We report a facile synthetic route for size-controlled preparation of gold nanoparticles. Nearly monodisperse gold nanoparticles with core diameters of 1-6 nm were obtained by reducing AuP(Phenyl)(3)Cl with tert-butylamine borane in the presence of dodecanethiol in the solvent mixture of benzene and CHCl(3). Mechanism studies have shown that the size control is achieved by the solvent-controlled nucleation in which the nuclei concentration increases with increasing the fraction of CHCl(3), leading to smaller particles. It was also found that, following the solvent-controlled nucleation, particle growth occurs via ligand replacement of PPh(3) on the nuclei by Au(I)thiolate generated by the digestive etching of small particles. This synthetic strategy was successfully demonstrated with other alkanethiols of different chain length with which size-controlled, monodisperse gold nanoparticles were prepared in remarkable yield without requiring any postsynthesis treatments.

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Semiconductor-metal nanocomposites prepared with well-defined gold nanoclusters, such as Au25, Au144, and Au807, showed size-dependent photocatalytic activities for the reduction of nile blue and azobenzene. Whereas the photoreduction of nile blue was directly related with the charge separation and transfer rate from the photoexcited ZnO to gold nanoclusters, the photoreaction of azobenzene showed unexpected size effect with a clear threshold. Mechanistic investigations revealed that the photoreduction of azobenzene proceeded via a proton-coupled electron transfer process. The photocatalytic activity of the ZnO-Au nanocomposites was also dependent on the excitation intensity, demonstrating that the multielectron/multiproton process was controlled by the charge separation and transfer in the nanocomposites.

Graphene oxide (GO) thin films on various substrates show surprising variations of their structural and optical properties. These variations were also studied by depositing GO via introducing a gold nanoparticles buffer layer on quartz substrate. The effect of the substrate as well as buffer layer results in short range order crystallization in deposited GO films with an increase in inter-planar spacing. XPS analysis shows that GO undergoes reduction when spin coated on ITO/glass substrate. The deposited GO films exhibit luminescence emission, and the introduction of gold buffer layer results in a blue shift of the photoluminescent emission spectra. The GO on gold buffer layer shows almost constant optical absorption in the whole visible spectral region like graphene. The present study indicates that buffer layer effects and the interaction between different substrates and GO is strong enough to affect the oxygen linkages in GO which in turn changes its structural and optical properties, which may find potential application in graphene based optoelectronic device fabrication.

We describe the nonaqueous redox‐matched flow battery (RMFB), where charge is stored on redox‐active moieties covalently tethered to non‐circulating, insoluble polymer beads and charge is transferred between the electrodes and the beads via soluble mediators with redox potentials matched to the active moieties on the beads. The RMFB reported herein uses ferrocene and viologen derivatives bound to crosslinked polystyrene beads. Charge storage in the beads leads to a high (approximately 1.0–1.7 M) effective concentration of active material in the reservoirs while preventing crossover of that material. The relatively low concentration of soluble mediators (15 mM) eliminates the need for high‐solubility molecules to create high energy density batteries. Nernstian redox exchange between the beads and redox‐matched mediators was fast relative to the cycle time of the RMFB. This approach is generalizable to many different redox‐active moieties via attachment to the versatile Merrifield resin.

We describe the nonaqueous redox-matched flow battery (RMFB), where charge is stored on redox-active moieties covalently tethered to non-circulating, insoluble polymer beads and charge is transferred between the electrodes and the beads via soluble mediators with redox potentials matched to the active moieties on the beads. The RMFB reported herein uses ferrocene and viologen derivatives bound to crosslinked polystyrene beads. Charge storage in the beads leads to a high (approximately 1.0-1.7 M) effective concentration of active material in the reservoirs while preventing crossover of that material. The relatively low concentration of soluble mediators (15 mM) eliminates the need for high-solubility molecules to create high energy density batteries. Nernstian redox exchange between the beads and redox-matched mediators was fast relative to the cycle time of the RMFB. This approach is generalizable to many different redox-active moieties via attachment to the versatile Merrifield resin.

Organic photovoltaics are again gaining traction as device power conversion efficiencies have increased substantially over the last two years. Despite these improved efficiencies, long-term device stability remains a challenge because the physical blend of an electron-donor and -acceptor in the active layer can phase-separate into larger domains over time. Copolymers that are miscible with both the donor and acceptor can stabilize the active layer blend morphology, but these additives are often tailored to match the specific donor/acceptor blend. We demonstrate herein that a single copolymer containing a conjugated poly­(3-hexylthiophene) backbone and fullerene-functionalized side chains serves as a general blend stabilizer. Optical microscopy revealed that phase separation was suppressed in three different conjugated polymer/fullerene blends (PTB7, PTB7-Th, and PffBT4T-2OD with PC71BM) when annealed with the copolymer in thin films. Moreover, phase separation was suppressed in photovoltaic devices containing PffBT4T-2OD:PC71BM with the copolymer in the active layer. We also investigated factors beyond morphology that affect the initial power conversion efficiency, which was lower for devices with the copolymer. Overall, our results demonstrate that a single fullerene-functionalized poly­(3-hexylthiophene) copolymer additive suppresses phase separation in multiple conjugated polymer/fullerene thin film blends as well as in a photovoltaic device.

Redox flow batteries (RFBs) are one of the most promising battery technologies for grid-scale energy storage due to their scalability and inexpensive cost. The energy capacity of RFBs can be increased with higher concentrations of redox-active molecules in solution. However, the performance is limited by the solubility of redox-active molecules and increased viscosity at higher concentrations. There have been a few studies aimed at exploring new redox-active molecules with higher solubilities. In this talk, we will present a hybrid non-aqueous RFB with higher capacity by adopting a redox-targeting reaction with solid-state redox-active materials.