Universiẗat, Diss., 2004--Würzburg. / Erscheinungsjahr an der Haupttitelstelle: 2003.

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O presente trabalho é um estudo detalhado do cálculo de perfis de excitação Raman pelo método de transformada. A principal característica do método é o emprego do espectro de absorção para gerar diretamente os perfis Raman. Os programas aqui desenvolvidos para microcomputador foram testados pela comparação com perfis conhecidos da literatura, e usados para o estudo teórico de novas possibilidades de modelagem em sistemas conhecidos e também aplicados para novas espécies. Investigamos, a nível teórico , o uso do método de transformada em casos onde ocorre interferência eletrônica, e em perfis de modos não-totalmente simétricos . As novas espécies estudadas pelo método de transformada foram os íons complexos [Zn(dmit)2 ]2- and [Ni(dmit)2]2- , além da espécie TiI4, onde calculamos simultaneamente o perfil da fundamental e de harmônicas, tanto Stokes como anti-Stokes, do modo totalmente simétrico de estiramento Ti - I. Através do ajuste das intensidades relativas dos vários perfis, foi possível obter a variação da distância de equilíbrio Ti - l no estado eletrônico excitado em relação ao fundamental / The present work is a detailed study on the calculation of Raman excitation profiles by the transform method . The main feature of the transform method is to use the absorption spectra to generate the Raman excitation profiles. The computer programs here developed were tested by comparison with known profiles from the literature, and used to explore new possibilities in modelling the Raman profiles of new chemical species, as well as to improve already investigated profiles . We investigated , by use of the transform method, cases where electronic interference must be taken into account, and Raman excitation profiles of non-totally simetric modes [Zn(dmit)2 ]2- and [Ni(dmit)2]2- were now studied for the first time by the transform method. For TiI4 of the resonance profiles for the v1 fundamental and overtones, both Stokes and anti-Stokes, were calculated with a single set of parameters being possible to evaluate the displacement of the Ti - I equilibrium distance in the resonance electronic state relative to the ground state

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.

Orientador: Jorge Humberto Nicola / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-07-14T23:28:51Z (GMT). No. of bitstreams: 1 Couto_RosaMariadeOliveira_D.pdf: 2633970 bytes, checksum: 69f20bc7fca568d2a8a055e816ee59e3 (MD5) Previous issue date: 1981 / Resumo: Foi realizado um estudo através de Espalhamento Raman Eletrônico dos níveis eletrônicos da configuração fundamental do Sm2+ ( 7FJ J = 0,1,....6 ) desdobrados pelo campo cristalino do fluoreto de cálcio. Foi feita uma análise do tensor "espalhamento Ramn Eletrônico" determinando-se a forma e simetria dos tensores irredutíveis para o espalhamento Raman Eletrônico relevantes para o nosso caso, assim como as regras de seleção. Foi feit uma série de medidas do espectro RE e da banda fluorescente do Sm2+ : CaF2, usando-se como excitação as linhas 5145 Å, 4965 Å, 4880 Å, 4765 Å e UV ( 3638 Å ) de um laser de argônio, entre a temperatura de 5 K a 300 K. Foram observadas seis transições RE, que com auxilio da análise da estrutura da banda fluorescente, foram identificados como sendo transições entre os estados: 7F0 ( A1g ) ® 7F1 ( T1g ) ; 7F1 ( T1g ) ® 7F2 ( Eg ), 7F2 ( T2g ) ; 7F2 ( Eg ) ® 7F3 ( T2g ), 7F3 ( T1g ) e 7F2 ( T2g ) ® 7F3 ( T1g ) ficando ao mesmo tempo determinada as energias do níveis 7F1 ; 7F2 e 7F3 em relação ao estado fundamental 7F0. Foram feitas mediads com análise de polarização destas transições RE, sendo determinada a simetria dos picos RE como T1g, ficando então confirmado que o tensor irredutível para o RE responsável pelas transições é o a1estático. Foram feitas medidas do espectro RE Ressonante, observando-se um aumento na intensidade relativa entre as TRE observadas e as TR do fónon. Entretanto, devido a restrições experimentais, não se detectou um número de contagens suficientes que permitisse fazer-se o estudo da propriedade de antissimetria do tensor irredutível RE a1estático como é previsto pela teoria. Foi observada uma anomalia nas intensidades relativas entre as TRE em 266 cm-1, 254 cm-1 e 249 cm-1 quando a linha de excitação é a 4965 Å e o cristal está orientado. O fato de que este efeito não é observado quando o cristal não está orientado talvez seja uma indicação de que este efeito seja devido a propriedade de antissimetria do tensor irredutível a1estático. As transições RE devido ao tensor a2estático não foram observadas, possivelmente porque, como é previsto pela teoria, a intensidade do espalhamento RE devido ao tensor irredutível a2estático é muito menor comparada com a intensidade do espalhamento RE devido ao tensor irredutível a1estático / Abstract: The groud state, 7F0, and crystal field components of the 7F1, 7F2 and 7F3 manifolds of the ion Sm2+ in CaF2, have been studied by Eletronic Raman Spectroscopy. A theory of the scattering tensor for Eletronic Raman transitions ( ERT ) without the severe approximations usually emploeyd hes been developed. Both the symmetric and antissymmetric part of the irreducible spherical representation of the scattering tensor were determinad,as well as the selection rules for the Eletronic Raman effect for Sm2+ in CaF2. Six ERT were observed.With the aid of the fluorescence band spectrum these features were identified as the transitions: 7F0 ( A1g ) ® 7F1 ( T1g ) ; 7F1 ( T1g ) ® 7F2 ( Eg ), 7F2 ( T2g ) ; 7F2 ( Eg ) ® 7F3 ( T2g ), 7F3 ( T1g ) and 7F2 ( T2g ) ® 7F3 ( T1g ). The energy of these states relative to the ground state 7F0 were determinated. The symmetry of the ERT was determinated experimentally by polarized Eletronic Raman Spectroscopy as T1g. This fact confirm that the irreducible scattering tensor a1static is the responsable for all the ERT observed. The Ressonant Eletronic Raman Effect has also benn investigated. An anhancement in the intensity of the ERT as comparated with the Raman transition by phonon was observated. For oriented sample as anomaly in the relative intensities of the features at 249 cm-1, 254 cm-1 and 266 cm-1 was observed when excited by the 4965 Å Laser line. This suggests that this effect is related to the propertie of antisymmetry of irreducible scatering tensor a1static. The ERT by irreducible scattering tensor a2static was not observed. This can be expected since in our case the symmetric part of the irreducible scattering tensor can be negleted as compared with the antisymmetric part / Doutorado / Física / Doutor em Ciências

Pas de résumé en français / One of the new challenges of conservation science is the development of field instrumentation to analyze works of art. In order to get the most information on the material, it is often necessary to perform complementary analyses by juggling different analytical techniques. This time-consuming drawback involves a difficulty to analyze the artwork on the same spot of the surface. However, some of spectroscopies have in common to use the same laser as excitation source and the collection of the emitted signal could be recorded by the same spectrometer. In this spirit, the aim of this research project is the development of a hybrid system in laboratory grouping together three analytical techniques (LIBS, LIF and Raman spectroscopy) in a single instrument. The relevance for combining these three spectroscopies is to identify a material (molecular and elemental analysis) without any preliminary preparation, regardless of its organic or inorganic nature, on the surface and in depth, without any surrouding light interference thanks to time-resolution. Such instrumentation would allow to characterize different materials from cultural heritage such as copper corrosion products and wall paintings organized in stratigraphic layers which are the example of applications in this work. A complete study on LIBS-LIF-Raman hybrid was carried out from conception to instrumental achievement, as well as automatic control to data fusion processings in order to elaborate a strategy of analysis according to the material and to be able to address conservation issues.

Surface enhanced Raman scattering (SERS) has achieved much attention since its conception in 1974. The analytical technique overcomes many difficulties associated with conventional Raman whilst also increasing sensitivity. However, the increased interest and work in the field has also identified flaws, many of which are centred on the irreproducibility of the SERS enhancement effect. The majority of the work described in this thesis focusses on the ‘optimisation’ of solid-state and solution based SERS systems. Optimisation plays a crucial role in maximising both enhancement effects and reproducibility. Here criteria are outlined for the synthesis of high performance solid-state SERS substrates and the synthesis of a range of substrates is assessed, each with associated pros and cons. The most successful substrate was synthesised by exploiting redox potentials which allow for the direct deposition of silver onto copper foil. The deposition times and temperatures were optimised sequentially to generate a high performance substrate capable of detecting Rhodamine 6G at trace levels. Reproducibility comparisons of the silver on copper (SoC) substrate were carried out against commercial substrates: Klarite and QSERS, multiple univariate and multivariate methods were used to assess the substrates performance. The results confirmed that the SoC substrate performed better than both the commercial substrates. The work also highlights the importance of using multiple data analysis methods in order to assess the performance of a solid-state SERS substrate. Deposition of the silver surface was also successful on British 2p coins allowing the for the detection and discrimination of illegal and legal drugs when coupled with multivariate data analysis methods such as PCA and PLS. Solution based SERS analyses were also carried out successfully using different optimisation strategies. The initial investigation involved careful control of the individual components of a SERS system (nanoparticles, aggregating agents and analyte) in order to establish a low limit of detection for the increasingly abused ‘legal high’ MDAI. The use of a reduced factorial design was then successfully employed to explore a greater number of SERS variables and define a low limit of detection for the class B drug mephedrone. The robust experimental design also allowed an insight into the importance of each of the individual components within a solution based SERS system. The final piece of work carried out was the SERS discrimination of antibiotics: ampicillin, ticarcillin and carbenicillin. Optimisation of the solution based experiment allowed the in-situ hydrolysis of the β-lactam moiety present in ampicillin rendering it pharmacologically inactive to be followed under acidic conditions at concentrations of 10 ppm.