Doctor of Philosophy / Department of Chemistry / Ryszard J. Jankowiak / Low-temperature laser-induced fluorescence spectroscopy has various applications in analytical, physical, and biophysical chemistry. This technique provides information on the fluorescence origin band, zero-phonon lines and phonon-sidebands, inhomogeneous broadening, electron-phonon coupling strength, and ground- and excited-state vibrational frequencies of studied molecules. Examples discussed in this work include studies of DNA/metabolites and monoclonal antibody (mAb)/antigen interactions. The structural basis for the increased reactivity of BPDE towards guanines at 5-methylcytosine ([superscript]M[superscripte]eC):G sites in DNA was investigated by low temperature laser-based spectroscopy, studying the nature of physical complexes of benzo[a]pyrene tetraol in a series of 5-methylcytosine structural DNA analogs. We found that the presence of a C-5 substituent on cytosine and related structural modifications influences the conformation of BPT in DNA analogs, and could explain the increase in guanine reactivity at [superscript]M[superscript]eC:G sites of the p53 tumor suppressor gene that contains endogenenous 5-([superscript]M[superscript]eC. It has been demonstrated that various mAbs can bind a particular cross-reactant by adopting two distinct "red" and "blue" conformations of its binding sites. We showed that the blue conformation of pyrene in several mAbs (including 4D5 mAb) is consistent with [pi]-cation interactions, underscoring the importance of [pi]-cation interaction in ligand binding. We propose that considerable narrowing of the fluorescence origin band of the ligand in the protein environment could be regarded as a simple indicator of [pi]-cation interactions. It is also shown that time-resolved delta fluorescence line-narrowing ([delta]FLN) spectroscopy, using excitation within the (0,0)-transition band, provides more reliable information of the frequency dependence of the electron-phonon coupling (Huang-Rhys factor, (S < 1). Finally, analytical formulas were developed to describe FLN spectra with excitation energy transfer present. Our calculated FLN spectra are compared with spectra obtained by a simple convolution method (SC) and a more rigorous treatment using Redfield theory. We demonstrate that, under the condition of weak coupling between pigments (i.e., the coupling constant is smaller than the reorganization energy) and weak electron-phonon coupling strength (S < 1), our analytical formulas provide an excellent approximation of the SC and Redfield methodologies. We argued that our approach could also model FLN spectra obtained for very complex biological systems.

Les verres dopés par des ions de terres rares ou/et des nanoparticules de semi-conducteurs continue à faire l’objet de plusieurs recherches grâce à leur efficacité dans les domaines d’optoélectroniques. En effet, ces matériaux sont parmi les candidats potentiels pour des applications en photonique tels que les amplificateurs à fibre optique, les convertisseurs de lumière, les capteurs et les guides d'ondes 3D.Dans le cadre de cette thèse, des verres à base de silice (SiO2)dopé par des ions d’europium (Eu3+) ont été préparés par le processus sol-gel. Afin de mieux disperser les ions de terres rares et d’améliorer leur émission, les verres ont été codopés par le phosphore et/ou l’aluminium. Des nanoparticules de semi-conducteur (CdS) ont été aussi introduite dans le verre afin d’augmenter l’absorbance de la lumière excitatrice et d’obtenir une émission plus intense des ions Eu3+. Les verres préparés ont été analysés par photoluminescence et par la technique de rétrécissement des raies de luminescence (FLN). Ces mesures ont été suivi par des simulations par la méthode de dynamique moléculaire (DM)afin d’étudier l’effet de phosphore et/ou de l’aluminium sur l’environnement local des ions d’europium et la dispersion de ces ions dans la matrice vitreuse. La présence de deux types de sites des ions d’europium dans le verre de silicophosphates a été mise en évidence et a été confirmé par les deux techniques (FLN et DM). L’effet des nanoparticules de CdS sur l'émission des ions Eu3+dans un verre de silicophosphate a été aussi étudié et il a été montré que l’émission des ions Eu3+ est considérablement dépendante de la concentration des nanoparticules de CdS et de la température de recuit. / Glasses doped with rare earth ions and/or semiconductor nanoparticles continues to be the subject of several studies due to their effectiveness in optoelectronic fields. Indeed, these materials are among the potential candidates for photonic applications such as optical fiber amplifiers, light converters, sensors and 3D waveguides. As part of this thesis, silica-based glasses (SiO2) doped with europium ions (Eu3+) were prepared by the sol-gel process. In order to better disperse the rare earth ions and improve their emission, the glasses were codoped with phosphorus and/or aluminum. Semiconductor nanoparticles (CdS) were also introduced into the glass in order to increase the absorbance of the excitation light and to obtain a more intense emission of Eu3+ ions. The prepared glasses were analyzed by photoluminescence and by the technique of Fluorescence line narrowing (FLN). These experimental measurements were followed by theoretical simulations using the molecular dynamics method (DM) to study the effect of phosphorus and/or aluminum on the local environment of the europium ions and their dispersion in the vitreous matrix. The presence of two types of europium ion sites in the glass silicophosphates has been demonstrated and confirmed by two techniques (FLN and DM). The effect of CdS nanoparticles on the emission of Eu3+ ions in a glass silicophosphate was also studied and it was shown that the emission of Eu3+ ions is considerably dependent on theconcentration of CdS nanoparticles and annealing temperature.

Hole-Burning (HB) und Fluorescence Line-Narrowing (FLN) bei 4.2 K sowie Experimente zur Temperaturabhängigkeit werden angewendet, um Energieniveaustruktur und Elektron-Phonon- Wechselwirkung im Antennenkomplex LHC II grüner Pflanzen zu untersuchen. Besondere Aufmerksamkeit gilt dabei der Vermeidung systematischer Meßfehler durch Reabsorption von Fluoreszenz oder durch Lichtstreuung und unerwünschtes Lochbrennen bei FLN-Experimenten. Durch die Auswertung von Lochspektren können erstmals drei niederenergetische elektronische Zustände bei 677.1, 678.4 und 679.8 nm nachgewiesen werden. Die inhomogene Breite der zugehörigen Absorptionsbanden beträgt etwa 4 nm. Wahrscheinlich stellt jeder dieser Zustände das tiefste Energieniveau einer Untereinheit des LHC II-Trimers dar und ist weitgehend an jeweils einem Chl a-Molekül lokalisiert. Die energetische Differenz zwischen den drei Zuständen kann durch strukturelle Heterogenität erklärt werden. Es kann nachgewiesen werden, daß die Meßergebnisse praktisch frei von Effekten durch unerwünschte Aggregation sind. Die homogene Linienbreite des energetisch tiefsten Zustandes bei 4.7 K wird vorwiegend durch phasenzerstörende Prozesse (pure dephasing) bestimmt. Die Lochbreiten innerhalb der 650 nm Absorptionsbande entsprechen Chl b-Chl a Energietransferzeiten von 1 ps und etwa 240 fs bei 4.2 K, während Lochbreiten innerhalb der 676 nm Absorptionsbande Chl a-Chl a Energietransferzeiten in der Größenordnung von 6-10 ps ergeben. In einer theoretischen Betrachtung werden die Beiträge zu Phonon-Seitenbanden bei HB und FLN separat analysiert. Auf dieser Grundlage können Ergebnisse von HB und FLN Experimenten an LHC II erstmals in einem konsistenten Modell durch schwache Elektron-Phonon-Wechselwirkung mit einem Huang-Rhys-Faktor von 0.9 und ein breites, stark asymmetrisches Ein-Phonon-Profil erklärt werden. / Spectral hole-burning (HB) is combined with fluorescence line-narrowing (FLN) experiments at 4.2 K and studies of temperature-dependent fluorescence spectra in order to investigate low-energy level structure as well as electron-phonon coupling of the LHC II antenna complex of green plants. Special attention has been paid to eliminate effects owing to reabsorption of fluorescence and to assure that the FLN spectra are virtually unaffected by hole-burning or scattering artifacts. For the first time, analysis of the 4.2 K hole spectra reveals three low-energy electronic states at 677.1, 678.4 and 679.8 nm, respectively. The inhomogeneous width of their absorption bands is approximately 4 nm. It is likely that each of these states is associated with the lowest energy state of one trimer subunit with the energetic separations being due to structural heterogeneity. It is likely that each of the low-energy states is highly localized on a single Chl a molecule of the corresponding trimer subunit. The results are shown to be virtually free from aggregation effects. The homogeneous width for the lowest state at 4.7 K is predominantly due to pure dephasing. Widths of holes burned into the 650 nm absorption band correspond to Chl b-Chl a energy transfer times of 1 ps and about 240 fs at 4.2 K while holewidths for the 676 nm absorption band lead to Chl a-Chl a energy transfer times in the 6-10 ps range. The complexities associated with the interpretation of the phonon structure in HB and FLN spectra are discussed by theoretically analyzing the different phonon sideband contributions. On this basis, 4.2 K HB and FLN data can be consistently interpreted for the first time by weak electron-phonon coupling with a Huang-Rhys factor of about 0.9 to protein phonons with a broad and strongly asymmetric one- phonon profile.

L’efficacité des cellules solaires peut être améliorée en exploitant pleinement la partie UV-bleue du spectre solaire, par un mécanisme de conversion de fréquence de type down-conversion. Ce processus utilisant des transferts d’énergie entre ions de terre rare (TR) ou métal de transition 3d (paires TR3+/Yb3+ avec TR = Pr, Tm,… et Cr3+/Yb3+) requiert des matrices à basse énergie de phonon pour réduire les relaxations non radiatives.Jusqu’à présent, les matériaux étudiés sont principalement sous forme de poudre polycristalline, ce qui limite leur utilisation à cause de la diffusion, ou de monocristaux dont le coût de fabrication est élevé.Dans le cadre de cette thèse, les verres fluorés à base de fluorozirconate ZLAG (ZrF4-LaF3-AlF3-GaF3) et ZBLA (ZrF4-BaF2-LaF3-AlF3) ont été préparés par la technique de fusion-coulée. Ces derniers sont adaptés du fait de leurs propriétés intrinsèques de transparence et de leur faible énergie de phonon. Les matériaux obtenus ont ensuite été caractérisés par, analyse thermique, diffraction des rayons X, microscopie électronique à transmission et luminescence.Des études par dynamique moléculaire et fluorescence par affinement de raies ont été effectuées sur la matrice ZLAG afin de suivre les modifications structurales lors du passage du verre à la vitrocéramique.La luminescence de l’ion Yb3+ a été observée dans l’infra-rouge à 980 nm sous excitation bleue dans toutes les séries étudiées, signature d’un transfert d’énergie. ans le verre ZLAG, l’efficacité atteint 92% pour le transfert d’énergie Pr3+ → Yb3+ et 65% pour le transfert d’énergie Tm3+ → Yb3+. L’efficacité est plus faible dans le verre ZBLA et la vitrocéramisation du verre ZLAG n’améliore pas les performances. / The efficiency of solar cells can be improved by fully exploiting the UV-blue portion of the solar spectrum, through a frequency converting mechanism of type downconversion. This process using energy transfer between rare earth ions (RE) or 3d transition metal (pairs RE3+/Yb3+ with TR = Pr, Tm,… and Cr3+/Yb3+) requires a matrix with low phonon energy to reduce non radiative relaxation.So far, the studied materials are mainly in the form of polycristalline powder, which limits their use due to diffusion or single crystals which manufacturing cost is high.As part of this thesis, fluoride glasses based on fluorozirconate ZLAG (ZrF4-LaF3-AlF3-GaF3) and ZBLA (ZrF4-LaF2-LaF3-AlF3) have been prepared by the melting-casting technique. These are suitable because of their intrinsic properties of transparency and low phonon energy. The resulting materials were then characterized by thermal analysis, X-ray diffraction, transmission electron microscopy and luminescence.Molecular Dynamics simulation and Fluorescence line narrowing of ZLAG matrix have been performed in order to investigate the structural modification during the transformation of the glass into the glass-ceramic.Luminescence of Yb3+ ion was observed in the near IR at 980 nm under blue excitation in all studied series, which is the signature of energy transfer. In the ZLAG glass, the efficiency reaches 92% for Pr3+ → Yb3+ energy transfer and 65% for Tm3+ → Yb3+ energy transfer. The efficiency is lower in the ZBLA glass and the ZLAG ceramisation does not improve the performances.