values were computed from the optical absorption data. The changes in the band gap values observed were attributed to the changes in the oxidation state of CNPs as opposed to the quantum confinement effects, as expected in other nanoparticle systems. The work presented in this dissertation demonstrates, with evidence, that in order to obtain a comprehensive understanding of the properties of nanoscale materials it is of paramount importance to monitor their behavior over relatively longer periods of time under various ambient environments. While the solution based techniques offer a versatility and low cost route to study the fundamental properties of nanomaterials, they suffer some inherent problems such as precursor contamination and uncontrolled chemical reactions. Especially when analyzing the behavior of ceria-based materials for applications like solid oxide fuel cells, a great control in the density and crystalline quality are desired. In order to achieve this, as a first step pure ceria thin films were synthesized using oxygen plasma assisted molecular beam epitaxy (OPA-MBE). The ceria films were analyzed using various in situ and ex situ techniques to study the crystal structure, growth mode and epitaxial quality of the films. It was observed that the epitaxial orientation of the ceria films could be tuned by varying the deposition rate. When the films were grown at low deposition rate (< 8 Å/min) ceria films with epitaxial (200) orientation were observed where as the films grown at high deposition rates (up to 30 Å/min) showed (111) orientation. Theoretical simulations were used to confirm some of the experimental facts observed in both nanoparticles and thin films.
Show less
Date Issued: 2008
Identifier: CFE0002163, ucf:47499
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002163

Title: SELF-ASSEMBLED LIPID TUBULES: STRUCTURES, MECHANICAL PROPERTIES, AND APPLICATIONS.
Creator: Zhao, Yue, Fang, Jiyu, University of Central Florida
Abstract / Description: Self-assembled lipid tubules are particularly attractive for inorganic synthesis and drug delivery because they have hollow cylindrical shapes and relatively rigid mechanical properties. In this thesis work, we have synthesized lipid tubules of 1,2-bis(tricosa-10,12-dinoyl)-sn-glycero-3-phosphocholine (DC8,9PC) by self-assembly and polymerization in solutions. We demonstrate for the first time that both uniform and modulated molecular tilt orderings exist in the tubule walls, which have been...
Show moreSelf-assembled lipid tubules are particularly attractive for inorganic synthesis and drug delivery because they have hollow cylindrical shapes and relatively rigid mechanical properties. In this thesis work, we have synthesized lipid tubules of 1,2-bis(tricosa-10,12-dinoyl)-sn-glycero-3-phosphocholine (DC8,9PC) by self-assembly and polymerization in solutions. We demonstrate for the first time that both uniform and modulated molecular tilt orderings exist in the tubule walls, which have been predicted by current theories, and therefore provide valuable supporting evidences for self-assembly mechanisms of chiral molecules. Two novel methods are developed for studying the axial and radial deformations of DC8,9PC lipid tubules. Mechanical properties of DC8,9PC tubules are systematically studied in terms of persistence length, bending rigidity, strain energy, axial and radial elastic moduli, and critical force for collapse. Mechanisms of recovery and surface stiffening are discussed. Due to the high aspect ratio of lipid tubules, the hierarchical assembly of lipid tubules into ordered arrays and desired architectures is critical in developing their applications. Two efficient methods for fabricating ordered arrays of lipid tubules on solid substrates have been developed. Ordered arrays of hybrid silica-lipid tubes are synthesized by tubule array-templated sol-gel reactions. Ordered arrays of optical anisotropic fibers with tunable shapes and refractive indexes are fabricated. This thesis work provides a paradigm for molecularly engineered structures.
Show less
Date Issued: 2007
Identifier: CFE0001918, ucf:47486
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001918

Title: Developing surface engineered liquid crystal droplets for sensing applications.
Creator: Bera, Tanmay, Fang, Jiyu, Suryanarayana, Challapalli, Huo, Qun, Cho, Hyong, Deng, Weiwei, Wu, Shintson, University of Central Florida
Abstract / Description: Diagnosis plays a very crucial role in medicine and health care, which makes biosensors extremely important in modern technological context. Till date, various types of biosensors have been developed that are capable of detecting a wide range of biologically important species with great sensitivity and selectivity. However, most of these sensing units require highly sophisticated instrumentation and often lack the desired portability. Liquid crystal (LC) droplets, on the other hand, are a new...
Show moreDiagnosis plays a very crucial role in medicine and health care, which makes biosensors extremely important in modern technological context. Till date, various types of biosensors have been developed that are capable of detecting a wide range of biologically important species with great sensitivity and selectivity. However, most of these sensing units require highly sophisticated instrumentation and often lack the desired portability. Liquid crystal (LC) droplets, on the other hand, are a new type of functional material that are finding increasing research attention as a new sensing unit due to their tunable optical property, high surface area, portability and cost-effectiveness. In this dissertation, functionalized LC droplets for biosensing at aqueous-LC interface are highlighted. Chemically functionalized LC droplets dispersed in aqueous solution were prepared by the self-assembly of amphiphilic molecules at the aqueous/LC interface. These functionalized LC droplets showed a well-defined director of configuration and a specific optical pattern when observed with a polarizing light microscope. It was discovered that the interaction of chemically functionalized LC droplets with an analyte triggers transition of the director of configuration of the LC within the droplets, providing a simple and unique optical sign for the detection of the analyte. Moreover, the director of configuration transition happened in a concentration dependent manner, allowing both qualitative and quantitative detection of the analyte. The sensitivity of chemically functionalized LC droplets depends not only on the nature of amphiphilic molecules but also the size and number of the droplets.The dissertation essentially deals with the application of these chemically functionalized LC droplets in detecting several biologically important species. It was observed that the adsorption of charged macromolecules (dendrimers, proteins, and viruses) on polyelectrolyte functionalized LC droplets triggered a bipolar-to-radial configuration transition based on the polar verses non-polar interaction. By using a simple optical microscope, microgram per milliliter concentrations of bovine serum albumin, cowpea mosaic virus, and tobacco mosaic virus could be detected in aqueous solution. The detection limit of Mastoparan X polypeptide decorated LC droplets in detecting E. coli could reach to approximately 10 bacteria per milliliter. In this case, the high affinity of the polypeptide towards the bacterial causes the former to detach from the LC droplets, triggering the director of configuration transition of the LC inside the droplets. Finally, surfactant decorated LC droplets were used to detect lithocholic acid (LCA), a toxic bile acid used as a specific biomarker for colon cancers. In this case, the director of configuration transition of the LC inside the droplets is a result of the replacement of the surfactant from the aqueous/LC interface by LCA. The microgram per milliliter concentration of LCA, a clinically significant concentration, could be easily detected by changing the length of surfactants. These studies highlight the novel use of surface functionalized LC droplets to detect biologically important species. Due to their tunable optical property, coupled with high surface area and portability, surface functionalized LC droplets have great potentials in the design of next generation biosensors.
Show less
Date Issued: 2012
Identifier: CFE0004307, ucf:49471
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004307

self-assembly (5)	+ -
Bile acid (2)	+ -
Self-Assembly (2)	+ -
Agglomeration (1)	+ -
Aminoglycoside (1)	+ -

Band Gap (1)	+ -
BioMEMS (1)	+ -
Biosening (1)	+ -
COPOLYMER (1)	+ -
Ceria (1)	+ -
Cerium Oxide (1)	+ -
Gibbs ensemble (1)	+ -
Gold nanoparticle (1)	+ -
HRTEM (1)	+ -
IRON OXIDE NANOPARTICLES (1)	+ -
Liquid crystal droplets (1)	+ -
Liquid crystals (1)	+ -
Lithocholic acid (1)	+ -
Lyotropic (1)	+ -
MAGNETIC FERROFLUIDS (1)	+ -
MBE (1)	+ -
Molecular Dynamics (1)	+ -
Morphology (1)	+ -
NORBORNENE (1)	+ -
Nanocomposite (1)	+ -
Nanoparticles (1)	+ -
Nanotube (1)	+ -
Neomycin (1)	+ -
Oxidation State (1)	+ -
SELF-ASSEMBLED (1)	+ -

ETD Collection (11)	+ -
Honors Collection (1)	+ -

University of Central Florida (12)	+ -
Fang, Jiyu (5)	+ -
Huo, Qun (3)	+ -
Deng, Weiwei (2)	+ -
BELFIELD, KEVIN (1)	+ -

Belfield, Kevin (1)	+ -
Bera, Tanmay (1)	+ -
Bhattacharya, Aniket (1)	+ -
Bourov, Geuorgui (1)	+ -
Chen, Hui (1)	+ -
Cho, Hyong (1)	+ -
Hickman, James (1)	+ -
Kuchibhatla, Satyanarayana (1)	+ -
Leong, Michael (1)	+ -
Liang, Wenlang (1)	+ -
Qaddoura, Maher (1)	+ -
Seal, Sudipta (1)	+ -
Self, William (1)	+ -
Suryanarayana, Challapalli (1)	+ -
Tamhane, Karan (1)	+ -
Wilson, Kerry (1)	+ -
Wu, Shintson (1)	+ -
ZHANG, LI (1)	+ -
Zhang, Xuejun (1)	+ -
Zhao, Yue (1)	+ -

Search In

Sort Results By:

Narrow results by:

Topical Subject

Collection

Type of Resource

Language

Creator

Format

Owner