Nanoporous metal oxides (TiO 2 , Al 2 O 3 ) have been synthesized using activated carbon templates with supercritical fluid solvents by using the nanoscale casting (NC) process. The precursors were dissolved in supercritical CO 2 and attached to activated carbon fibers or powders as templates. After removal of the activated carbon templates by calcination in air at 873 K or by treatment in oxygen plasma, the nanoporous TiO 2 or Al 2 O 3 replicating the macroscopic shapes of the activated carbon templates was obtained. The surface area of the titania sample was 387 m 2 /g. The titania sample crystallized in the anatase form. The alumina samples have mesopores corresponding to the graphene crystallite size of the activated carbon. The alumina samples crystallized in the γ-alumina form.

We report a three-dimensional (3D) porous carbon electrode containing both nanoscale and microscale porosity, which has been hierarchically organized to provide efficient ion and electron transport. The electrode organization is provided via the colloidal self-assembly of monodisperse starburst carbon spheres (MSCSs). The periodic close-packing of the MSCSs provides continuous pores inside the 3D structure that facilitate ion and electron transport (electrode electrical conductivity ∼0.35 S m(-1)), and the internal meso- and micropores of the MSCS provide a good specific capacitance. The capacitance of the 3D-ordered porous MSCS electrode is ∼58 F g(-1) at 0.58 A g(-1), 48% larger than that of disordered MSCS electrode at the same rate. At 1 A g(-1) the capacitance of the ordered electrode is 57 F g(-1) (95% of the 0.24 A g(-1) value), which is 64% greater than the capacitance of the disordered electrode at the same rate. The ordered electrode preserves 95% of its initial capacitance after 4000 charging/discharging cycles.

300 wileyonlinelibrary.com COMMUNICATION www.MaterialsViews.com www.advopticalmat.deColloidal crystals have attracted considerable attention due to their deterministic three-dimensional (3D) structures, interesting optical properties and ease of assembly. [1][2][3][4][5] The use of colloidal crystals as templates to impart periodic patterns into various materials has been broadly employed to create, for example, unique optoelectronic devices, [ 6,7 ] sensors, [8][9][10][11][12] and energy storage devices. [ 13,14 ] The general motivation for templating is to utilize the opals' interconnected 3D structure to defi ne the 3D structure of a material which is inherently diffi cult to form into a highly regular 3D structure on its own. A single replication yields a structure which is an inverse of the colloidal template, and a double replication yields the original structure of the template. This process is only successful if the colloidal template can withstand the deposition conditions of the material to be templated and there exist conditions whereby the original template can be removed without damaging the templated material. Given that the most popular template, silica, can only be removed with hydrofl uoric acid or strong base, chemicals that dissolve many materials, this can be challenging. Polymer templates (e.g. polystyrene or poly(methyl methacrylate)) are easy to remove, but cannot withstand high temperature deposition strategies, limiting their use. [ 2 ] Thermally-stable colloids which could be removed under orthogonal conditions, i.e., conditions that do not damage the templated material, would allow currently inaccessible materials templating strategies. Additionally, if the templates contained additional desirable structural complexities (e.g. a high surface area) which are replicated in the templated material, additional applications may emerge; for example, dye sensitized solar cells require high-surface area electrodes, [ 15 ] as do many other catalytic devices. In this communication, we fi rst demonstrate the fabrication of high-quality colloidal crystals from mesoporous carbon colloidal crystals which meet these requirements by tailoring the surface charge on the mesoporous carbon colloids. We then demonstrate the use of these colloidal crystals as high-surface area templates for traditionally diffi cult to template materials, employing carbon removal processes that are not destructive to the deposited materials, creating unique, nanostructured inverse opal structures.Porous carbon is broadly utilized both for fundamental studies and large scale commercial applications, including water purifi cation, ion exchange, [ 16 ] catalysis, [ 17 ] conventional battery electrodes, [ 18 ] emerging battery electrode designs, [ 19 ] capacitor electrodes, [ 13 ] and as a polymer fi ller. The incorporation of small amounts of carbon-black into polymer-based opals have resulted in brilliant colors by absorbing the scattered light. [ 1 ] While carbon spheres [20][21][22][23][24][25] and inverse opals [ 13,26,27 ] h...

Techniques for depositing silicon into nanosized spaces are vital for the further scaling down of next-generation devices in the semiconductor industry. In this study, we filled silicon into 3.5-nm-diameter nanopores with an aspect ratio of 70 by exploiting thermodynamic behaviour based on the van der Waals energy of vaporized cyclopentasilane (CPS). We originally synthesized CPS as a liquid precursor for semiconducting silicon. Here we used CPS as a gas source in thermal chemical vapour deposition under atmospheric pressure because vaporized CPS can fill nanopores spontaneously. Our estimation of the free energy of CPS based on Lifshitz van der Waals theory clarified the filling mechanism, where CPS vapour in the nanopores readily undergoes capillary condensation because of its large molar volume compared to those of other vapours such as water, toluene, silane, and disilane. Consequently, a liquid-specific feature was observed during the deposition process; specifically, condensed CPS penetrated into the nanopores spontaneously via capillary force. The CPS that filled the nanopores was then transformed into solid silicon by thermal decomposition at 400 °C. The developed method is expected to be used as a nanoscale silicon filling technology, which is critical for the fabrication of future quantum scale silicon devices.

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