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Photophysical studies of intramolecular excimer formationYin, Jie January 1992 (has links)
No description available.
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Photo-processes of tetrapyrrolic sensitisers studied laser flash photolysis, pulse radiolysis and singlet oxygen luminescence techniquesMcGarvey, D. J. January 1988 (has links)
No description available.
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Photophysical Properties of Binuclear and Trinuclear Monovalent Coinage Metal Complexes for Applications in Molecular DevicesHarris, Lauren Michelle 05 1900 (has links)
Monovalent coinage metal complexes have been of significant interest due to their rich photophysical properties. This dissertation focuses on the design, synthesis, and characterization of gold, silver, and copper phosphors. Chapter 2 investigates new physical and photophysical properties of a gold diphosphine dimer in the solid state. Thermally activated luminescence switching between two structural states is discussed. Chapter 3 includes the photochemistry of closed shell group 11 transition metals with dithiophosphonate and diphosphine ligands as heteroleptic, homoleptic and heterometallic systems. Chapter 4 reports the synthesis and characterization of a cyclic trinuclear gold imidazolate complex with high electron dentistry and π- base properties. The trinuclear gold (I) complexes reactivity with silver(I) and sodium cations is explored. The photochemistry of all complexes are screened for efficiency, emission profiles and lifetimes as potential materials to be used in OLEDs and other molecular devices.
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Avaliação dos agregados (\'clusters\') da amilopectina em solução aquosa / Evaluation of Aggregates (Clusters) of Amylopectin in Aqueous SolutionMiranda, Jacques Antonio de 27 March 2008 (has links)
Neste trabalho, investigamos o microambiente da amilopectina na ausência e presença de tensoativos não-iônicos como o éter dodecil (7 e 23)-polioxietilênico (Unitol L-70 e L-230) e o nonilfenol (9,5)-polioxietilênico (Renex 95), por meio das propriedades físico-químicas de sondas de polaridade: pireno, xantona e Reichardt. Os estudos foram realizados através de técnicas espectroscópicas em estado estacionário (absorção de luz ultravioleta-visível e fluorescência) e resolvidas no tempo (baseadas na contagem de fótons únicos da emissão de fluorescência e na absorção triplete-triplete (T-T) e de intermediários reativos formados após a fotólise da amostra por pulso de laser). Estas técnicas forneceram os valores de: concentração de agregação crítica (cac), concentração micelar crítica (cmc), número de agregação (Nag) e polaridade (escala py e ET30) para os sistemas avaliados. Os dados obtidos foram comparados com as soluções contendo a presença ou não dos tensoativos não-iônicos e a carboximetil celulose (CMC) e 2-hidroxietilamido (2-HEAM). Por fim, a estabilidade do cátion 2-fenilbenzopirílio foi avaliada em diferentes solventes orgânicos, nas micelas dos tensoativos estudados, nos biopolímeros e nos complexos biopolímero-tensoativo. Dois procedimentos experimentais diferentes foram adotados para o preparo das soluções de amilopectina. As diferenças na preparação das soluções de amilopectina tornaram evidente que este biopolímero possui diferentes ambientes para a localização das sondas. Estas diferenças não foram observadas na presença de CMC e de 2-HEAM. Os resultados experimentais confirmaram a interação cooperativa entre a amilopectina e os tensoativos Unitol L-70 e L-230. Esta interação é menos pronunciada para os sistemas formados entre os tensoativos e 2-HEAM e desfavorecidos na presença de CMC. Nos experimentos onde foi avaliado o equilíbrio monômero-excímero do pireno, verificou-se que os complexos amilopectina-tensoativo agrupam um número maior de moléculas de pireno do que os clusters de amilopectina sozinhos. Estes ambientes favoreceram ambos os movimentos de rotação e translação entre as moléculas, para a formação do excímero. Os estudos resolvidos no tempo, utilizando a xantona como sonda fotofísica para as técnicas de fluorescência resolvida no tempo ou de fotólise por pulso de laser, demonstraram que na amilopectina, a sonda ocupa preferencialmente o ambiente aquoso, ao invés dos microambientes internos do polímero. Isto possivelmente é uma decorrência da proteção das cadeias ramificadas do seu esqueleto polimérico. Estes mesmos estudos indicaram que na presença de concentrações mais elevadas de CMC, a xantona migra do seio da solução aquosa para ambientes próximos à cadeia polimérica onde podem ocorrer sua protonação ou associação em sítios não protonados. Em relação à estabilização do cátion 2-fenilbenzopirílio, nas condições estudadas envolvendo tanto os biopolímeros quanto os sistemas biopolímero tensoativo, predominaram os isômeros da chalcona. Os maiores tempos de meia-vida foram observados em CMC, o que pode ser justificado pela maior viscosidade do meio. / In this work, the amylopectin microenvironment was studied in the presence and absence of the non-ionic surfactants polyoxyethylene (7 and 23) dodecyl ether (Unitol L-70, and L-230, respectively) and polyoxytethylene (9.5) nonylphenol ether (Renex 95), through the physical-chemical properties of the polarity probes: pyrene, xanthone, and Reichardt. Steady-state (UV-visible absorption, and fluorescence), and time-resolved (time-correlated single photon counting fluorometry, and laser flash photolysis) techniques were used to evaluate the critical aggregation concentration (cac), critical micellar concentration (cmc), average micellar aggregation numbers (Nag), and polarity (py, and ET30 scales) of the complexes of amylopectinnon-ionic surfactants. The amylopectin experimental results were compared with the obtained ones from aqueous solutions of carboxymethyl cellulose (CMC) and 2-hydroxyethyl starch (2-HEAM) in the absence and presence of nonionic surfactants. The stability of 2-phenylbenzopyrilium cation was also investigated in several organic solvents, in the non-ionic surfactant micelles, in the biopolymers and in the complexes of biopolymer-surfactants. The amylopectin aqueous solutions were prepared by two different experimental procedures. The determined results of the relative intensities of pyrene fluorescence emission bands 1 to 3, and excimer and monomer ratio have pointed out that the amylopectin presents different microenvironments for photophysical probes relocation. Such differences were not observed in the presence of CMC and 2-HEAM. The cooperative interaction between the amylopectin, and the Unitol-L70 and L- 230 surfactants were comproved by the experimental results. The complexes of 2- HEAMnon-ionic surfactant were less stable than the amylopectin ones, while CMC does not form complexes of biopolymer-surfactants. The single-photon timing and laser flash photolysis techniques employing xanthone as probe have shown that this probe remains at the aqueous bulk of the amylopectin solutions. There is no interaction between xanthone and the amylopectin backbone, probably due to the great extent of the polymeric branching. On the other hand, in presence of higher concentrations of CMC solutions, xanthone can relocate from the aqueous solution to the polymeric microenvironment, where the probe can be or not protonated. The evaluation of the stability of 2-phenylbenzopyrilium cation in the presence of biopolymer or complexes of biopolymer-surfactants has shown the predominance of the chalcone isomers. The higher half-life times were determined in the CMC because of the higher viscosity of the medium.
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Structural and Photophysical Properties of Internal Charge Transfer 2-Arylidene and 2,5-Diarylidene CyclopentanonesZoto, Christopher A 27 July 2012 (has links)
" A series of symmetric and asymmetric 2-arylidene and 2,5-diarylidene cyclopentanone dyes have been synthesized. Their electronic absorption and fluorescence spectra have been measured in a wide variety of nonpolar and polar, aprotic and protic solvents. Absorption and fluorescence spectral maxima have been correlated with the ET(30) empirical solvent polarity scale. Lippert-Mataga analysis (in aprotic solvents) demonstrates the increase in the electronic dipole moment from the ground singlet to excited singlet states, consistent with the internal charge transfer (ICT) nature of the S0 --> S1 excitation. TD-DFT spectral calculations support the ICT natures of these compounds. Photophysical properties of these compounds involved measuring both fluorescence quantum yields and lifetimes in various solvents. Investigation of the deactivation kinetics involved determining the first-order radiative and nonradiative rates of decay upon knowledge of the quantum yield and lifetime data. Fluorescence quantum yields and lifetimes of the compounds studied varied depending on the nature of the solvent environments. Excited state protonation in acetic acid was observed for several 2,5-diarylidene cyclopentanones and deltapKa’s have been determined via the Forster Cycle. Thorough work on the photochemistry of (2E,5E)-2,5-bis(p-dimethylaminobenzylidene)-cyclopentanone (bis-dmab) was carried out, consisting of testing bis-dmab as a singlet oxygen photosensitizer, and examination of both the chemical reactivity of bis-dmab with singlet state oxygen (self-sensitized photooxidation) and (E,E) --> (E,Z) photoisomerization. "
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Photophysical studies of 2-Aminopurine in DNAMcKenzie, Grant January 2017 (has links)
Deoxyribonucleic acid (DNA) forms the basis of all known living organisms. Despite the essential role played by DNA, its dynamic system and functional behaviour are still not completely understood. The work presented in this thesis aims to explore the structural dynamics of DNA systems, using fluorescence-based approaches, and to attempt to develop a technique for the measurement of fluorescence decays of biological molecules on the ultrafast (femtosecond) timescale. Absorption of UV radiation by DNA is known to lead to mutations and damage to DNA structure and functionality. For the majority of absorbed photons, the excitation energy dissipates harmlessly as heat, but in some instances this energy transfers to regions of DNA that are more susceptible to damage. 2-Aminopurine (2AP), a fluorescent analogue of the native DNA base adenine, can be incorporated into DNA with minimal perturbation to the DNA structure, and can be used to investigate inter-base electronic energy transfer. By selectively exciting the native DNA base in 2AP-containing dinucleotides and utilising 2AP fluorescence as an energy acceptor, the mechanism of electronic energy transfer has been investigated. Analysis of the resulting fluorescence lifetimes of 2AP has revealed that energy transfer preferentially excites conformations in which the bases are highly stacked, and the fluorescence of 2AP is highly quenched. This has led to a re-evaluation of energy transfer efficiencies between the natural bases and 2AP, and has shown that transfer efficiencies cannot be determined correctly from steady-state fluorescence measurements. To investigate the influence of base dynamics on the quenching of 2AP fluorescence in DNA, time-resolved fluorescence measurements were carried out on 2AP-containing systems in frozen solution at 77 K. These studies included dinucleotides, single–strand oligonucleotides and their corresponding duplexes. In all cases, comparison of the fluorescence decay parameters measured at room temperature with those measured at 77 K showed that elimination of base dynamics prevented rapid quenching, on the 10s of ps timescale or faster, although quenching on the 100s of ps timescale persisted for 2AP in single strands and duplexes. The multi-exponential fluorescence decay of 2AP in DNA and its high sensitivity to local environment is commonly exploited to investigate DNA-enzyme interactions. Transposases are enzymes involved in the movement of sections of DNA (transposons) within the genome. The Mos1 transposase catalyses the movement of a transposon via a cut-and-paste mechanism involving several intermediate complexes. Understanding the complex mechanism by which the transposase can remove and insert a section of DNA would allow these enzymes to be used as biomolecular tools. The structure of the intermediate Mos1 strand-transfer complex (STC) has been investigated by incorporating 2AP into several regions of the transposon and analysing the fluorescence decay. The involvement of a base-flipping-like mechanism has been identified in the mechanism of strand transfer for the Mos1 transposon. The time-resolved fluorescence measurements performed in this thesis are limited to time resolution of ~20 ps and longer using TSCPC. However, an abundance of photophysical events in DNA occur on the femtosecond timescale. Development of a methodology utilising fluorescence gating techniques (such as sum-frequency generation or diffraction from a transient grating) have been attempted, in order to construct an experimental system that enables the broadband detection of ultrafast fluorescence decays. Despite the lack of immediate success in recording the fluorescence decay from a sample, due to technical issues and time-constraints, initial characterisation of the set-up was performed and the prospect of broadband detection was demonstrated. Overall, this thesis gives insight into some of the dynamic processes taking place in DNA and presents work performed to develop a system that would allow the extension of these studies to processes occurring on the fs timescale.
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Fotofisica e relaxações em siliconas / Photophysical and relaxations in siliconesDomingues, Raquel Aparecida, 1981- 15 February 2008 (has links)
Orientador: Teresa Dib Zambon Atvars / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-11T02:18:36Z (GMT). No. of bitstreams: 1
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Previous issue date: 2008 / Resumo: O objetivo deste trabalho foi o estudo de processos de relaxações em redes poliméricas obtidas a partir de poli(dimetilsiloxano-co-metilhidrogêniosiloxano) dimetilsililhidrogênio terminal (PDHS) e o poli(dimetilsiloxano-co-metilvinilsiloxano) dimetilvinil terminal (PDVS) por reação de hidrossililação, utilizando-se a espectroscopia de fluorescência em uma ampla faixa de temperaturas (de 20 a 400 K). Estes processos de relaxações foram comparados com outros métodos de análises térmicas como calorimetria diferencial de varredura (DSC) e análise dinâmico mecânica (DMA). A temperatura de transição vítrea foi mais facilmente visualizada pela técnica de fluorescência que por DSC e foi compatível com o resultado obtido por DMA. Os filmes de silicona também foram caracterizados por espectro infravermelho (FTIR) e termogravimetria (TGA). Como as siliconas não são intrinsicamente fluorescentes, duas estratégias foram utilizadas para a inserção da sonda no filme: a primeira envolveu dispersão física de uma molécula fluorescente nas redes poliméricas, e na segunda foi incorporado um grupo fluorescente na cadeia lateral da silicona concomitantemente à obtenção das redes poliméricas também por reação de hidrossililação. Nesse último caso, o grupo fluorescente foi covalentemente ligado à cadeia polimérica. Os estudos do sinal de fluorescência em função da temperatura foram analisados utilizando-se modelos cinéticos para a desativação não-radiativa das moléculas fluorescentes. Incorporou-se também as sondas fluorescente (9-vinil antraceno e 9-vinil carbazol) na cadeia do PDHS linear por reação de hidrossililação, sem a presença do PDVS, para que fosse possível a obtenção de um fluído de silicona fluorescente. Neste caso, utilizou-se a relação 1:1 em termos de Si-H (grupo reativo do PDHS) e CH2=CH2 (grupo reativo do material fluorescente) para que o novo material pudesse ser caracterizado por RMN e FTIR, e a proporção de 1:1x10 de Si-H:CH2=CH2 para que o material fluido pudesse ser caracterizado por espectroscopia de fluorescência / Abstract: The aim of this research work was the study of relaxation processes in siloxane polymeric network obtained from poli(dimethylsiloxane-co-methylhidrogensiloxane) dimethylsilihidrogen terminal (PDHS) and poli(dimethylsiloxane-co-methylvinylsiloxane) dimethylvinyl terminal (PDVS) by hydrosilylation reaction, using fluorescence spectroscopy in a range of temperature from 20 to 400 K. The results of these relaxation processes were compared with those of thermal analysis methods as the differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The glass transition temperature was easier demonstrated using fluorescence spectroscopy than using DSC and compatible with the result obtained from DMA. The siloxane films were characterized using also infrared spectroscopy and thermogravimetry (TGA). The silicones are not intrinsically fluorescent, so two strategies were used to insert a fluorescent probe in the siloxane film: the first involved a physical dispersion of fluorescent probe in the network, and in the second were incorporated fluorescent groups in the lateral chain of siloxane, concurrently the web formation, by hidrosilylation reaction too. In this last case, fluorescent probe was covalently bonded to polymeric chain. The fluorescence in function of the temperature signal studies was analyzed using a non radioactive deactivation of fluorescents molecules kinetic model. PDHS was reacted with vinyl fluorescents probes without PDVS, to be possible to obtain a fluorescent fluid of siloxane. In this case, was used the relation of 1:1 in terms of Si-H (PDHS reactive group) and CH2=CH2 (fluorescent material reactive groups) to be possible characterize the new material using RMN and FTIR, and the proportion of 1:1x10 of Si-H:CH2=CH2 to be possible characterize using fluorescence spectroscopy / Mestrado / Físico-Química / Mestre em Química
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Avaliação dos agregados (\'clusters\') da amilopectina em solução aquosa / Evaluation of Aggregates (Clusters) of Amylopectin in Aqueous SolutionJacques Antonio de Miranda 27 March 2008 (has links)
Neste trabalho, investigamos o microambiente da amilopectina na ausência e presença de tensoativos não-iônicos como o éter dodecil (7 e 23)-polioxietilênico (Unitol L-70 e L-230) e o nonilfenol (9,5)-polioxietilênico (Renex 95), por meio das propriedades físico-químicas de sondas de polaridade: pireno, xantona e Reichardt. Os estudos foram realizados através de técnicas espectroscópicas em estado estacionário (absorção de luz ultravioleta-visível e fluorescência) e resolvidas no tempo (baseadas na contagem de fótons únicos da emissão de fluorescência e na absorção triplete-triplete (T-T) e de intermediários reativos formados após a fotólise da amostra por pulso de laser). Estas técnicas forneceram os valores de: concentração de agregação crítica (cac), concentração micelar crítica (cmc), número de agregação (Nag) e polaridade (escala py e ET30) para os sistemas avaliados. Os dados obtidos foram comparados com as soluções contendo a presença ou não dos tensoativos não-iônicos e a carboximetil celulose (CMC) e 2-hidroxietilamido (2-HEAM). Por fim, a estabilidade do cátion 2-fenilbenzopirílio foi avaliada em diferentes solventes orgânicos, nas micelas dos tensoativos estudados, nos biopolímeros e nos complexos biopolímero-tensoativo. Dois procedimentos experimentais diferentes foram adotados para o preparo das soluções de amilopectina. As diferenças na preparação das soluções de amilopectina tornaram evidente que este biopolímero possui diferentes ambientes para a localização das sondas. Estas diferenças não foram observadas na presença de CMC e de 2-HEAM. Os resultados experimentais confirmaram a interação cooperativa entre a amilopectina e os tensoativos Unitol L-70 e L-230. Esta interação é menos pronunciada para os sistemas formados entre os tensoativos e 2-HEAM e desfavorecidos na presença de CMC. Nos experimentos onde foi avaliado o equilíbrio monômero-excímero do pireno, verificou-se que os complexos amilopectina-tensoativo agrupam um número maior de moléculas de pireno do que os clusters de amilopectina sozinhos. Estes ambientes favoreceram ambos os movimentos de rotação e translação entre as moléculas, para a formação do excímero. Os estudos resolvidos no tempo, utilizando a xantona como sonda fotofísica para as técnicas de fluorescência resolvida no tempo ou de fotólise por pulso de laser, demonstraram que na amilopectina, a sonda ocupa preferencialmente o ambiente aquoso, ao invés dos microambientes internos do polímero. Isto possivelmente é uma decorrência da proteção das cadeias ramificadas do seu esqueleto polimérico. Estes mesmos estudos indicaram que na presença de concentrações mais elevadas de CMC, a xantona migra do seio da solução aquosa para ambientes próximos à cadeia polimérica onde podem ocorrer sua protonação ou associação em sítios não protonados. Em relação à estabilização do cátion 2-fenilbenzopirílio, nas condições estudadas envolvendo tanto os biopolímeros quanto os sistemas biopolímero tensoativo, predominaram os isômeros da chalcona. Os maiores tempos de meia-vida foram observados em CMC, o que pode ser justificado pela maior viscosidade do meio. / In this work, the amylopectin microenvironment was studied in the presence and absence of the non-ionic surfactants polyoxyethylene (7 and 23) dodecyl ether (Unitol L-70, and L-230, respectively) and polyoxytethylene (9.5) nonylphenol ether (Renex 95), through the physical-chemical properties of the polarity probes: pyrene, xanthone, and Reichardt. Steady-state (UV-visible absorption, and fluorescence), and time-resolved (time-correlated single photon counting fluorometry, and laser flash photolysis) techniques were used to evaluate the critical aggregation concentration (cac), critical micellar concentration (cmc), average micellar aggregation numbers (Nag), and polarity (py, and ET30 scales) of the complexes of amylopectinnon-ionic surfactants. The amylopectin experimental results were compared with the obtained ones from aqueous solutions of carboxymethyl cellulose (CMC) and 2-hydroxyethyl starch (2-HEAM) in the absence and presence of nonionic surfactants. The stability of 2-phenylbenzopyrilium cation was also investigated in several organic solvents, in the non-ionic surfactant micelles, in the biopolymers and in the complexes of biopolymer-surfactants. The amylopectin aqueous solutions were prepared by two different experimental procedures. The determined results of the relative intensities of pyrene fluorescence emission bands 1 to 3, and excimer and monomer ratio have pointed out that the amylopectin presents different microenvironments for photophysical probes relocation. Such differences were not observed in the presence of CMC and 2-HEAM. The cooperative interaction between the amylopectin, and the Unitol-L70 and L- 230 surfactants were comproved by the experimental results. The complexes of 2- HEAMnon-ionic surfactant were less stable than the amylopectin ones, while CMC does not form complexes of biopolymer-surfactants. The single-photon timing and laser flash photolysis techniques employing xanthone as probe have shown that this probe remains at the aqueous bulk of the amylopectin solutions. There is no interaction between xanthone and the amylopectin backbone, probably due to the great extent of the polymeric branching. On the other hand, in presence of higher concentrations of CMC solutions, xanthone can relocate from the aqueous solution to the polymeric microenvironment, where the probe can be or not protonated. The evaluation of the stability of 2-phenylbenzopyrilium cation in the presence of biopolymer or complexes of biopolymer-surfactants has shown the predominance of the chalcone isomers. The higher half-life times were determined in the CMC because of the higher viscosity of the medium.
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Efeito do substrato/espessura na indução de alterações conformacionais em poli(fluorenos) / Influence of substrate and thickness in conformational changes of poly(fluorenes)Domingues, Raquel Aparecida, 1981- 25 August 2018 (has links)
Orientador: Teresa Dib Zambon Atvars / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-25T12:38:23Z (GMT). No. of bitstreams: 1
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Previous issue date: 2013 / Resumo: Neste trabalho foram estudadas as propriedades fotofísicas de dois derivados de polifluoreno, F8BT e PFO-MEHPPV, visando determinar a influência de substratos sobre as mesmas. Os materiais na forma de filme foram depositados por spin coating em substrato de vidro e de vidro recoberto com ITO, sendo que as espessuras variaram de 50 nm a 600 nm, além de um filme preparado por casting com espessura de 50 ?m. As propriedades fotofísicas estudadas foram: os espectros de emissão, a largura à meia altura (FWHM) dos espectros, a posição do máximo de emissão da banda 0-0 em função da temperatura e a progressão vibrônica dos espectros de emissão. Para ambos os polímeros e dentro da faixa de espessura estudada foi verificado que a diminuição na espessura do filme causa também uma diminuição na temperatura de transição vítrea, sendo que abaixo de 450 nm o filme fino apresenta desvios de comportamento de bulk. O tipo de substrato não influenciou nas temperaturas de relaxação. Foi possível dividir os filmes de F8BT em dois grupos: espessuras de 52-185 nm que induzem maiores alargamentos inomogêneos e, portanto possuem ambientes cibotáticos heterogêneos para os fluoróforos inseridos na matriz; e espessuras maiores que 450 nm que possuem Tg maiores e menores alargamentos inomogêneos com ambientes mais homogêneos ao longo da matriz. Para o PFO-MEHPPV temos a relação que quanto maior a espessura, maior a Tg e maior o alargamento inomogêneo. Filmes mais espessos de PFO-MEHPPV encontram-se localmente menos organizados, e diferentemente do observado para os filmes de F8BT, o substrato estaria favorecendo algum grau de organização nos filmes em relação ao bulk. Medidas de tempo de vida de fluorescência foram utilizadas para estudar as interações nas interfaces do polímero orgânico com ITO e alumínio. A camada de alumínio foi considerada supressora para as diversas espessuras estudadas, e esta supressão foi atribuída aos processos de interferência, transferência de energia para o eletrodo metálico e difusão excitônica. O processo de interferência foi determinado através de modelo existente na literatura e sua menor contribuição ocorre em espessuras menores, nas quais os processos de transferência de energia são importantes. Com isso, foi possível concluir, a partir de todos os dados fotofísicos obtidos, que para espessuras acima de 450 nm os filmes deixam de ter comportamento de filme fino / Abstract: In this work, the influence of substrate on the photophysical properties of two polyfluorene derivatives, F8BT and PFO-MEHPPV was studied. The films were prepared by spin-coating solutions of the polymers, using glass and ITO coated glass as the substrates. The thickness was varied from 50 nm to 600 nm. A cast film with a thickness of 50 ìm was also prepared using both polymers. The photophysical properties of the two polyfluorene derivatives, F8BT and PFO-MEHPPV were studied using their emission spectra, the full width at half maximum (FWHM) of the spectra, the temperature dependence of the peak position of the 0-0 emission band and the vibronic progression of the emission spectra. For both polymers, F8BT and PFO-MEHPPV, as the film thickness decreased the glass transition temperature decreased. Below a film thickness of 450 nm, a deviation from bulk behavior was observed. It is also importante note that the substrate type did not affect the relaxation temperature. It was possible to classify the F8BT films into two groups. Those with thicknesses between 52 nm to 185 nm have shown greater inhomogeneous broadening and very heterogeneous cybotatic environments for the fluorophores, while those with film thicknesses greater than 450 nm have shown higher Tg values which induce lower inhomogeneous broadening. PFO-MEHPPV also has shown a similar trend. As the thickness of the film increased, a higher Tg was observed. However, thicker films of PFO-MEHPPV were observed to be less locally organized, in contrast to the F8BT films of the same thickness. This might be due to the substrate, which would favor some degree of organization in the films in comparison to the bulk material. Time-resolved PL measurements have also been used to characterize the interface interactions between the polymer film and ITO (polymer/ITO) or aluminum (polymer/aluminum). The aluminum layer acted as a quencher through an interference effect, energy transfer to the metal and excitonic diffusion. The interference effect was determined by using a model described in the literature however, it has a minimal effect in thinner films. The evidence gained from the photophysical measurements indicates that these films with thicknesses above 450 nm do not show thin film behavior / Doutorado / Físico-Química / Doutora em Ciências
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Propriedades fotofisicas de polimeros modificados com grupos emissores : polietilenos reticulados e poli (metacrilato de metila) / Photophysical properties of polymers modified with light-emitting groups : crosslinked polyethylenes and poly (methyl methacrylate)Martins, Tatiana Duque 10 February 2006 (has links)
Orientador: Teresa Dib Zambon Atvars / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-07T18:45:42Z (GMT). No. of bitstreams: 1
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Previous issue date: 2006 / Doutorado / Físico-Química / Doutor em Ciências
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