Dissertations / Theses on the topic 'Fiber optic chemical'
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1
Ferguson, Jane A. "Fiber optic chemical sensors : the evolution of high-density fiber-optic DNA microarrays /." Thesis, Connect to Dissertations & Theses @ Tufts University, 2001.
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Thesis (Ph.D.)--Tufts University, 2001.Adviser: David R. Walt. Submitted to the Dept. of Chemistry, Includes bibliographical references (leaves 197-208). Access restricted to members of the Tufts University community. Also available via the World Wide Web;
2
Hamner, Vince. "A fiber optic polarimeter for use in chemical analysis /." This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-06082009-170841/.
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3
Hamner, Vincent N. "A fiber optic polarimeter for use in chemical analysis." Thesis, Virginia Tech, 1990. http://hdl.handle.net/10919/42892.
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Polarimetry, as applied to chemical analysis, deals with the
determination of the extent and direction that an optically
active chemical species will rotate incident linearly
polarized light. Although well developed for physical
sensing, the technique of fiber optic polarimetry for
chemical sensing remains in its infancy. This thesis is
concerned with the design and development of an optical fiber
polarimeter which measures the optical rotation of linearly
polarized light that occurs in a sensing region between two
multi-mode optical fibers. Over short distances, the
polarization preserving capabilities of large-core multi-mode
optical fibers were investigated. Polarimetric analyses were
performed using sucrose and quinine hydrochloride. The
instrument has a resolution of O.O8·, and is an excellent
platform for an LC or FIA detector. Its more intriguing
future lies in evanescent field sensor applications and
studies of chiroptical surface interactions.
Master of Science
4
Petersen, James Vincent. "Investigation into the fundamental principles of fiber optic evanescent sensors." Diss., This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-02052007-081233/.
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5
Wang, Yunjing. "Fiber-Optic Sensors for Fully-Distributed Physical, Chemical and Biological Measurement." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/19222.
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Distributed sensing is highly desirable in a wide range of civil, industrial and military applications. The current technologies for distributed sensing are mainly based on the detection of optical signals resulted from different elastic or non-elastic light-matter interactions including Rayleigh, Raman and Brillouin scattering. However, they can measure temperature or strain only to date. Therefore, there is a need for technologies that can further expand measurement parameters even to chemical and biological stimuli to fulfill different application needs. This dissertation presents a fully-distributed fiber-optic sensing technique based on a traveling long-period grating (T-LPG) in a single-mode fiber. The T-LPG is generated by pulsed acoustic waves that propagate along the fiber. When there are changes in the fiber surrounding medium or in the fiber surface coating, induced by various physical, chemical or biological stimuli, the optical transmission spectrum of the T-LPG may shift. Therefore, by measuring the T-LPG resonance wavelength at different locations along the fiber, distributed measurement can be realized for a number of parameters beyond temperature and strain.
Based on this platform, fully-distributed temperature measurement in a 2.5m fiber was demonstrated. Then by coating the fiber with functional coatings, fully-distributed biological and chemical sensing was also demonstrated. In the biological sensing experiment, immunoglobulin G (IgG) was immobilized onto the fiber surface, and the experimental results show that only specific antigen-antibody binding can introduce a measurable shift in the transmission optical spectrum of the T-LPG when it passes through the pretreated fiber segment. In the hydrogen sensing experiment, the fiber was coated with a platinum (Pt) catalyst layer, which is heated by the thermal energy released from Pt-assisted combustion of H2 and O2, and the resulted temperature change gives rise to a measurable T-LPG wavelength shift when the T-LPG passes through. Hydrogen concentration from 1% to 3.8% was detected in the experiment. This technique may also permit measurement of other quantities by changing the functional coating on the fiber; therefore it is expected to be capable of other fully-distributed sensing applications.
Ph. D.
6
Bansal, Lalitkumar El-Sherif Mahmoud Abd-El-Rahman. "Development of a fiber optic chemical sensor for detection of toxic vapors /." Philadelphia, Pa. : Drexel University, 2004. http://dspace.library.drexel.edu/handle/1860/372.
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7
Tang, Xiling. "Development of Inorganic Thin Film Coated Long-Period Grating Fiber Optic Chemical Sensors." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1321372750.
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8
Lin, Zhihao. "Second order fiber optic chemical sensors based upon membrane separation and spectroscopic detection /." Thesis, Connect to this title online; UW restricted, 1994. http://hdl.handle.net/1773/11588.
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9
Remmel, Kurtis. "Development of Copper Doped Zirconia Incorporated Fiber Optic Sensor for High Temperature Carbon Monoxide Detection." University of Cincinnati / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1291059330.
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10
Jiang, Hongmin. "Development of Ceramic Thin Films for High Temperature Fiber Optic Sensors." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1367937316.
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11
Ton, Xuan-Anh. "Fiber optic chemical sensors based on molecularly imprinted polymers for the detection of mycotoxins." Phd thesis, Université de Technologie de Compiègne, 2013. http://tel.archives-ouvertes.fr/tel-01002117.
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This thesis describes the development of highly selective fiber optic sensors using molecularly imprinted polymers (MIPs) as recognition elements associated with fluorescence for detection. Additionally, we extended the study to the development of other MIP-based optical sensors and sensing methods. MIPs are synthetic biomimetic receptors possessing specific cavities designed for a target molecule. Produced by a templating process at the molecular level, MIPs are capable of recognizingand binding target molecules with selectivities and affinities comparable to those of natural receptors. Compared to biological recognition elements, MIPs are more stable, cheaper and easier to integrate into standard industrial fabrication processes. Hence, MIPs have become interesting alternatives to biomolecules as recognition elements for biosensing. In the first part of this thesis (Chapter 2), MIPs were synthesized by in-situ laser-induced photopolymerization in only a few seconds, as a micrometer-sized tip at the extremity of a telecommunication optical fiber. Photonic and physico-chemical parameters were optimized to tailor the properties of the polymer micro-objects. Gold nanoparticles were incorporated into the MIP microtip for signal enhancement. To prove the efficiency of the sensor, initial studies were performed with a MIP templated with N-carbobenzyloxy-L-phenylalanine (Z-L-Phe) and the fluorescent amino acid derivative dansyl-L-phenylalanine as analyte. The fluorescence was collected either externally at the tip level by an optical fiber connected to a spectrofluorimeter or by collection of the fluorescent signal re-emitted into the fiber through the second arm of a Y-shaped bifurcated fiber. The fluorescent analyte could be detected in the low nM concentrations. In order to monitor nonfluorescent analytes, a naphthalimide-based fluorescent monomer was incorporated into the MIP during its synthesis; fluorescence enhancement was observed when analyte binding occurs. Using this system, the sensor containing a MIP specific for the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D), could detect and quantify this analyte at concentrations as low as 2.5 nM. The signaling MIP-based sensor was also applied to analytes of interest for food safety and biomedical applications, such as the mycotoxin citrinin and the sphingolipid, D-erythro-sphingosine-1-phosphate. In the second part of the thesis (Chapter 3), a different type of fiber optic sensor: cheap, fast and made for "single-use", was developed by using 4-cm long disposable polystyrene evanescent wave optical fiber waveguides. The coating of the MIP was either performed ex-situ, by dip-coating the fiber in a suspension of MIP particles synthesized beforehand, or in-situ by evanescent-wave photopolymerization directly on the fiber. The resulting fiber optic sensor could detect 2,4-D in the low nM range and demonstrated specific and selective recognition of the herbicide over its structural analogues and other non-related carboxyl-containing analytes. Additionally, we demonstrated the versatility of the system by applying the evanescent wave fiber optic sensor to detect citrinin, a mycotoxin, by simply coating the waveguide with a MIP specific for citrinin. This type of technology could possibly be extended to detect other carboxyl-containing analytes, as long as a specific MIP for the concerned analyte is available. In parallel, the technique of evanescent-wave photopolymerization was used for the synthesis of signaling MIP microdots on continuous and nanostructured gold films. This study lays the foundations for future development of plasmonic MIP nanosensors and microchips. In the last part of the thesis (Chapter 4), an innovative sensing method, based on the use of MIPs and analysis by fluorescence polarization, was developed in order to allow the fast and directquantification of analytes in food and environmental samples.
12
Wooddell, Michael Gary. "Increased Functionality Porous Optical Fiber Structures." Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/35324.
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A novel fiber optic structure, termed stochastic ordered hole fibers, has been developed
that contains an ordered array of six hollow tubes surrounding a hollow core, combined
with a nanoporous glass creating a unique fully three dimensional pore/fiber
configuration. The objective of this study is to increase the functionality of these
stochastic ordered hole fibers, as well as porous clad fibers, by integrating electronic
device components such as conductors, and semiconductors, and optically active
materials on and in the optical fiber pore structures. Conductive copper pathways were
created on/in the solid core fibers using an electroless deposition technique. A chemical
vapor deposition system was built in order to attempt the deposition of silicon in on the
porous clad fibers. Additionally, conductive poly(3,4-ethylenedioxythiophene)-
poly(styrene sulfonate) (PEDOT:PSS) and photoactive polymer blend poly(3-
hexylthiophene) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-)6,6)C61 (P3HT: PCBM)
were deposited on the fibers using dip coating techniques. Quantum dots of Cadmium
Selenide (CdSe) with particle sizes of ranging from 2- 10 nm were deposited in the
stochastic ordered hole fibers. SEM and EDS analysis confirm that copper, polymer
materials, and quantum dots were deposited in the pore structure and on the surface of the
fibers. Finally, resistance measurements indicate that the electrolessly deposited copper
coatings have sufficient conductivity to be used as metallic contacts or resistive heating
elements.Master of Science
13
Attridge, John Worthington. "Fibre optic chemical sensing." Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/37931.
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14
Nagarajan, Anjana. "Chemical sensing applications of fiber optics." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-07102009-040555/.
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15
McCulloch, Scott. "Fibre optic microsensors for intracellular chemical measurements." Thesis, University of Strathclyde, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248617.
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16
Davies, Megan L. "Modified hydrogel matrices in fibre optic sensors." Thesis, Aston University, 1989. http://publications.aston.ac.uk/9710/.
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Common problems encountered in clinical sensing are those of non-biocompatibility, and slow response time of the device. The latter, also applying to chemical sensors, is possibly due to a lack of understanding of polymer support or membrane properties and hence failure to optimise membranes chosen for specific sensor applications. Hydrogels can be described as polymers which swell in water. In addition to this, the presence of water in the polymer matrix offers some control of biocompatibility. They thus provide a medium through which rapid transport of a sensed species to an incorporated reagent could occur. This work considers the feasibility of such a system, leading to the design and construction of an optical sensor test bed. The development of suitable membrane systems and of suitable coating techniques in order to apply them to the fibre optics is described. Initial results obtained from hydrogel coatings implied that the refractive index change in the polymer matrix, due to a change in water content with pH is the major factor contributing to the sensor response. However the presence of the colourimetric reagent was also altering the output signal obtained. An analysis of factors contributing to the overall response, such as colour change and membrane composition were made on both the test bed, via optical response, and on whole membranes via measurement of water content change. The investigation of coatings with low equilibrium water contents, of less than 10% was carried out and in fact a clearer signal response from the test bed was noted. Again these membranes were suprisingly responding via refractive index change, with the reagent playing a primary role in obtaining a sensible or non-random response, although not in a colourimetric fashion. A photographic study of these coatings revealed some clues as to the physical nature of these coatings and hence partially explained this phenomenon. A study of the transport properties of the most successful membrane, on a coated wire electrode and also on the fibre optic test bed, in a series of test environments, indicated that the reagent was possibly acting as an ion exchanger and hence having a major influence on transport and therefore sensor characteristics.
17
Tou, Zhi Qiang. "Fiber optics chemical sensors based on responsive polymers." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/25627.
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Fiber optic chemical sensors (FOCS) have made tremendous progress since developments began in the 1960s with continuous reports of new configurations, materials and applications even today. Techniques like interferometry and plasmonic resonance are set to form the next generation of FOCS, representing a deviation from conventional luminescence based techniques. The thesis presents an optic fiber sensor platform for localized surface plasmon resonance (LSPR) by using a speciality photonic crystal fiber (PCF) to excite LSPR via cladding modes. The sensor offers facile fabrication and achieves high refractive index sensitivity of -731 % transmittance/RIU with limit of detection (LOD) 1.76 x 10-5 refractive index unit (RIU). Responsive polymers, exhibiting physio-chemical changes when exposed to specific stimuli are investigated for feasibility in FOCS based on LSPR and interferometry. A pH sensor is proposed by formation of a gold nanoparticles (AuNPs) embedded polyelectrolyte multilayer (PEM) consisting of Chitosan and poly(styrene sulfonate) (PSS) onto the forementioned sensor. The sensor exhibits pH responsiveness between physiological range of pH 6.5 to 8 and its behavior can be modeled by the Henderson-Hasselbach equation. The biocompatibility of the materials enables in-vivo application of the sensor. Interferometry FOCS using hydrogel as sensing material are investigated. Mach Zehnder interferometers (MZI) can be constructed from PCF. A proposed double- pass MZI shows higher Q factor and higher resolution than a single-pass MZI. By coating a thin poly(HEMA-co-DMAEM) hydrogel film, the MZI pH sensor shows a linear pH response with pH 6.75 to 8.25 (R2 = 0.986) with LOD pH 0.004. The sensor is successfully applied to the monitoring of cell culture media. A generalized approach in fabricating hydrogel based interferometric sensors is demonstrated through use of poly(vinyl alcohol) (PVA)-co- poly(acrylic acid) (PAA) hydrogel. The PVA/PAA offers tremendous ease in obtaining thin films on optical fiber via simple dip coating without need for additional cross linkers and polymerisation initiators. The carboxyl groups on PAA offer efficient coupling to a variety of aminated receptors using carbodiimide coupling to realise a myriad of sensing possibilities. The biocompatibility of both PVA and PAA also makes the proposed sensing film suitable for in-vivo applications. The sensor is demonstrated for sensing of small chemical species like Ni2+. It was found that sensitivity of the PVA/PAA is affected by the PVA/PAA ratio and duration of heat induced esterification which controls the degree of cross linking and the maximum amount of receptors that can be immobilised. The optimal PVA/PAA hydrogel is fabrication from a 12:6 wt % ratio and cross linked at 130 oC for 30 min. By modifying the PVA/PAA hydrogel with hydroxyquinoline, the sensor is able to detect Ni2+ with good sensitivity 0.214 nm/μM and LOD 1nM adequate for continuous monitoring of drinking water.
18
Flannery, D. "Fibre optic chemical sensing using Langmuir-Blodgett overlay waveguides." Thesis, Cranfield University, 1998. http://dspace.lib.cranfield.ac.uk/handle/1826/10719.
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Fibre
optic chemical sensing has been demonstrated using side-polished single mode
optical bre, evanescently coupled to chemically sensitive Langmuir-Blodgett overlay
waveguides. The sensors exhibit a channel dropping response centred on a wavelength
dependent upon the thickness and refractive index of the overlay waveguide. It has been
shown that
chemically sensitive organic dyes prove to be suitable materials for forming
the
overlay waveguide whereas the Langmuir-Blodgett deposition technique provides the
required overlay thickness control.
A brief
optic pH sensor has been demonstrated by
depositing a merocyanine dye onto a
side-polished optical fibre which exhibits a change in transmission of 9.7 ± 0.8 dB pH" at
a
working wavelength of 750 n and 4.2 ± 0.5 dB pH`1 at 780 nm, with a shift in the
channel
dropping centre wavelength of 18.8 ± 0.8 n pH`1. The response time of the
sensor to a
step change in pH has been measured to be ~ 20 s.
The
advantage of being able to chemically engineer the organic materials used to form
the
overlay waveguides has been demonstrated by manufacturing a second pH sensor
designed to operate at longer wavelengths using a second, modified merocyanine dye.
The overall
wavelength response of this second sensor to pH has been shown to be non-
linear but a
sensitivity of 23.3 ± 0.3 n pH`l is observed over a linear region. Finally, i
order to
investigate the non-linear response, a computer model based on the Kramers-
Kronig relations has been devised and shows good agreement with experimental values.
l
19
Flannery, Damian. "Fibre optic chemical sensing using Langmuir-Blodgett overlay waveguides." Thesis, Cranfield University, 1998. http://dspace.lib.cranfield.ac.uk/handle/1826/10719.
Full textAbstract:
Fibre optic chemical sensing has been demonstrated using side-polished single mode optical bre, evanescently coupled to chemically sensitive Langmuir-Blodgett overlay waveguides. The sensors exhibit a channel dropping response centred on a wavelength dependent upon the thickness and refractive index of the overlay waveguide. It has been shown that chemically sensitive organic dyes prove to be suitable materials for forming the overlay waveguide whereas the Langmuir-Blodgett deposition technique provides the required overlay thickness control. A brief optic pH sensor has been demonstrated by depositing a merocyanine dye onto a side-polished optical fibre which exhibits a change in transmission of 9.7 ± 0.8 dB pH" at a working wavelength of 750 n and 4.2 ± 0.5 dB pH`1 at 780 nm, with a shift in the channel dropping centre wavelength of 18.8 ± 0.8 n pH`1. The response time of the sensor to a step change in pH has been measured to be ~ 20 s. The advantage of being able to chemically engineer the organic materials used to form the overlay waveguides has been demonstrated by manufacturing a second pH sensor designed to operate at longer wavelengths using a second, modified merocyanine dye. The overall wavelength response of this second sensor to pH has been shown to be non- linear but a sensitivity of 23.3 ± 0.3 n pH`l is observed over a linear region. Finally, i order to investigate the non-linear response, a computer model based on the Kramers- Kronig relations has been devised and shows good agreement with experimental values.
20
McDowell, Gary R. "The development of fibre-optic chemical sensors for subsea applications." Thesis, Glasgow Caledonian University, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.726771.
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Hale, Zoe Miranda. "Fibre optic sensors using adiabatically tapered single mode fibres." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320155.
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Sloan, William D. "The development of a fibre-optic chemical sensor for calcium ions." Thesis, Glasgow Caledonian University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251184.
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Fneer, Mohamed K. "Development of fibre optic based ammonia sensor for water quality management." Thesis, City University London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363350.
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Campbell, Alexander. "Chemical sensors based on fibre optics and fluorescence measurements." Thesis, University of Strathclyde, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.400313.
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Mouaziz, Zoheir. "Development of fibre-optic based techniques for measurement of aqueous chemical species." Thesis, City University London, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385976.
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26
Tonnelé, Claire. "Modélisation des propriétés photophysiques de capteurs chimiques pour des applications de détection de cations par fibre optique." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2013. http://tel.archives-ouvertes.fr/tel-00918201.
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La présence croissante de diverses substances dans notre environnement, conséquencedes activités anthropiques de ces dernières décennies, a entraîné un besoingrandissant et urgent de nouveaux matériaux et dispositifs dans la quête de senseurschimiques efficaces et fiables. D'énormes progrès technologiques ont permis de mettreà disposition toute une gamme d'outils techniques pour leur développement, enprenant en compte les exigences à respecter en terme de sélectivité ou de rapidité deréponse, entre autres. Dans ce contexte, les méthodes de chimie quantique permettentune compréhension fondamentale des processus en jeu dans la détection des espèceschimiques, et par extension, l'élaboration de manière rationnelle de nouveauxmatériaux sensibles. Certaines molécules organiques pouvant être largementfonctionnalisées, elles constituent un point de départ idéal en raison des importantesmodulations possibles de leurs propriétés par des modifications structuralesappropriées.Cette étude vise à développer de manière rationnelle des chromoionophores pour lacomplexation de cations par une approche combinant méthodes de chimiecomputationnelles et caractérisation par spectroscopie optique. Deux pointsprincipaux ont été traités à l'aide de la Théorie de la Fonctionnelle de la Densité(DFT) et son extension dépendante du temps (TD-DFT): d'une part les relationsstructure moléculaire-propriétés optiques de chromophores, d'autre part le phénomènede complexation. En particulier, la détection de l'ion Zn2+, démontrée de manièrethéorique et expérimentale, est finalement réalisée après intégration du senseurmoléculaire dans un dispositif à fibre optique.
27
Choi, Ming Fat. "Investigations into fibre optic sensing systems for gaseous oxygen and carbon dioxide." Thesis, University of the West of England, Bristol, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240829.
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28
Xu, Yu. "Light intensity attenuation-based fibre-optic chemical sensors : theoretical analyses and design studies." Thesis, University of Leicester, 2000. http://hdl.handle.net/2381/30184.
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In the thesis light intensity attenuation-based fibre-optic chemical sensors are investigated. The investigation proceeds along two lines: theoretical analyses and design studies. Both intrinsic and extrinsic types of sensors are discussed from both aspects. The theoretical analyses are concentrated on the construction of theoretical models and numerical calculations, which were previously not well developed but have been attracting a great deal of attention of researchers for some time. Under this topic, fibre-optic evanescent wave absorption sensors and fibre-optic surface plasmon resonance (SPR) sensors are studied as examples of the intrinsic type of sensors, and two-wavelength Beer-Lambert law based fibre-optic sensors as the extrinsic example. The design studies are concentrated on the design of novel types of sensors which have potentially valuable applications. As the intrinsic type of sensors, novel types of fibre-optic surface plasmon resonance (SPR) chemical sensors are proposed and studied in both point and distributed systems. A fibre-optic sensor for concentration determination of the infusible anaesthetic Propofol is studied in detail as an example of an extrinsic type of sensor.
29
Badini, G. E. "Investigation of porous glass-like substrates for use in fibre-optic chemical sensors." Thesis, City University London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.281842.
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Bronk, Karen Srour. "Imaging based sensor arrays /." Thesis, Connect to Dissertations & Theses @ Tufts University, 1996.
Find full textAbstract:
Thesis (Ph.D.)--Tufts University, 1996.Adviser: David R. Walt. Submitted to the Dept. of Chemistry. Includes bibliographical references. Access restricted to members of the Tufts University community. Also available via the World Wide Web;
31
Wei, Tao. "Fabrication of long-period fiber gratings by CO₂ laser irradiation for high temperature applications." Diss., Rolla, Mo. : Missouri University of Science and Technology, 2008. http://scholarsmine.mst.edu/thesis/pdf/Wei_09007dcc804a8ac2.pdf.
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Thesis (M.S.)--Missouri University of Science and Technology, 2008.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed March 31, 2008) Includes bibliographical references (p. 33-36).
32
Austin, Edward Alfred Denzil. "Studies of measurement techniques for indirect chemical sensing based on fluorescence spectroscopy and applications for fibre-optic sensors." Thesis, University of Southampton, 2002. https://eprints.soton.ac.uk/50196/.
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This thesis describes experimental and theoretical studies of interrogation systems for determining fluorescent decays of order a few microseconds. The studies have enabled optimised design of interrogators for sensing oxygen using a fluorescent polymerencapsulated ruthenium complex. Two basic interrogation methods were explored, using blue LED excitation. The Rapid Lifetime Detection (RLD) scheme, a fluorescence interrogation method based on direct interrogation of the decay curve following pulsed excitation was generalised, and a novel method for optimising measurement precision derived. The effect of background light on the optimum was quantified. Dissolved (aqueous) oxygen concentration was measured to a precision of 1 part per billion using a 1 second response time (the peak fluorescence power was only 12.5±0.5pW). A second interrogation method, where the phase delay between an intensity modulated excitation source and the resultant fluorescence is processed to make measurements, was for the first time, fully analysed for measurement of exponential decays. When measuring fluorescence lifetimes in the range 2.9-3.3μs, a precision of 2.3 x 10-10 s Hz-0.5 was achieved. (The peak fluorescence power was 500±25pW). A novel combination of ruby optical temperature sensor insert and oxygen sensing layer was demonstrated as a simultaneous temperature and oxygen sensor. A new fluorescence calibration standard consisting of thermally stabilised titanium-dopedsapphire sample was constructed to calibrate and test the indicators. This work was sponsored by a BRITE EuRam European project, which helped determine the priorities of the research.
33
Stolyarov, Alexander. "Integrated Optofluidic Multimaterial Fibers." Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10080.
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The creation of integrated microphotonic devices requires a challenging assembly of optically and electrically disparate materials into complex geometries with nanometer-scale precision. These challenges are typically addressed by mature wafer-based fabrication methods, which while versatile, are limited to low-aspect-ratio structures and by the inherent complexity of sequential processing steps. Multimaterial preform-to-fiber drawing methods on the other hand present unique opportunities for realizing optical and optoelectronic devices of extended length. Importantly, these methods allow for monolithic integration of all the constituent device components into complex architectures. My research has focused on addressing the challenges and opportunities associated with microfluidic multimaterial fiber structures and devices. Specifically: (1) A photonic bandgap (PBG) fiber is demonstrated for single mode transmission at 1.55 µm with 4 dB/m losses. This fiber transmits laser pulses with peak powers of 13.5 MW. (Chapter 2) (2) A microfluidic fiber laser, characterized by purely radial emission is demonstrated. The laser cavity is formed by an axially invariant, 17-period annular PBG structure with a unit cell thickness of 160nm. This laser is distinct from traditional lasers with cylindrically symmetric emission, which rely almost exclusively on whispering gallery modes, characterized by tangential wavevectors. (Chapter 4)(3) An array of independently-controlled liquid-crystal microchannels flanked by viscous conductors is integrated in the fiber cladding and encircles the PBG laser cavity in (2). The interplay between the radially-emitting laser and these liquid-crystal modulators enables controlled directional emission around a full azimuthal angular range. (Chapter 4) (4) The electric potential profile along the length of the electrodes in (3) is characterized and found to depend on frequency. This frequency dependence presents a new means to tune the transversely-directed transmission at a given location along the fiber axis. (Chapter 5) (5) A chemical sensing system is created within a fiber. By integrating a chemiluminescent peroxide-sensing material into the hollow core of a PBG fiber, a limit-of-detection of 300 ppb for peroxide vapors is achieved. (Chapter 3)Engineering and Applied Sciences
34
Mahendran, Ramani Salmalee. "Characterisation of cross-linking and moisture ingress detection in an epoxy/amine resin using fibre-optic sensors." Thesis, University of Birmingham, 2010. http://etheses.bham.ac.uk//id/eprint/1083/.
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Themosetting resins are being used increasingly as matrix materials in advanced fibre-reinforced composites. It is well known that the processing conditions used to manufacture the composite can have a major influence on its mechanical integrity in service. In addition, the processing parameters can also affect the ingress of moisture in thermosetting resin and composites. The feasibility of using optical fibre-based sensor systems for monitoring cross-linking reaction has been demonstrated previously. However, little work has been reported on the deployment of a single sensor to study the cross-linking kinetics and the diffusion of moisture. In the current work, four low-cost sensor designs were evaluated for in situ monitoring of the cross-linking reactions of an epoxy/amine resin system. One of these sensor designs was selected and used to investigate in detail the cross-linking kinetics. Excellent correlation was observed between the cross-linking data obtained form the sensors and conventional transmission spectroscopy. Semi-empirical models were used successfully to describe the cross-linking behaviour of the epoxy/amine resin system that was used in this study. Subsequent to monitoring the cross-linking reactions, the fibre-optic sensors were used to study the diffusion of moisture in the cross-linked resin system. Conventional gravimetric measurements were also carried out to enable the correlation with the data obtained from the fibre optic sensors. It was demonstrated that the fibre-optic sensors were capable of giving information on the “localised” diffusion of moisture in the neat-resin plaques. Three previously published models were investigated and localised diffusion of moisture in the neat-resin showed non-Fickian behaviour.
35
Gamez, Jimmy Ray. "The Effects of Diameter Fluctuations and Coiling on the Sensitivity of Sapphire Single Crystal Optical Fiber Evanescent Wave Fluorescence Sensors." Scholar Commons, 2009. https://scholarcommons.usf.edu/etd/1980.
Full textAbstract:
The purpose of this research was to determine the effect of diameter fluctuations on the sensitivity of sapphire multimode optical fibers used as evanescent wave fluorescence sensors. It was predicted that fluctuations in the diameter of the fiber would act as a series of bi-tapers converting lower order modes to higher order modes increasing the evanescent wave penetration depth thereby increasing the excitation of a cladding of fluorescent fluid. Induced fluorescence from the fluid cladding would then couple back into the fiber more efficiently increasing the sensitivity of the sensor.
The effect of coiling the fiber on the sensitivity of the sensor was also explored. Coiling the fiber converts lower order modes into higher order modes and increases the sensing length while maintaining a small probe size. However, coiling experiments produced unexpected results and in the course of studying these results a layer of material was discovered coating the surface of the sapphire fibers.
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Fraser, Michael John. "Optical Fiber Microstructures for Self-Contained Whispering Gallery Mode Excitation." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/73659.
Full textAbstract:
Optical resonators, which confine light by resonant recirculation, serve as the basis for a wide variety of optical components. Though they appear in many geometric forms, the most effective of optical resonators show axial symmetry in at least one dimension. A popular variation that finds broad application is the dielectric sphere. Acclaimed for their high quality (Q) factor and small modal volume, spheres owe credit of these attractive features to their support of whispering gallery mode (WGM) resonances. The sensitivity of a resonance's frequency and Q to strain, temperature, and other parameters of the surrounding medium can be the basis for ultracompact modulators and sensors.
Physically, WGMs are special optical modes which can be understood as light rays that orbit the equator of the sphere guided by total internal reflection. Like a smooth stone can be skipped along the surface of a pond, light can be confined to the inside of a sphere by successive reflections. To best excite WGMs, the source light should initially trace a line tangent to the sphere's circumference. But incorporating a tiny sphere with such nanometric tolerances into a practical sensor structure has its challenges and the prospects for microsphere applications have suffered because of the plight of this problem.
The work in this dissertation details the fabrication and function of three new "press fit" spherical resonators. These etched fiber micro-devices were developed to meet the demand for a robust, self-integrated means of coupling light between an optical fiber and WGMs in a microsphere resonator. The etching processes have been tuned to enable secure storage of a microsphere while also providing efficient excitation and interrogation of WGMs. Furthermore, the methods have been designed to be staightforward, quick, and repeatable. Using standard etchants on common polarization-maintaining fiber with readily purchased microspheres, the press fit resonators demonstrated here can be batch-fabricated and assembled. The press fit spherical resonator offers an alignment-free and conveniently pigtailed WGM coupler that has great potential for bio-science sensing applications and studies of resonant bispheres.Ph. D.
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Grossman, Michael. "Evanescent Field Absorption Sensing Using Sapphire Fibers." Scholar Commons, 2007. http://scholarcommons.usf.edu/etd/3814.
Full textAbstract:
This thesis explores the application of coiled sapphire multimode optical fibers for evanescent wave chemical sensing in both the visible spectrum and the near infrared. As has been suggested in the literature pertaining to silica fibers, bending converts low-order modes to high order ones, which leads to more evanescent absorption and thus a more sensitive chemical detector. By coiling the fiber many times, it was expected that even greater sensitivity would be attained.
Experiments were performed to investigate the sensor response to different solutions and to characterize this response. In the first of three experiments, the large absorption peak of water at 3μm was examined in order to compare the sensitivity of a straight fiber versus a coiled one. In the second experiment, the effect of increasing the number of coils was investigated, as was the response of the sensor to varying concentrations of water in heavy water. In the third experiment, methylene blue dye was used to investigate the extent of adsorption of dye molecules on the sapphire fiber and its persistence
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Shrivastav, Anand Mohan. "Studies on localized and propagating surface plasmon resonance based fiber optic chemical/biosensors utilizing molecular imprimting technique." Thesis, 2018. http://localhost:8080/iit/handle/2074/7715.
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Singh, Sarika. "Studies on surface plasmon resonance based fiber optic chemical and biochemical sensors." Thesis, 2013. http://localhost:8080/iit/handle/2074/6554.
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Usha, Sruthi Prasood. "Surface plasmon and lossy mode resonance based fiber optic chemical and biosensors utilizing zinc oxide." Thesis, 2018. http://localhost:8080/iit/handle/2074/7664.
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洪介堯. "Fiber Optic Sensor for Studying the Physical Properties and Chemical Reaction of Epoxy." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/97355434477522035066.
Full textAbstract:
碩士逢甲大學
紡織工程學系
88
A fiber optic refractometric sensing system for analyzing the physical properties and the cure reaction of GPE/DDM epoxy system has been used in this study. The epoxy system consist of glycidyl phenyl ether（GPE） and curing agent diaminodiphenyl methane（DDM）. The results indicate that there is a discontinous point at 70℃ in the study of pure GPE on the linear relation between refractive index and temperature, and the temperature coefficient shows two different values. This is due to the different expansion coefficient in the two temperature regions. We also find the result that the density of GPE linearly increases with refractive index following the equations: ρGD = 3.5629n - 3.5985 and ρLL= 1.7454n - 1.5908, according to Gladstone-Dale and Lorentz-lorenz, respectively. Refractive index of GPE/DDM system increases with increasing reaction time at 110℃, and the increase of refractive index（Δn） of this system is 0.06. The refractive index is affected by density of system, and the density increases with reaction time, so the refractive index gains with reaction time. GPE/DDM system at lower cure temperature（60 and 70℃）, the curves are linear, however, at higher temperatures（80、90、100 and 110℃）, the refractive index increases linearly with the extent of cure only in the initial stages of cure. Because the shrinkage in volume of the epoxy is restricted by the local viscosity at the gel point, and the linear relationship doesn't hold beyond that. Two curves, including extent of cure and increment of refractive index versus reaction time is similar. This trend of reaction profile is match to those from DSC and FTIR. This suggests that using the fiber optic refractometric sensing system to in-situ real time monitor the curing of epoxy GPE/DDM.
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song-Lyu, Bing, and 呂秉菘. "Numerical simulation of chemical kinetics in the fiber-optic particle plasmon resonance sensor." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/05377752162339483665.
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Akbari, Khorami Hamed. "Hydrogen peroxide sensing with prussian blue-based fiber-optic sensors." Thesis, 2016. http://hdl.handle.net/1828/7585.
Full textAbstract:
Hydrogen peroxide (H2O2) is extensively used in a broad range of industrial and medical applications, such as aseptic processing of food and pharmaceuticals, disinfection, water treatment plants, and decontamination of industrial effluents. H2O2 is believed to be responsible for chemical degradation of polymer membranes in Polymer-Electrolyte-Membrane (PEM) fuel cells. Therefore, a versatile H2O2 sensor that functions in different environments with different conditions is of practical importance in various fields. This dissertation presents the fabrication of a fiber-optic H2O2 sensing probe (optrode) and its H2O2 sensing behavior in different conditions.
An H2O2 optrode is fabricated using chemical deposition of Prussian blue (PB) onto the tip of a multimode optical fiber. Sensing tests are performed in aqueous solutions at a constant pH and different concentrations of H2O2. Sensing features of the optrode (i.e. repeatability, durability, and reproducibility) are assessed by performing multiple sensing tests with several optrodes. The results show the prepared optrode is able to detect concentrations of H2O2 in aqueous solutions at a constant pH of 4 and the optrode features a repeatable and durable response at this condition.
The functionality of optrodes at different pH values is further investigated by performing additional sensing experiments. These experiments are carried out in aqueous solutions with different concentrations of H2O2 at different pH values (i.e. pH 2-7). The sensor detects the presence of H2O2 at a range of pH values. Sensing behavior of optrodes toward detection and measurement of H2O2 concentrations is studied at the pH value corresponding to an operating PEM fuel cell (i.e. pH 2). The optrode is able to detect concentrations of H2O2 at this condition with a repeatable and durable response.
The stability of PB films, prepared through different conditions, is investigated to address the stability of optrodes at elevated temperatures. PB films are first deposited onto the glass slides through three different chemical processes, and then at different synthesis temperatures. The PB films are left in Phosphate-Buffer-Solutions (PBS) with pH 2 and at elevated temperatures for a day. Finally, PB films are characterized using Fourier transform infrared spectroscopy (FTIR) to analyze their stability following PBS processing at operating temperatures and pH value corresponding to an operating PEM fuel cell (i.e. 80 °C and pH 2). The results of these experiments illustrate the PB films prepared through the single-source precursor (SSP) technique and at synthesis temperatures above 60 °C remain stable after the PBS processing.
The proposed optrode shows reliable sensing behavior toward detection and measurement of H2O2 concentrations in aqueous solutions at different conditions. The prepared optrode has the potential for being developed and used in different industrial and medical fields, as well as an operating PEM fuel cell, to detect and measure H2O2 concentrations.Graduate
0794
0548
0485
hakbarik@uvic.ca
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Elshereef, Rand. "Application of Multi-wavelength Fluorometry to Monitoring Protein Ultrafiltration." Thesis, 2009. http://hdl.handle.net/10012/4437.
Full textAbstract:
Membrane filtration of protein solutions is influenced by a wide range of processing
and physicochemical conditions. Monitoring and optimizing membrane filtration may
have advantages for achieving, in a cost effective manner, improved bioproduct
purification and membrane performance which is relevant to pharmaceutical and
biochemical applications. The motivation of this work was to examine the feasibility of
applying two-dimensional fluorescence spectroscopy in conjunction with chemometric
techniques for monitoring and possibly optimizing the performance of membrane
processes.
Preliminary work focused on assessing the use of multivariate calibration tools in
conjunction with the sensitivity of intrinsic protein fluorescence towards changes in
environmental conditions was to predict protein concentration and aggregation
behavior. A model protein, β-lactoglobulin (β-LG), was used as a first simple case
scenario. Results showed very good agreement between the fluorescence based
predictions and measurements obtained by HPLC and gravimetric analysis regardless
of the conditions. PLS analysis of excitation-emission matrices revealed unique
spectral fingerprints that are most likely associated with the heat-induced denaturation
and aggregation. Standard Normal Variate, a signal preprocessing and filtering tool,
was shown to have a significant effect on enhancing the predictive accuracy and
robustness of the PLS model as it reduced the effect of instrumental noise. The
methodology was then extended to a two-component protein system consisting of α-
lactlalbumin (α-LA) and β-lactoglobulin (β-LG). The process of thermal induced
aggregation of β-LG and α-LA protein in mixtures, which involves the disappearance
of native-like proteins, was studied under various treatment conditions including
different temperatures, pH, total initial protein concentration and proportions of α-LA
and β-LG. A Partial Least Squares (PLS) regression algorithm was used to correlate
the concentrations of α-LA and β-LG to the fluorescence spectra obtained for mixtures.The results illustrated that multivariate models could effectively deconvolute multiwavelength
fluorescence spectra collected for the protein mixtures and thereby provide
a fairly accurate quantification of respective native-like α-LA and β-LG despite the
significant overlap between their emission profiles. It was also demonstrated that a PLS
model could be used as a black-box prediction tool for estimating protein aggregation
when combined with simple mass balances.
Ultrafiltration experiments of the whey protein isolate solutions were carried out in
dead-end filtration mode and fluorescence measurements of permeate and retentate
solutions were acquired in synchronous scanning mode using a fiber optic probe. By
implementing a dilution strategy for the retentate side, the fluorescence based PLS
model encompassed a low protein concentration range where fluorescence was not
expected to be significantly influenced by concentration-dependent interferences. It
was also demonstrated that synchronous spectra can provide good predictions and
consequently the use of the full spectrum may not be necessary for monitoring with
corresponding savings in acquisition time. Membrane performance variables that are
difficult to measure, such as individual protein transmission and membrane selectivity
could be estimated directly from fluorescence-based predictions of protein
concentrations in the retentate and permeate streams.
Multiwavelength light scattering spectra, acquired using the fiber optic probe, were
shown to be a useful indicator for protein self-association behavior, which is known to
influence the membrane filtration. High fouling potential were observed for protein
solutions that exhibited significant Rayleigh scattering. A predictive PLS model for
estimating protein aggregation from Rayleigh scattering measurements was developed
and it was tested by using molecular weight experimental values obtained from the
literature. Although this comparison was only partial due to the limited amount of
molecular weight data available, the findings verified the possibility of estimating the
aggregate size from multiwavelength Rayleigh scattering spectra acquired using a
conventional spectrofluorometer. Thus, the results implied that both intrinsic fluorescence and light scattering multiwavelength measurements could provide
complementary information about the filtration process.
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LITMAN, JESSICA. "DETECTION OF CHEMICAL COMPOUNDS USING AMPLIFIED FIBER LOOP RING-DOWN SPECTROSCOPY." Thesis, 2011. http://hdl.handle.net/1974/6754.
Full textAbstract:
Cavity ring-down spectroscopy (CRDS) is an absorption spectroscopic technique. In
CRDS the concentration of an analyte is determined by measuring the reduction in finesse of an optical cavity made from two highly reflective (R>99.9%) mirrors once a sample is introduced.
Optical loss is traditionally determined from the exponential intensity decay of a short laser pulse that was injected into the cavity. This decay is the longest for an empty, high finesse cavity and
is reduced when the sample absorbs or scatters light.
In this project, the optical cavity is made from fiber optic waveguides and the light source is a continuous wave (cw) diode laser. It is used to detect analytes such as acetylene, ammonia
and other amines through their overtone absorption in the telecom region at 1500 nm. The experiment is done by increasing the ratio of desired loss (extinction caused by the sample), to undesirable loss (from the waveguide or solvents) through amplification of the ringdown signal using an erbium doped fiber amplifier (EDFA). The EDFA is inserted into a fiber-optic loop and its gain is increased above the lasing threshold. The gain of the, now lasing, fiber loop is "clamped" to a high and constant value, thereby removing unwanted gain fluctuations, and all losses in the loop are compensated for. If one now inserts a laser light pulse at the lasing wavelength of the loop it would circulate through the loop indefinitely, whereas a light pulse at a wavelength that is being absorbed by an analyte would experience a decrease with time at a rate that depends only on the magnitude of the sample absorption. By enclosing the sample gap with a gas cell both acetylene and ammonia have been detected down to ~25 ppm and ~5.9 Torr respectively. Subsequently, a 1% solution of aminotoluene was detected in an interrogation
volume of 5.65 pL by having inserted a fiber with a hole drilled in it as the sample gap. At present, the drilled fiber has been replaced with photonic crystal fiber such that small volumes of gases may be detected with a longer effective path length.Thesis (Master, Chemistry) -- Queen's University, 2011-09-23 18:27:47.65