No presente trabalho estudou-se os processos de interação entre uma série de porfirinas catiônicas e a melanina. Utilizou-se as porfirinas (Zn-(tetra(4-N-Metilpiridil)porfina): (\'ZN\'-(tetra(4-\'N\'-Metilpiridil)porfina): \'ZN\'-\'T\'\'M\'\'PY\'\'P\', (\'ZN\'-(tetra(4-\'N\'-Benzilpiridil)porfina): \'ZN\'-\'T\'\'BZ\'\'PY\'\'P\', as respectivas porfirinas de base livre (\'T\'\'M\'\'PY\'\'P\' e \'T\'\'BZ\'\'PY\'\'P\') e a melanina sintética obtida a partir da auto-oxidação da dihidroxifenilalanina (L-DOPA). O trabalho baseou-se em três técnicas espectroscópicas complementares: espectroscopia eletrônica (absorção na região do ultravioleta-visível), fluorescência e espalhamento Raman ressonante. Demonstrou-se a formação de complexos estáveis como resultado da interação porfirina-melanina. A partir dos dados de espectroscopia Raman fez-se uma atribuição de bandas vibracionais para as porfirinas, comparando-se com os dados disponíveis na literatura para porfirinas semelhantes. Discutiu-se as possíveis mudanças de estruturas provocadas pela melanina na porfirina, baseadas nas diferenças entre os espectros Raman das porfirinas puras e dos complexos porfirina-melanina. Sugeriu-se uma nova interpretação para os espectros eletrônicos das porfirinas baseada no modelo de Gouterman (modelo de quatro orbitais). A partir dessa interpretação do espectro eletrônico analisou-se a perturbação causada pela melanina nos orbitais moleculares da porfirina fazendo=se uma discussão dos espectros de emissão fluorescente das mesmas. Estimou-se a taxa de transferência de energia da porfirina para melanina através da supressão da fluorescência da porfirina, usando-se medidas de fluorescência com resolução temporal. Demonstrou-se que a fluorescência do complexo porfirina-melanina tem um tempo de vida menor que 5 ps. Utilizou-se as medidas de supressão de fluorescência em regime estacionário para determinar as constantes de dissociação do complexo porfirina-melanina e os possíveis sítios de ligação da melanina. Os resultados evidenciam a importante propriedade do polímero de melanina em atuar como eficiente meio para a dissipação não radiativa de estados eletrônicos excitados. / In this work we studied the interaction between some cationic porphyrins and melanin. The porphyrins used were (\'ZN\'-(tetra(4-\'N\'-Metilpiridil)porfina): \'ZN\'-\'T\'\'M\'\'PY\'\'P\', (\'ZN\'-(tetra(4-\'N\'-Benzilpiridil)porfina): \'ZN\'-\'T\'\'BZ\'\'PY\'\'P\', and their respective free bases porphyrins (\'T\'\'M\'\'PY\'\'P\' e \'T\'\'BZ\'\'PY\'\'P\'). Synthetic melanin was obtained from the auto-oxidation of the 3,4-dihydroxyphenylalanine (L-DOPA). From resonance Raman spectra an attribution is made to the vibrational bands of the porphirins, analyzing the effects of the substituents. The possible changes in the porphyrin structure due to the interaction with melanin are discussed based on the modifications of the resonance Raman spectra of the porphyrins in the presence of melanin. From optical absorption and fluorescence measurements it is suggested a new interpretation to the eletronic spectra of the porphyrins based on the Goutermans model. The perturbation due to the melanin in the molecular orbitals of the porphyrins is also analysed. An estimation of the energy transfer rate to the melanin by time resolved fluorescence measurements of the porphyrin-melanin solution is made. It is demonstrated that the fluorescence lifetime of the porphyrin-melanin complexes are lesser than 5ps. The dissociation constants of the porphyrin-melanin complexes and possible sites of binding of the melanin are determined by fluorescence quenching of the porphyrins as observed by steady state measurements. The results show clearly the important role of the melanin to act as an efficient way to the non-radiative dissipation of the excited electronic states of the porphyrins.

Amplificadores Ãticos amplificam a luz incidente atravÃs de emissÃo estimulada, o mesmo mecanismo que à usado pelos lasers. Com certeza, um amplificador Ãtico, nÃo à nada mais do que um laser sem realimentaÃÃo. Seu principal ingrediente à o ganho Ãtico que à percebido quando o amplificador à sujeito a um bombeio (oticamente ou eletricamente) para conseguir a inversÃo de populaÃÃo nos subniveis. O ganho Ãtico, em geral, depende nÃo somente da freqÃÃncia (ou comprimento de onda) do sinal incidente, mas tambÃm da intensidade do feixe local em qualquer ponto dentro do amplificador. Esse trabalho foi motivado por uma procura contÃnua do conhecimento e entendimento das caracterÃsticas e dos fenÃmenos envolvidos na amplificaÃÃo de regime de pulso curto que seriam relevantes como aplicaÃÃes para processos nos quais tais fenÃmenos nÃo podem ser negligenciados. Sem perda de generalidade, evitamos sistemas de vÃrios canais, consideramos aqui um Ãnico canal com relaÃÃo a outro, pelo fato de que o ganho e o Ãndice de refraÃÃo ambos dependem do nÃmero de canais envolvidos. Neste trabalho foi simulada inicialmente a amplificaÃÃo Ãptica onde o ganho era constante de modo a comparar com um novo modelo proposto aqui, aonde o ganho à periÃdico. Neste caso modelamos as parcelas de transferÃncia de energia do bombeio e do sinal em funÃÃes periÃdicas de onde foi simulado com diferentes parÃmetros das funÃÃes periÃdicas escolhidas. AlÃm do mais, os efeitos de dispersÃo, automodulaÃÃo de fase, pulso walkoff, efeito Raman e depleÃÃo de pulso foram considerados como fatores importantes para amplificaÃÃo Raman de pulsos curtos. Com relaÃÃo à forma dos pulsos de bombeio e a semente Raman para as simulaÃÃes toma um pulso Gaussiano e um sinal CW fraco respectivamente. O pulso de bombeio transfere energia para o sinal CW ao longo da fibra. Todas as simulaÃÃes foram realizadas usando um mÃtodo numÃrico espectral bem conhecido como Split-Step Fourier Method resolvendo as equaÃÃes acopladas nÃo lineares de SchrÃdinger. / Optical Amplifiers amplify incident light through stimulated emission, the same mechanism which is used by lasers. Indeed, an optical amplifier, it is not but a laser without feedback. Its main ingredient is optical gain which is realized when the amplifier is under pumping process (optically or electrically) in order to cause population inversion at electronic sublevels. In a long run, the optical gain will not only depend on frequency (wavelength) of incident signal, but it also depends on the local beam intensity of the optical gain that is entailed to the amplifier medium. This thesis was stimulated by the continuous pursue of knowledge and understanding of characteristics and phenomena involved in the Raman amplification process in the regime of short pulses which would be relevant as the appliance for processes in which such phenomena can not be neglected. Without loss of generality, we considered the case of where there is an only one channel to another one by the fact that the gain and the refractive index both depend on the number of channels. In this thesis, it has also been simulated the optical amplification where the gain was constant in order to comparing to the periodic gain presented in this thesis. In addition, the effects of dispersion, self phase modulation, pulse walk-off, Raman effects and pulse depletion were considered as important factors for Raman amplification of short pulses. That was also considered for our simulations a weak CW signal or a Raman seed to be amplified by an intense pump Gaussian pulse. All the simulations were achieved using a well-known spectral numerical method namely Split-Step Fourier Method for solving the coupled Nonlinear SchrÃdinger Equations.

No presente trabalho estudou-se os processos de interação entre uma série de porfirinas catiônicas e a melanina. Utilizou-se as porfirinas (Zn-(tetra(4-N-Metilpiridil)porfina): (\'ZN\'-(tetra(4-\'N\'-Metilpiridil)porfina): \'ZN\'-\'T\'\'M\'\'PY\'\'P\', (\'ZN\'-(tetra(4-\'N\'-Benzilpiridil)porfina): \'ZN\'-\'T\'\'BZ\'\'PY\'\'P\', as respectivas porfirinas de base livre (\'T\'\'M\'\'PY\'\'P\' e \'T\'\'BZ\'\'PY\'\'P\') e a melanina sintética obtida a partir da auto-oxidação da dihidroxifenilalanina (L-DOPA). O trabalho baseou-se em três técnicas espectroscópicas complementares: espectroscopia eletrônica (absorção na região do ultravioleta-visível), fluorescência e espalhamento Raman ressonante. Demonstrou-se a formação de complexos estáveis como resultado da interação porfirina-melanina. A partir dos dados de espectroscopia Raman fez-se uma atribuição de bandas vibracionais para as porfirinas, comparando-se com os dados disponíveis na literatura para porfirinas semelhantes. Discutiu-se as possíveis mudanças de estruturas provocadas pela melanina na porfirina, baseadas nas diferenças entre os espectros Raman das porfirinas puras e dos complexos porfirina-melanina. Sugeriu-se uma nova interpretação para os espectros eletrônicos das porfirinas baseada no modelo de Gouterman (modelo de quatro orbitais). A partir dessa interpretação do espectro eletrônico analisou-se a perturbação causada pela melanina nos orbitais moleculares da porfirina fazendo=se uma discussão dos espectros de emissão fluorescente das mesmas. Estimou-se a taxa de transferência de energia da porfirina para melanina através da supressão da fluorescência da porfirina, usando-se medidas de fluorescência com resolução temporal. Demonstrou-se que a fluorescência do complexo porfirina-melanina tem um tempo de vida menor que 5 ps. Utilizou-se as medidas de supressão de fluorescência em regime estacionário para determinar as constantes de dissociação do complexo porfirina-melanina e os possíveis sítios de ligação da melanina. Os resultados evidenciam a importante propriedade do polímero de melanina em atuar como eficiente meio para a dissipação não radiativa de estados eletrônicos excitados. / In this work we studied the interaction between some cationic porphyrins and melanin. The porphyrins used were (\'ZN\'-(tetra(4-\'N\'-Metilpiridil)porfina): \'ZN\'-\'T\'\'M\'\'PY\'\'P\', (\'ZN\'-(tetra(4-\'N\'-Benzilpiridil)porfina): \'ZN\'-\'T\'\'BZ\'\'PY\'\'P\', and their respective free bases porphyrins (\'T\'\'M\'\'PY\'\'P\' e \'T\'\'BZ\'\'PY\'\'P\'). Synthetic melanin was obtained from the auto-oxidation of the 3,4-dihydroxyphenylalanine (L-DOPA). From resonance Raman spectra an attribution is made to the vibrational bands of the porphirins, analyzing the effects of the substituents. The possible changes in the porphyrin structure due to the interaction with melanin are discussed based on the modifications of the resonance Raman spectra of the porphyrins in the presence of melanin. From optical absorption and fluorescence measurements it is suggested a new interpretation to the eletronic spectra of the porphyrins based on the Goutermans model. The perturbation due to the melanin in the molecular orbitals of the porphyrins is also analysed. An estimation of the energy transfer rate to the melanin by time resolved fluorescence measurements of the porphyrin-melanin solution is made. It is demonstrated that the fluorescence lifetime of the porphyrin-melanin complexes are lesser than 5ps. The dissociation constants of the porphyrin-melanin complexes and possible sites of binding of the melanin are determined by fluorescence quenching of the porphyrins as observed by steady state measurements. The results show clearly the important role of the melanin to act as an efficient way to the non-radiative dissipation of the excited electronic states of the porphyrins.

Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2003. / Includes bibliographical references. Also available in electronic version. Access restricted to campus users.

Η παρούσα διπλωματική εργασία πραγματοποιήθηκε στο εργαστήριο παρασκευής και μηχανικών ιδιοτήτων συνθέτων υλικών στο ΙΤΕ/ΙΕΧΜΗ στη πάτρα. Το κύριο μέρος της παρούσης μεταπτυχιακής εργασίας είναι η μεταφορά μονού στρώματος γραφενίου σε υποστρώματα PDMS και ο χαρακτηρισμός του μέσω της φασματοσκοπίας Raman καθώς επίσης και η μελέτη της αλληλεπίδρασης του γραφενίου με το υπόστρωμα. Και τέλος, εξίσου σημαντικό μέρος αποτελεί η θερμομηχανική μελέτη του μονοστρωματικού γραφενίου, το οποίο έχει αναπτυχθεί στην επιφάνεια του χαλκού. Πιο αναλυτικά, το πρώτο κεφάλαιο της διπλωματικής εργασίας αποτελεί μια πρώτη εισαγωγή στο γραφένιο, όπου απαντά σε διάφορα ερωτήματα όπως, πως ανακαλύφθηκε, τι είναι, τι ιδιότητες έχει, πως παρασκευάζεται, ποία είναι η δομή του (κρυσταλλική, ηλεκτρονική) και σε πολλά άλλα. Στη συνέχεια, στο δεύτερο κεφάλαιο περιγράφονται οι πειραματικές τεχνικές, οι φασματοσκοπικές μέθοδοι καθώς και οι πειραματικές διατάξεις που χρησιμοποιήθηκαν κατά την εκπόνηση της διατριβής. Για τον χαρακτηρισμό και την μελέτη του γραφενίου πάνω σε διάφορα υποστρώματα (PDMS, PMMA, Si/SiO2, χαλκού) χρησιμοποιούνται, κυρίως, η φασματοσκοπία Raman, αλλά και η οπτική μικροσκοπία, η ηλεκτρονική μικροσκοπία σάρωσης (SEM) και η διάταξη θέρμανσης-ψύξης (THMS600) της εταιρίας Linkam. Στο τρίτο κεφάλαιο περιγράφονται οι διαδικασίες παρασκευής των προς μελέτη δοκιμίων. Αρχικά αναλύουμε τον τρόπο με τον οποίο παρασκευάσαμε δοκίμια PDMS (πoλυδιμέθυλο σιλοξάνιο). Η πρώτη μέθοδος περιγράφει τον τρόπο με τον οποίο το γραφένιο, το οποίο έχει αναπτυχθεί σε υπόστρωμα χαλκού, μεταφέρεται σε άλλο υπόστρωμα, ενώ η δεύτερη μέθοδος (scotch tape method) περιγράφει πως μεταφέρουμε το γραφένιο από τον γραφίτη με χρήση κολλητικής ταινίας. Τέλος, αναλύουμε τον τρόπο με τον οποίο παρασκευάσαμε δοκίμια (πολυμεθακριλικός-μεθυλεστέρας) PMMA/Gr/Cu τα οποία χρησιμοποιήσαμε για την έρευνά μας. Το τέταρτο κεφάλαιο αποτελεί μια φασματοσκοπική μελέτη του γραφενίου. Περιγράφει το πρώτο μέρος των πειραματικών δεδομένων που αναφέρονται στην μελέτη του γραφενίου το οποίο τοποθετήσαμε σε υπόστρωμα PDMS. Για την μελέτη αυτή διαθέτουμε δυο δείγματα. Και στα δυο αυτά δείγματα έχουμε τοποθετήσει φύλλα γραφενίου πάνω σε PDMS. Στο πρώτο δείγμα έχουμε ακολουθήσει την μέθοδο της μικρομηχανικής αποφλοίωσης για να μεταφέρουμε το γραφένιο στην επιφάνεια του PDMS, ενώ στο δεύτερο έχουμε μεταφέρει γραφένιο, αφού πρώτα έχει αναπτυχθεί σε χαλκό με την μέθοδο CVD. Στο πρώτο μας δείγμα έχουμε μεταφέρει εκτός από μονά στρώματα γραφενίου, διπλά και τριπλά στρώματα αυτού. Επίσης, στο δεύτερο δείγμα, με κατάλληλη επεξεργασία έχουμε αναπτύξει ένα επαναλαμβανόμενο μοτίβο οπών. Σκοπός μας, λοιπόν, είναι η μελέτη και η ανάλυση της συμπεριφοράς του γραφενίου στην επιφάνεια του PDMS καθώς και η σύγκριση αυτής με άλλα υποστρώματα. Επίσης μελετάμε τις διαφορές, όσον αφορά των διαφορετικών μεθόδων μεταφοράς του γραφενίου που χρησιμοποιήσαμε, μεταξύ των δυο δειγμάτων που διαθέτουμε. Επιχειρούμε, δηλαδή, με την χαρτογράφηση των δειγμάτων μας να κατανοήσουμε τον τρόπο με τον οποίο τοποθετήθηκε (κάθισε) το γραφένιο πάνω στην επιφάνεια του υποστρώματος αλλά και τον τρόπο που αλληλεπιδρά με αυτό. Επιπρόσθετα παραθέτουμε και αναλύουμε φάσματα Raman για ένα, δύο και τρία στρώματα γραφενίου. Και τέλος, ερευνούμε τη διαφορετική συμπεριφορά του γραφενίου σε υπόστρωμα (supported graphene) και στον αέρα (suspended graphene). Στο πέμπτο κεφάλαιο ασχολούμαστε με την συμπεριφορά του γραφενίου, το οποίο αναπτύχθηκε στην επιφάνεια του χαλκού με τη μέθοδο της χημικής εναπόθεσης ατμών. Πρωταρχικός μας στόχος είναι η μελέτη της αλληλεπίδρασης του γραφενίου με το υπόστρωμα του χαλκού και κατ’ επέκταση η θερμομηχανική συμπεριφορά της μονής στρώσης γραφενίου, η οποίας εκτιμάται με τη θερμοκρασιακή εξάρτηση από την φασματοσκοπία Raman στην περιοχή θερμοκρασιών μεταξύ -1500C και 2400C. Για να επιτευχθεί η θερμοκρασιακή εξάρτηση του γραφενίου, τα φάσματα Raman λήφθηκαν και κατά την ψύξη και την θέρμανση των δειγμάτων με χρήση της διάταξής THM600 της εταιρίας Linkam. Στη συνέχεια σε αντίστοιχο δείγμα γραφενίου πάνω σε χαλκό εναποθέτουμε PMMA με τρείς διαφορετικούς ρυθμούς στροφών (4000rpm, 5000rpm, 6000rpm), με σκοπό να διαπιστώσουμε εάν και πώς με την εναπόθεση του πολυμερούς το φύλλο του γραφενίου επηρεάστηκε σε σχέση με πριν. / This thesis took place in the composite materials laboratory at ITE/IEXMH in Patras. The main part of this thesis is the transfer of a single-layer of graphene to a PDMS substrate and its characterization via Raman spectroscopy as well as the study of the interaction of graphene with the substrate. Last but not least the thermomechanical study of a single-layer of graphene which was grown on a copper surface. More specifically the first chapter of this thesis is a first introduction to graphene, answering various questions such as, how it was discovered, what it is, what properties it has, how it is produced, what its structure is (crystalline, electronic) and many others. The second chapter discusses the experimental techniques, the spectroscopic methods and also the experimental configurations that were used in the preparation of this thesis. In order to, characterize and study graphene placed on various substrates (PDMS, PMMA, Si/〖SiO〗_2, Cu) Raman spectroscopy is mainly used. We also use other methods, such as optical microscopy, scanning electron microscopy (SEM) and the Linkam’s company heating-cooling stage (THMS 600). The third chapter describes the preparation processes of the samples under consideration. We begin by analyzing the way in which we produce the PDMS samples. We then continue by examining the two main methods of transferring graphene. The first method describes how the graphene, grown on a copper substrate, is transferred on another, while the second one that is the micromechanical exfoliation method (also known as the scotch tape method), describes the way in which we transfer graphene from graphite to a substrate using a scotch tape. Finally, we analyze the way in which we produced PMMA/Gr/Cu samples which were used for our research. The fourth chapter constitutes a spectroscopic study of graphene. It describes the first part of our experimental data which pertain to the study of graphene placed on PDMS substrate. Our purpose is to study and analyze the graphene behavior on the PDMS surface as well as to compare it to other substrates. We also point out the differences of the various transfer methods of the graphene that was used to produce our samples. By mapping our samples we attempt to comprehend the way in which the graphene was placed over the substrate surface and the way it interacts with it. In addition, we present and analyze Raman spectra for one, two and three graphene layers. Finally, we investigate the difference in the behavior of graphene placed on a substrate (supported graphene) and free standing graphene (suspended graphene). The fifth chapter discusses the behavior of graphene which was developed on a copper surface via the chemical deposition method. Our initial goal is to study the interaction of graphene with the copper substrate and furthermore its temperature dependence in the temperature range between 150 (_ ^o)C and 240 (_ ^o)C. In order to achieve the temperature dependence of graphene, Raman spectra were obtained using the Linkam’s company stage THM 600 both during cooling and heating of the samples. Moreover, we place PMMA on a corresponding sample of graphene on copper with three different rates of speed (4000 rpm, 5000 rpm, 6000 rpm) in order to see whether and how the graphene sheet was affected by the deposition of the polymer.

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No description available.

Thesis (PhD)--Montana State University--Bozeman, 2008. / Typescript. Chairperson, Graduate Committee: John L. Carlsten. Includes bibliographical references (leaves 390-396).

Thesis (Ph. D.)--Marquette University, 2009. / James R. Kincaid, Daniel Sem, Michael D. Ryan, Advisors. Access available to Marquette University only.

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2007. / Includes bibliographical references. Also available in electronic version.