Heptamethine cyanine dyes are attractive compounds for imaging purposes in biomedical applications because of their chemical and photophysical properties exhibited in the near-infrared region. A series of meso amino-substituted heptamethine cyanine dyes with indolenine, benz[e]indolenine and benz[c,d]indolenine heterocyclic moieties were synthesized and their spectral properties including fluorescence quntum yield were investigated in ethanol and ethanol/water mixture. Upon substitution with amines, the absorption maxima of the dyes shifted to the lower wavelength region (~600 nm), showed larger Stokes shifts and stronger fluorescence which can be attributed to an excited state intramolecular charge transfer (ICT). High quantum yields were observed for primary amine derivatives and lower quantum yields were observed for secondary amine derivatives. Fluorescence quantum yields are greater for dyes with 3H-indolenine terminal moieties than for dyes with benz[e]indolenine end groups. Benz[c,d]indolenine based heptamethine cyanine dyes exhibited the lowest quantum yield due to aggregation in solution. In general, the benz[e]indolenine hepatemethine cyanines showed high Stokes shifts compared to indolenine dyes. For the meso-chloro dyes, the absorption maxima for the dyes shifted bathochromically in the order of indolenine, benz[e]indolenine and benz[c,d]indolenine.

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This dissertation aims to understand the effect of incompatible side chains on the complexes of pi-conjugated electron-rich donors and electron-deficient acceptors in solution. The role of incompatible side chains were studied in simple mixtures of organic donor and acceptor molecules that form donor-acceptor complexes. The incompatible branched and linear alkane side chains on the acceptor and donor respectively prevented complex formation between naphthalene diimide acceptor and naphthalene ether donor. However, the incompatible hydrocarbon-fluorocarbon and polar-non polar side chain pairs did not affect complex formation between the donor and acceptor. In quaterthiophene-naphthalene diimide dyads, the incompatibility of the side chain on the acceptor with respect to the side chain on the donor do not have any influence on the donor-acceptor complex formation. Irrespective of the attached side chains, all the dyads show charge transfer absorption bands and have similar electron transfer rates. The effect of point of attachment of the acceptor to the donor in the quaterthiophene-flavin dyad is also studied.

Phycocyanin (PC), a pigment-protein conjugate from Arthrospira platensis, is increasingly used in foods as a natural alternative to artificial blue dyes. Although PC has been classified as a color additive exempt from certification by the Food and Drug Administration, its limited stability has hindered its widespread application in food products. The objectives of this study were: a) to evaluate the photophysical properties of PC and their sensitivity to temperature, viscosity, and water activity, b) to monitor PC’s thermal degradation based on changes in the optical properties of its intrinsic fluorophores, namely its chromophores and aromatic amino acids, and c) to extract PC’s thermal degradation kinetics parameters from non-isothermal degradation profiles and validate their predictive ability. PC’s photophysical properties were monitored in solutions with viscosities from 1 to8000 mPa s and water activities, aw, from about 0 to 1. PC’s emission intensity showed high sensitivity to aw above 0.8 and mild sensitivity to the viscosity of its local environment. The effect of temperature on PC’s photophysical properties was tested in aqueous PC solutions (0.5 mM, pH: 6.1) subjected to non-isothermal temperature profiles with target temperatures from 42.5 to 80°C. The stability of PC was monitored in terms of its photophysical properties, i.e., fluorescence emission intensity, energy, and anisotropy (r) of its chromophore at set time intervals. Additionally, the photophysical properties of PC’s aromatic amino acids (AAs) tyrosine and tryptophan (lexc: 280 and 295 nm) were recorded. The thermal degradation kinetics of PC was assumed to follow a Weibullian model, and the temperature dependence of the degradation rate parameter, b(T), a logarithmic exponential model. Changes of PC fluorescence intensity under dynamic conditions were used to extract the degradation kinetics parameters using the endpoints method. Deviations between the estimated and experimental values were less than 10% for all temperature profiles. During thermal treatments, hypsochromic shifts of AAs’ emission spectra (from 340 to 315 nm) and significant increases in fluorescence anisotropy revealed that color losses were not solely associated with an alteration of the chromophore but with conformational changes and possible aggregation of the protein subunits. An increase in viscosity of the surrounding media provided a protected effect on discoloration during heating. Adequate modeling approaches and molecular spectroscopic techniques can help to develop effective strategies to enhance thermal stability, expand its use as a color and functional ingredient and operationalize it as an endogenous sensor of food quality.

Neste trabalho, estudamos as características fotofísicas da porfirina mesotetrasulfonatofenil (TPPS4) em sua forma protonada e não protonada. Foi obtido o conjunto completo dos parâmetros fotofísicos de estados excitados da TPPS4 em solução aquosa e na presença de micelas do surfactante catiônico brometo de cetiltrimetilamônio (CTAB). Os parâmetros obtidos foram: seções de choque do estado fundamental e dos excitados singleto e tripleto, tempos de vida dos estados excitados singleto e tripleto, taxas de decaimento radiativo, da conversão interna e do cruzamento intersistemas e rendimentos quânticos da fluorescência e do estado tripleto. Foram empregadas as técnicas ópticas lineares espectroscópicas de absorção UV/Vis, de fluorescência estática e resolvida no tempo, flash-fotólise e uma técnica óptica não linear Varredura-Z. Comparando os dados obtidos com os da literatura confirmamos que a técnica Varredura-Z em todos os regimes utilizados é confiável e útil para estudo das características dos estados excitados. Foi observado que a protonação afeta todos os parâmetros obtidos: aumenta todas as taxas da decaimento da energia de excitação, diminuindo assim os tempos de vida dos estados excitados, aumenta o rendimento quântico da fluorescência e diminui o do estado tripleto. Através de dois regimes da Varredura-Z: amplificação paramétrica (OPA) e de pulsos ultracurtos de luz branca (LB), foi obtido o espectro de absorção do estado singleto excitado na região de 460 a 800 nm. Foi observado que a forma da TPPS4 protonada possui uma alta absorção do estado singleto excitado na região de 460 a 620 nm. Analisando os resultados obtidos podemos concluir que a TPPS4 é um composto promissor para aplicação como limitador óptico na região espectral visível e como uma chave óptica, sendo que na forma não protonada ela será eficiente na escala de femto- a picossegundos, enquanto que na forma protonada na escala de femto- a nanossegundos. Na presença de micelas de CTAB os parâmetros obtidos estão próximos dos valores encontrados para porfirina não protonada e completamente diferente daqueles da forma protonada. Além disso, na aplicação da Varredura-Z em regime LB foi observado um efeito acumulativo, devido à dispersão temporal da luz branca (chirp). Este efeito é mais pronunciado para forma protonada, devido sua banda Q de absorção coincidir com a região de maior potência da luz branca. / In this work, we study photophysical characteristics of meso-tetrakis sulphonatophenyl porphyrin (TPPS4) in protonated and nonprotonated states. We obtained the whole set of photophysical parameters of TPPS4 excited states in homogeneous aqueous solution and in the presence of micelles from cationic detergent cetyltrimethylammonium bromide (CTAB). The parameters obtained were: ground and excited singlet and triplet states cross sections; intersystemcrossing, internal conversion and radiative rate constants; singlet and triplet states life times and fluorescence and triplet state quantum yields. The techniques employed were linear optical ones: UV/Vis absorption and fluorescence spectroscopies, time-resolved fluorescence, flash-photolysis, and nonlinear Z-scan. We have confirmed, comparing obtained date with those from literature, that Z-scan in all its applied regimes is reliable and useful to study the excited state characteristics. It was observed that protonation affects all TPPS4 photophysical parameters: increases all rate constants of the excited energy dissipation thus reducing the excited state lifetimes, increases the fluorescence quantum yield and reduces the triplet state quantum yield. The singlet excited state absorption spectrum was obtained in the 460-800 nm region, with two Z-scan regimes: optical parametric amplification - OPA with 120-140 fs pulses and white light ultrashort pulses. It was observed that the protonated TPPS4 form possesses intense absorption of its singlet excited state in the 460-620 nm region. Basing on the obtained date analysis we can conclude that TPPS4 is promising for application as optical limiters in the visible spectral range and optical switching: in its nonprotonated form it can be effective in the range from femto- up to picoseconds while in its protonated form in the range from femto- up to nanoseconds. In the presence of CTAB micelles the TPPS4 parameters were close to those found for its nonprotonated state and completely different from the values for the protonated one. Besides, we observed an accumulative effect due to white light time dispersion (chirp), which was more pronounced for the protonated state, since its Q absorption band coincided with white light high potency region.

Neste trabalho, estudamos as características fotofísicas da porfirina mesotetrasulfonatofenil (TPPS4) em sua forma protonada e não protonada. Foi obtido o conjunto completo dos parâmetros fotofísicos de estados excitados da TPPS4 em solução aquosa e na presença de micelas do surfactante catiônico brometo de cetiltrimetilamônio (CTAB). Os parâmetros obtidos foram: seções de choque do estado fundamental e dos excitados singleto e tripleto, tempos de vida dos estados excitados singleto e tripleto, taxas de decaimento radiativo, da conversão interna e do cruzamento intersistemas e rendimentos quânticos da fluorescência e do estado tripleto. Foram empregadas as técnicas ópticas lineares espectroscópicas de absorção UV/Vis, de fluorescência estática e resolvida no tempo, flash-fotólise e uma técnica óptica não linear Varredura-Z. Comparando os dados obtidos com os da literatura confirmamos que a técnica Varredura-Z em todos os regimes utilizados é confiável e útil para estudo das características dos estados excitados. Foi observado que a protonação afeta todos os parâmetros obtidos: aumenta todas as taxas da decaimento da energia de excitação, diminuindo assim os tempos de vida dos estados excitados, aumenta o rendimento quântico da fluorescência e diminui o do estado tripleto. Através de dois regimes da Varredura-Z: amplificação paramétrica (OPA) e de pulsos ultracurtos de luz branca (LB), foi obtido o espectro de absorção do estado singleto excitado na região de 460 a 800 nm. Foi observado que a forma da TPPS4 protonada possui uma alta absorção do estado singleto excitado na região de 460 a 620 nm. Analisando os resultados obtidos podemos concluir que a TPPS4 é um composto promissor para aplicação como limitador óptico na região espectral visível e como uma chave óptica, sendo que na forma não protonada ela será eficiente na escala de femto- a picossegundos, enquanto que na forma protonada na escala de femto- a nanossegundos. Na presença de micelas de CTAB os parâmetros obtidos estão próximos dos valores encontrados para porfirina não protonada e completamente diferente daqueles da forma protonada. Além disso, na aplicação da Varredura-Z em regime LB foi observado um efeito acumulativo, devido à dispersão temporal da luz branca (chirp). Este efeito é mais pronunciado para forma protonada, devido sua banda Q de absorção coincidir com a região de maior potência da luz branca. / In this work, we study photophysical characteristics of meso-tetrakis sulphonatophenyl porphyrin (TPPS4) in protonated and nonprotonated states. We obtained the whole set of photophysical parameters of TPPS4 excited states in homogeneous aqueous solution and in the presence of micelles from cationic detergent cetyltrimethylammonium bromide (CTAB). The parameters obtained were: ground and excited singlet and triplet states cross sections; intersystemcrossing, internal conversion and radiative rate constants; singlet and triplet states life times and fluorescence and triplet state quantum yields. The techniques employed were linear optical ones: UV/Vis absorption and fluorescence spectroscopies, time-resolved fluorescence, flash-photolysis, and nonlinear Z-scan. We have confirmed, comparing obtained date with those from literature, that Z-scan in all its applied regimes is reliable and useful to study the excited state characteristics. It was observed that protonation affects all TPPS4 photophysical parameters: increases all rate constants of the excited energy dissipation thus reducing the excited state lifetimes, increases the fluorescence quantum yield and reduces the triplet state quantum yield. The singlet excited state absorption spectrum was obtained in the 460-800 nm region, with two Z-scan regimes: optical parametric amplification - OPA with 120-140 fs pulses and white light ultrashort pulses. It was observed that the protonated TPPS4 form possesses intense absorption of its singlet excited state in the 460-620 nm region. Basing on the obtained date analysis we can conclude that TPPS4 is promising for application as optical limiters in the visible spectral range and optical switching: in its nonprotonated form it can be effective in the range from femto- up to picoseconds while in its protonated form in the range from femto- up to nanoseconds. In the presence of CTAB micelles the TPPS4 parameters were close to those found for its nonprotonated state and completely different from the values for the protonated one. Besides, we observed an accumulative effect due to white light time dispersion (chirp), which was more pronounced for the protonated state, since its Q absorption band coincided with white light high potency region.

Au cours de la dernière décennie, l’usage intensif des herbicides en agriculture a provoqué plusieurs crises sanitaires et environnementales. La recherche de nouveaux herbicides bio-inspirés est donc devenue une urgence, en particulier afin de réduire les risques de pollution. Les porphyrines, naturellement présentes dans les végétaux, sont des molécules photosensibles. En présence d’oxygène, leur photo-activation conduit à la production d’Espèces Réactives de l’Oxygène capables d’induire la mort cellulaire. Ce principe utilisé en thérapie photodynamique peut être transféré aux plantes, par exemple à l’aide de porphyrines chargées. Nous avons étudié les propriétés physicochimiques (absorption UV-Visible, émission de fluorescence, photo-stabilité et production d’EROs) ainsi que les effets sur des cellules de tabac TBY-2 d’une série de porphyrines chargées. Pour étudier les mécanismes d’action des porphyrines en tant qu’herbicides, ces molécules doivent être tracées et localisées dans la plante. Dans ce but, nous avons synthétisé des porphyrines liées de manière covalente à un marqueur fluorescent par plusieurs bras espaceurs ; ces derniers ont été choisis grâce à une étude en modélisation moléculaire de leur flexibilité conformationnelle. Les propriétés photo-physiques de ces nouvelles dyades ont été étudiées expérimentalement et théoriquement. / Over the past decade, intensive use of herbicide in agriculture has caused several sanitary and environmental problems. Finding new bio-inspired herbicides preventing pollution has appeared crucial. Naturally present in plants, porphyrins are photosensitive. In the presence of oxygen, their photo-activation leads to production of Reactive Oxygen Species, which induce cell death. Already used in Photodynamic Therapy, this effect can be used to plant. In that purpose, a series of charged porphyrins (commercial and synthesized) were selected, and their physicochemical properties (e.g. UV-Vis absorption, fluorescence emission, photostability, ROS production) as well as their effects on TBY-2 (Tobacco Bright Yellow) cells were evaluated. Second, localizing molecules in plants is mandatory to understand mechanisms of the herbicide action. In this context, porphyrins were covalently grafted to a fluorescent marker, by a series of spacers that were chosen according to a preliminary molecular modeling evaluation of their conformational flexibility. The new dyads obtained were thoroughly studied both theoretically and experimentally for their photophysical properties.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

Este trabalho apresenta a síntese dos plumbatos de estrutura tipo perovskita (ABO3) PbTiO3, PbZrO3 e Pb(Ti,Zr)O3 por rota sol-gel não aquosa, bem como da produção de filmes finos dos precursores desses compostos sobre substratos de polimetilmetacrilato. Os compostos PbTiO3, PbZrO3 e Pb(Ti,Zr)O3 foram preparados e em seguida caracterizados pela técnica de difração de raios X (DRX) e por análise termogravimétrica (ATG). A molhabilidade entre a solução precursora e o substrato foi avaliada pela medida do ângulo de contato. A deposição dos filmes sobre substratos de PMMA foi feita pelo método de spin-coating, e os filmes produzidos foram caracterizados por espectrofotometria UV-Visível, elipsometria espectral e microscopia eletrônica de varredura (MEV). Os compostos preparados apresentaram a fase perovskita quando tratados a 750°C, no entanto, com tratamentos térmicos a temperaturas abaixo do ponto de fusão do PMMA (120ºC) ainda há alta quantidade de matéria orgânica, o que impossibilita a verificação clara das fases cristalinas. A solução não aquosa do sol-gel apresentou-se molhante ao substrato, o que valida a utilização do método de spin-coating para deposição dos filmes. Os filmes obtidos apresentam transparência na faixa de luz visível, elevada uniformidade na espessura e presença de trincas cuja quantidade aumentou com o número de camadas de deposição. Os valores de índice de refração variaram de 1,7 e 2,0, sendo crescente na ordem PbZrO3, Pb(Ti,Zr)O3 e PbTiO3. Os valores de energia de band gap óptico determinados com base nos valores de transmitância e espessura dos filmes foram entre 3,3 e 3,4 eV para todos os plumbatos investigados. / This work describes the synthesis of plumbates of perovskite-type structure (ABO3) PbTiO3, PbZrO3 and Pb(Ti,Zr)O3 by non-aqueous sol-gel route as well as the production of thin films of these compounds precursors on polymethyl methacrylate substrates. The compounds PbTiO3, PbZrO3 and Pb(Ti,Zr)O3 were prepared and then characterized by of X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The wettability between the precursor solution and the substrate was evaluated by measuring the contact angle. The deposition of the films on PMMA substrates were made by spin-coating method, and the produced films were characterized by UV-Visible, spectral ellipsometry and scanning electron microscopy (SEM). The compounds had the perovskite phase when treated at 750 °C, however, with thermal treatments at temperatures below the melting point of PMMA (120 ° C) there is still high amount of organic matter, making it impossible to clear verification of crystalline phases. The non-aqueous sol-gel showed up wetting to the substrate, which validates the use of the spin-coating method for films deposition. The obtained films exhibit transparency in the visible light range, high uniformity in thickness and presence of cracks whose amount increased with the number of deposited layers. The refractive index values ranged from 1.7 to 2.0, and increasing in the order PbZrO3, Pb(Ti,Zr)O3 and PbTiO3. The optical band gap energy values based on the transmittance values and thickness of the films were between 3.3 and 3.4 eV for all investigated plumbates.