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This study focuses on the fabrication of two nanodevice prototypes which utilized vertical and horizontal carbon nanotubes used the focused ion beam to localize the catalysts, followed by plasma-enhanced chemical vapor deposition. First, metal-gated carbon nanotube field emitter arrays were fabricated on multilayer substrates containing an imbedded catalyst layer. Second, horizontally aligned single-walled carbon nanotubes were grown on a transmission electron microscopy grid. This allows the carbon nanotubes to be directly analyzed in a transmission electron microscope. It is expected that the methodology introduced here will open up opportunities for the direct fabrication of carbon nanotube based nanodevices.

Periodic heterogeneous structures exhibit color with brilliance through constructive interference of electromagnetic waves in accordance with Bragg's law. However, the wavelength of diffracted light is strictly angle-dependent, and such periodic structures generate only iridescent color. Here we report that periodically porous, microellipsoidal shells of diatom Pinnularia sp. wavelength-selectively backscatter light at arbitrary incidence. The biosilica frustules could be approximated as many polygonal faces of two-dimensional photonic crystal slabs. Furthermore, surface decoration of the frustule with magnetite nanoparticles produced photonic band gaps in the near-infrared. Magnetite nanoparticle-decorated frustules behave as angle-independent near-infrared reflectors and near-infrared contrast agents in optical coherence tomography.

We fabricated a solar cell using a hybrid film consisting of CdS nanoparticle-decorated TiO2 nanobelts, which were synthesized via a modified alkaline hydrothermal method. The hybrid film is flexible and contains homogeneous CdS nanoparticle light absorbers. Furthermore, the type II heterostructure of CdS/TiO2 facilitates charge separation in the CdS nanoparticle-decorated TiO2 nanobelts. The solar cell demonstrated a light-electricity power conversion efficiency of 2.52%. Next, we deposited the CdS nanoparticle-decorated TiO2 nanobelts onto a ZnO nanowire array forming an antireflective hybrid structure. The power conversion efficiency of the cell with the hybrid photoanode reached 2.84%.

Practical applications of ZnO are widely known, and it is one of the more prevalent wide band gap semiconductors being explored in research. It is most known for its potential as an n-type window material in solar cells. 1,2 ZnO has been thoroughly explored in many forms: as a thin film, nanowires, nanoparticles, etc. 3À5 It has also been demonstrated that Mn-doped ZnO has ferromagnetic properties at room temperature and is therefore of interest in spintronics applications. 6À8 In addition, the introduction of such impurities has been shown to red-shift the band gap of ZnO and cause other changes in its optical characteristics, such as its photoluminescence. 9 This allows the material to be potentially beneficial for solar cells, as the dopants can cause reduction of near band-edge electron-hole pair recombination as well as internal down-conversion of higher energy photons, which could be absorbed by a narrow band gap material. The ZnO/Mn 3 O 4 core-shell structures produced in this study also show promise for lithium-ion battery applications. The substrate-grown nanowires provide a large functional surface area and the manganese oxide crystallites would be a highly favorable cathode material once enriched with lithium. Based on the length and density of the structures grown in this study, an estimated 20À30-fold increase in surface area would be observed in comparison to a thin film. This would result in a corresponding increase in battery capacity. To explore the potential of this material, optimize synthesis procedures, and develop further insights about the doping mechanism, a study of growth processes and properties was implemented. Reagent concentrations were varied to establish doping and crystallite formation regimes. Upon establishment of optimal ratios, reactions were carried out for various times, and the results are presented herein.' EXPERIMENTAL METHODS Synthesis. Synthesis of nanowires was carried out by a seeded chemical bath method. The seed solution was prepared as 0.750 M Zn(CH 3 COO) 2 and 0.750 M methenamine in deionized (DI) H 2 O. To assist in dissolution of the zinc acetate, the solution was heated to 60°C for 30 min under agitation. SnO 2 :F-coated SiO 2 substrates were cleaned for use by a two-part washing process: a 10 min isopropyl alcohol bath followed by a 10 min DI-H 2 O bath, both involving sonication. The substrates were allowed to air-dry. The seed was transferred to the substrates via pipet and distributed via spin coating at 1500 rpm for 90 s. To ensure a uniform seed layer, the substrates were then annealed for 1 h at 400°C. To reduce thermal strain on substrates, the samples were inserted after the furnace was preheated to 100°C; the furnace was subsequently ramped to the target temperature at an average rate of 20°C/min. The samples were permitted to cool in the furnace after it was turned off until they had reached room temperature. Growth of ZnO nanowires was carried out by use of a growth solution of 27.8 mM Zn(NO 3 ) 2 and 27.8 mM methenamine in DI-H 2 O. The samples w...

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