Photoactivated fluorescence from individual silver nanoclusters ranging in size from 2 8 atoms has been demonstrated at room temperature. The optical properties of such clusters are far superior to those of fluorescence dyes with absorption cross sections ~50 times stronger than those of even the best organic dyes. The strong oscillator strengths produced from such nanoclusters has been shown to yield comparable enhancement factors in the surface-enhanced Raman spectroscopy (SERS) process to those observed in the presence of a plasmon- supporting nanoparticle. Raman transitions are in fact so strong that antistokes scattering is also observable on a single molecule (SM) level marking the first true demonstration of SM-SERS to date. Capable of generating true scaffold specific Raman scattering on the single molecule level, the combination of fluorescence from the small nanoclusters and strong observed Raman signals in the absence of a nanoparticle strongly indicate a chemical or charge transfer SERS enhancement mechanism.

Finding materials with high stability, high yield, and excellent catalytic performance has been an outstanding research challenge. Thiol-stabilized atomically precise metal nanoclusters (NCs) have attracted a lot of interest in recent years due to their unique properties and industrial applications, including catalysis, toxic metal-ion sensing, and magnetism. Unlike classical nanoparticles (NPs) which have larger sizes ranging between 10-100 nm, the size of nanoclusters typically ranges from 1 to 3 nm. Thus, nanoclusters represent good candidates to gain fundamental insights into optical and catalytic properties from the atomic to the molecular level. The majority of nanoclusters are based on Ag, Au, and more recently Cu. The major goal of this dissertation is the synthesis and structure determination of silver and copper nanoclusters. The first part of this dissertation addresses a shape-controlled synthesis strategy based on an isomeric dithiol ligand to yield the smallest crystallized silver nanocluster to date, formulated as Ag9. The second part discusses the preparation of different sizes of copper nanoclusters using a one-pot synthesis method and attempted to understand the structure-dependent catalytic pathways at the atomic level. Moreover, three novel Cu nanoclusters were developed: Cu29, Cu45, and Cu67. In terms of size, Cu67 represents a milestone towards high-nuclearity nanoclusters with interesting optical and structural properties. In terms of catalytic properties, Cu45 was found to be promising catalyst in hydroboration reactions of alkynes/alkenes and B2pin2, which affords hydroborated products with good to excellent yield. Mechanistic studies showed single-electron oxidation of an in-situ formed ate complex ([B2pin2]OH-) by the Cu45 catalyst, enabling hydroboration of unsaturated double bonds via a boryl-centred radical. These findings motivate us to extend the library of ligand-protected nanoclusters and focus deeply on exploiting metal nanoclusters based on Cu for catalysis.

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Mes travaux de recherche concernent la synthèse et la caractérisation des nanoclusters stabilisés pardes ligands thiolés, et plus particulièrement des nanoclusters d’or et d’argent. L’étude de ces clusterspar des méthodes de caractérisation optique en solution, séparation sur le gel d’électrophorèse et laspectrométrie de masse à haute résolution a permis de sonder quelques propriétés structurelles etélectroniques. L’originalité de ce travail de thèse vient, du couplage d’un spectromètre de masse avecun laser accordable en longueur d’onde UV/Visible pour étudier les propriétés optiques de clusters enphase gazeuse. En effet, ce travail a permis d’obtenir le premier spectre sur des mesures optiques deces espèces.Une partie de ce travail est consacrée à la synthèse et la caractérisation des nanoclusters d’or stabiliséspar les glutathions allant de Au4(SG) 4 à Au25(SG) 18. Les expériences de fragmentation induite parcollision sont réalisées sur les clusters afin de sonder leurs structures. Nous avons développé unenouvelle méthode basée sur l’analyse des structures isotopiques expérimentales pour déterminer lenombre d’électrons accommodés le coeur métallique.Ces études expérimentales ont été étendues à d’autres systèmes tels que les clusters d’argent stabiliséspar les glutathions. Deux méthodes de synthèse des clusters Agx(SG)y ont été développées aulaboratoire. Dans le cadre de ce travail, pour la première fois, nous avons pu déterminer la stichométriede ces clusters Ag31(SG) 19 et Ag15(SG) 11. / My research works concerns the synthesis and characterization of nanoclusters stabilized by thiolates(SG), particularly the gold and silver nanoclusters. The study of these clusters by opticalcharacterization techniques in solution, separation by gel electrophoresis and high-resolution massspectrometry has allowed to probe some structural and electronic proprieties. The origin of this workcome from experimental setup coupled mass spectrometry to UV/Visible optical parametric oscillatortunable laser for understanding the optical proprieties of the clusters in gas phase. In fact, this workhas allowed to get the first optical gas phase spectrum of this species. The first part of this work is dedicated to the synthesis and characterization of glutathione stabilizedgold nanoclusters with size between Au4 (SG) 4 and Au25 (SG) 18. Collision induced dissociationexperiments are performed to probe some structural proprieties of the clusters. We have developednew method based on the analysis of the experimental isotopic distribution allowed to find the numberof electrons bear in metallic core.These experimental studies have been extended to other systems such as glutathione stabilized silvernanoclusters. Two synthesis methods Agx(SG)y have been developed in the laboratory. For the firsttime, we have found the stoicheiometry of these clusters as Ag31 (SG) 19 and Ag15 (SG) 11.