Using reduced graphene oxide (RGO) as a two-dimensional support, we have succeeded in selective anchoring of semiconductor and metal nanoparticles at separate sites. Photogenerated electrons from UV-irradiated TiO(2) are transported across RGO to reduce silver ions into silver nanoparticles at a location distinct from the TiO(2) anchored site. The ability of RGO to store and shuttle electrons, as visualized via a stepwise electron transfer process, demonstrates its capability to serve as a catalyst nanomat and transfer electrons on demand to adsorbed species. These findings pave the way for the development of next generation catalyst systems and can spur advancements in graphene-based composites for chemical and biological sensors.

Confined straight and branched CdSe nanowires (NWs) are synthesized using a solutionbased approach which leverages advances in the synthesis of colloidal CdSe quantum dots (QDs) with incipient approaches for the seeded (solution) synthesis of semiconductor NWs. The resulting straight and branched NWs have typical diameters below 10 nm with accompanying lengths between 1 and 10 µm. In the case of branched NWs, tripod, v-shaped, and y-shaped morphologies are observed. Variations in this preparation lead to higher order structures with multiple arms. The branching transition is discussed, and a possible mechanism based upon geminate NW nucleation is proposed. Such solution-grown straight, branched, and higher-order NWs exhibit potentially interesting optical, electrical, and transport properties due to their narrow radii below the corresponding bulk exciton Bohr radius of CdSe. Furthermore, this transition from straight to branched morphologies opens up avenues for investigating not only size-but also shape-dependent optical/electrical properties of one-dimensional (1D) and quasi-1D materials.

We report 30-nm-gate-length InAlN/AlN/GaN/SiC high-electron-mobility transistors (HEMTs) with a record current gain cutoff frequency (f T ) of 370 GHz. The HEMT without back barrier exhibits an extrinsic transconductance (g m.ext ) of 650 mS/mm and an on/off current ratio of 10 6 owing to the incorporation of dielectric-free passivation and regrown ohmic contacts with a contact resistance of 0.16 Ω · mm. Delay analysis suggests that the high f T is a result of low gate-drain parasitics associated with the rectangular gate. Although it appears possible to reach 500-GHz f T by further reducing the gate length, it is imperative to investigate alternative structures that offer higher mobility/velocity while keeping the best possible electrostatic control in ultrascaled geometry.

Time-resolved spectroscopy has been used to examine the elastic properties of single crystal gold nanorods with a [100] growth direction. These rods were produce by seed-mediated growth in the presence of silver ions, using both chemical and photochemical reduction. Analysis of the experimental data yields a value of Young's modulus for the nanorods of E NR = 31 ¡ 1 GPa. This is approximately 26% smaller than the value for bulk gold of E [100] = 42 GPa. The reduction in the size of Young's modulus is consistent with our previous studies of penta-twinned, [110] growth direction nanorods, where we found E NR = 64 ¡ 2 GPa compared to E [110] = 81 GPa for bulk gold. The fact that both the single crystal and the penta-twinned nanorods show a similar reduction in E compared to the bulk values (20%-30%) shows that this effect does not arise from the presence of twin planes in the nanorods. Our data show a weak correlation between the measured values of E NR for the [100] nanorods and the surface-to-volume ratio of the rods. The larger value of Young's modulus at small size is possibly due to defect elimination. These results underscore the importance of growth direction in determining the elastic properties of nanorods and nanowires.

The synthesis, characterization, and catalytic ability of gold/bismuth (Au/Bi) core/shell nanocrystals for promoting asymmetric 1D nanowire growth is described. A biphasic gold reduction approach is initially used to create small (∼1.5 nm diameter) Au particles passivated with trioctylphosphine (TOP). The alkylphosphine ligands render the Au nanocrystals soluble in common organic solvents used for II-VI semiconductor nanocrystal/nanorod growth. Subsequent surface passivation with elemental bismuth is accomplished through the thermolysis of trialkylbismuthines at 100 °C in a mildly coordinating solvent. The resulting core/shell particles are characterized by using a variety of techniques including transmission electron microscopy (TEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDXS) to demonstrate successful overcoating of the Au nanoparticles. Resulting diameters range from 1.43 to 2.53 nm, with the as-made Au/Bi nanocrystals stable for weeks to months when stored at low temperature under an inert atmosphere. Catalytic activity, promoting the asymmetric growth of II-VI semiconductor nanowires, is demonstrated for the particular case of CdSe, illustrating a relatively simple route for making high-quality, narrow-diameter (<10 nm) 1D materials capable of exhibiting quantum confinement.