This thesis is focused on understanding the interactions between molecules and surface-enhanced Raman scattering (SERS) substrates that are typically unresolved due to the diffraction limit of light. Towards this end, we have developed and tested several different sub-diffraction-limited imaging techniques in order to observe these interactions. First, we utilize an isotope-edited bianalyte approach combined with super-resolution imaging via Gaussian point-spread function fitting to elucidate the role of Raman reporter molecules on the location of the SERS emission centroids. By using low concentrations of two different analyte molecules, we find that the location of the SERS emission centroid depends on the number and positions of the molecules present on the SERS substrate. It is also known that SERS enhancement partially results from the molecule coupling its emission into the far-field through the plasmonic nanostructure. This results in a particle-dictated, dipole-like emission pattern, which cannot be accurately modeled as a Gaussian, so we tested the applicability of super-resolution imaging using a dipole-emission fitting model to this data. To test this model, we first fit gold nanorod (AuNR) luminescence images, as AuNR luminescence is primarily coupled out through the longitudinal dipole plasmon mode. This study showed that a three-dimensional dipole model is necessary to fit the AuNR emission, with the model providing accurate orientation and emission wavelength parameters for the nanostructure, as confirmed using correlated AFM and spectroscopy. The dipole fitting technique was next applied to single- and multiple-molecule SERS emission from silver nanoparticle dimers. We again found that a three-dimensional dipole PSF was necessary to accurately model the emission and orientation parameters of the dimer, but that at the single molecule level, the movement of the molecule causes increased uncertainty in the orientation parameters determined by the fit. Finally, we describe progress towards using a combined atomic force/optical microscope system in order to position a carbon nanotube analyte at known locations on the nanoparticle substrate. This would allow for the simultaneous mapping of nanoparticle topography and exact locations of plasmonic enhancement around the nanostructure, but consistently low signal-to-noise kept this technique from being viable. / text

Ce travail est consacré au développement de luminophores ultraphosphatés de formule LnP5O14 (Ln=Gd, La et Y) activés par les ions Eu3+ et/ou Tb3+, synthétisés par la technique sol-gel sous forme de poudres. Les conditions opératoires optimales ont été déterminées, la caractérisation des intermédiaires de réaction et de matériaux finaux a été menée d'un point de vue structural (DRX, IR, Raman, RMN) ou morphologique (MEB, granulométrie laser). L'activation par une sonde fluorescente comme l'ion Eu3+ a aussi permis d'affiner la caractérisation des matériaux en identifiant les signatures spectrales des centres émetteurs corrélativement à leur environnement cristallographique. Une étude structurale a permis de caractériser les variétés monoclinique C2/c et orthorhombique Pnma de l'ultraphosphate d'yttrium YP5O14 à partir des données de la diffraction X sur monocristal. Une étude cristallochimique approfondie des ultraphosphates de formule LnP5O14 a révélé l'existence des variétés monocliniques C2/c pour les ultraphosphates EuP5O14 et GdP5O14 et invalidé l'existence de la variété orthorhombique Pnma pour les ultraphosphates de terres rares de plus grands rayons ioniques. L'étude des propriétés de luminescence sous excitation VUV a montré que les matrices ultraphosphates étudiées dopées en ions Eu3+, répondent favorablement aux conditions requises pour être employées dans les dispositifs plasma. Dans la matrice au gadolinium, un processus de down-conversion est à l'origine du transfert d'énergie entre les ions Gd3+ Et Eu3+ lorsque l'excitation est portée dans la bande d'adsorption caractéristique de la matrice ultraphosphate.

Ce travail concerne, la synthèse, la caractérisation structurale, morphologique et optique de matrices de titanates de baryum (BaTiO3) activées par les ions Eu3+, Er3+ et Yb3+. Trois voies de synthèse sont étudiées : sol-gel, hydrothermale et solide. Il a été montré que la synthèse hydrothermale conduisait à des poudres nanométriques constituées de particules de 20 nm, dix fois plus petites que celles rencontrées dans les poudres obtenues par les techniques classiques de céramisation. L' influence de ce paramètre sur la structure cristallographique des titanates a pu être mise en évidence. L'ajout d'agents chélatants au cours de la synthèse sol-gel permet de modifier la morphologie des poudres et de stabiliser les sols destinés à l'élaboration de revêtements. Des films épais monocouche ( 800 nm) de titanates de baryum dopés Er3+ et Eu3+ ont été ainsi obtenus. Une étude des propriétés optiques des ions de terres rares dans les différents systèmes synthétisés a été menée en enregistrant les différents spectres d'exitation et d'émission. Les phénomènes de transfert d'énergie entre les ions de terres rares ont été étudiés dans les matrices co-dopées

<p>The main aim of this thesis was to contribute with detailed information of regional environmental change during the Holocene through studies of speleothems and their growth environments from two caves, Korallgrottan and Labyrintgrottan in northwestern Sweden, and a cellar vault in Uppsala. This was done through studies of stable isotopes and luminescence properties in the speleothems in combination with a detailed monitoring study in Korallgrottan.</p><p>The monitoring study suggests that stalagmites fed by stalactites with slow and stable drip rates from deep inside the cave may be suitable as palaeoclimate archives. Similarities between oxygen isotope signals of contemporary samples from Labyrintgrottan and Korallgrottan emphasize the potential of speleothems from Labyrintgrottan to also provide high resolution regional palaeoclimate information.</p><p>Except for a number of cold events stalagmite δ¹⁸O records from northern Scandinavia indicate that temperatures were warmer than today between 9500 and 6000 years ago. During this period the interval between 7800 and 6000 years ago seems to have been the warmest. The area above Labyrintgrottan was most likely covered by much denser vegetation than today at the time of stalagmite growth (9500-7500 years ago) and was, unlike today, probably situated below the local tree-limit between 9000 and 8000 years ago. The δ¹⁸O record of a stalagmite from Korallgrottan covering the last 4000 years agrees with the concept of a warmer period, the so called Medieval Warm Period, centred around AD1000 and a colder period, the so called Little Ice Age, somewhere between AD1000 and today.</p><p>Studies of luminescence properties in fast growing speleothems from Uppsala indicate that the variations in luminescence intensity are annual and that the annual lamiae of the luminescent record represent a flush of organic material.</p>

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Chlorins, as the core structures of chlorophylls, have been extensively studied for harvesting solar energy, fluorescent imaging and photodynamic therapy against cancer. This thesis is concerned with design and synthesis of novel chlorins as antennae for harvesting light and sensitising near infrared lanthanide luminescence. In the first part, a series of chlorin monomers, dimers and polymers were synthesised and their photophysical properties were characterised. The chlorin monomers were substituted with five-membered heterocycles, such as thiophenes and furans. These heterocycles function as auxochromes analogous to the natural ones in chlorophylls, and extend chlorin absorption and emission strongly to the red (up to λem = 680 nm). A borylation method was developed to prepare borylated chlorins, which gave access to directly linked chlorin dimers through Suzuki coupling reaction. Different regioisomers of chlorin dimer were prepared, including β-meso homodimers, meso-meso homodimers and heterodimers. The dimerisation resulted in red-shifted absorption and emission. Chlorin polymerisations were performed both electrochemically and chemically. Bis-thienylchlorins yielded chlorin films and an organic solvent soluble copolymer with hexylthiophene, respectively. These polymers from both polymerisations have red absorptions beyond 700 nm, and might be used as light-harvesting antennae. In the second part, chlorins were used as chromophores to sensitise near infrared lanthanide luminescence. Two types of chlorin-lanthanide dyads were prepared through lanthanide coordination with cyclen derivatives and dipicolinic acids (DPA). The cyclen-based dyads were poorly soluble in water, thus their near infrared emissions were not observed. The other type of complexes was fully soluble in H2O and THF. Both Nd and Yb emission were recorded even upon excitation into the Q bands of chlorins. In the dyads with free base chlorins, the singlet state of chlorins might be involved in the sensitisation of lanthanide luminescence. These DPA-based dyads presented two-color emission based on one chlorin and two-color excitation based on one lanthanide ion. These dyads would enable in theory 4-color imaging. In the last part, a microwave-assisted two-step synthesis was described to prepare dipyrromethanes, which are the key intermediates in the chlorin synthesis. This mild method took advantage of the nucleophilicity of pyrrole and the electrophilicity of N,N-dimethylaminomethyl pyrroles. The usually used acid catalysis is detrimental to many functionalities, thus our methods enable the synthesis of dipyrromethanes with acid sensitive groups or a formyl group.