The solar radiation in general and UV radiation in particular has been recognized to stimulate plant litter decomposition through photochemical mineralization of photosensitive organic molecules, such as lignin, facilitating microbial decomposition, with great relevance role in dryland ecosystems where microbial activity is low, however little is known about how photodegradation could influence other ecosystems without moisture limitations and under what conditions may be favored, therefore the mechanisms has not yet been established. Decomposition in tropical ecosystem is a complex process and can be induced by a number of environmental factors with certain differences when compared to arid and semi-arid ecosystems. To assess the mechanisms underlying UV-B photodegradation, we designed a 300 days field experiment at a tropical ecosystem with high levels of annual precipitation and exposure litter to three levels of radiation combined with a biocide treatment. Results show that the removal of UV-B radiation decelerated plant litter decomposition during the later stage compared to litter exposure to full sun, however shaded litter had similar mass loss compared to litter exposed to full sun. Furthermore, differences in the decay constant among radiation treatments due to UV-B effect is independent of lignin loss. Overall, our study suggest that UV-B contributes to the plant litter decomposition through carbon losses, however, had no effect on nitrogen, neither lignin nor cellulose loss. However, more studies are needed in order to investigate the positive and negative effects of UV exposure on microbial activity in tropical ecosystems. / A radiação solar em geral e a radiação ultravioleta (UV) em particular têm sido reconhecida por estimular a decomposição da serapilheira através da mineralização fotoquímica de moléculas fotossensíveis, como a lignina, facilitando a decomposição microbiana, com um papel de grande relevância em ecossistemas áridos onde a atividade microbiana é baixa, no entanto pouco se sabe como a fotodegradação pode influenciar outros ecossistemas como por exemplo os mais úmidos e sob quais condições a fotodegradação é favorecida, portanto os mecanismos ainda não foram estabelecidos. Decomposição em ecossistemas tropicais é um processo complexo e pode ser influenciado por vários fatores ambientais e com certas diferenças quando comparada com ecossistemas áridos e semiáridos. Para avaliar os mecanismos subjacentes à fotodegradação via radiação UV-B, um experimento de campo de 300 dias foi estabelecido em um ecossistema tropical com alto índice de precipitação anual onde a serapilheira foi exposta a três níveis de radiações diferentes, combinada com um tratamento com biocida. Resultados mostram que a remoção da radiação UV-B desacelerou a decomposição da serapilheira durante o último estágio do experimento comparado com a serapilheira exposta a radiação ambiente, no entanto a serapilheira quando sombreada teve perda de massa similar à exposta a radiação ambiente. Além disso, diferenças na taxa de decaimento entre os tratamentos de radiação devido ao efeito da radiação UV-B foram independentes da perda de lignina. No geral, nosso estudo sugere que a radiação UV-B contribui com a decomposição da serapilheira através da perda de carbono, no entanto não teve efeito na perda de massa de nitrogênio, lignina e celulose. Portanto, mais estudos são necessários para investigar o efeito positivo e negativo da exposição à radiação UV-B na atividade microbiana e na decomposição da serapilheira em ecossistemas tropicais.

Submitted by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2018-04-20T13:07:11Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação Jucilene Lopes.pdf: 2211418 bytes, checksum: 953a473330915d500a4941021f07c45c (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2018-04-20T13:08:40Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação Jucilene Lopes.pdf: 2211418 bytes, checksum: 953a473330915d500a4941021f07c45c (MD5) / Made available in DSpace on 2018-04-20T13:08:40Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação Jucilene Lopes.pdf: 2211418 bytes, checksum: 953a473330915d500a4941021f07c45c (MD5) Previous issue date: 2017-10-30 / FAPEAM - Fundação de Amparo à Pesquisa do Estado do Amazonas / Metallic sulfates when used to modify acidic solids have conferred an increase in the acidity of the acidic sites of Lewis and Brønsted, presenting Hammett acidity constant superior to that of sulfuric acid, being called superacid materials. For this reason, superacid materials have been developed and used in many catalytic reactions. In this work the nickel sulfate (NiSO4) and metakaolinite obtained from the kaolinite soil of Manaus - AM were used to synthesize superacid materials varying NiSO4 concentration and calcination temperature. The materials were characterized by chemical analysis (FRX), thermogravimetry (TGA), Infrared Spectroscopy with Fourier Transform (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), adsorption-desorption of N2 (BET method) and still the acidity of the materials was studied by infrared spectroscopy technique of adsorbed pyridine. The catalytic activity was investigated by photodegradation of methylene blue. The characterization results showed that the addition of sulfate ions on the surface of metakaolinite did not alter the structure and morphology of the catalytic support. Bands relative to Lewis acid sites were observed at 1445 and 1607 cm -1 and Brønsted at approximately 1638 cm -1. The metakaolinite sample showed a 43.2% degradation of methylene blue, presenting better performance among all samples tested. Therefore, the characterization of the materials showed that there was interaction between the nickel sulfate and the catalytic support, resulting in the obtaining of the superacid materials and also the addition of nickel sulfate in the catalytic support caused some modification in the surface acidity of metakaolinite. However, the catalytic tests showed that the superacid materials had little catalytic activity for methylene blue photodegradation reactions. / Sulfatos metálicos quando utilizados para modificar sólidos ácidos tem conferido um aumento na acidez dos sítios ácidos de Lewis e Brønsted, apresentando constante de acidez de Hammett superior ao do ácido sulfúrico, sendo chamados de materiais superácidos. Por esse motivo, materiais superácidos têm sido desenvolvidos e utilizados em muitas reações catalíticas. Nesse trabalho o sulfato de níquel (NiSO4) e metacaulinita obtida de solo caulinitico de Manaus – AM, foram utilizados para sintetizar materiais superácidos variando concentração de NiSO4 e temperatura de calcinação. Os materiais obtidos foram caracterizados por meio de análise química (FRX), termogravimetria (TGA), infravermelho com transformada de Fourier (FTIR), difração de raios X (DRX), microscopia eletrônica de varredura (MEV), adsorção-desorção de N2 (método BET) e ainda a acidez dos materiais foram estudadas por meio da técnica de espectroscopia na região do infravermelho de piridina adsorvida. A atividade catalítica foi investigada por meio da fotodegradação do azul de metileno. Os resultados de caracterização mostraram que a adição de íons sulfatos na superfície da metacaulinita não alterar a estrutura e morfologia do suporte catalítico. As bandas referentes aos sítios ácidos de Lewis foram observadas em 1445 e 1607 cm-1 e de Brønsted em aproximadamente 1638 cm–1. A amostra de metacaulinita apresentou 43,2% de degradação do azul de metileno, apresentando melhor desempenho entre todas as amostras testadas. Portanto, a caracterização dos materiais demonstrou que houve interação entre o sulfato de níquel e o suporte catalítico, resultando na obtenção dos materiais superácidos e ainda a adição de sulfato de níquel no suporte catalítico causou alguma modificação na acidez superficial da metacaulinita. Porém, os testes fotocatalíticos demonstraram que os materiais superácidos apresentaram pouca atividade catalítica para reações de fotodegradação do azul de metileno.

Submitted by Marilene Donadel (marilene.donadel@unioeste.br) on 2018-10-31T19:51:37Z No. of bitstreams: 1 Pablo_Pretto_2017.pdf: 4307957 bytes, checksum: c984bdcee5f8ac1801f6afea4050e774 (MD5) / Made available in DSpace on 2018-10-31T19:51:38Z (GMT). No. of bitstreams: 1 Pablo_Pretto_2017.pdf: 4307957 bytes, checksum: c984bdcee5f8ac1801f6afea4050e774 (MD5) Previous issue date: 2017-03-13 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The microcontaminants occurrence, such as pharmaceuticals found in the environment, causes concern about the environmental impact of the pollution from anthropic activities. Thus, this work aimed the evaluation of the photocatalytic system efficiency in removing the sulfamethoxazole active principle, using the titanium dioxide (TiO2) catalyst impregnated in grinded glass with two different particle sizes. The catalyst impregnation was performed by two methods: A overlay and B solvothermal. The obtained materials were characterized by total reflection X ray fluorescence (TXRF), X ray diffraction (XRD), Scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), thermogravimetry (TG) and nitrogen physisorption. Considering the results, the TiO2 was verified in the grinded glass carrier, achieving a 2.5% immobilization proportion. The DRX analysis evidenced the presence of the anatase crystalline phase in the catalyst of used methods. Method A achieved the best catalyst fixation on the carrier. The photocalytic assays indicated a SMX removal of 97% for method A and 71% for method B after 360 minutes of reaction. The kinetic analysis indicated the pseudo first order model as the one that best fit the experimental data with degradation constants of 0.008 and 0.004 min-1 for the SMX methods A and B, respectively. The system efficiency is reduced as a function of the photodegradation assays reproducibility due to the catalyst loss by erosion to the SMX aqueous phase. The difference on the efficiency between methods A and B is probably due to the different proportion of anatase crystalline phase that is present in each support impregnation method. According to the toxicological essays, the treated samples presented higher toxicity when compared to the raw one, which possibly occurred because of a partial mineralization of the SMX and the production of intermediate compounds. / A ocorrência de microcontaminantes, tais como produtos farmacêuticos encontrados no meio ambiente despertam preocupações devido ao impacto ambiental derivado da poluição gerada pelas atividades antrópicas. Diante disso, o objetivo deste foi avaliar a eficiência do sistema fotocatalítico na remoção do princípio ativo sulfametoxazol, utilizando o catalisador dióxido de titânio (TiO2) imobilizado em vidro moído, de duas granulometrias diferentes. A impregnação do catalisador foi realizado pelo método direto de recobrimento de TiO2 e pelo método solvotérmico de produção de TiO2. Os materiais obtidos foram caracterizados por fluorescência de raio X com reflexão total, difratometria de raios X (DRX), microscopia eletrônica de varredura (MEV) com espectroscopia por energia dispersiva (EDS), termogravimetria (TG) e fisissorção de nitrogênio. Considerando os resultados foi possível visualizar a presença de TiO2 fixado nos suportes de vidro moído, num teor de TiO2 2,5% em massa. As análises de (DRX), permitiram verificar que a fase cristalina anatase está presente nos catalisadores dos obtidos pelos dois métodos utilizados. Observou-se que o método direto proporcionou-se a melhor fixação do catalisador no suporte. Os ensaios fotocatalíticos indicaram remoção de SMX foi de 97% pelo uso de catalisador obtido pelo método direto e de 71% com o catalisador obtido pelo método solvotérmico após 360 minutos de reação. A análise de cinética da recirculação fotocatalitica indicou que o modelo pseudo-primeira ordem melhor se ajustou aos dados experimentais, com constante de degradação de 0,008 e 0,004 min-1 para método direto e solvotérmico respectivamente. A eficiência do sistema reduziu em função da repetibilidade dos ensaios de fotodegradação, devido a perda do catalisador por erosão para o meio da solução aquosa de SMX. Provavelmente essa diferença na eficiência dos método de impregnação, seja pela diferença na proporção da fase cristalina anatase presente para cada método de impregnação no suporte. Os ensaios toxicológicos indicaram que as amostras tratadas apresentaram maior toxicidade que a amostra bruta, provavelmente pelo fato de ocorrer uma mineralização parcial da SMX e a produção de produtos intermediários.

O uso de técnicas espectroscópicas para o estudo de questões ambientais é uma área de pesquisa que vem experimentando importante desenvolvimento em tempos recentes. Essas técnicas abrangem métodos espectroscópicos intensificados, que proporcionam grande sensibilidade e seletividade para a detecção de espécies químicas em baixas concentrações. Nesta dissertação, propomos a introdução de uma nova metodologia aplicada ao estudo da fotodegradação de moléculas de interesse ambiental. Utilizamos técnicas de espectroscopia Raman intensificada pela superfície (SERS) para a análise dos processos de fotodegradação de azo-corantes mediados por dióxido de titânio. Nosso primeiro passo para o desenvolvimento dessa metodologia foi realizar um estudo comparativo acerca de diferentes métodos para preparação de um substrato SERS-ativo - sobre cuja superfície viríamos a proceder a fotodegradação de corantes e simultaneamente o estudo espectroscópico desse processo. A dificuldade na preparação do substrato reside no fato de que é necessário produzir uma superfície simultaneamente fotocatalítica (pela presença do semicondutor TiO2) e com atividade SERS (pela presença de partículas de Ag nanoestruturadas). Assim, três diferentes métodos para a preparação do substrato foram estudados, buscando obter atividade SERS aliada à reprodutibilidade. Escolhido o método mais satisfatório, utilizamos o substrato para realizar estudos SERS dos processos de fotodegradação de dois corantes: vermelho do Congo e verde de Janus. Considerando que a degradação fotocatalítica pode envolver oxidação e redução das moléculas, foi realizado também o estudo espectroeletroquímico dos dois corantes, buscando correlações que ajudassem a esclarecer as transformações envolvidas nas etapas iniciais da fotodegradação dessas substâncias. Nossos estudos revelaram que as primeiras etapas dos processos de fotodegradação dos dois corantes seguem mecanismos diferentes: enquanto no caso do vermelho do Congo há evidências de oxidação, no caso do verde de Janus as evidências apontam para um processo de redução. A combinação de dados da fotodegradação de corantes com seu estudo via eletroquímica - utilizando técnicas de espectroscopia intensificada para a identificação e caracterização de produtos - mostrou-se bastante promissora, no sentido de oferecer informações relevantes sobre os complexos mecanismos envolvidos nos processos de fotodegradação. / The use of spectroscopic techniques for the study of environmental questions is a research area has been experiencing important developments in recent years. These techniques embrace intensified spectroscopic methods, which offer great sensibility and selectivity for the detection of chemical species in low concentrations. In this work, we propose the introduction of a new methodology to be applied to the study of photodegradation of environmentally relevant molecules. We employed surface-enhanced Raman spectroscopy to the analysis of photodegradation of azo-dyes mediated by titanium dioxide. First, we performed a comparative study concerning the different methods for the preparation of SERS-active substrate, onto which we would carry out simultaneously the photodegradation of dyes and the spectroscopic study of the process. The difficulty in the preparation of such substrates resides in the fact that it is necessary to produce a surface which is all together photocatalytic (by the presence of the semiconducting TiO2) and SERS-active (by the presence of nanostructured silver). In this context, three different preparation methods were investigated, with the purpose of achieving good SERS activity and reproducibility. The optimized SERS-active substrate was employed to study the photodegradation of two azo-dyes: Congo red and Janus green. Considering that the photocatalitic degradation process might involve either the oxidation or the reduction of molecules, the spectroelectrochemical study of both dyes was also performed, in order to in order to search for important correlations that would help to clarify the transformations involved in the initial steps of the photochemical decomposition of these substances. The obtained results revealed that the first steps of the degradation processes of both dyes followed different routes: whereas for Congo red there are evidences of an oxidation process, for Janus green the evidences point to a reduction mechanism. The combination of the data relative to the photochemical behavior of the dyes and their electrochemical study - using enhanced spectroscopic techniques for identification and characterization of products - has proven to be very promising, in the sense of offering relevant information with respect to the complex mechanisms that are involved in photodegradation processes.

A lercanidipina (LER) é uma dihidropiridina bloqueadora de canais de cálcio disponível comercialmente como uma mistura racêmica, ou seja, uma mistura equimolar dos enantiômeros (R)-LER e (S)-LER. Os efeitos farmacológicos da LER residem essencialmente no enantiômero (S)-LER, e estudos in vitro mostram que este enantiômero apresenta cerca de 100-200 vezes maior afinidade pelos canais de cálcio que o enantiômero (R)-LER. Consequentemente, os efeitos farmacodinâmicos da LER são devidos, principalmente, ao enantiômero (S)-LER. Neste sentido, fármacos racêmicos são exaustivamente estudados, para avaliar suas propriedades farmacocinéticas e farmacodinâmicas estereosseletivas e verificar se existem vantagens na produção do enantiômero puro. Além disso, devido às diferenças na atividade dos enantiômeros, é imprescindível realizar o controle de qualidade enantiosseletivo destas formulações. Associado a isto, as moléculas pertencentes a esta classe de fármacos são fotossensíveis. Assim, o objetivo deste trabalho foi desenvolver e validar um método enantiosseletivo para análise da LER e aplicá-lo no controle de qualidade de formas farmacêuticas e também avaliar sua fotodegradação. A análise enantiosseletiva da LER e aplicação no controle de qualidade de formas sólidas foi realizado por eletroforese capilar (CE) utilizando tampão acetato de sódio 200 mmol L-1, pH 4,0 como eletrólito de corrida, adicionado de TM-?-CD (2, 3, 6-O-metil-?-ciclodextrina) 10 mmol L-1 como seletor quiral, na temperatura de 15 °C e 25 kV de tensão. Os parâmetros de desempenho analítico, linearidade, precisão, exatidão, limite de quantificação e detecção, seletividade e robustez foram avaliados e estão de acordo com os requisitos preconizados pelos guias oficiais. O método foi aplicado para análise de comprimidos comerciais contendo LER, e mostrou ser adequado para quantificação das amostras, apresentando valores de coeficiente de variação (CV, %) e erro relativo (E, %) inferiores a 5 %. Além disso, foi avaliada a fotoestabilidade dos enantiômeros da LER na mistura racêmica e também dos enantiômeros separados, quando expostos à luz UVC (254 nm) e visível, por HPLC. A separação dos enantiômeros da LER foi alcançada empregando a coluna quiral Chiralpak® AD 250 × 4,6 mm, partículas de 10 ?m e fase móvel composta por hexano-etanol-dietilamina (97:3:0,3, v/v/v) e vazão de 1,0 mL min-1. O método foi validado e aplicado nos estudos de fotodegradação em soluçãos-padrão de LER. Em relação à exposição na luz UVC (254 nm) e visível foi observada degradação significativa dos enantiômeros da LER após 0,5 h de exposição. Além disso, os produtos de degradação foram caracterizados por LC/MS/MS e foi observada que a principal fragmentação ocorre no anel dihidropiridínico, assim como para outros fármacos desta classe, formando piridinas sem efeitos farmacológicos. / Lercanidipine (LER) is a dihydropyridine calcium channel blocker commercially available as a racemic mixture, or an equimolar mixture of enantiomers (R) and LER (S)-LER. The pharmacological effects of LER essentially reside in the enantiomer (S)-LER, and in vitro studies show that this enantiomer has about 100-200 times greater affinity for calcium channels that the enantiomer (R)-LER. Consequently, the pharmacodynamic effects of LER are due mainly to the enantiomer (S)-LER. Thus, racemic drugs are extensively studied to evaluate their pharmacokinetic and pharmacodynamic properties stereoselective and check if there are advantages in the production of pure enantiomer. Moreover, due to differences in the activity of the enantiomers is essential to perform quality control enantioselective these formulations. Additonally, the molecules of this class of drugs are photosensitive. The objective of this study was to develop and validate a method for enantioselective analysis of LER and apply it in the quality control of pharmaceutical forms and also evaluate their photodegradation. The enantioselective analysis of LER and application in quality control of solid forms was performed by capillary electrophoresis (CE) using sodium acetate buffer 200 mmol L-1, pH 4.0 as background electrolyte, 10 mmol L-1TM-?-CD (2, 3, 6-O-methyl-?-cyclodextrin) as chiral selector, at temperature of 15 °C and 25 kV voltage. The analytical parameters, linearity, precision, accuracy, limit of quantification and detection, selectivity and robustness were evaluated and accordance with the requirements recommended by official guideline. The method was applied for the analysis of commercial tablets containing LER, and proved to be suitable for quantification of the samples, with of CV (%) and E (%) less than 5%. In addition, the photostability was evaluated on the LER enantiomers and racemic mixture of the enantiomers also separated when exposed to UVC (254 nm) and visible light by HPLC. Separation of enantiomers of LER was achieved using the chiral column Chiralpak ® AD 250 × 4.6 mm, particles of 10 micrometres and a mobile phase composed of hexane-ethanol-diethylamine (97:3:0.3 v/v/v ) and flow rate of 1.0 mL min-1. The method was validated and applied in studies of photodegradation of standard solutions of LER. The method was validated and applied in studies of photodegradation in soluçãos standard of LERR With relation to UVC exposure (254 nm) and visible light, significant degradation was observed after 0.5 hour exposure of the solution containing the racemic mixture and after 1 h of exposure the solution containing the isolated enantiomers of LER. Also, the degradation products were characterized by LC/MS/MS and it was observed that the major fragmentation occurs in dihydropyridine ring, as well as other drugs of this class, forming pyridines no pharmacological effects.

Le processus de photo-oxydation induite a été étudié au laboratoire en conditions contrôlées à l’aide de cultures non-axéniques sénescentes de diverses souches phytoplanctoniques. Le suivi de la dégradation de l’acide cis-vaccénique (marqueur bactérien) nous a permis de confirmer l’existence d’un flux d’1O2 des phytodétritus vers les bactéries attachées et de mettre en évidence une corrélation significative entre l’état de photodégradation des bactéries et la concentration en chlorophylle a (photosensibilisateur) des cellules phytoplanctoniques. Nous avons également démontré que les photoproduits formés au sein des bactéries et du phytoplancton (hydropéroxyacides) étaient rapidement dégradés dans nos conditions expérimentales en cétoacides et hydroxyacides correspondants. L’effet des matrices siliceuses et carbonatées sur l’efficacité du transfert d’1O2 des phytodétritus vers les bactéries attachées a également été étudié. Les résultats ont montré que contrairement aux matrices carbonatées (coccolithes) des coccolithophoridés, les matrices siliceuses (frustules) des diatomées, inhibaient fortement le transfert de l’1O2 limitant ainsi la photodégradation des bactéries attachées. L’étude des effets de l’1O2 sur la dynamique des communautés bactériennes attachées aux phytodétritus a montré que près de 90 % des bactéries attachées étaient mortes dans une culture d’E. huxleyi en phase stationnaire prolongée et que les bactéries vivantes étaient dominées par des bactéries pigmentées dont la résistance à l’1O2 serait liée à leurs fortes teneurs en caroténoïdes. Des analyses en DGGE ont montré que la diversité bactérienne était affectée par l’irradiation lumineuse. / Induced photo-oxidation processes were studied in the laboratory under controlled conditions using non- axenic senescent cultures of several phytoplankton strains. The monitoring of the cis- vaccenic acid (bacterial marker) degradation allowed us to confirm the existence of a 1O2 flow from phytodetritus to the attached bacteria and to highlight a significant correlation between the photodegradation state of bacteria and chlorophyll a (photosensitizer) concentration in phytoplankton cells. We also demonstrated that photoproducts formed, within bacteria and phytoplankton (hydroperoxyacids), were rapidly degraded under our experimental conditions into corresponding ketoacids and hydroxyacids. The effect of siliceous and carbonate matrices (mineral polar medium) on the efficiency of singlet oxygen transfer from phytodetritus to the attached bacteria was also studied. Results showed that, in contrast to the carbonate matrix (coccoliths) of coccolithophorids, siliceous matrix (frustules) of diatoms, strongly inhibited the transfer of 1O2, thus limiting the photodegradation of attached bacteria. The study of the effects of 1O2 on the dynamics of bacterial communities attached to phytodetritus showed that nearly 90 % of attached bacteria were killed in a culture of E. huxleyi in late stationary phase and showed that living bacteria were dominated by pigmented bacteria whose resistance toward 1O2 results likely from their high carotenoid contents. DGGE and lipid tracer analyses showed that bacterial diversity was significantly affected by light irradiation.

Les lampes à LEDs s’imposent comme la solution d’avenir pour l’éclairage vert de demain. Malgré des durées de vie annoncées par les constructeurs supérieures à 50 000h, une dérive prématurée de la qualité colorimétrique a été constatée. Ce travail de thèse porte sur l’influence de la photodégradation sur les propriétés optiques de l’un des composants d’un module LED : le composite luminescent qui est associé à la puce semi-conductrice. Des composites luminescents ont été élaborés à partir d’une matrice polymère (EVA ou PMMA) et d’un luminophore inorganique : Y3BO6 : 15% Eu3+. L’évolution des propriétés physico-chimiques et optiques de ces composites a été étudiée sous irradiation dans des conditions accélérées (λ>300 nm) et dans les conditions d’usage (LED UV, λ=365 nm). Le luminophore n’a pas montré d’effet prodégradant sur la photooxydation du polymère. Une perte des propriétés optiques du composite sous l’effet de la photodégradation du polymère a été mise en évidence dans le cas de la matrice EVA. L’évolution des paramètres photométriques de la lumière émise par les composites luminescents au cours du photovieillissement a pu être reliée à l’accumulation des photoproduits dans les films. En revanche, pour les composites PMMA/luminophore, la structure chimique et les propriétés optiques de ces composites ne sont pas modifiés pour des durées de photovieillissement accélérés de 4000h. / Phosphor-converted LEDs are emerging as an eco-friendly solution for the next generation lighting. Despite lifetimes claimed over 50 000h, a loss of the optical properties was noticed. This work focuses on the influence of photodegradation of the materials on the optical properties of the polymer/phosphor composite that is used to encapsulate the semiconductor chip. Luminescent composites were made from a polymer matrix (EVA or PMMA) and an inorganic phosphor: Y3BO6 :15% Eu3+. The evolution of physical, chemical and optical properties of these composites was investigated under irradiation in accelerated conditions (λ>300 nm) and in the use conditions of UV LED (λ=365 nm). The phosphor showed no pro-degrading effect on the photooxidation of the polymer. A loss of the optical properties of the composite was observed and ascribed to the photodegradation of the polymer in the case of the EVA matrix. The evolution of photometric parameters of the emitted light by the luminescent composite during photoaging can be attributed to the accumulation of photoproducts in films. However, for PMMA/phosphor composites, the chemical structure and optical properties of such composites are kept for accelerated photoaging time up to 4000h.

L’activité agricole présente la principale source de contamination de l’atmosphère par les pesticides. Les niveaux de concentration des pesticides dans l’atmosphère méritent une attention particulière de la part de la recherche compte tenu de leurs impacts potentiels sur la population et les écosystèmes. Bien que la volatilisation depuis la plante soit reconnue plus intense et plus rapide que la volatilisation depuis le sol, cette voie de transfert est à ce jour la moins bien renseignée avec peu de modèles disponibles pour sa description. Le manque de connaissances est lié essentiellement à la complexité des interactions entre les processus ayant lieu à la surface de la feuille et qui sont en compétition avec la volatilisation, notamment la pénétration foliaire et la photodégradation. Un système de chambre de volatilisation a été développé afin d’étudier d’une manière simultanée les processus de volatilisation et de pénétration foliaire. Les expérimentations réalisées avec 3 fongicides (époxyconazole, chlorothalonil et fenpropidine) appliqués sur feuilles de blé ont permis une description affinée du processus de pénétration foliaire grâce au protocole d’extraction des feuilles mis en place. Des coefficients de pénétration indispensables à la modélisation du devenir des pesticides à la surface des feuilles ont été calculés ainsi que des relations entre les propriétés physico-chimiques des pesticides et les processus qui contrôlent leur distribution sur et dans la feuille. L’étude expérimentale portant sur le processus de photodégradation a consisté en une irradiation de films de cire simulant les feuilles de blé traités avec des pesticides dans un simulateur solaire Suntest. Les résultats ont démontré que les pertes par photodégradation sont négligeables dans les conditions expérimentales et les pesticides choisis. Le modèle d’échange Sol-Végétation-Atmosphère SURFATM a été adapté aux pesticides selon une approche inspirée du modèle PEARL avec dans un premier temps des coefficients empiriques des processus de pénétration et de photodégradation. L’originalité de ce modèle réside dans sa description mécaniste des conditions micro-météorologiques à l’intérieur du couvert végétal. Ensuite, une approche de distribution des résidus de pesticides dans différents compartiments de la surface foliaire a été définie en se basant sur les résultats expérimentaux, permettant ainsi de prédire la fraction disponible à la volatilisation. La combinaison de cette approche avec les relations déduites entre les propriétés physico-chimiques des pesticides et le processus de pénétration foliaire améliore la généricité du modèle. Par ailleurs, l’effet de la formulation observé expérimentalement a été intégré via des coefficients empiriques permettant ainsi de mieux simuler les flux de volatilisation des produits systémiques. La comparaison entreles sorties du modèles et les résultats expérimentaux recueillis à partir de deux jeux de données acquis sur deux sites différents donne des résultats satisfaisants. Une fois activée la volatilisation depuis le sol, le modèle SURFATM-Pesticides permettra de prédire les émissions vers l’atmosphère de pesticides par volatilisation depuis les parcelles traitées. / The agricultural activity presents the main source of the atmospheric contamination by pesticides. The occurrence of pesticides in the atmosphere concerns the research community due to their potential impacts on population and ecosystems. The volatilization from plants is higher and faster than the volatilization from soil. However, this transfer pathway is difficult to assess with few available models. The lack of knowledge on pesticide volatilization from plants is essentially linked to the complex interactions between processes occurring at the leaf surface and competing with volatilization, such as leaf penetration and photodegradation. A laboratory volatilization chamber was developed in order to study simultaneously the processes of volatilization and leaf penetration of 3 fungicides (epoxyconazole, chlorothalonil and fenpropidine) applied on wheat leaves. These experimentations allowed a refined description of leaf penetration process using a well-defined sequential extraction procedure of leaves. Leaf penetration coefficients, which are necessary to modelling the pesticide fate in plants, were calculated. Moreover relationships between physicochemical properties of pesticides and processes regulating their distribution on and in plant leaves were identified. The experimental study on the photodegradation process consisted in irradiating wax films using simulated solarlight. The results showed that for experimental conditions and pesticides chosen in our study, photodegradation seems to have played a minor role as dissipation process.The soil-vegetation-atmosphere exchange model SURFATM was adapted for pesticides using an approach inspired from the parameterization developed in the PEARL model. The originality of this model resides in its mechanistic description of the micro-meteorological conditions inside the canopy. As a first step the SURFATM-Pesticides model describes leaf penetration and photodegradation processes using empirical coefficients. Then a distribution of pesticide residues in the different compartments of the leaf surface was identified based on the experimental results. This approach allowed the quantification of pesticide fraction on the leaf surface available for volatilization. The combination of this compartmental approach and the identified relationships between physicochemical properties of pesticides and the leaf penetration process improves the genericity of the model. Moreover, the effect of the pesticide formulation in the commercial preparations was integrated in the model via empirical coefficients allowing a better simulation of the volatilization fluxes in the case of systemic pesticides. Comparison of model results and experimental measurements collected from two datasets showed satisfactory results. Once the contribution of soil volatilization has been activated, the SURFATM-Pesticides model will allow us to predict the overall pesticide volatilization at the field scale.

Ce travail est consacré à l’étude du comportement photochimique d’un encapsulant multifonctionnel de cellules photovoltaïques organiques (CPO) dont la finalité est d’augmenter à la fois la durée de vie et le rendement de conversion des cellules. L’étude rapportée dans ce manuscrit porte sur le développement d’un revêtement permettant la conversion lumineuse du rayonnement UV solaire, ce dernier étant un facteur important de dégradation des CPO à base de P3HT et ne contribuant que faiblement à la conversion photovoltaïque. Dans un premier temps cette étude a porté sur l’élaboration d’une couche de conversion à partir d’une matrice polymère en EVA et d’une charge luminescente inorganique (SrAl2O4 : Eu2+, Dy3+). Dans un second temps, l’évolution des propriétés physiques et chimiques de cette couche de conversion sous irradiation à des longueurs d’onde supérieures à 300 nm a été étudiée. La présence des charges s’est révélée être un facteur pro-dégradant des films composites, sans pour autant que le mécanisme de dégradation du polymère ne soit affecté. L’étude des conditions de propagation de la lumière dans les films diffusants par l’application de la théorie de Mie a mis en évidence une possible augmentation du trajet optique des photons dans certains films composites. Ce phénomène pourrait contribuer à expliquer l’origine du comportement photochimique particulier des films étudiés. C’est finalement une preuve de concept qui a été recherchée pour l’utilisation d’un revêtement multifonctionnel pour l’amélioration et la conservation des propriétés de conversion d’une CPO à base de P3HT. / This work is devoted to the study of the photochemical behavior of a multifunctional coating dedicated to the encapsulation of organic solar cells (OSC), elaborated with the aim of improving both the lifetime of the cells and their efficiency. The study reported in this manuscript focuses on the development of a coating allowing the conversion of UV sunlight, this last greatly damaging P3HT based OSC and poorly contributing to the photovoltaic conversion. A composite film was then elaborated by incorporating an inorganic luminescent filler (SrAl2O4 : Eu2+, Dy3+) in Ethyl Vinyl Acetate copolymer (EVA). The modifications of chemical and physical properties of these films were investigated upon irradiation using wavelengths beyond 300 nm. The presence of fillers was revealed to be a pro-degrading factor of the composite films, without existence of any change of the degradation mechanism of the polymer. The propagation of light within these films was carefully investigated by applying Mie theory. The results highlight a possible increase of the light optical path in composite films due to scattering. This phenomenon might contribute to explain the photochemical behavior of the studied films. At last, a proof of concept was searched for the design of multifunctional coatings able to increase and preserve the conversion properties of a P3HT based OSC.

Sous l’impact des agressions environnementales (lumière, température, eau …), les peintures de carrosseries automobiles voient leurs propriétés (couleur, brillant, …) se dégrader. L’amélioration de leur tenue dans le temps est l’un des enjeux importants auxquels sont confrontés les constructeurs automobiles. La compréhension des phénomènes mis en jeu nécessite un travail de recherche important. Les objectifs de cette thèse ont été d’étudier les mécanismes de photovieillissement de polymères tridimensionnels (acrylique-mélamine et acrylique-uréthane) depuis l’échelle moléculaire (structure chimique du polymère) jusqu’à l’échelle macroscopique (propriétés fonctionnelles du matériau). L’étude de l’influence de chacune des contraintes (lumière, eau, …) indépendamment les unes des autres a permis de comprendre le comportement du matériau dans les conditions naturelles où toutes ces contraintes se superposent. Nous avons montré que le photovieillissement des vernis mettait en jeu la dégradation des fonctions chimiques formées lors de l’étape de réticulation du vernis, entraînant une densification du réseau au cours du vieillissement et menant à l’apparition d’un faïençage lorsqu’un seuil de contraintes internes était atteint. On a également montré qu’il existait une relation étroite entre le mécanisme chimique de dégradation, l’obtention d’un palier de dureté et l’apparition du faïençage. Sur la base de comparaisons entre vieillissement naturel et vieillissement artificiel accéléré, des facteurs d’accélération ont été calculés, permettant de prévoir à partir d’une irradiation en conditions de vieillissement artificiel accéléré, la durée de vie des vernis. / It is well known that under environmental stresses impact (light, temperature,water, ...), car paints properties (color, gloss, ...) deteriorate. Improving clearcoats performance over time is one of the most important issues that car manufacturers have to solve. This necessitates an important research activity. The main objectives of this thesis were to study the mechanisms of photoageing of crosslinked polymers (acrylic-melamine and acrylic-urethane) from the molecular (chemical structure of the polymer) to the macroscopic scale (functional properties of the material). The study of the influence of individual stress (light,water, ...) independently each from other has allowed us to understand the behavior of the material under natural conditions where all these stresses overlap. We have demonstrated that the photoageing of clearcoats leads to the degradation of the chemical function formed along with the crosslinking process. We have observed that this results in a significant network densification, leading to the appearance of cracking when a threshold of internal stresses is reached. We have also demonstrated a close relationship between the degradation mechanism, the hardness values and the time required for cracks appearance. Based on comparisons between natural and artificial ageing, acceleration factors were calculated to predict clearcoats service life from an accelerated ageing.