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Colloidal nanocrystals of metals, semiconductors, and other functional materials can self-assemble into long-range ordered crystalline and quasicrystalline phases, but insulating organic surface ligands prevent the development of collective electronic states in ordered nanocrystal assemblies. We reversibly self-assembled colloidal nanocrystals of gold, platinum, nickel, lead sulfide, and lead selenide with conductive inorganic ligands into supercrystals exhibiting optical and electronic properties consistent with strong electronic coupling between the constituent nanocrystals. The phase behavior of charge-stabilized nanocrystals can be rationalized and navigated with phase diagrams computed for particles interacting through short-range attractive potentials. By finely tuning interparticle interactions, the assembly was directed either through one-step nucleation or nonclassical two-step nucleation pathways. In the latter case, the nucleation was preceded by the formation of two metastable colloidal fluids.

Coarse-grained molecular modeling and active learning enable the design of polarizable nanoparticles capable of triggered assembly and disassembly.

Microscale patterning of colloidal nanocrystal (NC) films is important for their integration in devices. Here, we introduce the direct optical patterning of all-inorganic NCs without the use of additional photosensitive ligands or additives. We determined that photoexposure of ligand-stripped, "bare" NCs in air significantly reduces their solubility in polar solvents due to photo-oxidation of surface ions. Doses as low as 20 mJ/cm

Thiol ligands bound to the metallic core of nanoparticles determine their interactions with the environment and self-assembly. Recent studies suggest that equilibrium between bound and free thiols alters the ligand coverage of the core. Here, X-ray scattering and MD simulations investigate water-supported monolayers of gold-core nanoparticles as a function of the core-ligand coverage that is varied in experiments by adjusting the concentration of total thiols (sum of free and bound thiols). Simulations demonstrate that the presence of free thiols produces a nearly symmetrical coating of ligands on the core. X-ray measurements show that above a critical value of core-ligand coverage the nanoparticle core rises above the water surface, the edge-to-edge distance between neighboring nanoparticles increases, and the nanoparticle coverage of the surface decreases. These results demonstrate the important role of free thiols: they regulate the organization of bound thiols on the core and the interactions of nanoparticles with their surroundings.

In contrast to molecular systems, which are defined with atomic precision, nanomaterials generally show some heterogeneity in size, shape, and composition. The sample inhomogeneity translates into a distribution of energy levels, band gaps, work functions, and other characteristics, which detrimentally affect practically every property of functional nanomaterials. We discuss a novel synthetic strategy, colloidal atomic layer deposition (c-ALD) with stationary reactant phases, which largely circumvents the limitations of traditional colloidal syntheses of nano-heterostructures with atomic precision. This approach allows for significant reduction of inhomogeneity in nanomaterials in complex nanostructures without compromising their structural perfection and enables the synthesis of epitaxial nano-heterostructures of unprecedented complexity. The improved synthetic control ultimately enables bandgap and strain engineering in colloidal nanomaterials with close to atomic accuracy. To demonstrate the power of the new c-ALD method, we synthesize a library of complex II-VI semiconductor nanoplatelet heterostructures. By combining spectroscopic and computational studies, we elucidate the subtle interplay between quantum confinement and strain effects on the optical properties of semiconductor nanostructures.

Many man-made structures within Grand Teton National Park (GTNP) provide suitable, if not ideal habitat for bats, especially the Little Brown Myotis (Myotis lucifugus) and the Big Brown Bat (Eptesicus fuscus). In 1995 and 1996, Tom Haraden (GTNP Naturalist) observed many maternity colonies of these species residing within park residences and other buildings. From these observations, this project was developed to expand the knowledge on the local bat populations in GTNP and assess the risk bats might pose to humans within the park buildings they share. Public health concerns are often associated with the status of wild animal populations as potential carriers for a number of diseases. Bats have previously been shown to carry vesicular stomatitis, western equine encephalitis and rabies. Although the ability for bats to carry these and other diseases has been established, there has not been significant research, other than work done with bat Rabies Virus, on the risk that bats and their diseases pose to the human populations. This is despite the presence of bats often living in close proximity to humans. The roofs and attics of manmade structures provide ideal habitat for bat species, especially Myotis lucifugus and Eptesicus fuscus. The ideal daytime bat roost is warm, generally over 90 degrees Fahrenheit, high off the ground to prevent predation, dry, in proximity to a source of water, with adequate sites for clinging or hanging. Nearly every building in Grand Teton National Park fits this description due to the age of the buildings and cracks for bat entrance are common as they require a hole as small as 1/2" to 1" in diameter to gain access. Vesicular Stomatitis, Western Equine Encephalitis, and Rabies Virus are zoonotic diseases that may be carried by bats. If bats of Grand Teton National Park carry these diseases, they would pose a potential risk to the wildlife, domestic animals (including livestock species), and humans living in and around Grand Teton National Park. This risk would potentially extend into the surrounding gateway communities and Yellowstone National Park. The species ranges for Myotis lucifugus and Eptesicus fuscus, the two principle species in this study, cover most of North America, leaving the potential dispersion of a disease over the entire continent and possibly even into South America if transmitted and carried by other bat or bird species. All three viruses cause disease in livestock species including pigs, horses, and cattle, and zoonotic infection in humans. Infections can cause production loss such as severe mastitis in dairy cattle or low weight gain in pigs from vesicular stomatitis, as well as disease in humans ranging from flu-like symptoms to death due to western equine encephalitis infection. Disease from Rabies Virus infection is fatal in all mammalian species, and Vesicular Stomatitis and Western Equine Encephalitis infection does not confer immunity. The aim of this study is to identify the potential risk of bats as carriers of these diseases to provide park managers with baseline information to pursue further disease study and establish structural bat exclusion measures, if needed. As with all park research, the results of this project will also provide information for educational programs.