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Title: SQUARAINE DYES FOR TWO-PHOTON FLUORESCENCE BIOIMAGING APPLICATIONS.
Creator: Colon Gomez, Maria, Belfield, Kevin, University of Central Florida
Abstract / Description: Near-infrared emitting squaraine dyes are promising candidates for bioimaging applications. Two-photon fluorescence microscopy (2PFM) imaging is a powerful tool being used for studying biological function since it produces 3D images with minimal damage to cells and lower fluorophore photobleaching. The fluorescence wavelength of squaraine dyes normally falls in the near infrared region, providing deeper penetration through biological samples such as thick tissue sections. Squaraine dyes that...
Show moreNear-infrared emitting squaraine dyes are promising candidates for bioimaging applications. Two-photon fluorescence microscopy (2PFM) imaging is a powerful tool being used for studying biological function since it produces 3D images with minimal damage to cells and lower fluorophore photobleaching. The fluorescence wavelength of squaraine dyes normally falls in the near infrared region, providing deeper penetration through biological samples such as thick tissue sections. Squaraine dyes that could work for imaging cells and tissues for 2PFM imaging were synthesized and underwent comprehensive photophysical characterization, such as UV-Vis absorption, fluorescence, and anisotropy. The squaraine dyes were tested for cell toxicity to determine the concentration at which the cells should be incubated with the dye for 2PFM. In addition, the squaraine dyes were incubated with cancer cells to evaluate their utility in the bioimaging process. The squaraine dye that is not soluble in water can be incorporated in silica nanoparticles or micelles to facilitate dispersal in water for evaluation of its use as a probe. The prospective squaraine dyes can be used in cells and tissues for imaging that can then be analyzed to ascertain its use as a probe for biomedical applications, such as early cancer detection.
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Date Issued: 2013
Identifier: CFH0004338, ucf:45020
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFH0004338

Title: SILICON CARBIDE AND AGILE OPTICS BASED SENSORS FOR POWER PLANT GAS TURBINES, LASER BEAM ANALYSIS AND BIOMEDICINE.
Creator: Sheikh, Mumtaz, Riza, Nabeel, University of Central Florida
Abstract / Description: Proposed are novel sensors for extreme environment power plants, laser beam analysis and biomedicine. A hybrid wireless-wired extreme environment temperature sensor using a thick single-crystal Silicon Carbide (SiC) chip embedded inside a sintered SiC probe design is investigated and experimentally demonstrated. The sensor probe employs the SiC chip as a Fabry-Perot (FP) interferometer to measure the change in refractive index and thickness of SiC with temperature. A novel temperature sensing...
Show moreProposed are novel sensors for extreme environment power plants, laser beam analysis and biomedicine. A hybrid wireless-wired extreme environment temperature sensor using a thick single-crystal Silicon Carbide (SiC) chip embedded inside a sintered SiC probe design is investigated and experimentally demonstrated. The sensor probe employs the SiC chip as a Fabry-Perot (FP) interferometer to measure the change in refractive index and thickness of SiC with temperature. A novel temperature sensing method that combines wavelength-tuned signal processing for coarse measurements and classical FP etalon peak shift for fine measurements is proposed and demonstrated. This method gives direct unambiguous temperature measurements with a high temperature resolution over a wide temperature range. An alternative method using blackbody radiation from a SiC chip in a two-color pyrometer configuration for coarse temperature measurement and classical FP laser interferometry via the same chip for fine temperature measurement is also proposed and demonstrated. The sensor design is successfully deployed in an industrial test rig environment with gas temperatures exceeding 1200 C. This sensor is proposed as an alternate to all-electrical thermocouples that are susceptible to severe reliability and lifetime issues in such extreme environments. A few components non-contact thickness measurement system for optical quality semi-transparent samples such as Silicon (Si) and 6H SiC optical chips such as the one used in the design of this sensor is proposed and demonstrated. The proposed system is self-calibrating and ensures a true thickness measurement by taking into account material dispersion in the wavelength band of operation. For the first time, a 100% repeatable all-digital electronically-controlled pinhole laser beam profiling system using a Texas Instruments (TI) Digital Micro-mirror Device (DMD) commonly used in projectors is experimentally demonstrated using a unique liquid crystal image generation system with non-invasive qualities. Also proposed and demonstrated is the first motion-free electronically-controlled beam propagation analyzer system using a TI DMD and a variable focus liquid lens. The system can be used to find all the parameters of a laser beam including minimum waist size, minimum waist location and the beam propagation parameter M2. Given the all-digital nature of DMD-based profiling and all-analog motion-free nature of the Electronically Controlled Variable Focus Lens (ECVFL) beam focus control, the proposed analyzer versus prior-art promises better repeatability, speed and reliability. For the first time, Three Dimensional (3-D) imaging is demonstrated using an electronically controlled Liquid Crystal (LC) optical lens to accomplish a no-moving parts depth section scanning in a modified commercial 3-D confocal microscope. The proposed microscopy system within aberration limits has the potential to eliminate the sample or objective motion-caused mechanical forces that can distort the original sample structure and lead to imaging errors. A signal processing method for realizing high resolution three dimensional (3-D) optical imaging using diffraction limited low resolution optical signals is also proposed.
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Date Issued: 2009
Identifier: CFE0002922, ucf:47995
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002922

Title: NON-DESTRUCTIVE MICROSTRUCTURAL EVALUATION OF YTTRIA STABILIZED ZIRCONIA, NICKEL ALUMINIDES AND THERMAL BARRIER COATINGS USING ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY.
Creator: Vishweswaraiah, Srinivas, Sohn, Yongho, University of Central Florida
Abstract / Description: There has been an urge for increasing the efficiency in advanced gas turbine engines. To fulfill these needs the inlet gas temperatures should be increased in the gas turbine engines, thermal barrier coatings (TBCs) have gained significant applications in increasing the gas inlet temperatures. Insulating characteristics of ceramic TBCs allow the operation at up to 150~250 ˚C higher gas temperatures. Because of the severe turbine engine operating conditions that include high...
Show moreThere has been an urge for increasing the efficiency in advanced gas turbine engines. To fulfill these needs the inlet gas temperatures should be increased in the gas turbine engines, thermal barrier coatings (TBCs) have gained significant applications in increasing the gas inlet temperatures. Insulating characteristics of ceramic TBCs allow the operation at up to 150~250 ˚C higher gas temperatures. Because of the severe turbine engine operating conditions that include high temperature, steep temperature gradient, thermal cycling, oxidation and hot-corrosion, TBCs can fail by spallation at the interface between the metal and ceramic. The lack of understanding in failure mechanisms and their prediction warrant a development of non-destructive evaluation technique that can monitor the quality and degradation of TBCs. In addition, the development of NDE technique must be based on a robust correlation to the characteristics of TBC failure.The objective of this study is to develop electrochemical impedance spectroscopy (EIS) as a Non-destructive evaluation (NDE) technology for application to TBCs. To have a better understanding of the multilayer TBCs using EIS they were divided into individual layers and EIS were performed on them. The individual layers included polycrystalline ZrO2-7~8 wt.%Y2O3 (YSZ) (topcoat) of two different densities were subjected to sintering by varying the sintering temperature and holding time for three different thickness and hot extruded NiAl alloy buttons which were subjected to isothermal oxidation with varying temperature and time. NiAl is as similar to the available commercial bondcoats used in TBCs. Then degradation monitoring with electrolyte penetration was carried out on electron beam physical vapor deposited (EB-PVD) TBCs as a function of isothermal exposure. Quality control for air plasma sprayed TBCs were carried out as a function of density, thickness and microstructure. Dense vertically cracked TBCs were tested as a function of vertical crack density and thickness.Electrochemical impedance response was acquired from all specimens at room temperature and analyzed with an AC equivalent circuit based on the impedance response as well as multi-layered structure and micro-constituents of specimens. Physical and microstructural features of these specimens were also examined by optical and electron microscopy. The EIS measurement was carried out in a three-electrode system using a standard Flat Cell (K0235) from Princeton Applied Research and IM6e BAS ZAHNER frequency response analyzer. The electrolyte employed in this investigation was 0.01M (molar) potassium Ferri/Ferro Cyanide {(K3Fe(CN)6/K4Fe(CN)6•3H2O)}.The thickness and density were directly related to the resistance and capacitance of the polycrystalline YSZ with varying thickness and open pores. As the effective thickness of the YSZ increased with sintering time and temperature, the resistance of the YSZ (RYSZ) increased proportionally. The variation in capacitance of YSZ (CYSZ) with respect to the change in porosity/density and thickness was clearly detected by EIS. The samples with high porosity (less dense) exhibited large capacitance, CYSZ, compared to those with less porosity (high density), given similar thickness. Cracking in the YSZ monoliths resulted in decrease of resistance and increase in capacitance and this was related to the electrolyte penetration.Growth and spallation of TGO scale on NiAl alloys during isothermal oxidation at various temperatures and holding time was also correlated with resistance and capacitance of the TGO scale. With an increase in the TGO thickness, the resistance of the TGO (RTGO) increased and capacitance of the TGO (CTGO) decreased. This trend in the resistance and capacitance of the TGO changed after prolonged heat treatment. This is because of the spallation of the TGO scale from the metal surface. The parabolic growth of TGO
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Date Issued: 2004
Identifier: CFE0000041, ucf:52855
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000041

Title: DEVELOPMENT OF OPTICAL COHERENCE TOMOGRAPHY FOR TISSUE DIAGNOSTICS.
Creator: Meemon, Panomsak, Rolland, Jannick, University of Central Florida
Abstract / Description: Microvasculature can be found in almost every part of the human body, including the internal organs. Importantly, abnormal changes in microvasculature are usually related to pathological development of the tissue cells. Monitoring of changes in blood flow properties in microvasculature, therefore, provides useful diagnostic information about pathological conditions in biological tissues as exemplified in glaucoma, diabetes, age related macular degeneration, port wine stains, burn-depth, and...
Show moreMicrovasculature can be found in almost every part of the human body, including the internal organs. Importantly, abnormal changes in microvasculature are usually related to pathological development of the tissue cells. Monitoring of changes in blood flow properties in microvasculature, therefore, provides useful diagnostic information about pathological conditions in biological tissues as exemplified in glaucoma, diabetes, age related macular degeneration, port wine stains, burn-depth, and potentially skin cancer. However, the capillary network is typically only one cell in wall thickness with 5 to 10 microns in diameter and located in the dermis region of skin. Therefore, a non-invasive flow imaging technique that is capable of depth sectioning at high resolution and high speed is demanded. Optical coherence tomography (OCT), particularly after its advancement in frequency domain OCT (FD-OCT), is a promising tool for non-invasive high speed, high resolution, and high sensitivity depth-resolved imaging of biological tissues. Over the last ten years, numerous efforts have been paid to develop OCT-based flow imaging techniques. An important effort is the development of phase-resolved Doppler OCT (PR-DOCT). Phase-resolved Doppler imaging using FD-OCT is particularly of interest because of the direct access to the phase information of the depth profile signal. Furthermore, the high speed capability of FD-OCT is promising for real time flow monitoring as well as 3D flow segmentation applications. However, several challenges need to be addressed; 1) Flow in biological samples exhibits a wide dynamic range of flow velocity caused by, for example, the variation in the flow angles, flow diameters, and functionalities. However, the improvement in imaging speed of FD-OCT comes at the expense of a reduction in sensitivity to slow flow information and hence a reduction in detectable velocity range; 2) A structural ambiguity so-called 'mirror image' in FD-OCT prohibits the use of maximum sensitivity and imaging depth range; 3) The requirement of high lateral resolution to resolve capillary vessels requires the use of an imaging optics with high numerical aperture (NA) that leads to a reduction in depth of focus (DOF) and hence the imaging depth range (i.e. less than 100 microns) unless dynamic focusing is performed. Nevertheless, intrinsic to the mechanism of FD-OCT, dynamic focusing is not possible. In this dissertation, the implementation of PR-DOCT in a high speed swept-source based FD-OCT is investigated and optimized. An acquisition scheme as well as a processing algorithm that effectively extends the detectable velocity dynamic range of the PR-DOCT is presented. The proposed technique increased the overall detectable velocity dynamic range of PR-DOCT by about five times of that achieved by the conventional method. Furthermore, a novel technique of mirror image removal called Ã‚Â'Dual-Detection FD-OCTÃ‚Â' (DD-FD-OCT) is presented. One of the advantages of DD-FD-OCT to Doppler imaging is that the full-range signal is achieved without manipulation of the phase relation between consecutive axial lines. Hence the full-range DD-FD-OCT is fully applicable to phase-resolved Doppler detection without a reduction in detectable velocity dynamic range as normally encountered in other full-range techniques. In addition, PR- DOCT can utilize the maximum signal-to-noise ratio provided by the full-range capability. This capability is particularly useful for imaging of blood flow that locates deep below the sample surface, such as blood flow at deep posterior human eye and blood vessels network in the dermis region of human skin. Beside high speed and functional imaging capability, another key parameter that will open path for optical diagnostics using OCT technology is high resolution imaging (i.e. in a regime of a few microns or sub-micron). Even though the lateral resolution of OCT can be independently improved by opening the NA of the imaging optics, the high lateral resolution is maintained only over a short range as limited by the depth of focus that varies inversely and quadratically with NA. Recently developed by our group, Ã‚Â'Gabor-Domain Optical Coherence MicroscopyÃ‚Â' (GD-OCM) is a novel imaging technique capable for invariant resolution of about 2-3 microns over a 2 mm cubic field-of-view. This dissertation details the imaging protocol as well as the automatic data fusion method of GD-OCM developed to render an in-focus high-resolution image throughout the imaging depth of the sample in real time. For the application of absolute flow measurement as an example, the precise information about flow angle is required. GD-OCM provides more precise interpretation of the tissue structures over a large field-of-view, which is necessary for accurate mapping of the flow structure and hence is promising for diagnostic applications particularly when combined with Doppler imaging. Potentially, the ability to perform high resolution OCT imaging inside the human body is useful for many diagnostic applications, such as providing an accurate map for biopsy, guiding surgical and other treatments, monitoring the functional state and/or the post-operative recovery process of internal organs, plaque detection in arteries, and early detection of cancers in the gastrointestinal tract. Endoscopic OCT utilizes a special miniature probe in the sample arm to access tubular organs inside the human body, such as the cardiovascular system, the lung, the gastrointestinal tract, the urinary tract, and the breast duct. We present an optical design of a dynamic focus endoscopic probe that is capable of about 4 to 6 microns lateral resolution over a large working distance (i.e. up to 5 mm from the distal end of the probe). The dynamic focus capability allows integration of the endoscopic probe to GD-OCM imaging to achieve high resolution endoscopic tomograms. We envision the future of this developing technology as a solution to high resolution, minimally invasive, depth-resolved imaging of not only structure but also the microvasculature of in vivo biological tissues that will be useful for many clinical applications, such as dermatology, ophthalmology, endoscopy, and cardiology. The technology is also useful for animal study applications, such as the monitoring of an embryoÃ‚Â's heart for the development of animal models and monitoring of changes in blood circulation in response to external stimulus in small animal brains.
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Date Issued: 2010
Identifier: CFE0003442, ucf:48392
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003442

Title: GABOR DOMAIN OPTICAL COHERENCE MICROSCOPY.
Creator: Murali, Supraja, Rolland, Jannick, University of Central Florida
Abstract / Description: Time domain Optical Coherence Tomography (TD-OCT), first reported in 1991, makes use of the low temporal coherence properties of a NIR broadband laser to create depth sectioning of up to 2mm under the surface using optical interferometry and point to point scanning. Prior and ongoing work in OCT in the research community has concentrated on improving axial resolution through the development of broadband sources and speed of image acquisition through new techniques such as Spectral domain OCT ...
Show moreTime domain Optical Coherence Tomography (TD-OCT), first reported in 1991, makes use of the low temporal coherence properties of a NIR broadband laser to create depth sectioning of up to 2mm under the surface using optical interferometry and point to point scanning. Prior and ongoing work in OCT in the research community has concentrated on improving axial resolution through the development of broadband sources and speed of image acquisition through new techniques such as Spectral domain OCT (SD-OCT). In SD-OCT, an entire depth scan is acquired at once with a low numerical aperture (NA) objective lens focused at a fixed point within the sample. In this imaging geometry, a longer depth of focus is achieved at the expense of lateral resolution, which is typically limited to 10 to 20 µm. Optical Coherence Microscopy (OCM), introduced in 1994, combined the advantages of high axial resolution obtained in OCT with high lateral resolution obtained by increasing the NA of the microscope placed in the sample arm. However, OCM presented trade-offs caused by the inverse quadratic relationship between the NA and the DOF of the optics used. For applications requiring high lateral resolution, such as cancer diagnostics, several solutions have been proposed including the periodic manual re-focusing of the objective lens in the time domain as well as the spectral domain C-mode configuration in order to overcome the loss in lateral resolution outside the DOF. In this research, we report for the first time, high speed, sub-cellular imaging (lateral resolution of 2 µm) in OCM using a Gabor domain image processing algorithm with a custom designed and fabricated dynamic focus microscope interfaced to a Ti:Sa femtosecond laser centered at 800 nm within an SD-OCM configuration. It is envisioned that this technology will provide a non-invasive replacement for the current practice of multiple biopsies for skin cancer diagnosis. The research reported here presents three important advances to this technology all of which have been demonstrated in full functional hardware conceived and built during the course of this research. First, it has been demonstrated that the coherence gate created by the femtosecond laser can be coupled into a scanning optical microscope using optical design methods to include liquid lens technology that enables scanning below the surface of skin with no moving parts and at high resolution throughout a 2×2×2 mm imaging cube. Second, the integration the variable-focus liquid lens technology within a fixed-optics microscope custom optical design helped increase the working NA by an order of magnitude over the limitation imposed by the liquid lens alone. Thus, this design has enabled homogenous axial and lateral resolution at the micron-level (i.e., 2 µm) while imaging in the spectral domain, and still maintaining in vivo speeds. The latest images in biological specimens clearly demonstrate sub-cellular resolution in all dimensions throughout the imaging volume. Third, this new modality for data collection has been integrated with an automated Gabor domain image registration and fusion algorithm to provide full resolution images across the data cube in real-time. We refer to this overall OCM method as Gabor domain OCM (GD-OCM). These advantages place GD-OCM in a unique position with respect to the diagnosis of cancer, because when fully developed, it promises to enable fast and accurate screening for early symptoms that could lead to prevention. The next step for this technology is to apply it directly, in a clinical environment. This step is underway and is expected to be reported by the next generation of researchers within this group.
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Date Issued: 2009
Identifier: CFE0002771, ucf:48137
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002771

Title: SYNTHESIS AND APPLICATIONS OF RING OPENING METATHESIS POLYMERIZATION BASED FUNCTIONAL BLOCK COPOLYMERS.
Creator: Biswas, Sanchita, Belfield, Kevin, University of Central Florida
Abstract / Description: Ring opening metathesis polymerization (ROMP) is established as one of the efficient controlled living polymerization methods which have various applications in polymer science and technology fields. The research presented in this dissertation addresses several applications of multifunctional well-defined norbornene-based block copolymers synthesized by ROMP using ruthenium-based Grubbs catalysts. These novel block copolymers were applied to stabilize maghemite nanoparticles, creating the...
Show moreRing opening metathesis polymerization (ROMP) is established as one of the efficient controlled living polymerization methods which have various applications in polymer science and technology fields. The research presented in this dissertation addresses several applications of multifunctional well-defined norbornene-based block copolymers synthesized by ROMP using ruthenium-based Grubbs catalysts. These novel block copolymers were applied to stabilize maghemite nanoparticles, creating the superparamagnetic polymeric nanocomposites. The J-aggregation properties of the porphyrin dyes were improved via self-assembly with a customized norbornene polymer. Novel multimodal copolymer probes were synthesized for two-photon fluorescence integrin-targeted bioimaging. In Chapter 1 a brief overview of ROMP along with ruthenium metal catalysts and selected applications of the polymers related to this research is presented. Superparamagnetic maghemite nanoparticles are important in biotechnology fields, such as enhanced magnetic resonance imaging (MRI), magnetically controlled drug delivery, and biomimetics. However, cluster formation and eventual loss of nano-dimensions is a major obstacle for these materials. Chapter 2 presents a solution to this problem through nanoparticles stabiulized in a polymer matrix. The synthesis and chracterization of novel diblock copolymers, consisting of epoxy pendant anchoring groups to chelate maghemite nanoparticles and steric stabilizing groups, as well as generation of nanocomposites and their characterization, including surface morphologies and magnetic properties, is discussed in Chapter 2. In Chapter 3, further improvement of the nanocomposites by ligand modification and the synthesis of pyrazole-templated diblock copolymers and their impact to stabilize the maghemite nanocomposite are presented. Additionally, the organic soluble magnetic nanocomposites with high magnetizations were encapsulated in an amphiphilic copolymer and dispersed in water to assess their water stability by TEM. To gain a preliminary measure of biocopatibility of the micelle-encapsulated polymeric magnetic nanocomposites, cell-viability was determined. In Chapter 4, aggregation behaviors of two porphyrin-based dyes were investigated. A new amphiphilic homopolymer containing secondary amine moieties was synthesized and characterized. In low pH, the polymer became water soluble and initiated the stable J-aggregation of the porphyrin. Spectroscopic data supported the aggregation behavior. Two photon fluorescence microscopy (2PFM) has become a powerful technique in bioimaging for non-invasive imaging and potential diagnosis and treatment of a number of diseases via excitation in the near-infrared (NIR) region. The fluorescence emission upon two-photon absorption (2PA) is quadratically dependent with the intensity of excitation light (compared to the linear dependence in the case of one-photon absoprtion), offering several advantages for biological applications over the conventional one-photon absorption (1PA) due to the high 3D spatial resolution that is confined near the focal point along with less photodamage and interference from the biological tissues at longer wavelength (~700-900 nm). Hence, efficient 2PA absorbing fluorophores conjugated with specific targeting moieties provides an even better bioimaging probe to diagnose desired cellular processes or areas of interest The αVβ3 integrin adhesive protein plays a significant role in regulating angiogenesis and is over-expressed in uncontrolled neovascularization during tumor growth, invasion, and metastasis. Cyclic-RGD peptides are well-known antagonists of αVβ3 integrin which suppress the angiogenesis process, thus preventing tumor growth. In Chapter 5 the synthesis, photophysical studies and bioimaging is reported for a versatile norbornene-based block copolymer multifunctional scaffold containing biocompatible (PEG), two-photon fluorescent (fluorenyl), and targeting (cyclic RGD peptide) moieties. This water-soluble polymeric multi scaffold probe with negligible cytotoxicity exhibited much stronger fluorescence and high localization in U87MG cells (that overexpress integrin) compared to control MCF7 cells. The norbornene-based polymers and copolymers have quite remarkable versatility for the creation of advanced functional magnetic, photonic, and biophotonic materials.
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Date Issued: 2010
Identifier: CFE0003065, ucf:48296
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003065

Title: Mesoscopic Interactions in Complex Photonic Media.
Creator: Rezvani Naraghi, Roxana, Dogariu, Aristide, Tetard, Laurene, Rahman, Talat, Abouraddy, Ayman, University of Central Florida
Abstract / Description: Mesoscale optics provides a framework for understanding a wide range of phenomena occurring in a variety of fields ranging from biological tissues to composite materials and from colloidal physics to fabricated nanostructures. When light interacts with a complex system, the outcome depends significantly on the length and time scales of interaction. Mesoscale optics offers the apparatus necessary for describing specific manifestations of wave phenomena such as interference and phase memory in...
Show moreMesoscale optics provides a framework for understanding a wide range of phenomena occurring in a variety of fields ranging from biological tissues to composite materials and from colloidal physics to fabricated nanostructures. When light interacts with a complex system, the outcome depends significantly on the length and time scales of interaction. Mesoscale optics offers the apparatus necessary for describing specific manifestations of wave phenomena such as interference and phase memory in complex media. In-depth understanding of mesoscale phenomena provides the required quantitative explanations that neither microscopic nor macroscopic models of light-matter interaction can afford. Modeling mesoscopic systems is challenging because the outcome properties can be efficiently modified by controlling the extent and the duration of interactions.In this dissertation, we will first present a brief survey of fundamental concepts, approaches, and techniques specific to fundamental light-matter interaction at mesoscopic scales. Then, we will discuss different regimes of light propagation through randomly inhomogenous media. In particular, a novel description will be introduced to analyze specific aspects of light propagation in dense composites. Moreover, we will present evidence that the wave nature of light can be critical for understanding its propagation in unbounded highly scattering materials. We will show that the perceived diffusion of light is subjected to competing mechanisms of interaction that lead to qualitatively different phases for the light evolution through complex media. In particular, we will discuss implications on the ever elusive localization of light in three-dimensional random media. In addition to fundamental aspects of light-matter interaction at mesoscopic scales, this dissertation will also address the process of designing material structures that provide unique scattering properties. We will demonstrate that multi-material dielectric particles with controlled radial and azimuthal structure can be engineered to modify the extinction cross-section, to control the scattering directivity, and to provide polarization-dependent scattering. We will show that dielectric core-shell structures with similar macroscopic sizes can have both high scattering cross-sections and radically different scattering phase functions. In addition, specific structural design, which breaks the azimuthal symmetry of the spherical particle, can be implemented to control the polarization properties of scattered radiation. Moreover, we will also demonstrate that the power flow around mesoscopic scattering particles can be controlled by modifying their internal heterogeneous structures.Lastly, we will show how the statistical properties of the radiation emerging from mesoscopic systems can be utilized for surface and subsurface diagnostics. In this dissertation, we will demonstrate that the intensity distributions measured in the near-field of composite materials are direct signatures of the scale-dependent morphology, which is determined by variations of the local dielectric function. We will also prove that measuring the extent of spatial coherence in the proximity of two-dimensional interfaces constitutes a rather general method for characterizing the defect density in crystalline materials. Finally, we will show that adjusting the spatial coherence properties of radiation can provide a simple solution for a significant deficiency of near-field microscopy. We will demonstrate experimentally that spurious interference effects can be efficiently eliminated in passive near-field imaging by implementing a random illumination.
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Date Issued: 2017
Identifier: CFE0006647, ucf:51253
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006647

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.
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Date Issued: 2007
Identifier: CFE0001918, ucf:47486
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001918

Title: PROBING THE NANOSCALE INTERACTION FORCES AND ELASTIC PROPERTIES OF ORGANIC AND INORGANIC MATERIALS USING FORCE-DISTANCE (F-D) SPECTROSCOPY.
Creator: Vincent, Abhilash, Seal, Sudipta, University of Central Florida
Abstract / Description: Due to their therapeutic applications such as radical scavenging, MRI contrast imaging, Photoluminescence imaging, drug delivery, etc., nanoparticles (NPs) have a significant importance in bio-nanotechnology. The reason that prevents the utilizing NPs for drug delivery in medical field is mostly due to their biocompatibility issues (incompatibility can lead to toxicity and cell death). Changes in the surface conditions of NPs often lead to NP cytotoxicity. Investigating the role of NP surface...
Show moreDue to their therapeutic applications such as radical scavenging, MRI contrast imaging, Photoluminescence imaging, drug delivery, etc., nanoparticles (NPs) have a significant importance in bio-nanotechnology. The reason that prevents the utilizing NPs for drug delivery in medical field is mostly due to their biocompatibility issues (incompatibility can lead to toxicity and cell death). Changes in the surface conditions of NPs often lead to NP cytotoxicity. Investigating the role of NP surface properties (surface charges and surface chemistry) on their interactions with biomolecules (Cells, protein and DNA) could enhance the current understanding of NP cytotoxicity. Hence, it is highly beneficial to the nanotechnology community to bring more attention towards the enhancement of surface properties of NPs to make them more biocompatible and less toxic to biological systems. Surface functionalization of NPs using specific ligand biomolecules have shown to enhance the protein adsorption and cellular uptake through more favorable interaction pathways. Cerium oxide NPs (CNPs also known as nanoceria) are potential antioxidants in cell culture models and understanding the nature of interaction between cerium oxide NPs and biological proteins and cells are important due to their therapeutic application (especially in site specific drug delivery systems). The surface charges and surface chemistry of CNPs play a major role in protein adsorption and cellular uptake. Hence, by tuning the surface charges and by selecting proper functional molecules on the surface, CNPs exhibiting strong adhesion to biological materials can be prepared. By probing the nanoscale interaction forces acting between CNPs and protein molecules using Atomic Force Microscopy (AFM) based force-distance (F-D) spectroscopy, the mechanism of CNP-protein adsorption and CNP cellular uptake can be understood more quantitatively. The work presented in this dissertation is based on the application of AFM in studying the interaction forces as well as the mechanical properties of nanobiomaterials. The research protocol employed in the earlier part of the dissertation is specifically aimed to understand the operation of F-D spectroscopy technique. The elastic properties of thin films of silicon dioxide NPs were investigated using F-D spectroscopy in the high force regime of few 100 nN to 1 Ã‚ÂµN. Here, sol-gel derived porous nanosilica thin films of varying surface morphology, particle size and porosity were prepared through acid and base catalyzed process. AFM nanoindentation experiments were conducted on these films using the F-D spectroscopy mode and the nanoscale elastic properties of these films were evaluated. The major contribution of this dissertation is a study exploring the interaction forces acting between CNPs and transferrin proteins in picoNewton scale regime using the force-distance spectroscopy technique. This study projects the importance of obtaining appropriate surface charges and surface chemistry so that the NP can exhibit enhanced protein adsorption and NP cellular uptake.
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Date Issued: 2010
Identifier: CFE0003079, ucf:48305
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003079

Title: STRUCTURAL CHARACTERIZATION OF SPUTTER-DEPOSITED SS304+XAL (X = 0, 4, 7 AND 10 WT.%) COATINGS AND MECHANICALLY MILLED TI, ZR AND HF POWDERS.
Creator: Seelam, Uma Maheswara, Suryanarayana, Challapalli, University of Central Florida
Abstract / Description: Study of the metastable phases obtained by non-equilibrium processing techniques has come a long way during the past five decades. New metastable phases have often given new perspectives to the research on synthesis of novel materials systems. Metastable materials produced by two non-equilibrium processing methods were studied for this dissertation- 304-type austenitic stainless steel (SS304 or Fe-18Cr-8Ni)+aluminum coatings produced by plasma enhanced magnetron sputter-deposition (PEMS) and...
Show moreStudy of the metastable phases obtained by non-equilibrium processing techniques has come a long way during the past five decades. New metastable phases have often given new perspectives to the research on synthesis of novel materials systems. Metastable materials produced by two non-equilibrium processing methods were studied for this dissertation- 304-type austenitic stainless steel (SS304 or Fe-18Cr-8Ni)+aluminum coatings produced by plasma enhanced magnetron sputter-deposition (PEMS) and nanocrystalline Ti, Zr and Hf powders processed by mechanical milling (MM). The objective of the study was to understand the crystallographic and microstructural aspects of these materials. Four SS304+Al coatings with a nominal Al percentages of 0, 4, 7 and 10 wt.% in the coatings were deposited on an SS304 substrate by PEMS using SS304 and Al targets. The as-deposited coatings were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and three-dimensional atom probe microscopy (3DAP). Surface morphology and chemical analysis were studied by SEM. Phase identification was carried out by XRD and TEM. The microstructural features of all the coatings, as observed in the TEM, consisted of columnar grains with the columnar grain width (a measure of grain size) increasing with an increase in the Al content. The coatings had grains with average grain sizes of about 100, 290, 320 and 980 nm, respectively for 0, 4, 7 and 10 wt.% Al. The observed grain structures and increase in grain size were related to substrate temperature during deposition. XRD results indicated that the Al-free coating consisted of the non-equilibrium ferrite and sigma phases. In the 4Al, 7Al and 10Al coatings, equilibrium ferrite and B2 phases were observed but no sigma phase was found. In 10Al coating, we were able to demonstrate experimentally using 3DAP studies that NiAl phase formation is preferred over the FeAl phase at nano scale. During mechanical milling of the hexagonal close packed (HCP) metals Hf, Ti and Zr powders, unknown nanocrystalline phases with face centered cubic (FCC) structure were found. The FCC phases could be either allotropes of the respective metals or impurity stabilized phases. However, upon MM under high purity conditions, it was revealed that the FCC phases were impurity stabilized. The decrease in crystallite size down to nanometer levels, an increase in atomic volume, lattice strain, and possible contamination were the factors responsible for the transformation.
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Date Issued: 2010
Identifier: CFE0003161, ucf:48595
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003161

Title: Growth and doping of MoS2 thin films for electronic and optoelectronic applications.
Creator: Abouelkhair, Hussain, Peale, Robert, Kaden, William, Stolbov, Sergey, Coffey, Kevin, University of Central Florida
Abstract / Description: MoS2 high absorption coefficient, high mobility, mechanical flexibility, and chemical inertness is very promising for many electronic and optoelectronic applications. The growth of high-quality MoS2 by a scalable and doping compatible method is still lacking. Therefore, the suitable dopants for MoS2 are not fully explored yet. This dissertation consists mainly of four main studies. The first study is on the growth of MoS2 thin films by atmospheric pressure chemical vapor deposition. Scanning...
Show moreMoS2 high absorption coefficient, high mobility, mechanical flexibility, and chemical inertness is very promising for many electronic and optoelectronic applications. The growth of high-quality MoS2 by a scalable and doping compatible method is still lacking. Therefore, the suitable dopants for MoS2 are not fully explored yet. This dissertation consists mainly of four main studies. The first study is on the growth of MoS2 thin films by atmospheric pressure chemical vapor deposition. Scanning electron microscope images revealed the growth of microdomes of MoS2 on top of a smooth MoS2 film. These microdomes are very promising as a broadband omnidirectional light trap for light harvesting applications. The second study is on the growth of MoS2 thin films by low pressure chemical vapor deposition (LPCVD). Control of sulfur vapor flow is essential for the growth of a pure phase of MoS2. Turning off sulfur vapor flow during the cooling cycle at 700 (&)#186;C leads to the growth of highly textured MoS2 with a Hall mobility of 20 cm2/Vs. The third study was on the growth of Ti-doped MoS2 thin films by LPCVD. The successful doping was confirmed by Hall effect measurement and secondary ion mass spectrometry (SIMS). Different growth temperatures from 1000 to 700 ? were studied. Ti act as a donor in MoS2. The fourth study is on fluorine-doped SnO2 (FTO) which has many technological applications including solar cells and transistors. FTO was grown by an aqueous-spray-based method. The main objective was to compare the actual against the nominal concentration of fluorine using SIMS. The concentration of fluorine in the grown films is lower than the concentration of fluorine in the aqueous solution.?
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Date Issued: 2017
Identifier: CFE0006847, ucf:51767
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006847

Title: Harnessing Spatial Intensity Fluctuations for Optical Imaging and Sensing.
Creator: Akhlaghi Bouzan, Milad, Dogariu, Aristide, Saleh, Bahaa, Pang, Sean, Atia, George, University of Central Florida
Abstract / Description: Properties of light such as amplitude and phase, temporal and spatial coherence, polarization, etc. are abundantly used for sensing and imaging. Regardless of the passive or active nature of the sensing method, optical intensity fluctuations are always present! While these fluctuations are usually regarded as noise, there are situations where one can harness the intensity fluctuations to enhance certain attributes of the sensing procedure. In this thesis, we developed different sensing...
Show moreProperties of light such as amplitude and phase, temporal and spatial coherence, polarization, etc. are abundantly used for sensing and imaging. Regardless of the passive or active nature of the sensing method, optical intensity fluctuations are always present! While these fluctuations are usually regarded as noise, there are situations where one can harness the intensity fluctuations to enhance certain attributes of the sensing procedure. In this thesis, we developed different sensing methodologies that use statistical properties of optical fluctuations for gauging specific information. We examine this concept in the context of three different aspects of computational optical imaging and sensing. First, we study imposing specific statistical properties to the probing field to image or characterize certain properties of an object through a statistical analysis of the spatially integrated scattered intensity. This offers unique capabilities for imaging and sensing techniques operating in highly perturbed environments and low-light conditions. Next, we examine optical sensing in the presence of strong perturbations that preclude any controllable field modification. We demonstrate that inherent properties of diffused coherent fields and fluctuations of integrated intensity can be used to track objects hidden behind obscurants. Finally, we address situations where, due to coherent noise, image accuracy is severely degraded by intensity fluctuations. By taking advantage of the spatial coherence properties of optical fields, we show that this limitation can be effectively mitigated and that a significant improvement in the signal-to-noise ratio can be achieved even in one single-shot measurement. The findings included in this dissertation illustrate different circumstances where optical fluctuations can affect the efficacy of computational optical imaging and sensing. A broad range of applications, including biomedical imaging and remote sensing, could benefit from the new approaches to suppress, enhance, and exploit optical fluctuations, which are described in this dissertation.
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Date Issued: 2017
Identifier: CFE0007274, ucf:52200
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007274

Title: Investigating New Guaiazulenes and Diketopyrropyrroles for Photonic Applications.
Creator: Ghazvini Zadeh, Ebrahim, Belfield, Kevin, Campiglia, Andres, Yuan, Yu, Zou, Shengli, Cheng, Zixi, University of Central Florida
Abstract / Description: ?-Conjugated systems have been the focus of study in recent years in order to understand their charge transport and optical properties for use in organic electronic devices, fluorescence bioimaging, sensors, and 3D optical data storage (ODS), among others. As a result, several molecular building blocks have been designed, allowing new frontiers to be realized. While various successful building blocks have been fine-tuned at both the electronic and molecular structure level to provide advanced...
Show more?-Conjugated systems have been the focus of study in recent years in order to understand their charge transport and optical properties for use in organic electronic devices, fluorescence bioimaging, sensors, and 3D optical data storage (ODS), among others. As a result, several molecular building blocks have been designed, allowing new frontiers to be realized. While various successful building blocks have been fine-tuned at both the electronic and molecular structure level to provide advanced photophysical and optoelectronic characteristics, the azulene framework has been under-appreciated despite its unique electronic and optical properties. Among several attributes, azulenes are vibrant blue naturally occurring hydrocarbons that exhibit large dipolar character, coupled with stimuli-responsive behavior in acidic environments. Additionally, the non-toxic nature and the accompanying eco-friendly feature of some azulenes, namely guaiazulene, may set the stage to further explore a more (")green(") route towards photonic and conductive materials.The first part of this dissertation focuses on exploiting guaiazulene as a natural building block for the synthesis of chromophores with varying stimuli-responsiveness. Results described in Chapter 1 show that extending the conjugation of guaiazulene through its seven-membered ring methyl group with aromatic substituents dramatically impacts the optical properties of the guaiazulenium carbocation. Study of these ?(-)stabilized tropilium ions enabled establishing photophysical structure-property trends for guaiazulene-terminated ?-conjugated analogs under acidic conditions, including absorption, emission, quantum yield, and optical band gap patterns. These results were exploited in the design of a photosensitive polymeric system with potential application in the field of three dimensional (3D) optical data storage (ODS).Chapter 2 describes the use of guaiazulene reactive sites (C-3 and C-4 methyl group) to generate a series of cyclopenta[ef]heptalenes that exhibit strong stimuli-responsive behavior. The approach presents a versatile route that allows for various substrates to be incorporated into the resulting cyclopenta[ef]heptalenes, especially after optimization that led to devising a one-pot reaction toward such tricyclic systems. Examining the UV-vis absorption profiles in neutral and acidic media showed that the extension of conjugation at C(4) of the cyclopenta[ef]heptalene skeleton results in longer absorption maxima and smaller optical energy gaps. Additionally, it was concluded that these systems act as sensitizers of a UV-activated ((<) 300 nm) photoacid generator (PAG), via intermolecular photoinduced electron transfer (PeT), upon which the PAG undergoes photodecomposition resulting in the generation of acid.In a related study, the guaiazulene methyl group at C-4 was employed to study the linear and nonlinear optical properties of 4-styrylguaiazulenes, having the same ?(-)donor with varying ?-spacer. It was realized that the conjugation length correlates with the extent of bathochromic shift of the protonated species. On the other hand, a trend of decreasing quantum yield was established for this set of 4-styrylguaiazulenes, which can be explained by the increasingly higher degree of flexibility.The second part of this dissertation presents a comprehensive investigation of the linear photophysical, photochemical, and nonlinear optical properties of diketopyrrolopyrrole (DPP)-based derivatives, including two-photon absorption (2PA), femtosecond transient absorption, stimulated emission spectroscopy, and superfluorescence phenomena. The synthetic feasibility, ease of modification, outstanding robustness, and attractive spectroscopic properties of DPPs have motivated their study for fluorescence microscopy applications, concluding that the prepared DPP's are potentially suitable chromophores for high resolution stimulated emission depletion (STED) microscopy.
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Date Issued: 2015
Identifier: CFE0006034, ucf:50986
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006034

Title: Experimental confirmation of ballistic nanofriction and quasiparticle interference in Dirac materials.
Creator: Lodge, Michael, Ishigami, Masahiro, Kaden, William, Schelling, Patrick, Del Barco, Enrique, Roy, Tania, University of Central Florida
Abstract / Description: This dissertation is broadly divided into two parts. The first part details the development and usage of an experimental apparatus to measure the dry nanofriction for a well-defined interface at high sliding speeds. I leverage the sensitivity of a quartz crystal microbalance (QCM) to determine the drag coefficient of an ensemble of gold nanocrystals sliding on graphene at speeds up to 11 cm/s. I discuss the theories of velocity-dependent friction, especially at high sliding speeds, and QCM...
Show moreThis dissertation is broadly divided into two parts. The first part details the development and usage of an experimental apparatus to measure the dry nanofriction for a well-defined interface at high sliding speeds. I leverage the sensitivity of a quartz crystal microbalance (QCM) to determine the drag coefficient of an ensemble of gold nanocrystals sliding on graphene at speeds up to 11 cm/s. I discuss the theories of velocity-dependent friction, especially at high sliding speeds, and QCM modeling. I also discuss our synthesis protocols for graphene and molybdenum disulfide, as well as our protocol for fabricating a clean, graphene-laminated QCM device and nanocrystal ensemble. The design and fabrication of our QCM oscillator circuit is presented in detail. The quantitatively-measured the drag coefficient is compared against molecular dynamics simulations at both low and high sliding speeds. We show evidence of a predicted ultra-low friction regime and find that the interaction energy between gold nanocrystals and graphene is lower than previously assumed. In the second part of this dissertation, I detail the band structure measurement of a novel semimetal using scanning tunneling microscopy. In particular, I measured the energy-dependenceof quasiparticle interference patterns at the surface of zirconium silicon sulfide (ZrSiS), a topological nodal line semimetal whose charge carrier quasiparticles possess a pseudospin degree offreedom. The aims of this study were to (1) discover the shape of the band structure above the Fermi level along a high-symmetry direction, (2) discover the energetic location of the line node inthe same high-symmetry direction, and (3) discover the selection rules for k transitions. This study confirms the predicted linearity in E(k) of the band structure above the Fermi level. Additionally,we observe an energy-dependent mechanism for pseudospin scattering. This study also provides the first experimentally-derived estimation of the line node position in E(k).
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Date Issued: 2018
Identifier: CFE0007218, ucf:52222
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007218

Title: LIQUID CRYSTAL OPTICS FOR COMMUNICATIONS, SIGNAL PROCESSING AND 3-D MICROSCOPIC IMAGING.
Creator: Khan, Sajjad, Riza, Nabeel, University of Central Florida
Abstract / Description: This dissertation proposes, studies and experimentally demonstrates novel liquid crystal (LC) optics to solve challenging problems in RF and photonic signal processing, freespace and fiber optic communications and microscopic imaging. These include free-space optical scanners for military and optical wireless applications, variable fiber-optic attenuators for optical communications, photonic control techniques for phased array antennas and radar, and 3-D microscopic imaging. At the heart of...
Show moreThis dissertation proposes, studies and experimentally demonstrates novel liquid crystal (LC) optics to solve challenging problems in RF and photonic signal processing, freespace and fiber optic communications and microscopic imaging. These include free-space optical scanners for military and optical wireless applications, variable fiber-optic attenuators for optical communications, photonic control techniques for phased array antennas and radar, and 3-D microscopic imaging. At the heart of the applications demonstrated in this thesis are LC devices that are non-pixelated and can be controlled either electrically or optically. Instead of the typical pixel-by-pixel control as is custom in LC devices, the phase profile across the aperture of these novel LC devices is varied through the use of high impedance layers. Due to the presence of the high impedance layer, there forms a voltage gradient across the aperture of such a device which results in a phase gradient across the LC layer which in turn is accumulated by the optical beam traversing through this LC device. The geometry of the electrical contacts that are used to apply the external voltage will define the nature of the phase gradient present across the optical beam. In order to steer a laser beam in one angular dimension, straight line electrical contacts are used to form a one dimensional phase gradient while an annular electrical contact results in a circularly symmetric phase profile across the optical beam making it suitable for focusing the optical beam. The geometry of the electrical contacts alone is not sufficient to form the linear and the quadratic phase profiles that are required to either deflect or focus an optical beam. Clever use of the phase response of a typical nematic liquid crystal (NLC) is made such that the linear response region is used for the angular beam deflection while the high voltage quadratic response region is used for focusing the beam. Employing an NLC deflector, a device that uses the linear angular deflection, laser beam steering is demonstrated in two orthogonal dimensions whereas an NLC lens is used to address the third dimension to complete a three dimensional (3-D) scanner. Such an NLC deflector was then used in a variable optical attenuator (VOA), whereby a laser beam coupled between two identical single mode fibers (SMF) was mis-aligned away from the output fiber causing the intensity of the output coupled light to decrease as a function of the angular deflection. Since the angular deflection is electrically controlled, hence the VOA operation is fairly simple and repeatable. An extension of this VOA for wavelength tunable operation is also shown in this dissertation. A LC spatial light modulator (SLM) that uses a photo-sensitive high impedance electrode whose impedance can be varied by controlling the light intensity incident on it, is used in a control system for a phased array antenna. Phase is controlled on the Write side of the SLM by controlling the intensity of the Write laser beam which then is accessed by the Read beam from the opposite side of this reflective SLM. Thus the phase of the Read beam is varied by controlling the intensity of the Write beam. A variable fiber-optic delay line is demonstrated in the thesis which uses wavelength sensitive and wavelength insensitive optics to get both analog as well as digital delays. It uses a chirped fiber Bragg grating (FBG), and a 1xN optical switch to achieve multiple time delays. The switch can be implemented using the 3-D optical scanner mentioned earlier. A technique is presented for ultra-low loss laser communication that uses a combination of strong and weak thin lens optics. As opposed to conventional laser communication systems, the Gaussian laser beam is prevented from diverging at the receiving station by using a weak thin lens that places the transmitted beam waist mid-way between a symmetrical transmitter-receiver link design thus saving prime optical power. LC device technology forms an excellent basis to realize such a large aperture weak lens. Using a 1-D array of LC deflectors, a broadband optical add-drop filter (OADF) is proposed for dense wavelength division multiplexing (DWDM) applications. By binary control of the drive signal to the individual LC deflectors in the array, any optical channel can be selectively dropped and added. For demonstration purposes, microelectromechanical systems (MEMS) digital micromirrors have been used to implement the OADF. Several key systems issues such as insertion loss, polarization dependent loss, wavelength resolution and response time are analyzed in detail for comparison with the LC deflector approach. A no-moving-parts axial scanning confocal microscope (ASCM) system is designed and demonstrated using a combination of a large diameter LC lens and a classical microscope objective lens. By electrically controlling the 5 mm diameter LC lens, the 633 nm wavelength focal spot is moved continuously over a 48 ƒÝm range with measured 3-dB axial resolution of 3.1 ƒÝm using a 0.65 numerical aperture (NA) micro-objective lens. The ASCM is successfully used to image an Indium Phosphide twin square optical waveguide sample with a 10.2 ƒÝm waveguide pitch and 2.3 ƒÝm height and width. Using fine analog electrical control of the LC lens, a super-fine sub-wavelength axial resolution of 270 nm is demonstrated. The proposed ASCM can be useful in various precision three dimensional imaging and profiling applications.
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Date Issued: 2005
Identifier: CFE0000750, ucf:46596
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000750

Title: THE APPLICATION OF TWO-PHOTON ABSORBING PROBES IN LYSOSOMAL, ZINC ION SENSING AND FOLATE RECEPTOR-TARGETED BIOIMAGING.
Creator: WANG, XUHUA, Belfield, Kevin D., University of Central Florida
Abstract / Description: Two-photon fluorescence microscopy (2PFM) has become a powerful technique for bioimaging in non-invasive cancer diagnosis and also investigating the mechanization and original of a variety of diseases by tracking various biological processes. Because the fluorescence emission by two photon absorbing (2PA) is directly proportional to the square of the intensity of excitation light, this intrinsic property of 2PA provides 2PFM great advantages over traditional one-photon fluorescence microscopy...
Show moreTwo-photon fluorescence microscopy (2PFM) has become a powerful technique for bioimaging in non-invasive cancer diagnosis and also investigating the mechanization and original of a variety of diseases by tracking various biological processes. Because the fluorescence emission by two photon absorbing (2PA) is directly proportional to the square of the intensity of excitation light, this intrinsic property of 2PA provides 2PFM great advantages over traditional one-photon fluorescence microscopy (1PFM), including high 3D spatial localization, less photodamage and interference from biological tissue because of using longer wavelength excitation (700-1300 nm). However, most 2PA probes are hydrophobic and their photostabilities are questionable, severely limiting their biological and medical applications. In addition, probes with significant specificity for certain organelles for tracking cellular processes or metal ions for monitoring neural transmission are somewhat rare. Moreover, it is also very significant to deliver the probes to specific disease sites for early cancer diagnosis. In order to increase the water solubility of probes, polyethylene glycol (PEG) was introduced to a fluorene-based 2PA probe LT1 for lysosomal 2PFM cell imaging. The 2PFM bioimaging application of the novel two-photon absorbing fluorene derivative LT1, selective for the lysosomes of HCT 116 cancer cells is described in Chapter II. Linear and nonlinear photophysical and photochemical properties of the probe were investigated to evaluate the potential of the probe for 2PFM lysosomal imaging. After the investigation of the cytotoxicity of this new probe, colocalization studies of the probe with commercial lysosomal probe Lysotracker Red in HCT 116 cells were conducted. A high colocalization coefficient (0.96) was achieved and demonstrated the specific localization of the probe in lysosomes. A figure of merit, FM, was introduced by which all fluorescent probes for 2PFM can be compared. LT1 was demonstrated to have a number of properties that far exceed those of commercial lysotracker probes, including much higher 2PA cross sections, good fluorescence quantum yield, and, importantly, high photostability, all resulting in a superior figure of merit. Consequently, 2PFM was used to demonstrate lysosomal tracking with LT1. In addition to lysosomes, it is also very significant to investigate the physiological roles of free metal ions in biological processes, especially Zn2+, because Zn2+ normally serves either as the catalytic elements in enzymatic activity centers or as structural elements in enzymes and transcription factors. However, biocompatible and effective Zn2+ probes for 2PFM bioimaging are infrequent. In Chapter III, 2PFM bioimaging with a hydrophilic 2PA Zn2+ sensing fluorescent probe, bis(1,2,3-triazolyl)fluorene derivative, is described. 2PFM bioimaging of the probe in living HeLa cancer cells was demonstrated. The results revealed a significant fluorescence increase upon introduction of Zn2+ into the cancer cells, and a reversible Zn2+ binding to the probe was also demonstrated, providing a robust probe for two-photon fluorescence zinc ion sensing. Early cancer diagnosis is another critical application for 2PFM, but there are still huge challenges for this new technique in clinical areas. Most 2PA probes with large two-photon absorbing cross sections and fluorescence quantum efficiency are synthetically more accessible in hydrophobic forms. In order to increase the efficiency of the probes and minimize the effect of the probe on the human body, delivery of the probe specifically to cancer sites is desired. The synthesis and characterization of narrow dispersity organically modified silica nanoparticles (SiNPs), diameter ~30 nm, entrapping a hydrophobic two-photon absorbing fluorenyl dye, are reported in Chapter IV. The surface of the SiNPs was functionalized with folic acid to specifically deliver the probe to folate receptor (FR) over-expressing HeLa cells, making these folate 2PA dye-doped SiNPs potential candidates as probes for two-photon fluorescence microscopy (2PFM) bioimaging. In vitro studies using FR over-expressing HeLa cells demonstrated specific cellular uptake of the functionalized nanoparticles. However, when the concentration of the dye in SiNPs increased for higher signal output, the fluorescence quantum efficiency of a probe normally decreases because of self-quenching. In Chapter V, a near-infrared (NIR) emitting probe is reported to overcome this limitation through both aggregate-enhanced fluorescence emission and aggregate enhanced two-photon absorption. The dye was encapsulated in SiNPs and the surface of the nanoparticles was functionalized with PEG followed by a folic acid derivative to specifically target folate receptors. NIR emission is important for deep tissue imaging. In vitro studies using HeLa cells that upregulate folate receptors indicated specific cellular uptake of the folic acid functionalized SiNP nanoprobe. Meanwhile, the probe was also investigated for live animal imaging by employing mice bearing HeLa tumors for in vivo studies. Ex vivo 2PFM tumor imaging was then conducted to achieve high quality 3D thick tissue tumor images.
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Date Issued: 2011
Identifier: CFE0003640, ucf:48891
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003640

Atomic Force Microscopy (5)	+ -
Microscopy (3)	+ -
Raman Spectroscopy (3)	+ -
fluorescence microscopy (3)	+ -
microscopy (3)	+ -

two-photon absorption (3)	+ -
Coherence (2)	+ -
Optical Sensing (2)	+ -
Statistical optics (2)	+ -
atomic force microscopy (2)	+ -
photostability (2)	+ -
transmission electron microscopy (TEM) (2)	+ -
two-photon fluorescence microscopy (2)	+ -
304 stainless steel (1)	+ -
AFM (1)	+ -
AFM Nanoindentation (1)	+ -
Adhesion (1)	+ -
Asteroid Surfaces (1)	+ -
Azulene (1)	+ -
Bioimaging (1)	+ -
Bioimaging probe (1)	+ -
Block copolymer (1)	+ -
Carbon nanotube (1)	+ -
Cell Mechanics (1)	+ -
Cohesion (1)	+ -
Computational Imaging and Sensing (1)	+ -
Confocal Microscopy (1)	+ -
Confocal Raman Microscopy (1)	+ -
Database (1)	+ -
Diffusion (1)	+ -

ETD Collection (35)	+ -
Honors Collection (1)	+ -

University of Central Florida (36)	+ -
Dogariu, Aristide (5)	+ -
Tetard, Laurene (5)	+ -
Belfield, Kevin (4)	+ -
Coffey, Kevin (4)	+ -

Peale, Robert (3)	+ -
Britt, Daniel (2)	+ -
Campiglia, Andres (2)	+ -
Challapalli, Suryanarayana (2)	+ -
Fang, Jiyu (2)	+ -
Kaden, William (2)	+ -
Kang, Hyeran (2)	+ -
Riza, Nabeel (2)	+ -
Rolland, Jannick (2)	+ -
Santra, Swadeshmukul (2)	+ -
Sigman, Michael (2)	+ -
Sohn, Yongho (2)	+ -
Thomas, Jayan (2)	+ -
Vaidyanathan, Raj (2)	+ -
Zhai, Lei (2)	+ -
Abouelkhair, Hussain (1)	+ -
Abouraddy, Ayman (1)	+ -
Akhlaghi Bouzan, Milad (1)	+ -
Al-Joubori, Ahmed (1)	+ -
Ali, Haider (1)	+ -
Apostol, Adela (1)	+ -
Atia, George (1)	+ -
Bai, Yuanli (1)	+ -
Baleine, Erwan (1)	+ -
Belfield, Kevin D. (1)	+ -

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