abstract: Environmental pollution has been one of the most challenging problems in modern society and more and more health issues are now linked to environmental pollution and especially, air pollution. Certain sensitive group like patients with asthma are highly influenced by the environmental air quality and knowledge of the daily air pollution exposure is of great importance for the management and prevention of asthma attack. Hence small form factor, real time, accurate, sensitive and easy to use portable devices for environmental monitoring are of great value. Three novel image-based methods for quantitative real time environmental monitoring were introduced and the sensing principle, sensor performances were evaluated through simulation and field tests. The first sensing principle uses surface plasmon resonance (SPR) image and home-made molecular sieve (MS) column to realize real time chemical separation and detection. SPR is sensitive and non-specific, which makes it a desirable optical method for sensitive biological and chemical sensing, the miniaturized MS column provides small area footprint and makes it possible for SPR to record images of the whole column area. The innovative and system level integration approach provide a new way for simultaneous chemical separation and detection. The second sensor uses scattered laser light, Complementary metal-oxide-semiconductor (CMOS) imager and image processing to realize real-time particulate matter (PM) sensing. Complex but low latency algorithm was developed to obtain real time information for PM including PM number, size and size distribution. The third sensor uses gradient based colorimetric sensor, absorbance light signal and image processing to realize real-time Ozone sensing and achieved high sensitivity and substantially longer lifetime compared to conventional colorimetric sensors. The platform provides potential for multi-analyte integration and large-scale consumer use as wearable device. The three projects provide novel, state-of-the-art and sensitive solutions for environmental and personal exposure monitoring. Moreover, the sensing platforms also provide tools for clinicians and epidemiologists to conduct large scale clinical studies on the adverse health effects of pollutants on various kinds of diseases. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2019

Made available in DSpace on 2016-04-18T21:39:46Z (GMT). No. of bitstreams: 3 Jackson Sen Kiat Ong1.pdf: 336586 bytes, checksum: 52b71abae661534b419bd2bda584dc4a (MD5) Jackson Sen Kiat Ong2.pdf: 1278219 bytes, checksum: ec194da3074f4dd751b05ea76d3b09f6 (MD5) Jackson Sen Kiat Ong4.pdf: 1869905 bytes, checksum: e24bb294662a8c0696b7e5fda65c5f7c (MD5) Previous issue date: 2008-01-29 / Fundação de Amparo a Pesquisa do Estado de São Paulo / Photonic Crystal Fibers (PCFs) have led to renewed attention to the fiber optics field due to the several unique properties resulting from their microstructured profile. In particular, this profile enables one to insert liquids and polymers into the fiber so that they efficiently interact with light, which can be used for chemical and biological sensing, nonlinear optics, and the development of active photonic devices. Several applications require selectively inserting the sample into the core of a hollow-core PCF, leaving cladding holes unfilled. This dissertation presents two contributions toward the development of core-filled PCFs. Loss mechanisms in liquid-core PCFs are studied and fluorescence from a quantum-dot-doped polymer-core PCF is demonstrated. Loss studies were motivated by the evaluation of the transmission of light at 633 nm in 5-7 cm long water-core PCF samples the tips of which are cleaved at left in air. It was generally found that transmission was less than 5%, while water attenuation alone would lead to ~98% transmission. Liquid evaporation was found to be an important additional loss mechanism and its rate was determined both through microscopy and optical coherence tomography (OCT) in capillary fibers and PCFs filled with deionized water, ethanol and toluene. Although the evaporation rate in ethanol was found to be higher, for all samples a few hundreds of micrometers at the fiber tips are emptied over minutes. A method to prevent evaporation consisting of sealing the fiber tips with a clear UV curable polymer (NOA 73) was successfully tested. Filling a PCF with active elements can lead to optical amplification and laser action. Researchers at NTT recently observed fluorescence at 609nm from CdSe quantum dots in the core of a 1m long PCF. In this dissertation, the fluorescence emission is described from ~2.2 nm PbS quantum dots was observed with a specified emission peak of 890 nm. The quantum dots were suspended in NOA73 and inserted in the core of 7-9 cm long PCFs of with a hollow core diameter of 10.9 5m. The fiber was pumped by a 2.5 mW He-Ne laser or a 679 nm, 390 mW diode laser and its emission was characterized. A maximum fluorescence power of 2.2 5W and a maximum efficiency of 0.03% were achieved. Varying the quantum dot concentration revealed that lower concentrations lead to higher efficiencies. / Fibras de cristal fotônico (PCFs) têm levado a uma atenção renovada ao campo das fibras ópticas devido às diversas propriedades exclusivas resultantes do seu perfil microestruturado. Em particular, este perfil permite a introdução de líquidos e polímeros na fibra de modo que estes interajam eficientemente com a luz, levando a aplicações em sensoriamento químico e biológico, óptica não-linear, e o desenvolvimento de dispositivos fotônicos ativos. Diversas aplicações requerem a inserção seletiva da amostra no núcleo de uma PCF de núcleo oco, deixando buracos da casca sem preenchimento. Esta dissertação apresenta duas contribuições para o desenvolvimento de PCFs de núcleo preenchido. Os mecanismos de perda em PCFs de núcleo líquido são estudados e a fluorescência de uma PCF de núcleo polimérico dopado com pontos quânticos é demonstrada. Os estudos da perda foram motivados pela análise da transmissão da luz em 633 nm em amostras de 5-7 cm de PCF de núcleo de água cujas pontas eram clivadas e deixadas no ar. Geralmente a transmissão encontrada era menor do que 5%, enquanto que a atenuação da água poderia levar a ~98% de transmissão. Verificou-se que a evaporação do líquido era um mecanismo de perda importante e sua taxa foi determinada através de microscopia e de tomografia por coerência óptica (OCT) em fibras capilares e PCFs preenchidas com água deionizada, etanol e o tolueno. Embora a taxa da evaporação no etanol seja maior, para todas as amostras algumas centenas de micrômetros nas pontas da fibra são esvaziadas em minutos. Um método para impedir a evaporação que consiste em selar as pontas da fibra com um polímero curável por UV (NOA 73) foi testado com sucesso. O preenchimento de uma PCF com elementos ativos pode conduzir a amplificação óptica e ação laser. Pesquisadores da NTT observaram recentemente fluorescência em 609 nm em pontos quânticos de CdSe no núcleo de uma PCF de 1 m de comprimento. Nesta dissertação, a emissão de fluorescência é observada com pontos quânticos de PbS de ~2,2 nm e pico de emissão nominal em 890 nm. Os pontos quânticos foram suspensos em NOA73 e introduzidos no núcleo de PCFs de 7-9 cm de comprimento e núcleo oco de 10,9 5m de diâmetro. A fibra foi bombeada por um laser de He-Ne de 2,5 mW ou um laser de diodo de 679 nm e 390 mW e sua emissão foi caracterizada. Uma fluorescência com potência máxima de 2,2 5W e eficiência máxima de 0,03% foi obtida. Variando a concentração de pontos quânticos observou-se que baixas concentrações levam a eficiências mais elevadas.

This dissertation presents the novel creation of a surface relief fiber Bragg grating on the flat surface of a D-shaped optical fiber. In order to produce an efficient surface relief grating the grating must be etched into the surface of the glass fiber close to the core. A short etch that removes the cladding above the core is performed in order to decrease the core-to-flat distance and allow the light to interact with the grating on the flat surface. Due to the unique D-shape of the optical fiber the mechanical integrity of the fiber remains high even after the fabrication process. For traditional fiber Bragg gratings the index modulation occurs in the core of the optical fiber. While this method can produce highly reflective gratings they are not well suited for many sensing applications. For example, the operating temperature range is limited to a few hundred degrees Celsius before the index modulation returns to a more uniform index profile. Also because the gratings are created in the core of the fiber, interaction with the surrounding environment is limited. The surface relief fiber Bragg grating created for this work overcomes some of the sensing challenges of traditional gratings. The major accomplishments of this dissertation show a dramatic increase in operating temperature to over 1000 degrees Celsius, the ability to measure multi-dimensional bend, the ability to measure material changes around the fiber such as chemical concentration, and the ability to use a Vernier effect to dramatically increase the sensors sensitivity. In addition to the sensing applications of this work a more thorough understanding of the reflection and transmission properties of the surface relief grating is also presented. Implementation of the transfer matrix method for simulation of the gratings is also shown to be a fast and accurate modeling tool for predicting the grating response.

The identification and quantification of atoms, molecules, or ions concentrations in gaseous samples are in great demand for medical, environmental, industrial, law enforcement and national security applications. These applications require in situ, high-resolution, non-destructive, sensitive, miniature, inexpensive, rapid detection, remotely accessed, real time and continuously operating chemical sensing devices. The aim of this work is to design a miniature optical sensing device that is capable of detecting and measuring chemical species, compatible with being integrated into a large variety of monitoring systems, and durable enough to be used under extreme conditions. The miniature optical sensor has been realized by employing technologies from the optical communication industry and spectroscopic methods and techniques. Fused silica capillary tubing along with standard communication optical fibers have been utilized to make miniature gas sensor based on near-infrared spectroscopy for acetylene gas detection. In this work, the basic principles of infrared spectroscopy are reviewed. Also, the principle of operation, fabrication, testing, and analysis of the proposed sensor are discussed in details. / Master of Science

Die Verbindung von hoch entwickelten Nanomaterialien mit fluoreszenzbasierten Technologien hat sich zu einem aufstrebenden Forschungsbereich entwickelt. Nichtsdestotrotz ist bis heute der Schritt von einem organischen Indikatormolekül zum anwendbaren Sensorsystem ein komplexer Prozess. Diese Arbeit zielte darauf ab, sensorische Materialien verschiedener chemischer Natur für diverse Analyten zu entwickeln, zu charakterisieren und zu etablieren. Hierbei wurden zunächst pH sensitive Fluoreszenzfarbstoffe entwickelt und in dünnen Membranen immobilisiert. Der Teststreifen ermöglicht die Beurteilung von pH-Änderungen mit dem Auge. Darüber hinaus wurde gezeigt, wie diese Farbstoffe auch in eine wasserlösliche Form überführt werden können. Damit konnten lokale pH-Änderungen an der Wachstumsfront von Silikat-Biomorphs detektiert werden. Auch partikuläre Systeme stellten sich als geeignete Materialien heraus. Es konnte gezeigt werden, wie die Silikat-Matrix von Partikeln zu verbesserten Eigenschaften für Farbstoffe führt. Mittels farbstoffbeladener Partikel konnte in einem Lateral-Flow-Assay ein schneller Nachweis von TATP etabliert werden. Ein anderer Ansatz verfolgte das Ziel des sensitiven Nachweises von Quecksilberionen in Wasser. In einem anderen System konnten Silikat-Nanopartikeln so funktionalisiert werden, dass ein sensitiver und selektiver Nachweis von Schwermetallionen und Anionen über ein Quencher-Displacement-Assay gelang. Zusätzlich wurde die einzigartige Oberfläche von Zellulosepartikeln mithilfe eines neu entwickelten Fluoreszenzfarbstoffs untersucht. Die untersuchten Materialien und Strategien zeigen, wie leicht innovative Moleküle für potentielle sensorische Systeme im wässrigen Medium auf Basis von fluoreszierenden Partikeln und dünnen Schichten geschaffen werden können. Das Verhalten der hergestellten Materialien wurde über spektroskopische Methoden evaluiert und dabei, wenn möglich, die Parameter Sensitivität, Selektivität und Ansprechzeit beurteilt. / The combination of fluorescence and nanomaterials has developed into an emerging research area. Nonetheless until now the step from an organic sensory molecule to a final sensor format is a complex endeavor. This thesis aimed at the preparation of particulate and thin-film based platforms for various analytes through combining the features of an appropriate host material with outstanding properties of dyes concomitant with sensitive fluorescence detection techniques. In particular, pH sensitive fluorescent probes were sterically immobilized into a thin membrane. The dip-stick allows the assessment upon change in pH with the eye. Especially a probe working at high basic pH range was converted into a water-soluble analogue and was directly applied at the growth front of silica biomorphs to detect local pH changes. But also particulate structures are suitable host materials. It is shown how the silica matrix of nanoparticles lead to improved optical properties for embedded dyes. The interactions of silica and fluorescent dyes within the pores of mesoporous particles were exploited to develop an actual sensor format based detection of TATP. In another approach it was possible to detect mercury ions in water. Heavy metal ions were also successfully detected in a quencher displacement assay involving receptor-dye functionalized silica nanoparticles. The impact of the unique surface properties of cellulose microparticles was shown by a fluorescent dye which allows an assessment of the surface functional groups and microenvironment through the reactivity and its changes in the optical properties. The performance of the prepared materials were evaluated mostly by spectroscopic methods and if possible assessed in terms of sensitivity, selectivity and response time. The newly developed and investigated materials based on fluorescent particulate and thin-films show the facile application of innovative sensor probes for potentially sensing devices.