The use of Raman spectroscopy in ultra high vacuum to assess structure and reactivity at the interface of tris-(8-hydroxyquinoline) aluminum (Alq3) with vapordeposited metals is presented. Understanding the structure of the interface between electron transport layer materials such as Alq3 and low work function metals such as Al, Mg and Ca is vital for engineering organic light emitting diodes with high efficiency and low driving voltage. Reactivity at the interface of Al, Mg and Ca with Alq₃ thin films is examined with Raman spectroscopy along with the non-reactive Ag/Alq₃ interface for comparison. Additionally, the effect of a thin LiF barrier layer on reactivity at the Al/Alq₃ and Mg/Alq₃ interfaces is also examined. Raman spectroscopy of post-deposited Ag on Alq3 films confirms preservation of the Alq₃ structure along with evolution of simple surface enhancement of Alq₃ spectral intensities. Changes in key vibrational modes of Alq₃ upon Ag deposition are consistent with weak interaction of Ag with the conjugated ring of the ligand. In contrast, vapor deposition of Al onto Alq₃ films results in the appearance of new Raman modes linked to the formation of an Al-Alq₃ adduct. Additionally, Raman modes associated with graphitic carbon are also noted for the Al/Alq₃ interface and are attributed to partial degradation of the organic film. The Raman spectral results for deposition of Mg onto Alq3 films also indicate formation of a complex interfacial region composed primarily of Mg-Alq₃ adducts and small-grained amorphous or nanocrystalline graphite. Raman spectroscopy of the Ca/Alq₃ interface is also indicative of formation of a Ca-Alq₃ complex; however, the graphitic carbon in this system is noted to be more disordered, sp³-type carbon compared to that observed for Al/Alq₃ and Mg/Alq₃. Examination of the Al/LiF/Alq₃ and Mg/LiF/Alq₃ interfaces illustrates that 5 Å-thick LiF layers partially block reaction chemistry between the metal and organic, while 10 Å thick LiF films completely eliminates reactivity at these interfaces. Implications of the presence of chemical species observed at these metal/organic interfaces on charge transport in devices are also discussed.

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A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg, 2015. / Surface enhanced Raman spectroscopy (SERS) has emerged as a surface sensitive vibrational technique that leads to the enhancement of the Raman scattering molecules on or close to the surface of a plasmonic nanostructure. The enhancement is found to be in orders of 104 to 1015, which allows the technique to be sensitive enough to detect a single molecule. In this study, we report on the synthesis of different sizes of gold and silver nanoparticles (AuNPs and AgNPs) and gold nanorods (AuNRs). These are functionalized or co-stabilized with different stoichiometric ratios of HS-(CH2)11-PEG-COOH and alkanethiols (Raman reporters), i.e.; HS-(CH2)11-NHCO-coumarin(C), HS-(CH2)11-triphenylimidazole (TPI), HS- (CH2)11-indole (HSI), HS-(CH2)11-hydroquinone (HQ) to form mixed monolayer protected clusters (MMPCs). The alkanethiols were chosen as Raman reporters to facilitate the selfassembled formation of monolayers on the metal surface, thus resulting in stable MMPCs. The optical properties and stability of MMPCs were obtained using ultraviolet-visible (UVvis) spectrophometry and a zeta sizer. Size and shape of the as-synthesized nanoparticles were obtained using transmission electron microscopy (TEM). The tendency of thiolcapped nanoparticles to form self-assembled ordered superlattices was observed. Their Raman activities were evaluated using Raman spectroscopy, with the enhancement factor (EF) being calculated from the intensities of symmetric stretch vibrations of C-H observed in the region of about 2900 to 3000 cm-1 in all SERS spectra. In all four different alkanethiols (Raman reporters), smaller size metal nanoparticles (14 nm for AuNPs and 16 nm AgNPs) showed higher EF compared to 30 and 40 nm metal nanoparticles. The EF was observed to increase proportionally with stoichiometric ratios of alkanethiols from 1% iv | P a g e to 50%. The prepared MMPCs with small sizes were used as a SERS probe for the detection of malaria and tuberculosis biomarkers.

Uma classe de compostos presente no material particulado atmosférico que desperta particular interesse e constitui-se em motivo de preocupação são os chamados hidrocarbonetos policíclicos aromáticos (HPA). Estes caracterizam-se por possuir dois ou mais anéis aromáticos condensados e são formados pela queima de combustíveis orgânicos na presença de quantidade limitada de oxigênio. Além dos próprios HPA, são importantes, sob o ponto de vista ambiental, seus derivados nitrados e oxigenados. Sua identificação e quantificação são passos importantes no processo de se esclarecer os mecanismos que conduzem à formação desses derivados. Neste trabalho, estudou-se reações fotoquímicas de HPA e nitro-HPA adsorvidos sobre o fotocatalisador dióxido de titânio (TiO2) ou sobre sílica (SiO2) através de técnicas de espectroscopia Raman. Foram conduzidos também estudos espectroeletroquímicos dos HPA através de espectroscopia eletrônica e Raman intensificada (efeito SERS) visando a caracterização vibracional dos produtos de processos faradáicos desses compostos sobre eletrodos, para comparação com os produtos de fotodegradação. Os HPA estudados foram: antraceno, 9-nitroantraceno, fenantreno, fluoreno, fluoranteno, pireno e criseno. Para o estudo das reações fotoquímicas foi feita uma pré-adsorção dos diversos HPA e nitro-HPA sobre TiO2 ou SiO2, que foram então irradiados em 254 nm em intervalos de tempo pré-determinados. Verificou-se mudanças nas estruturas das moléculas em função da exposição à luz ultravioleta. Os resultados obtidos revelaram a formação de intermediários oxidados, com grupamentos C=O. A combinação de dados da fotodegradação de HPA com seu estudo via eletroquímica - utilizando técnicas espectroscópicas para a identificação e caracterização de produtos - trouxe correlações importantes para esclarecer as transformações envolvidas nas etapas iniciais da fotodegradação dessas substâncias. A comparação das estruturas dos intermediários de fotodegradação e dos produtos de oxidação eletroquímica de HPA mostra que o início do processo fotocatalítico de HPA envolve uma etapa de oxidação de maneira análoga ao processo eletroquímico. / One class of chemicals that is present in the particulate matter in the atmosphere is of the so-called polycyclic aromatic hydrocarbons (PAH). They are object of special interest and concern due to their mutagenic properties and carcinogenic effects. PAH are characterized by the presence of two or more aromatic rings in their structure, and they are produced by the burning of organic fuels in a limited amount of oxygen. The study of the photochemical behavior of PAHs is relevant for clarifying some aspects of these complex systems. In this work, we perform experiments that include the UV irradiation of PAH, to observe which species are produced in such condition. Such investigations include the use of a photocatalysts, titanium dioxide – TiO2 – and that will allow the comparison between degradation products in the absence and in the presence of catalysts. Spectroscopic techniques were employed to monitorate the intermediates formed in the photoinduced degradation of PAH and their nitro derivates adsorbed or not on the photocatalyst TiO2. To perform the study of the photochemical reactions, the several PAH and nitro PAH were pre-adsorbed on TiO2 or SiO2, and then irradiated in 254 nm, in pre-determined time intervals. Changes in the structure of the molecules were observed after the exposure to the ultraviolet radiation. Results thus obtained revealed the production of oxidized intermediates bearing the C=O group. The joint analysis of the photodegradation data with those produced by electrochemical means - using spectroscopic techniques to the identification and characterization of the products - lead to important correlations that helped to clarify the transformations that take place in the initial steps of the photodegradation of PAH. By comparing the structures of the intermediates formed both in the photodegradation processes and in the electrochemical oxidation of PAH, it was possible to conclude that the first part of the photocatalytical degradation of those PAH include an oxidation step that is analogous to the electrochemical process.

Raman spectroscopy based activities were developed and implemented into the first year chemistry undergraduate curriculum. The implementation of these experiences and experiments and the utility of Raman spectroscopy as a teaching tool to convey anchoring chemistry concepts using a hands-on Raman spectroscopy based approach are discussed. Fundamental principles of chemistry, such as the interaction of light with matter, molecular bonding, equilibrium, and acid base reactions are facilitated through use of these Raman spectroscopy based experiments and experiences. An assessment of student learning gains as a result of participation in a Raman spectroscopy experience was also conducted and is discussed. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection

Thesis. 1977. M.S.--Massachusetts Institute of Technology. Dept. of Biology. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Includes bibliographical references. / M.S.

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This dissertation is divided into two separate parts covering my research in two different fields of optics. Part I consists of chapters 1-3 and covers experiments on periodically poled lithium niobate while Part II consists of chapters 4-6 and covers various spectroscopic methods designed for the application of in vivo blood analysis. Chapter 1 serves as a brief introduction to periodically poled lithium niobate and its fabrication process. In chapter 2, the key results of Part I, derived from a series of experiments on poling of thinned lithium niobate, are presented. Building upon these experiments, chapter 3 concludes Part I with a study on poling of crystal ion sliced lithium niobate. Part II begins with chapter 4, which describes a spectroscopic approach for non-invasive blood analysis in vivo. In chapter 5, experiments analyzing aqueous glucose solutions with mid-infrared and Raman spectroscopy are discussed. Chapter 6 concludes this dissertation with the design and demonstration of a innovative stimulated Raman spectroscopy system. In Part I, ferroelectric poling fabrication procedures were developed, optimized, and implemented for periodic poling of thinned lithium niobate. The free-standing samples of thickness from 500 μm down to 25 μm were thinned by chemical mechanical planarization and annealed before poling. Domain structure was investigated as a function of sample thickness using Raman, scanning electron, atomic force, and optical microscopy, and broadening of poled domains was consistently found to vary with sample thickness in a strong linear correlation. Domain broadening was reduced by 38% as the thickness of the poled sample was reduced from 500 to 25 μm. Micro Raman probe measurements showed a thickness-dependent contrast in Raman active mode intensity between poled and unpoled regions, with the thinner samples having a higher intensity contrast. To explore poling on even thinner free-standing samples, crystal ion sliced lithium niobate thin films of 10 μm in thickness were fabricated. Chemical mechanical planarization of the ion-implanted layer and annealing was performed to prepare the thin films for poling. Ferroelectric poling of the crystal ion sliced samples was attempted, but unsuccessful, suggesting that alternative fabrication processes may be necessary for poling of crystal ion sliced thin films. In Part II, several disparate experiments were conducted to progress towards a common overarching goal of developing a spectroscopic method for non-invasive whole blood analysis and metabolite monitoring. A portable visible and near-infrared spectroscopy system for in vivo blood spectral identification was developed and demonstrated in a clinical setting. A custom-designed clip attached the illumination and collection optics to opposite sides of the patients’ fifth fingertip, and applied gentle pressure, gradually pushing a small quantity of blood away from the measurement site, and inducing a time-dependent change in the effective path length of blood. Time-dependent visible and near-infrared spectra were measured from the collected transmitted and scattered light. A maximum likelihood model was developed to leverage the time-dependent spectral component and identify the spectrum of blood, isolating it from that of surrounding tissue. A second set of experiments were conducted to develop a model for predicting glucose concentrations from measured mid-infrared transmission and spontaneous Raman scattering spectra. Partial least squares regression models were trained, validated, and tested on the spectra of aqueous 0-10 mM glucose solutions measured by both spectroscopic modalies. The models proved to be accurate predictors of glucose concentration as the mean squared error of the model based on mid-infrared spectra ranged from 0.10 - 0.74 mM, and that of the Raman-based model ranged from 0.26 - 0.93 mM. Finally, an LED-based stimulated Raman system was innovated to improve upon the relatively weak spontaneous Raman signal in a cost-effective manner. Stimulated Raman gain using a broadband LED Stokes source was demonstrated in the measuring of vibrational spectra of aqueous 0-10 mM glucose solutions. Scattered light was detected via photomultiplier tube and measured using either a photon counter or a lock-in amplifier in two alternative versions of the system. Both stimulated and spontaneous Raman spectra were collected with each instrument for a total of four measurement modalities. The stimulated Raman spectra measured with the photon counter showed up to 100% higher intensity for some glucose modes compared to the corresponding spontaneous Raman spectra, but also had significantly greater noise. For the spectra measured with the lock-in amplifier, the glucose modes of the stimulated Raman spectra were only 20-30% higher in intensity than those of the spontaneous Raman spectra, but had similar levels of noise. Partial least squares regression models based on spectra measured by each modality were developed and compared. The model based on stimulated Raman spectra measured with the lock-in amplifier had the strongest predictive power of all modalities and predicted the concentrations of the aqueous 0-10 mM glucose solutions with a mean squared error as low as 9.96x10-4 mM, an order of magnitude lower than that of the model based on spontaneous Raman spectra.