In this dissertation, I will look into the size distribution of silver nanoparticles produced by laser ablation of microparticles (LAM). I will investigate the role of both pulsed and continuously operating nozzles on the size distribution. In addition, I will examine any deviations from the previously observed log-normal size distribution for silver nanoparticles comparing previous collection techniques involving supersonic jet impaction with a current time of flight mass spectrometer (TOF-MS). These new observations will be made in situ using a Wiley-McLaren TOF-MS with a reflector and multiphoton ionization and will mainly focus on the smaller sized nanoparticles. An introduction to enhancing a second harmonic optically generated signal will also be investigated involving silver nanocomposites while utilizing a polarized crossed-beam femtosecond laser technique. / text

Monothiolate protected gold nanoclusters with near IR luminescence underwent a five-to-ten fold enhancement of quantum efficiency by heating in the presence of excess thiols. Two monothiolate nanoclusters, mercaptosuccinic acid and tiopronin, were shown to benefit from this procedure. Emission maximum around 700-900 nm is favorable for bioimaging applications due to reduction of background signal from autofluorescence. Dithiolate lipoic acid protected gold nanoclusters with higher near IR quantum efficiency present an interesting candidate for biological imaging due to the difference in hydrophobicity, resistance to quenching by divalent cations and cell growth media, and retained quantum efficiency when coupled to agents such as polyethylene glycol. Intracellular and nuclear internalization of mercaptosuccinic gold nanoclusters demonstrate a potential vector for delivery of nuclear targeting agents. The small size, chemical stability, high luminescence, and potential for targeting various intracellular domains make gold nanoclusters worthwhile for further studies as potential bioimaging probes.

Anthropogenic climate change presents an unrivalled threat to environmental stability and the prosperity of future generations. Utilising abundant, renewable resources in energy generation and storage will be essential to halt climate change and its effects. Solar water splitting is an excellent tool in the renewable energy arsenal for countering climate change, as it utilises both sunlight and water, two of the most abundant resources available on earth. Furthermore, the direct formation of a chemical fuel, hydrogen, is thought to be more practical for storing in large quantities than electricity. Work in this thesis covers the investigation of a variety of materials, fabricated by aerosol assisted chemical vapour deposition (AACVD), for their ability to carry out photoelectrochemical water splitting. In one project, thin films of Bi2Ti2O7 (BTO), specifically of the pyrochlore crystal structure, are fabricated by AACVD and analysed for their photoelectrochemical properties. The resulting thin films are found to be phase pure with a band gap of 2.88 eV, which is 0.32 eV smaller than TiO2. Efforts to dope the BTO thin films are further investigated through the addition of iron. Significant modification to the band gap is observed, leading to a confirmed pyrochlore thin film exhibiting a band gap of 2.5 eV, a reduction of 0.38 eV from undoped BTO. The resulting thin film had a photocurrent 5 times higher than that of undoped BTO. Finally, efforts to fabricate Fe2Ti2O7 are outlined. It is discovered that a stable phase of Fe2TiO5 is preferentially formed over the pyrochlore phase, even with dramatic modification to the deposition parameters and precursor stoichiometry. The high stability of this phase, coupled with the limiting features of the glass substrates, highlights the challenges with forming certain pyrochlore thin films. In a second project, the effect of depositing titanium nanoclusters onto the surface of bismuth vanadate is investigated. Nanoclusters are of huge interest because their properties lie between those of atoms and bulk materials. Additionally, nanoscale clusters can be fabricated with incredible precision, allowing one to select discrete diameter particles for deposition on surfaces. Ti nanoclusters over a range of sizes are deposited onto BiVO4 photoanodes. It is discovered that the deposition of ultralow loadings of Ti2000 clusters results in an 80 % enhancement in the photocurrent of the BiVO4 substrates. Further experimentation highlights that the photocurrent enhancement is linked to the size of the nanocluster and the density of the clusters on the surface. A mechanism is outlined, whereby the Ti nanoclusters partially reduce the surface of the BiVO4, leading to enhanced electron transport within the thin films due to the presence of oxygen vacancies. In a final project, polycrystalline InN, GaN and systematically controlled InxGa1-xN composite thin films are fabricated on FTO glass by a facile, low-cost and scalable aerosol assisted chemical vapor deposition technique. Variation of the indium content in the composite films leads to a dramatic shift in the optical absorbance properties, which correlates with the band edges shifting between those of GaN to InN. Moreover, the photoelectrochemical properties are shown to vary with indium content, with the 50 % indium composite having an external quantum efficiency of around 8 %. Whilst the overall photocurrent is found to be low, the photocurrent stability is shown to be excellent, with little degradation seen over 1 hour. Subsequent attempts to modify the morphology by conducting vertical-AACVD are also outlined. Thin films fabricated using vertical-AACVD are found to grow via a different mechanism, leading to undesired split phase growth, where two different compositions form on the same substrate.

A strategy based on reticulating metal ions and organic ligands into atomically precise gold and silver nanoclusters (NCs) with high monodispersity has been advanced to a point that allows the design of NCs with strict stoichiometries, functionalities and valence. Of the Ag NCs discovered, Ag44 is the most studied, not only due to its high absorption that transcends the visible spectrum suitable for photovoltaics but also because of its long excited state lifetime, as revealed by nanosecond transient absorption spectroscopy. A major principle discovered in this dissertation is the ability to produce Ag44 in scalable amounts and with high stability in addition to modulation of the functional groups of the organic ligands via a fast and complete ligand exchange process. This new discovery has led to the development of synthetic designs in which new sizes were obtained by varying the reaction parameters (e.g., ligands functionality, reaction temperature and time), namely, Ag29 using dithiols and phosphines. The synthesized NCs possess tetravalent functionalities that facilitate their crystallization and characterization. Furthermore, Ag29 glows red and is therefore a possible candidate for sensing and imaging applications.

No description available.

O uso de nanomateriais em aplicações como catálise e medicina, despertou nos últimos anos o interesse no estudo das propriedades de nanoclusters. O estudo das propriedades termodinâmicas desses sistemas é essencial, pois mudanças estruturais originadas de mudanças de fase podem alterar propriedades como atividade catalítica, momento magnético e propriedades óticas. A dinâmica molecular vêm sendo utilizada para o estudo computacional das propriedades termodinâmicas de diversos nanomateriais, enquanto o uso de métodos de Monte Carlo (MC), nesse contexto, tem se restringido ao estudo de nanoclusters de Lennard-Jones (LJ). Para avaliar a viabilidade do uso de métodos de MC no estudo de propriedades de sistemas reais, uma implementação do método Parallel Tempering Monte Carlo (PTMC) utilizando algoritmos do estado da arte para realização de trocas, determinação de temperaturas e ajuste de deslocamentos foi construída. Através de testes, é mostrado que alguns dos algoritmos implementados podem não ser adequados ao estudo do problema em questão. A implementação foi validada com o estudo das propriedades termodinâmicas de nanoclusters de LJ com 38, 55 e 147 átomos, que possuem resultados conhecidos na literatura. Além disso, resultados para propriedades do nanocluster LJ98 são apresentados, e devido à características estruturais desse sistema, é observada uma transição sólido-sólido entre as estruturas tetraédricas e icosaédricas em temperatura abaixo da de fusão. A hipótese do uso do algoritmo PTMC para o estudo de propriedades de materiais reais, foi testada nas nanoligas (PtCo)55 e (PtNi)55, descritas pelo potencial de Gupta. Através da comparação das estruturas de mais baixa energia com resultados de teoria do funcional da densidade (DFT, do inglês), é mostrado que o uso do potencial de Gupta pode ser justificado, dados os baixos desvios no comprimento de ligação (menores que 2.4%) e a semelhança de outras características estruturais. Os resultados obtidos indicam que o método PTMC é capaz de identificar as mudanças de fase das nanoligas estudadas. Essas mudanças são ilustradas e analisadas com o uso de um algoritmo para a comparação da similaridade de estruturas, com o qual foi possível analisar a fusão dos nanoclusters Co55, Ni55, Pt30Co25 e Pt40Ni15 (obtida em temperaturas entre 900 e 1100 K); além da fusão, a 727 K, e transição sólido-sólido, a 300 K, para a Pt55. Com as estruturas mais frequentes, encontradas através da análise de similaridade, e com a realização de cálculos DFT, foi possível observar um deslocamento do centro da banda d em direção ao HOMO (Highest Occupied Molecular Orbital) causado pelo aumento da temperatura. Esse deslocamento, segundo o modelo da banda d válido para superfícies, pode indicar uma maior reatividade dos nanoclusters nesses casos. / The use of nanomaterials in applications such as catalysis and medicine, aroused in the last years interest in studying properties of nanoclusters. The study of thermodynamic properties of these systems is essential, since structural changes originated from phase changes can alter properties such as catalytic activity, magnetic moment and optical properties. Molecular dynamics have been used for the computational study of thermodynamic properties of various nanomaterials, while the use of Monte Carlo methods (MC), in this context, has been restricted to the study of Lennard-Jones (LJ) nanoclusters. To evaluate the feasibility of using MC methods to study properties of real systems, an implementation of the Parallel Tempering Monte Carlo (PTMC) method using state of the art algorithms to perform exchanges, determine the temperature set and adjust the maximum displacement, was built. Through testing, it is shown that some of the implemented algorithms may not be suitable for the study of the problem in question. The implementation was validated by studying the thermodynamic properties of LJ nanoclusters with 38, 55 and 147 atoms, which have results known in the literature. In addition, results for the properties of the LJ98 nanocluster are reported, and due to the structural features of this system, a solid-solid transition between the tetrahedral and icosahedral structures in a temperature below melting is observed. The possibility of using the PTMC algorithm in the study of properties of real materials, is tested in the (PtCo)55 and (PtNi)55 nanoalloys, described by the Gupta potential. By comparing the lowest energy structures with density functional theory (DFT) results, it is shown that the use of the Gupta potential can be justified, given the small deviation in the bond lenght (less than 2.4%) and the similarity of other structural features. The results indicate that the PTMC method is able to identify the phase changes in the studied nanoalloys. These changes are illustrated and analyzed with the use of an algorithm for comparing the structure similarity, which made possible the analysis of the melting of the Co55, Ni55, Pt30Co25 e Pt40Ni15 nanoclusters (obtained at temperatures between 900 e 1100 K); and the melting at 727 K, and solid-solid transition at 300 K, for Pt55. With the most frequent structures, obtained by the similarity analysis, and through DFT calculations, it was possible to observe a shift in the d band center to the HOMO (Highest Occupied Molecular Orbital) caused by the temperature increase. This shift, following the d band model valid for surfaces, may indicate a higher reactivity of the nanocluster in these cases.

O uso de nanomateriais em aplicações como catálise e medicina, despertou nos últimos anos o interesse no estudo das propriedades de nanoclusters. O estudo das propriedades termodinâmicas desses sistemas é essencial, pois mudanças estruturais originadas de mudanças de fase podem alterar propriedades como atividade catalítica, momento magnético e propriedades óticas. A dinâmica molecular vêm sendo utilizada para o estudo computacional das propriedades termodinâmicas de diversos nanomateriais, enquanto o uso de métodos de Monte Carlo (MC), nesse contexto, tem se restringido ao estudo de nanoclusters de Lennard-Jones (LJ). Para avaliar a viabilidade do uso de métodos de MC no estudo de propriedades de sistemas reais, uma implementação do método Parallel Tempering Monte Carlo (PTMC) utilizando algoritmos do estado da arte para realização de trocas, determinação de temperaturas e ajuste de deslocamentos foi construída. Através de testes, é mostrado que alguns dos algoritmos implementados podem não ser adequados ao estudo do problema em questão. A implementação foi validada com o estudo das propriedades termodinâmicas de nanoclusters de LJ com 38, 55 e 147 átomos, que possuem resultados conhecidos na literatura. Além disso, resultados para propriedades do nanocluster LJ98 são apresentados, e devido à características estruturais desse sistema, é observada uma transição sólido-sólido entre as estruturas tetraédricas e icosaédricas em temperatura abaixo da de fusão. A hipótese do uso do algoritmo PTMC para o estudo de propriedades de materiais reais, foi testada nas nanoligas (PtCo)55 e (PtNi)55, descritas pelo potencial de Gupta. Através da comparação das estruturas de mais baixa energia com resultados de teoria do funcional da densidade (DFT, do inglês), é mostrado que o uso do potencial de Gupta pode ser justificado, dados os baixos desvios no comprimento de ligação (menores que 2.4%) e a semelhança de outras características estruturais. Os resultados obtidos indicam que o método PTMC é capaz de identificar as mudanças de fase das nanoligas estudadas. Essas mudanças são ilustradas e analisadas com o uso de um algoritmo para a comparação da similaridade de estruturas, com o qual foi possível analisar a fusão dos nanoclusters Co55, Ni55, Pt30Co25 e Pt40Ni15 (obtida em temperaturas entre 900 e 1100 K); além da fusão, a 727 K, e transição sólido-sólido, a 300 K, para a Pt55. Com as estruturas mais frequentes, encontradas através da análise de similaridade, e com a realização de cálculos DFT, foi possível observar um deslocamento do centro da banda d em direção ao HOMO (Highest Occupied Molecular Orbital) causado pelo aumento da temperatura. Esse deslocamento, segundo o modelo da banda d válido para superfícies, pode indicar uma maior reatividade dos nanoclusters nesses casos. / The use of nanomaterials in applications such as catalysis and medicine, aroused in the last years interest in studying properties of nanoclusters. The study of thermodynamic properties of these systems is essential, since structural changes originated from phase changes can alter properties such as catalytic activity, magnetic moment and optical properties. Molecular dynamics have been used for the computational study of thermodynamic properties of various nanomaterials, while the use of Monte Carlo methods (MC), in this context, has been restricted to the study of Lennard-Jones (LJ) nanoclusters. To evaluate the feasibility of using MC methods to study properties of real systems, an implementation of the Parallel Tempering Monte Carlo (PTMC) method using state of the art algorithms to perform exchanges, determine the temperature set and adjust the maximum displacement, was built. Through testing, it is shown that some of the implemented algorithms may not be suitable for the study of the problem in question. The implementation was validated by studying the thermodynamic properties of LJ nanoclusters with 38, 55 and 147 atoms, which have results known in the literature. In addition, results for the properties of the LJ98 nanocluster are reported, and due to the structural features of this system, a solid-solid transition between the tetrahedral and icosahedral structures in a temperature below melting is observed. The possibility of using the PTMC algorithm in the study of properties of real materials, is tested in the (PtCo)55 and (PtNi)55 nanoalloys, described by the Gupta potential. By comparing the lowest energy structures with density functional theory (DFT) results, it is shown that the use of the Gupta potential can be justified, given the small deviation in the bond lenght (less than 2.4%) and the similarity of other structural features. The results indicate that the PTMC method is able to identify the phase changes in the studied nanoalloys. These changes are illustrated and analyzed with the use of an algorithm for comparing the structure similarity, which made possible the analysis of the melting of the Co55, Ni55, Pt30Co25 e Pt40Ni15 nanoclusters (obtained at temperatures between 900 e 1100 K); and the melting at 727 K, and solid-solid transition at 300 K, for Pt55. With the most frequent structures, obtained by the similarity analysis, and through DFT calculations, it was possible to observe a shift in the d band center to the HOMO (Highest Occupied Molecular Orbital) caused by the temperature increase. This shift, following the d band model valid for surfaces, may indicate a higher reactivity of the nanocluster in these cases.

Cette thèse est consacrée à l'étude approfondie de formes exotiques de matériaux nano-structurés qui pourraient conduire à une avancée significative dans les nano-composants. Deux thèmes distincts ont été ainsi abordés. Le premier concerne les nano-clusters aromatiques de silicium synthétisés par plasma (SiNCs), tandis que le second est dédié aux structures silicium et germanium bi-dimensionnelles. Grâce à des simulations de type dynamique moléculaire et des calculs ab initio, ainsi que sur des recherches expérimentales, nous nous proposons d’explorer les propriétés intrigantes, mais à fort potentiel, de ces matériaux exotiques.Dans la première partie, nous commençons par des études théoriques et montrons qu'il est possible d'obtenir un comportement aromatique pour des SiNCs hydrogénés ayant une taille de ~1nm. Nous démontrons que les plasmas silane/hydrogène à basse température, proches de la formation de particules de poussière, présentent l'environnement idéal pour exploiter la tendance naturelle du silicium à la sur-coordination et donc pour la synthèse de structures à liaisons déficitaires en électrons. Ces nano-clusters qui se forment spontanément par auto-assemblage dans le plasma, ne possèdent pas de structure tétraédrique, sont plus stables que tous les autres SiNCs connus de cette taille et ont de fortes propriétés aromatiques dues à leur forte délocalisation électronique. Nous montrons également que les SiNCs non tétraédriques, présentent des modes de liaison à caractère métallique qui ressemblent fortement à celui d'un gaz d'électrons homogène dans des nano-clusters de métaux. Les SiNCs tétraédriques standards de cette taille ne peuvent absorber que dans l'ultraviolet, alors que nos calculs ont montré que des SiNCs purs, mais sur-coordonnés, absorbent dans la région spectrale ultraviolette, mais aussi dans le visible et l’infrarouge. Nous présentons ensuite une première preuve expérimentale pour nos prédictions théoriques. Nous avons mesuré in situ, dans un réacteur plasma l'absorption de la lumière visible des SiNCs. De plus, nos mesures réalisées en présence d'un champ électrique ont prouvées clairement que les SiNCs aromatiques possèdent un moment dipolaire permanent, que nous avons estimé entre 2 et 2,5 Debye, en excellent accord avec les calculs ab initio. Enfin, nos images de microscopie électronique à transmission des SiNCs, déposés dans des conditions de plasma optimisées, ont révélé la présence d'une autre forme exotique de silicium à structure hexagonale. Une telle structure se forme habituellement à des pressions extrêmement élevées appliquées sur des structures cubiques (diamant) de silicium. Nous souhaitons affirmer que c’est grâce à la «chimie au marteau» que ces conditions ont été atteintes.Dans la seconde partie, nous avons entrepris des études théoriques et expérimentales approfondies sur la croissance d'une nouvelle forme allotropique de silicium et de germanium: le silicène et le germanène, à savoir, une mono-couche d'atomes intégrée dans un réseau hexagonal qui ressemble fortement au graphène. Afin d'exclure tout mélange entre les atomes de silicium ou de germanium avec le substrat et de conserver leurs caractéristiques prometteuses comme de nouveaux matériaux de Dirac, nous avons effectué nos dépôts, sur un substrat de graphite chimiquement inerte. Une de nos découvertes cruciales est que les mono-couches de silicène ou de germanène interagissent avec le substrat de graphite uniquement via des forces de van der Waals. Cette interaction est suffisamment forte pour stabiliser les mono-couches, déposées même au-dessus de la température ambiante, mais suffisamment faible pour empêcher toute hybridation ou alliage entre le silicium ou le germanium et les atomes de carbone du substrat. Par conséquent, les propriétés électroniques exceptionnelles du silicène et du germanène, tels que les cônes de Dirac et les électrons sans masse, sont préservées même après leur dépôt sur les surfaces de graphite. / This thesis is devoted to the study of advanced, exotic forms of nanostructured materials that could lead to the next big advance for nanodevices. Two distinct topics have been considered. The first one is related to plasma-born aromatic silicon nanoclusters (SiNCs), while the second is dedicated to two-dimensional silicon and germanium materials. Based on molecular dynamics simulations and ab initio calculations, as well as, on experimental investigations, we explore a variety of intriguing properties of those exotic materials that are expected to be far superior to those of their conventional counterparts.In the first part of the thesis, we begin with theoretical studies and show that it is possible to obtain aromatic behavior in simple hydrogenated SiNCs with size of ~1nm. We demonstrate that low-temperature silane/hydrogen plasmas close to dust formation present the ideal environment to exploit the natural tendency of silicon to over-coordination for the construction of structures with electron-deficient bonds. Those nanoclusters form spontaneously by self-assembly in plasmas, do not possess tetrahedral structures, are more stable than any other known SiNCs of this size, and have strong aromatic-like properties due to their high electron delocalization. We demonstrate that non-tetrahedral SiNCs exhibit metallic-like bonding schemes that strongly resemble the one of a homogeneous electron gas in small metal clusters. Standard tetrahedral SiNCs of this size can absorb light only in the ultraviolet, while our calculations have shown that pure, but over-coordinated SiNCs absorb light in the ultraviolet, visible, and infrared spectral region. In this thesis, we present first experimental evidence that supports our theoretical predictions. Using incoherent broadband cavity enhanced absorption spectroscopy, we have measured the absorption of SiNCs, in situ, in a plasma reactor and found that they do absorb light in the visible region. In addition, our absorption measurements in the presence of an applied electric field have provided clear evidence that aromatic SiNCs possess a permanent dipole moment, and we have measured it to be between 2 and 2.5 Debye, in excellent agreement to prior ab initio calculations. Finally, our transmission electron microscopy images of such SiNCs, after their deposition under optimized plasma conditions, have revealed the presence of another exotic form of silicon with a primitive hexagonal structure. Such a structure usually forms after exposing diamond-cubic silicon to extremely high pressures. We tentatively claim that those conditions were, actually, achieved in our experiments due to the “chemistry with a hammer”.In the second part of the thesis, we have undertaken in-depth theoretical and experimental studies on the growth of a new allotropic form of silicon and germanium: a single layer of silicon or germanium atoms, only one atom thick and packed in a hexagonal lattice that closely resembles the lattice of graphene, namely silicene and germanene. In order to rule out any intermixing between silicon or germanium atoms and the underneath substrate atoms, as it was the case for metallic substrates, and to maintain their promising features to be new Dirac materials, we have performed our depositions on a chemically inert graphite substrate. One of our crucial findings is that the silicene or germanene monolayers interact with the graphite substrate via van der Waals forces only. The van der Waals interaction is strong enough to stabilize the deposited monolayers even above room temperature, but weak enough to prevent any hybridization or alloying between silicon or germanium and carbon atoms. Consequently, the outstanding electronic properties of free-standing silicene and germanene, such as Dirac cones and massless electrons, are preserved even after their deposition on graphite surfaces.

Ag thin and thick films have been experimentally deposited using a technique called Laser Ablation of a Microparticle Aerosol (LAMA). This technique is based on a supersonic jet accelerating NPs of a few nm diameter up to 1000 m/s and operating at room temperature. The deposited films have experimentally demonstrated interesting properties such as dense growth with good adherence on the substrate. Aerosol feed rates have been fixed to 10 mg/h which corresponds to rate depositions of 10¹⁰ to 10¹¹ NPs/s/cm². In order to model this deposition technique and possibly be able to predict the morphology and structure of deposited films using computational methods, we have designed MD programs simulating the depositions of several Ag nanoclusters onto a substrate at a fixed temperature (300 K). The variation of parameters such as cluster size, cluster impact energy, and deposition rate has influenced the morphology and structure of the deposited films. Cluster diameters have been set to 3 nm or 5 nm, cluster velocities set to 200 m/s (0.022 eV/atom), 400 m/s (0.069 eV/ atom), or 800 m/s (0.358 eV/atom), and the deposition rate adjusted to ensure relaxation times between impactions of 5 ps to 20 ps. The evolution of deposited film density, adherence, and crystal arrangement has been analyzed with the variation of the aforementioned parameters. The highest cluster velocities have enabled the deposition of smoother, denser, and more adherent films. NCs with an initial velocity of 200 m/s have shown ratios of flattening equal to 50 % as opposed to 85% flattening for NCs deposited at 800 m/s. These observations have enabled us to draw qualitative conclusions on the film density The deposited films are less porous when the cluster impaction velocity increases. Atomic mixing between substrate and impacted NC atoms increased with increasing deposition velocity, which can perhaps be correlated to an increase of adherence, assuming that more mixing will create stronger molecular binding in the cluster-substrate interaction. Finally, complete epitaxial growth was observed for the highest impaction velocities only, which indicates that recrystalization can occur for this range of impact energies (0.3 eV/atom - 0.5 eV/atom). Although experimental results have given more quantitative data on film density and sticking ratios, they agree with our modeling, and this comparison allows us to validate our MD simulations. However, some limitations have been faced, mainly because of long computing time requirements that a single laptop computer has not been able to support. / text

Thesis advisor: John T. Fourkas / One can extract a tremendous amount of information about the organizational and dynamic states of molecules, in situ and in real-time, through highly sensitive and noninvasive single particle optical probing. The highly efficient, multi-photon excited luminescence from stabilized metal nanoclusters renders these species useful as optical probes that can be used in detecting single particle and molecular dynamics. We generate stable, and monodisperse samples of Ag nanoclusters as small as 1 nm in diameter, and find that through substitution of various stabilizer molecules we can precisely tune the size of the clusters over a 1-6 nm range of diameters, ensuring monodispersity and stability at every stage. These clusters also exhibit highly efficient, polarized luminescence upon two photon excitation at 800 nm and remain highly photostable, not exhibiting the deleterious blinking that occurs with many single-molecule fluorophores. In order to demonstrate the utility of these clusters as single-molecule probes, we track their emission polarization over long periods in deeply supercooled liquids such as 4'(octahydro-4,7-methano-5H-inden-5-yliden) bisphenol dimethyl ether (ODE). Our results suggest that these clusters can detect nanoscale dynamics with high sensitivity. / Thesis (BS) — Boston College, 2004. / Submitted to: Boston College. College of Arts and Sciences. / Discipline: Chemistry. / Discipline: College Honors Program.