Nanostructured carbon materials are potentially of great technological interest for the development of electronic, catalytic and hydrogen-storage systems. Here we describe a general strategy for the synthesis of highly ordered, rigid arrays of nanoporous carbon having uniform but tunable diameters (typically 6 nanometres inside and 9 nanometres outside). These structures are formed by using ordered mesoporous silicas as templates, the removal of which leaves a partially ordered graphitic framework. The resulting material supports a high dispersion of platinum nanoparticles, exceeding that of other common microporous carbon materials (such as carbon black, charcoal and activated carbon fibres). The platinum cluster diameter can be controlled to below 3 nanometres, and the high dispersion of these metal clusters gives rise to promising electrocatalytic activity for oxygen reduction, which could prove to be practically relevant for fuel-cell technologies. These nanomaterials can also be prepared in the form of free-standing films by using ordered silica films as the templates.

Chlorine oxoanions with the chlorine atom at different oxidation states were introduced in an attempt to systematically tailor the electronic structures of single-walled carbon nanotubes (SWCNTs). The degree of selective oxidation was controlled systematically by the different oxidation state of the chlorine oxoanion. Selective suppression of the metallic SWCNTs with a minimal effect on the semiconducting SWCNTs was observed at a high oxidation state. The adsorption behavior and charge transfer at a low oxidation state were in contrast to that observed at a high oxidation state. Density functional calculations demonstrated the chemisorption of chloro oxoanions at the low oxidation state and their physisorption at high oxidation states. These results concurred with the experimental observations from X-ray photoelectron spectroscopy. The sheet resistance of the SWCNT film decreased significantly at high oxidation states, which was explained in terms of a p-doping phenomenon that is controlled by the oxidation state.

A thickness modulation effect of Hf O 2 interfacial layer between double-stacked Ag nanocrystals for nonvolatile memory device applications

We acknowledge ®nancial support of the Deutsche Forschungsgemeinschaft and of Roche Diagnostics. P. Go Èttig and R. Ramachandran helped with biochemical analyses. We thank G. Bourenkov and H. Bartunik, and G. Leonard for help with synchrotron data collection at DESY BW6 (Hamburg) and ESRF ID14-4 (Grenoble), respectively.

Owing to their extraordinary electrical, physical, and thermal properties as well as a high aspect ratio, carbon nanotubes (CNTs) have been intensively studied for such applications as nanometer-scale electronic devices, chemical and biological sensors, and polymeric nanocomposites. [1][2][3][4][5] Among the CNT systems considered to date, networks or arrays of CNTs as films on a substrate have attracted a great deal of attention because of their potential applications in the area of transparent conducting materials. Because these CNT films can be mechanically flexible, they are the most reliable candidates for flexible, transparent, conducting materials that complement indium tin oxide (ITO) for certain applications, including electrodes for solar cells, smart windows, and transparent transistors. [6][7][8][9][10][11] Therefore, the ability to fabricate uniform and continuous CNT films with good reproducibility is of great importance. Many approaches based on solution processes have been explored to fabricate continuous CNT films, including spin-coating, spray-coating, and filtration. [12][13][14] In thisCommunication, we present a novel method for the production of continuous CNT films with higher optical and electrical properties on a flexible plastic substrate. We also demonstrate that the physical properties of CNT films can be improved by manipulating the network structures. It is no wonder that conductivity and transparency will be major factors in CNT films intended to be used as transparent conducting media. Because these two physical properties depend primarily on the CNT density in the films, we can adjust that density to control these properties. However, it is difficult to fabricate CNT films with both high transparency and high conductivity solely through the adjustment of the CNT surface density, defined as CNT mass per unit surface area. [15] This is due to the fact that conductivity and transparency show an opposite dependence on the CNT surface density.[15] We have aimed to fabricate highly transparent CNT films with CNT densities sufficient for high conductivity. We expected that the transparency of the CNT films could be improved by manipulating the network structure of the CNTs. Specifically, colloidal arrays have been adopted as sacrificial templates in various nanostructuring schemes, termed colloidal lithography. [16][17][18][19][20][21][22] Therefore, we decided to use sacrificial 2D colloidal crystal templates to fabricate special network-structured CNT films for higher transparency. A schematic illustration of our procedure is shown in Figure 1. Using a suspension containing a mixture of colloidal particles and single-walled nanotubes (SWNTs), we first fabricated 2D colloid-CNT complex crystal COMMUNICATION

Monolayer arrays of monodispersed nanocrystals (<10 nm) onto three dimensional (3D) substrates have considerable potential for various engineering applications such as highly integrated memory devices, solar cells, biosensors and photo and electro luminescent displays because of their highly integrated features with nanocrystal homogeneity. However, most reports on nanocrystal arrays have focused on two dimensional (2D) flat substrates, and the production of wafer-scale monolayer arrays is still challenging. Here we address the feasibility of arraying nanocrystal monolayers in wafer-scale onto 3D substrates. We present both metal (Pd) and semiconductor (CdSe) nanocrystals arrayed in monolayer onto trenched silicon wafers (4 inch diameter) using a facile electrostatic adsorption scheme. In particular, CdSe nanocrystal arrays in the trench well showed superior luminescent efficiency compared to those onto the protruded trench flat, due to the densely arrayed CdSe nanocrystals in the vertical direction. Furthermore, the surface coverage controllability was investigated using a 2D silicon substrate. Our approach can be applied to generate highly efficient displays, memory chips and integrated sensing devices.

Monolayer arrays of monodispersed nanocrystals (<10nm) onto three-dimensional substrates have considerable potential for various engineering applications due to their highly integrated features with nanocrystal homogeneity. Here we address the feasibility of arraying nanocrystal monolayers in wafer-scale onto three-dimensional substrates. We present nanocrystal Pd metal arrayed in monolayers onto trenched silicon wafers (4 in. diam) using a facile electrostatic adsorption scheme. We also present three-dimensional electron tomography bright-field projection images, which reveal that the resulting arrays of Pd nanocrystals indeed have the monolayer nature on the overall trenched wafer surface and are not affected by trench geometry.

Charge loss rate of Pd-nanocrystal (NC)-based nonvolatile memories is reduced about 60% by employing an asymmetric tunnel barrier composed of stacked SiO 2 and HfO 2 layers or insulating ZrO 2 NCs between Pd NCs. Keywords-Pd nanocrystal; nonvoltile memory; asymmetric tunnel barrier; ZrO 2 nanocrystalI.