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The prototypical photocatalyst TiO2 exists in different polymorphs, the most common forms are the anatase- and rutile-crystal structures. Generally, anatase is more active than rutile, but no consensus exists to explain this difference. Here we demonstrate that it is the bulk transport of excitons to the surface that contributes to the difference. Utilizing(More)
GaN nanowires (NWs) have been grown on Si(111) substrates by plasma-assisted molecular beam epitaxy (PAMBE). The nucleation process of GaN-NWs has been investigated in terms of nucleation density and wire evolution with time for a given set of growth parameters. The wire density increases rapidly with time and then saturates. The growth period until the(More)
Graphene has been used to explore the fascinating electronic properties of ideal two-dimensional carbon, and shows great promise for quantum device architectures. The primary method for isolating graphene, micromechanical cleavage of graphite, is difficult to scale up for applications. Epitaxial growth is an attractive alternative, but achieving large(More)
In situ high-resolution transmission electron microscopy (HRTEM) was used to investigate the effect of heating on an organo-Ge polymer/nanoparticle composite material containing 4-8 nm diameter alkyl-terminated Ge nanoparticles. The product was obtained from the reduction of GeCl4 with Na(naphthalide) with subsequent capping of the -Cl surface with n-butyl(More)
Intercalation of metal atoms is an established route for tuning the coupling of graphene to a substrate. The extension to reactive species such as oxygen would set the stage for a wide spectrum of interfacial chemistry. Here we demonstrate the controlled modification of a macroscopic graphene-metal interface by oxygen intercalation. The selective oxidation(More)
We report on the synthesis, characterization, and electrochemical performance of novel, ultrathin Pt monolayer shell-Pd nanowire core catalysts. Initially, ultrathin Pd nanowires with diameters of 2.0 ± 0.5 nm were generated, and a method has been developed to achieve highly uniform distributions of these catalysts onto the Vulcan XC-72 carbon support.(More)
Using in situ liquid cell electron microscopy we investigate Pd growth in dilute aqueous Pd salt solutions containing Au nanoparticle seeds. Au-Pd core-shell nanostructures are formed via deposition of Pd(0), generated by the reduction of chloropalladate complexes by radicals, such as hydrated electrons (eaq(-)) induced by the electron beam in the solution.(More)
Using transmission electron microscopy, we identify the temperature-dependent interaction pathway of carbon-supported Au nanoparticles. At low temperature (room temp. to 400 degrees C), Au nanoparticles predominantly interact by coalescence initiated by an atomic Au bridge. At high temperature (400-800 degrees C), the particles assemble into Au/C core-shell(More)
The electronic structure of epitaxial monolayer, bilayer, and trilayer graphene on Ru(0001) was determined by selected-area angle-resolved photoelectron spectroscopy (micro-ARPES). Micro-ARPES band maps provide evidence for a strong electronic coupling between monolayer graphene and the adjacent metal, which causes the complete disruption of the graphene(More)
We use transmission electron microscopy observations to establish the parts of the phase diagram of nanometer sized Au-Ge alloy drops at the tips of Ge nanowires (NWs) that determine their temperature-dependent equilibrium composition and, hence, their exchange of semiconductor material with the NWs. We find that the phase diagram of the nanoscale drop(More)