Dot—or multiple dot—arrays of nanometer dimensions have applications in nanodevices. Control of the size and site of each dot is essential as variations can alter the optical or catalytic properties of the composite metal nanoparticles. A method is presented in which anodic porous alumina, a typical self‐organized structure, is used as an evaporation mask for the shadow evaporation of a metal beam, enabling the spatially resolved deposition of the metal—or several different metals—at the bottom of the apertures of the mask. Each dot in the array is composed of two or three deposits of one or more metals.
Size control of gold nanoparticles by tuning molecular cross section of stabilizer molecules is reported. A newly synthesized four-chained disulfide ligand was used as the stabilizer of gold nanoparticles, and the nanoparticles were prepared by NaBH4 reduction of gold ions. By the use of this stabilizer, smaller and monodispersed gold nanoparticles were obtained, when compared to those prapred by using conventional monoalkanethiols. The present design of stabilizer molecules can be used to systematically control the size of nanoparticles with atomic precision.
Electrochemical properties of nanoporous honeycomb diamond electrodes in an aqueous electrolyte were investigated. Highly ordered honeycomb diamond structures were fabricated by etching the microwave plasma-deposited diamond films using an oxygen plasma. The diamond honeycomb exhibited a wide electrochemical potential window (ca. 2.5 V), similar to the unetched diamond film. From impedance measurements, the capacitance of the diamond honeycomb film was found to be 1.97 ϫ 10 Ϫ3 F cm Ϫ2 (geometric area), which is ca. 200 times greater than that for the unetched, as-deposited surface. The results obtained with galvanostatic measurements were consistent with this value. The formation of the highly ordered porous structure, together with surface oxidation, was found to be responsible for the observed enhancement in the capacitance. The transmission line model for cylindrically porous electrodes was successfully applied to the present honeycomb structure. Based on an estimation of the capacitance of a hypothetical through-hole diamond membrane, the specific capacitance is ca. 16 F g Ϫ1 , which is within an order of magnitude of the range for activated carbon capacitors (100 to 400 F g Ϫ1 ).
By conducting a 1200 • C vacuum annealing of a 3C-SiC(111) ultrathin film preformed on a Si(110) surface, we have succeeded in forming a graphene layer on a Si substrate. Raman-scattering spectrum from this surface presents a distinct 2D band, whose deconvolution into four subcomponents indicates that the film mostly consists of a two-layer graphene. The peak position is blue-shifted from that of a free-standing graphene formed by a mechanical exfoliation method, suggesting a compressive stress in the film.
Alumina templates are used to assist the deposition of highly ordered polycrystalline diamond nanocylinders (see Figure) and diamond‐like carbon nanotubes. The growth of diamond is carried out by microwave plasma‐assisted CVD, using acetone as the carbon source. The dimensions of the nanofibers are easily controllable and this technique could be adopted to prepare arrays for various applications.
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