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Angela Meola1 Keith Reber1 Mary Sajini Devadas1

1, Towson University, Towson, Maryland, United States

Quantum dimensional gold clusters are at the forefront of research owing to their characteristic size dependent optical and electrochemical properties. Of recent interest is their use as sensing agents due to their UV, visible, and near-IR luminescence (the wavelength of emission is ligand dependent). In addition, their use as high frequency broad band semiconductor material creates interest in military technology development. Nanoparticles are studied for their observable ability to transfer electrons. Characteristically nanoparticles have sensing potential due to electronic variations in their emission spectra. Magic number icosahedron Au25L18, and Au144L60 clusters were synthesized using a one phase method with L = hexanethiol as a stabilizing ligand, and compared to the Au25L18 bi-icosahedron synthesized using an alternate one phase method. The electronic transition states of each particle were observed through optical and electrochemical analysis. The clusters were characterized through observation of documented HOMO/LUMO gap using both optical and electrochemical techniques. Au144-clusters indicated quantized double layer charge upon electrochemical analysis. Observation of quenching when coumarin is bound to gold core is observed through fluorescence quantum yield. Near IR luminescence was detected with the various geometries and observed enhancement between ligand variations. Transmission electron microscopy was employed to determine particle size, purity, and dispersity. The MPCs (Monolayer Protected Clusters) with the hexanethiol stabilizing ligand were then labelled with a coumarin dye via directed ligand exchange. The products of the exchange reaction were then compared with the MPC made from the coumarin ligand. Characterization details and applications will be presented.

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