Due to an increase of human activity, an increase health risk has emerged from the presence of pollutants in the environment. In the transition to renewable and sustainable life style, treatment of pollutants could support the shifting societies. A motivation behind material research for environmental applications is to maximize the efficiency of the materials to alleviate environmental pollution. In the case of titania, an increase of ultra-violet light absorption is needed to overcome its bandgap to produce reactive radicals, which is the basis for photocatalysis. It has been hypothesized that photonic crystal can enhance titania photocatalysis. They are structures made of at least two dielectrics with a high refractive index contrast, ordered in a periodic fashion. For a strong contrast, photonic band gaps emerge. The effect of the photonic band gap is to force complete reflection of the incoming light within its range and multiple internal reflections at its edges. By combining photonic and electronic band gap positions, it is possible to increase the absorption at the photonic band gap edges. In this thesis, fabrication method and structural analysis of titania and alumina/titania photonic structures were presented. A thorough optical analysis was performed at all steps of fabrication – beyond what previously has been reported. The photocatalytic activity was measured with two setups. Fourier Transform Infrared spectroscopy combined with arc lamps and bandpass filters was used to monitor the degradation of stearic acid in ambient air. A home-built setup was used to degrade methylene blue in solution with ultra-violet illumination. The results in this thesis show in general no correlation of the photocatalytic activity to the photonic band gap position, even though absorbance data displayed an increase absorption in this energy range. A more controlled environment might show the effect of the structure, as seen in some of the experiments.

The past decade and a half has seen the rapid emergence of a new material class known as photonic crystals (PCs), structures that exhibit 1, 2, or 3, dimensional periodicity of their dielectric constant, resulting in a modification of the dispersion characteristics from the normal w = vk relationship found in isotropic materials. Several remarkable electromagnetic phenomenon result, including the formation of photonic band gaps (PBGs), which are specific energy ranges where electromagnetic wave propagation is forbidden, and the existence of energies where the photon group velocity is slowed drastically from its normal value. The resulting modification of a materials photonic band structure allows unprecedented control of light, resulting in phenomena such as self-collimation, and spontaneous emission modification or lasing threshold reduction through either band edge effects (low group velocity) or microcavity defect incorporation. PCs for operation at visible wavelengths are difficult to form due to the need for nanoscale fabrication techniques. The research described focused on the fabrication of photonic crystal phosphors by using the infiltration and subsequent removal of self-assembled opal templates to make inverted opal-based photonic crystals. This thesis shows the advantages that atomic layer deposition (ALD) has as an important method for use in photonic crystal fabrication, and highlights the exciting results of use of ALD to fabricate luminescent ZnS:Mn and optically inactive titania inverse opals, as well as ZnS:Mntitania luminescent composite inverse opals.

Universiẗat, Diss., 2002--München.

Universiẗat, Diss., 2000--Freiburg (Breisgau).

Universiẗat, Diss., 2004--Freiburg (Breisgau).

Submitted by Almir Azevedo (barbio1313@gmail.com) on 2014-09-23T16:45:28Z No. of bitstreams: 1 Dissertação mestrado ien 2014 Gil Teixeira Sobrinho.pdf: 1948176 bytes, checksum: 02c0cdc7a1b1c9fa099cc0ba49de1a8e (MD5) / Made available in DSpace on 2014-09-23T16:45:28Z (GMT). No. of bitstreams: 1 Dissertação mestrado ien 2014 Gil Teixeira Sobrinho.pdf: 1948176 bytes, checksum: 02c0cdc7a1b1c9fa099cc0ba49de1a8e (MD5) Previous issue date: 2014 / A confiabilidade e segurança de um reator nuclear, seja de potência ou de pesquisa, tem como um de seus fatores críticos, o controle da temperatura do núcleo. Para isso, faz-se necessário um trocador de calor de placa que absorva a energia presente no refrigerante que será transferida para água de resfriamento. No trabalho em questão, adotamos como caso exemplo, um reator semelhante ao OPAL (Open Pool Australian Light Water Reactor). Para efeito de comparação, foram utilizados dados de entrada típicos de um Reator Multipropósito de Piscina. Realizaram-se análises termodinâmicas e se utilizou o conceito da efetividade para cálculo das temperaturas de saída do fluido resfriado e do fluido aquecido. Foi também calculado o número de placas mínimas, a partir do conhecimento da área de troca térmica, que garantiria a total remoção do calor produzido pelo reator em potência nominal. Os resultados obtidos foram comparados com os resultados obtidos com software comercial fechado WEBCALC, fornecido pela fabricante de trocadores Alfa Laval. / The reliability and safety of a nuclear reactor, either power or research, have as one of theirs critical factors the core temperature control. For this, it is necessary a plate heat exchanger that absorbs the refrigerant's energy that will be transferred to the cooling water stream. In the current study, we adopted as a case example, a reactor similar to OPAL (Open Pool Australian Light Water Reactor). Input data used for comparison were typical of a Multipurpose Pool Reactor. Thermodynamic analyzes were performed and the output temperatures of the heated and cold fluid were calculated by the effectiveness method. It was also calculated the minimum number of plates, obtained from knowledge of value of the total surface of heat transfer, which would ensure the total removal of the heat produced by the reactor at rated power. The results were compared with those obtained with the commercial software WEBCALC, which was developed by the heat exchanger manufacturer Alfa Laval .

Eksperimentai buvo atliekami su bandinėliais gautais iš Madrido, Maskvos ir St.Peterburgo, tai yra su fotoniniais kristalais. Darbe buvo nagrinėta fotoninio kristalo opalo struktūrą ir optines savybes draustinės stop juostos srityje bei defektų valdymo būdai, keičiant elektrinį lauką. Nagrinėjamas elektrinio lauko poveikis defektams, stop juostai. Nustatyta, kad elektriniame lauke susikuria defektai, kuriuos galima valdyti nuo 0V iki 7V įtampos intervale. Išmatuoti defektinės modos perjungimo laikai kurie sieka 200 s, tai 10 kart greičiau nei stop juostos. / We did structural and spectroscopic studies of bulk and thin film synthetic opal. Demonstrate that the photonic crystal, opal have defects, but these defects may be "good" when use it to control light in stop band.

The purpose of this study was to investigate the effects of a fluoride releasing orthodontic primer on demineralization adjacent to brackets. Twenty-two patients were recruited for this study. One premolar was randomly chosen as the experimental tooth, the contralateral tooth was the control. Teeth were visually analyzed for white spot lesions (WSLs). Knoop microhardness was used to determine hardness. Visual examination results showed no significant difference in the number of WSLs observed between Opal Seal and Transbond XT over the duration of this study. Solid conclusions could not be drawn from the results of microhardness testing. Therefore, it cannot be concluded that there is a difference in enamel hardness between Opal Seal and Transbond XT. However, prior to 90 days, teeth showed a significant difference in WSLs. Suggesting a protective effect of Opal Seal that diminished with time. Future studies are necessary to determine the clinical performance of this product.

Dans ce travail, nous nous intéressons à la spectroscopie optique par réflexion d’une vapeur diluée de césium infiltrée dans des opales artificielles Langmuir-Blodgett. Après une étude microscopique de la structure des opales, nous rapportons des expériences de réflexion, transmission et diffraction (sans atomes) effectuées sur diverses opales, dans le but d’explorer la propagation du champ lumineux dans ces milieux. En effectuant des expériences de réflexion sélective, nous observons que pour une polarisation TM, le signal atomique s’annule à 45° et à l’angle de Brewster, et entre ces deux zéros le signe du signal est inversé. Cet effet était prédit théoriquement mais n’avait jamais été observé. Nous rapportons aussi les expériences de spectroscopie par réflexion d’une vapeur infiltrée dans diverses opales et pour différentes longueurs d’onde. Sur des opales multicouches, nous observons des spectres sub-Doppler en incidence oblique, dont la forme est sensible à l’incidence, la polarisation et la longueur d’onde. Ces spectres ont été interprétés comme une signature d’un confinement tridimensionnel. Les expériences sur une opale multizone montre que sur une opale monocouche, nous observons aussi un signal sub-Doppler où il n’y a pas de confinement tridimensionnel. / In this work, we are interested in reflection optical spectroscopy of diluted cesium vapor infiltrated in Langmuir-Blodgett artificial opals. After a microscopic study of the structure of opals, we report experiments of reflection, transmission and diffraction (without atoms) carried out on various opals, with the aim of exploring the propagation of the light field in these media. By carrying out selective reflection experiments, we observe that for a TM polarization the atomic signal vanishes at 45° and the Brewster angle, and between these two zeros the sign of the signal is reversed. This effect was predicted theoretically but had never been observed. We also report the experiments of reflection spectroscopy of a vapor infiltrated in various opals and for different wavelengths. On multi-layered opals, we observe sub-Doppler spectra in oblique incidence, the shape of wich in sensitive to incidence, polarization and wavelength. These spectra were interpreted as a signature of a three-dimensional confinement. Experiments on a multi-zone opal show that on a monolayer opal, we also observe a sub-Doppler signal where there is no three-dimensional confinement.

Knowing what goes on in the upper atmosphere (∼80-140 km) is very important to the space science community. There are several competing forces that influence the temperature and densities of neutral molecules in that region. OPAL (Optical Profiling of the Atmospheric Limb) is funded by the National Science Foundation (NSF) to measure the temperature there using light from oxygen molecules (∼760 nm). To accomplish this,OPAL is built into a CubeSat (a satellite the size of a loaf of bread) to be launched from the International Space Station (ISS) at an altitude of about 400 km. This vantage point is needed to see the light that is absorbed before it makes it to the ground, so a satellite is the optimal choice. Similar to looking at a tennis ball in your hand and trying to see the details of the yellow fuzz fibers on the outer edges of the ball, OPAL is trying to see the light emitted from oxygen at the outer edge of the atmosphere (also called the limb). In order to see how well OPAL can detect space weather signatures affecting the oxygen emissions a suite of models are made to simulate its output. This suite is made of: simulating the flight path of CubeSat, modeling where the OPAL instrument is looking, and how the oxygen light changes with where the instrument is looking. Because we are currently in a solar minimum, the occurrence of solar storms and geomagnetic storms are considered rare events. This allows for the concentrating on detecting gravity waves in this region and the minimum values of detecting them with this developed model.