Call number: LD2668 .T4 1986 Y36 / Master of Science / Physics

Usefulness of a particular clinical assay is directly correlated with its ability to extract highest possible signal from available data. This is particularly relevant for personalized radiation therapy since early plan modifications confer greater benefits to treatment outcome. Recent studies have demonstrated capability of single-cell Raman microscopy to detect cellular radiation response at clinical (below 10Gy) doses, but only in certain strongly responding cell lines and after at least two day incubation. One possible cause is rather unoptimized signal processing used. This work investigates application of several advanced multivariate methods - weighted principal component analysis (WPCA), robust PCA, probabilistic PCA, and nonlinear PCA to increase radiation response signal. Representative datasets from strongly (H460 - human lung) and weakly (LNCaP - human prostate) responding cell lines were analysed in 0-50Gy and 0-10Gy dose ranges and results quantified to determine relative and absolute algorithm performance. It was found that with careful tuning, significant improvements in sensitivity and better signal separation could be achieved as compared to conventional PCA. / Graduate

[pt] Neste trabalho estudamos a síntese e caracterização de nanotubos de carbono de paredes simples com incorporação de fósforo. Os nanotubos foram produzidos em duas diferentes temperaturas (800 e 850 Graus Celsius), usando um precursor em pó (fase sólida) sem diluição em nenhum liquido. O sistema utilizado na síntese foi o CVD em alto vácuo. Para a caracterização comparamos as amostras incorporadas com SWNTs crescidos com etanol. Usamos a espectroscopia Raman, espectroscopia de fotoelétrons induzida por raios x (XPS) e microscopia eletrônica de transmissão (TEM) para caracterizar as amostras. A espectroscopia Raman e a microscopia eletrônica de transmissão foram usadas para confirmar a presença de SWNTs na amostra. Encontramos evidencia de que o fósforo foi incorporado nas amostras ao compararmos os espectros Raman dos SWNTs com amostra de referência. A partir dos resultados de XPS, observamos a presença de fósforo ligado a átomos de carbono que nós faz concluir que houve incorporação de fósforo nos nanotubos. / [en] In this work was studied the synthesis and characterization of single wall carbon nanotubes (SWCN) with phosphorus incorporation. The nanotubes were produced in two different temperatures (800 and 850 Degrees Celsius), using a powder precursor (solid phase) without liquid dilution. The system used for the synthesis was High Vacuum Chemical Vapor Deposition (HVCVD). The samples were characterized comparing the samples with phosphorus with SWNT synthetized with ethanol. Raman spectroscopy, x-ray photoelectron spectroscopy (XPS) on transmission electron microscopy (TEM) were employed to characterize the samples. The Raman spectroscopy and TEM were employed to confirm the presence of SWNT in the samples. We found evidences that phosphorus were incorporated comparing the Raman spectra with the reference sample. The XPS results showed the presence of phosphorus atoms bonded to carbon atoms which make us conclude that the phosphorus were incorporated to the nanotubes.

Nesta tese foram utilizadas as espectroscopias de espalhamento Raman intensificado pela superficie(Surface-EnhancedRaman Scattering- SERS) e Raman ressonante para monitorar a adsorção e o comportamento faradáico do ácido esquárico e seus derivados, além de um sal de transferência de carga de esquarato e tetratiofulvaleno e dois copolímeros de esquarato e pirróis. Outro tema desenvolvido neste estudo foi a construção de substratos SERS-ativos de elevado desempenho. A técnica SERS tem sido campo de grande interesse desde a detecção do espectro aman de uma única molécula, em 1997.O desenvolvimento de substratos SERS-ativos de elevado desempenho depende da apropriada manipulação de superficies metálicas nanoestruturadas, o que nos levou a adquirir conhecimento na síntese destes substratos. Colóides e filmes de Ag e Au foram preparados e seu desempenho SERS comparado com a superficie de eletrodos ativados por ciclos de oxidação-redução. A intensificação obtida para esses filmes foi comparávelà observada em eletrodos. O ânion esquarato, produto da dupla desprotonação do ácido esquárico, apresenta substancial delocalização de carga, sendo amplamente usado na síntese de materiais orgânicos condutores. Foram realizadas as caracterizações vibracionais do ácido esquárico, hidrogeno-esquarato e esquarato, além de seu radical, através da técnica SERS. Baseado nos resultados experimentais, um mecanismo de adsorção destas espécies sobre eletrodos de Au e filmes de ilhas de Ag ou Au foi proposto. Os resultados SERS também mostram que o ácido esquárico adsorvido sobre Au é decomposto em um processo catalisado pela superficie metálica, emboraestas espécies sejam muito estáveis em solução. Baseado nos resultados SERS do tetratiofulvaleno e de suas espécies oxidadas, foi eletroquimicamente, e formado pelo radical-cátion tetratiofulvaleno e o radical-ânion esquarato. Os elevados fatores de intensificação de Raman ressonante e SERS do tetratiofulvaleno impediram a detecção do esquarato no sal de transferência de carga. Duas poliesquaraínas polí(1-metilpirrol-co-ácido esquárico) e poli(1-dodecilpirrol-coácido esquárico) foram sintetizadas e caracterizadas pelas espectroscopias Raman ressonante, SERS e ressonância paramagnética de spin (EPR). Estes resultados nos levaram a propor uma estrutura polimérica diferente da apresentada pela literatura. Nossos resultados mostraram a presença de um radical orgânico delocalizado, do ânion esquarato protonadoe de dicátions similares aos presentes no polipirrol. / In this Thesis Surface-Enhanced Raman Scattering (SERS) and resonance Raman spectroscopy were used for monitoring the adsorption and faradaic behavior of squaric acid and its derived species. In addition, the charge transfer salt of squarate and tetrathiofulvalene and the copolymers of squarate and pyrroles were also studied. Another theme developed in this study was the manufacturing of. high performance SERS-active substrates. SERS technique has been a field of great interest since the detection of a single molecule Raman spectrum in 1997. The development of high perforrnance SERS-active substrates depends on the proper manipulation of nanostructured metal surfaces, and order to acquire know-how in the synthesis of such substrates. Ag and Au island films as well as colloid substrates were prepared and compared with electrode surfaces SERS activated by oxidation-reduction cycles. The enhancement factor obtained for such films is comparable to those observed in electrodes. The squarate anion, product of the double deprotonation of squaric acid, shows substantial charge delocalization, being largely used in the synthesis of conducting organic materiaIs. The vibrational characterization of squaric acid, hydrogen-squarate, squarate as well as its radical was carried out from the SERS data. Based on the experimental data an adsorption mechanism of such species on Au electrodes and Au or Ag islands was proposed. SERS results also show that squaric acid adsorbed on Au is decomposed in a process catalyzed by the metal surface, although in solution it proves to be a very stable specles. The vibrational characterization of an electrochemically forrned charge transfer salt between tetrathiofulvalene radical-cation and squarate radical-anion was done based on the SERS data of tetrathiofulvalene and its oxidation species. The large resonance Raman and SERS enhancement factors of tetrathiofulvalene preclude the detection of the squarate species in the charge transfer salt. Two polysquaraines: poly(1-methylpyrrole-co-squaric acid) and poly(1-dodecylpyrrole-co-squaric acid) were synthesized and characterized by resonance Raman, SERS and Electron Paramagnetic Resonance Spectroscopy (EPR) techniques. The results lead us to propose a polymeric structure different from that present in the literature. Our data showed a delocalized organic radical in the polymeric matrices together with dications similar to those present in polypirrole and protonated squarate anion.

Neste trabalho foi investigado o efeito exercido por microambientes sobre a estabilidade química e fotoquímica de corantes. Em particular, estudaram-se os fatores responsáveis pelo aumento da estabilidade química e fotoquímica de índigo quando em interação com paligorsquita, que compõem o pigmento histórico Azul Maia, sobre o qual ainda havia controvérsias na literatura. Os corantes investigados foram índigo, dehidroíndigo, alizarina, purpurina, luteolina e β-caroteno; os microambientes foram proporcionados pelas argilas paligorsquita, sepiolita, montmorilonita, laponita e HDL de Al3+ e Mg2+ (3:1). Paligorsquita e a sepiolita são as únicas argilas que apresentam microporos em sua estrutura. As técnicas de caracterização empregadas neste trabalho foram: espectroscopia vibracional (Raman e absorção no infravermelho), espectroscopia de absorção no UV-VIS, difratometria de raios X, análise térmica (TG e DSC), CG-MS, HLPC-MS, medidas de área superficial por isoterma de adsorção de N2 e SEM. Duas técnicas com resolução temporal em escala de sub-picosegundos (absorção de transiente e infravermelho resolvido no tempo) foram utilizadas. O sistema índigo+paligorsquita corresponde à mistura dos dois sólidos, seguida de aquecimento, sendo que a partir de 70 °C a coloração da mistura adquire tonalidade esverdeada e também apresenta maior estabilidade química e fotoquímica. Essa estabilidade e também a alteração na cor aumentam com a temperatura de aquecimento da mistura e o intervalo considerado engloba as temperaturas de perda de água zeolítica (70 - 150 °C) e coordenada (170 - 280 °C) da estrutura da argila. Os resultados de espectroscopia vibracional e eletrônica dos simulantes de Azul Maia indicam que o índigo interage através de ligações de hidrogênio com as moléculas de água coordenada. Essa interação, entretanto, só é possível com a remoção da água zeolítica, o que ocorre a partir de 70 °C. Com aquecimento em temperaturas acima de 170 °C o comportamento do espectro eletrônico e vibracional se altera, indicando a formação direta de complexos com os metais presentes nas bordas internas dos microporos. Os resultados de espectroscopia Raman indicam que com a interação por ligação de hidrogênio a simetria molecular do índigo diminua. Os estudos por espectroscopia com resolução temporal mostraram que o índigo apresenta transferência de próton no estado excitado (ESIPT) de um dos amino grupos para a carbonila adjacente; após esta transferência, há a formação da espécie mono-enol a qual relaxa ao estado fundamental após 120 ps, através de intersecção cônica, o que explica a alta fotoestabilidade do corante. No caso da mistura aquecida a 130 °C os resultados, obtidos pela primeira vez para uma molécula imobilizada em argila, confirmam que o índigo encontra-se em um ambiente hidrofílico, considerando o tempo de vida de decaimento do estado excitado (3,0 ps), comparável ao do índigo carmim em solução aquosa (2,7 ps). O tempo de vida também é muito curto, comparado ao em solução de DMSO (120 ps) o que pode explicar a alta estabilidade do corante quando dentro do microcanal da argila. Finalmente, constatou-se que o dehidroíndigo não é responsável pela coloração de simulantes de Azul Maia, a qual resulta de alterações no espectro de absorção no visível do corante que ocorrem com a interação com a argila / In this work, the role played by the microenvironment on the chemical and photochemical stability of dyes was investigated. The factors responsible for the enhanced stability of indigo when interacting with palygorskite were detailed studied; the indigo and palygorskite system constitutes a simulant of Maya Blue, a historical pigment with properties which are controversially described in the literature. The dyes here investigated were indigo, dehydroindigo, alizarin, purpurin, luteolin and β-carotene; the microenvironment was provided by palygorskite, sepiolite, montmorillonite, laponite and a layered double hydroxide (Al3+ e Mg2+, 3:1). Palygorskite and sepiolite are the only clays with micropores in their structure. Several characterization techniques were employed, namely vibrational spectroscopy (Raman and infrared), UV-VIS electronic absorption spectroscopy, X-ray diffractometry, thermal analysis (TG and DSC), CG-MS, HPLC-MS, surface area and porosity determination (N2 isotherm adsorption) and scanning electron microscopy. Two sub-picosecond time resolved techniques (transient absorption and infrared absorption) were also used. The indigo+palygorskite system corresponds to the intimate mixture of both solids, followed by heating; from 70 °C the mixture attains a greenish hue and an enhanced chemical and photochemical stability. Both stability and color change increase with the heating temperature, which also leads to loss of zeolitic and coordinated water (70 to 150 °C and 170 to 280 °C, respectively). Vibrational and electronic spectroscopies indicate that, in the Maya Blue simulants, the dye interacts with the clay through hydrogen bonds with the coordinated water molecules. Such interaction, however, is only possible with the removal of the zeolitic water, which starts at 70 °C. At temperatures above 170 °C, both vibrational and electronic spectral profiles change, indicating that the interaction is now proceeding directly with the metals that are at the internal borders of the micropores. Results from Raman spectroscopy suggest that with the hydrogen bond and metal interaction a symmetry lowering occurs. Time resolved spectroscopy results show that indigo present an excited state intramolecular proton transfer from one of the NH to the adjacent carbonyl group, originating a mono-enol species, which decays to the ground state after 120 ps through a conical intersection. Such fast decay explains the high photochemical stability of indigo. In the case of the ind+paly mixture heated at 130 °C, the time resolved data obtained for the first time for a dye+clay system confirms that indigo is in a hydrophilic environment, taking into account the excited state lifetime (3.0 ps), comparable to indigo carmine in aqueous solution (2.7 ps). The excited state lifetime of indigo in the clay is also very short when compared to the experimental data for the dye in DMSO solution (120 ps), which is possibly an explanation for the dye high stability when inside the clay micropores. Finally, dehydroindigo was not found to be responsible for the color of Maya Blue simulants, which results from the spectral changes in the dye absorption spectrum originated by the interaction with the clay.

Este trabalho apresenta um estudo sobre síntese, caracterização e propriedades de ftalocianinas metálicas na forma de filmes ultrafinos. Foi obtida mais de uma fração para cada ftalocianina. Para as ftalocianinas de paládio (PdPc) e de ródio (RhPc), apenas uma fração pôde ser totalmente purificada para trabalhos com a técnica Langmuir-Blodgett (LB). As frações de ftalocianina de rutênio (RuPc) não atingiram pureza suficiente para fabricação de filmes de Langmuir e LB. As propriedades das ftalocianinas de ródio e bisftalocianina de itérbio (YbPc2), sintetizada em trabalho anterior, foram estudadas na formação de filmes LB. Observou-se forte influência das condições exterimentais nos resultados. Para a YbPc2, a posição do sensor de medida de pressão altera a pressão de colapso dos filmes, algo que só é observado em filmes de compostos semi-anfifilicos. O potencial de superficie dos filmes de Langmuir depende da velocidade de compressão, mas tais diferenças não aparecem nos filmes LB depositados. Foi observada uma forte interação química entre a RhPc e o ácido esteárico, o que é atípico para ftalocianinas. Esta interação parece ser bem menos intensa nos filmes LB. As áreas ocupadas por molécula para as bisftalocianinas de itérbio e samário e a ftalocianina de ródio foram 69, 60 e 75 &#1962 e as pressões de colapso 52, 54 e 57 mN/m, respectivamente. Esses resultados mostram similaridade nas características das diferentes ftalocianinas. Entretanto, o potencial de superficie foi bem menor para a RhPc, provavelmente devido a uma menor componente de dipolo normal à superficie da água. O comportamento eletroquímico de filmes LB da YbPc2 dependeu da espessura dos filmes. Em filmes mais espessos, há maior dificuldade na difusão dos íons, principalmente no processo catódico. Filmes LB da YbPc2 e PdPc apresentaram eletrocromismo, mudando de cor com a aplicação de diferentes potenciais. Em espectroscopia Raman, observou-se que a banda em 675 cm-1 é a de maior intensidade para a RhPc e YbPc2, quando utilizada a linha de laser em 633 nm. A PdPc tem comportamento distinto apresentando a banda de maior intensidade em 1520 cm-1. Ao analisar estes resultados à luz de dados da literatura, conclui-se que o fator predominante para os espectros Raman é o estado de oxidação. Os metais Yb e Rh estariam no mesmo estado de oxidação, diferente do Pd. Comparando os resultados de microscopia de força atômica (AFM) e mapeamento Raman para a YbPc2, observou-se que filmes LB contendo maior porcentagem de YbPc2 são mais homogêneos / This work presents the synthesis, characterization and properties of metallic phthalocyanines. For the palladium phthalocyanine (PdPc) and rhodium phthalocyanine (RhPc), only one fraction could be totally purified for work with the Langmuir-Blodgett (LB) technique. The fractions of ruthenium phthalocyanine (RuPc) could not be sufficiently purified for the fabrication of Langmuir and LB films. The film properties of rhodium phthalocyanine and ytterbium bisphthalocyanine (YbPc2), synthesized in a previous work, were investigated, which showed results depending on the experimental conditions. For YbPc2, the positioning of the pressure sensor affects the collapse pressure of the Langmuir films. This is only observed in semi-amphiphilic compounds. The surface potential of the Langmuir films depends on the compression speed, but these differences are not observed in LB films. A strong chemical interaction between stearic acid and RhPc was observed, which is unprecedented for phthalocyanines. The interaction seems less intense in LB films than in solution. The arcas per molecule in the condensed phase for the ytterbium and samarium bisphthalocyanines and rhodium phthalocyanine were 69, 60 and 75 Å2 and the collapse pressures were 52, 54 and 57 mN/m, respectively. These results show the similar characteristics of the diferente phthalocyanines. However, the surface potential was lower for RhPc, probably due to a smaller dipole component normal to the water surface. The electrochemical behavior of YbPc2 LB films depends on film thickness. In thicker films, ion diffusion is hindered, mainly in the cathodic process. LB films of YbPc2 and PdPc showed electrochromism, with changes in color upon the application of distinct potentials. In Raman spectroscopy using the 633 nm laser line, the most intense band occurs at 675 cm-1 for RhPc and YbPc2. PdPc behaves differently, with the most intense band at 1520 cm-1. Analyzing the results in the light of data in the literature, it was concluded that the dominating factor for the Raman spectra is the oxidation state of the metal. Yb and Rh metais are likely to be in the same oxidation state, differently from Pd . Comparing results from atomic force microscopy (AFM) and Raman mapping with LB films from YbPc2 mixed with stearic acid, it was observed that LB films with a larger amount of YbPc2 are more homogeneous

Neste trabalho foram estudados três complexos de transferência de carga formados por aminas aromáticas e SO2. As aminas escolhidas foram a N,N-dimetilanilina (DMA), N,N-dietilanilina (DEA) e N-metilanilina (NMA). A interação entre a espécie doadora (amina) e a espécie aceptora (SO2) está bem esclarecida na literatura e trata-se de um reação típica de ácido-base de Lewis, porém existem alguns aspectos inexplorados e sem registros na literatura. Um desses aspectos é o fato de que complexos formados entre as aminas aromáticas e o SO2 dão origem a soluções oleosas com coloração vermelha intensa. O máximo de absorção eletrônica (UV-VIS) desses compostos está na faixa de 350 nm, com uma cauda que se estende pela região do visível, responsável pela cor. Um fato curioso é que a cor desses complexos se altera com a variação da temperatura de forma reversível. Em baixas temperaturas o complexo torna-se amarelo pálido e em altas temperaturas, vermelho escuro muito intenso. Um dos principais objetivos deste trabalho foi reinvestigar a interação de transferência de carga entre aminas aromáticas e SO2 na tentativa de responder tal questão. Para tal, foram utilizadas técnicas espectroscópicas (Raman e Infravermelho), sobretudo a espectroscopia Raman ressonante, com o auxílio de cálculos teóricos baseados na teoria do funcional da densidade (DFT). Os espectros Raman ressonante mostraram a intensificação seletiva de uma banda em cerca de 1140 cm-1 tanto com a variação da radiação quanto com a variação de temperatura. O fato dessa banda ter sido intensificada preferencialmente em radiações de excitação na região do visível e em altas temperaturas, permitiu que fosse proposta a presença de um outro cromóforo em solução. Portanto, além do complexo já bem caracterizado com estequiometria 1:1, propôs-se a presença de um complexo com estequiometria 2:1, ou seja, duas aminas conectadas por uma molécula de SO2, formando um complexo de transferência de carga com maior deslocalização eletrônica. A comparação entre as diferentes aminas mostrou que a formação dessas espécies associadas depende de um delicado balanço entre basicidade, impedimento estérico e possibilidade de interações específicas como ligações de hidrogênio. / In this work three charge-transfer complexes formed by aromatic amines and SO2 were studied. The chosen amines were N,N-dimethylaniline (DMA), N,N-diethylaniline (DEA) e N-methylaniline (NMA). The interaction between the donor (amine) and acceptor (SO2) is well established in the literature and is classified like a typical Lewis acid-base reaction, however there are some unexplored aspects that are lacking in the literature. One of such aspects is the fact that the complexes formed between the aromatic amines and SO2 gives origin of an oily intense red color solution. The maximum of electronic absorption (UV-VIS) of these complexes is near to 350 nm, with a tail that extends along the visible region, which is responsible for the color. A curious fact is that the complex color changes with the temperature variation in a reversible manner. At low temperatures, the color complex becomes pale yellow and at high temperatures, it turns a very intense dark red solution. One of the main objectives of this work was to reinvestigate the charge-transfer interaction between aromatic amines and SO2 trying to answer this question. For this, it was utilized spectroscopic techniques (Raman and Infrared), especially resonance Raman spectroscopy, with the support of theoretical calculations based on the Density Functional Theory (DFT). The resonance Raman spectra showed the selective enhancement of a band nearly 1140 cm-1 with both, the changing of the exciting radiation and the temperature variation. The fact of this band was preferentially enhanced with visible exciting radiations and at higher temperatures, allowed the proposition of the presence of another chromophore in solution. Therefore, besides the already well characterized complex with 1:1 stoichiometry, it was proposed the presence of a complex possessing a 2:1 stoichiometry, i.e. with two amines connected by a SO2 molecule, forming a charge transfer complex with higher electronic delocalization. The comparison among the different amines showed that the formation of such associated species depends on a delicate balance between basicity, sterical hindrance and the possibility of specific interactions such as hydrogen bonding

A formação de nanocompósitos de nanotubos de carbono e certos materiais tais como óxidos e polímeros abre a possibilidade de melhorar as propriedades mecânicas e eletrônicas dos seus constituintes, tornando-os candidatos para as mais diferentes aplicações. O preparo desses nanocompósitos com propriedades desejadas requer o conhecimento do tipo de interação entre os dois materiais. Atualmente, a espectroscopia Raman é considerada uma das principais técnicas utilizadas na caracterização de compósitos contendo os nanotubos. Este trabalho tem como objetivo o estudo espectroscópico, em conjunto com outras técnicas de caracterização, na investigação de evidências de interação de compósitos envolvendo nanotubos de carbono de parede única e nanotubos de carbono de paredes múltiplas formados com o semicondutor nanoestruturado, dióxido de titânio, como também com o polímero polipirrol. Todos os compósitos foram preparados a partir dos nanotubos oxidados em ácido nítrico. Essa etapa é bastante importante, pois além de influenciar sua solubilidade, possibilita gerar grupos funcionais oxigenados nas superfícies dos tubos capazes de formar ligações com outros materiais. Através dos espectros Raman foi possível obter evidência de interação entre os constituintes do compósito, através inversão da razão das intensidades relativas das bandas D e G. No caso dos nanotubos de carbono de parede única, sugerimos a formação do nanomaterial ligado nos nanotubos externos dos feixes e as bandas Raman D e G observadas nos espectros dos compósitos são originadas dos tubos internos dos feixes de nanotubos em ressonância com a energia do laser. Considerando os nanotubos de carbono de paredes múltiplas, a presença do material de tamanho nanométrico faz com que as paredes mais externas desses nanotubos percam sua identidade como nanotubo de carbono. Assim, as características das bandas Raman D e G observadas no espectro são originadas dos tubos mais internos que são semelhantes ao nanotubo pristina. Pelo estudo Raman ressonante dos compósitos de nanotubos de carbono de parede única e polipirrol foi verificada a transferência de carga do polímero em direção ao nanotubo através das modificações tanto nas características espectrais do nanotubo quanto do polímero. Foram observados também, processos de transferência eletrônica do dióxido de titânio para os nanotubos de carbono de parede única através dos deslocamentos das frequências Raman. Foi realizado ainda um estudo comparativo dos processos de degradação do corante verde de Janus B em suspensão de dióxido de titânio e em uma mistura de dióxido de titânio e nanotubos de carbono de paredes múltiplas em diferentes valores de pH iniciais do corante. Foi observado o aumento significativo na eficiência da degradação do corante na presença do nanotubo no sistema fotocatalítico. Além disso, a investigação dos intermediários formados nos sistemas de catalisadores foi realizada através dos espectros SERS das soluções degradadas e FT-Raman dos catalisadores sólidos / The formation of nanocomposites of carbon nanotubes and certain materials such as oxides and polymers opens the possibility of improving the mechanical and electronic properties of its constituents, making them candidates for a wide range of applications. The preparation of these nanocomposites with desired properties requires the knowledge of the type of interaction between the two materials. Currently, Raman spectroscopy is considered one of the main techniques in the characterization of composites containing nanotubes. This work aims the spectroscopic study combined with other characterization techniques in investigating evidences of interaction in composites involving single-wall nanotubes and multi-wall nanotubes with the nanostructured semiconductor, titanium dioxide, as well as with the polymer polypyrrole. All composites were prepared from the oxidized nanotubes in nitric acid. This step is very important since it influences nanotubes solubility, and enables the generation of oxygenated functional groups on the surfaces of tubes, allowing further functionalization with other materials. Through the Raman spectra, it was possible to obtain evidences of interaction between the constituents of the investigated composites through the inversion in the ratio of the relative intensities of D and G bands. In the case of single-wall nanotubes, it is suggested that the formation of the nanomaterial occurs on the external nanotube bundles, and D and G Raman bands observed in the spectrum are derived from the inner tubes in the bundles in resonance with the laser energy. Considering the multi-wall nanotubes, the presence of nanosized material causes the outer walls of these nanotubes to lose their identity as carbon nanotubes. Thus, the characteristics of the Raman D and G bands observed in the spectrum are derived from innermost tubes, which are similar to pristine nanotube. The resonance Raman study of single-wall nanotubes and polypyrrole composite revealed charge transfer of the polymer into the nanotube through modifications in the spectral characteristics of the nanotube and the polymer as well. Were also observed, electron-transfer process of titanium dioxide to the single-wall nanotubes through the downshift of the characteristic nanotube Raman frequencies. A comparative study of the degradation processes Janus green B dye in titanium dioxide suspension and mixture of multi-wall nanotubes and titanium dioxide was carried out at different pH values. We observed a significant increase in the degradation efficiency of the dye in the presence of nanotubes on the photocatalytic system. Furthermore, the investigation of the intermediates formed in the catalyst systems were performed using SERS spectra of the degraded solutions and FT-Raman of solid catalysts.

<p>Dioxins and poly-chlorinated biphenyl (PCB) compounds are high priority organic pollutants which are similar in structure and well known for their toxicity, bioaccumulation and persistence in the environment. Dioxins and PCBs have a high affinity for certain types of clay minerals. However, the molecular mechanism for the observed high affinity of these compounds to clay minerals is not well understood and has been the main focus of this research work. The mechanisms that govern dioxin-clay and PCB-clay interactions were investigated from two perspectives. First, the influence of selected properties clay minerals on dioxin sorption was investigated via in-situ spectroscopic techniques (ATR-FTIRand Raman) structural (XRD) and macroscopic batch sorption methods using dibenzo-p-dioxin (DD) as a model solute. Second, the influence of solute properties, especially position and degree of chlorination and molecular planarity, on sorption was investigated.</p> <p> Smectites, especially, Cs-saponite effectively adsorbs dibenzo-p-dioxin (DD) from water with values reaching 10,000 mg kg^-1, or one weight percent which greatly exceeds that by other naturally occurring sorbents such as soil organic matter. Adsorption was promoted by clay interlayer exchangeable cations with low hydration energies, and by smectites in which negative charge in the smectite originate from the tetrahedral siloxane sheets. IR-active bands of DD sorbed to saponite in the 1280 to 1500 cm^-1region were perturbed compared to the ‘reference’ IR spectra. Combined batch sorption, XRD and spectroscopic data confirm that the intercalation of DD occurred in the clay interlayer and site specific interactions occur between DD molecule and Cs⁺ cation. </p> <p> Sorption of 1-chloro-dibenzo-p-dioxin (1-ClDD) and 2-chloro-dibenzo-p-dioxin (2-ClDD) on homoionic (Na⁺, K⁺, Rb⁺, and Cs⁺) smectites was evaluated to explore the effect of chlorine substitution position (and steric hindrance) of dioxin on sorption mechanisms. Similar to DD, adsorption was influenced by the hydration energy of exchangeable cations and the origin of negative charge in the smectite. XRD measurements revealed that 1-ClDD molecules were oriented nearly parallel to the siloxane surface of the clay while 2-ClDD adopted a tilted orientation, similar to DD. The location of the chlorine constituent in 1-ClDD prevents the molecule from its apparent energetically more favorable orientation. In-situ ATR-FTIR spectra revealed that sorption of 1-ClDD to Cs-saponite resulted in the loss of interfacial H₂O and suggested that the sorption 1-ClDD displaces interlayer H₂O and 2-ClDD is less sterically restricted in the clay interlayer. </p> <p> Sorption of three dioxins (DD, 1-ClDD and 2-ClDD) was compared to three PCBs (PCB-1, PCB-4, and PCB47) with similar octanol-partition coefficients (log K_ow) but varying molecular planarity and degree of chlorination onto Cs-saponite, which was shown to be representative of other smectites, revealed that despite having similar structure and hydrophobicity, dioxins have higher affinity for smectites than PCBs. Sorption studies also showed that sorption of PCBs is influenced by molecular planarity and hydrophobicity. Polarizability and dipole-moment were identified as important solute properties that affect the sorption behavior of dioxins and PCBSs. Linear relationships between these properties and log K_f’(subcooled liquid solubility normalized Freundlich sorption coefficient) values suggest that high sorption affinity of planar dioxins could be due to a combination of <i>Van der Waals</i> interactions with the siloxane surface, steric effects, and site-specific interactions between dioxin and exchangeable cations. In contrast, the sorption of PCBs was highly influenced by their molecular orientation.</p>

<p>Conventional rocket propellants such as monomethyl hydrazine (MMH) and hydrazine have been used for decades due to their high specific impulse and performance. However, interest in greener alternatives, including HAN or HAN-based propellants, has grown due to high levels of toxicity and difficulties in the handling and storage of conventional fuels. Included among potential propellants are monopropellants nitromethane (NM) and isopropyl nitrate (IPN) and their blends. Though large-scale investigations on the ignition and combustion of these fuels have been done, the ignition and combustion processes of these monopropellant fuels are still not well understood. Droplet studies have been traditionally and extensively employed to decipher the influence of ambient conditions and fuel properties on ignition and combustion of different fuels. These fundamental studies allow for the isolation of different factors such as ambient temperature and initial droplet size among others, to provide a deeper understanding of their effects in overall spray combustion.</p> <p> </p> <p>The research described here seeks to add to the knowledge on the ignition and combustion processes of NM and IPN through single droplet ignition and combustion studies. To this end, the first effort has been to establish a suitable method of studying the ignition and combustion of droplets in conditions similar to those in practical systems. Droplet ignition delay measurements for NM and IPN droplets have also been conducted, and the influence of ambient temperature and droplet size has been studied. The double flame structures of NM and IPN, representative of hybrid combustion, have also been observed. In addition, the applicability of the hybrid combustion model, developed to predict mass burning rates for hypergolic fuels exhibiting hybrid burning including MMH, UDMH and hydrazine, has been assessed. Lastly, the ability of the quasi-steady droplet ignition model to predict ignition delays of IPN and NM monopropellant droplets is also discussed.</p>