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A fractal-featured metallic thin film with Sierpinski Carpet pattern is fabricated on silicon wafer by microfabrication techniques. Transmission infrared spectroscopy indicates that there exists extraordinary high transmission at specific wavelengths, which can be ascribed to the effect of surface plasmon resonance, and are determined by hierarchy of apertures of different sizes in the fractal structure. This patterned film provides a unique system to achieve enhanced transmission simultaneously at different selected frequencies of electromagnetic wave.

In this paper we report the spontaneous formation of a nanostructured film by electrodeposition from an ultrathin electrolyte layer of CuSO4. The film consists of straight periodic ditches and ridges, which corresponds to the alternating deposition of nanocrystallites of copper and copper plus cuprous oxide, respectively. The periodicity on the film may vary from 100 nm to a few hundred nanometers depending on the experimental conditions. In the formation of the periodically nanostructured film, oscillating voltage/current has been observed across the electrodes, and the frequency depends on the pH of the electrolyte and the applied current/voltage. A model based on the coupling of [Cu2+] and [H+] in the electrodeposition is proposed to describe the oscillatory phenomena in our system. The calculated results are in agreement with the experimental observations.

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Os óxidos M 2 BiNbO 7 (M = In e Ga) foram sintetizados através de reações no estado sólido, e suas propriedades estruturais e fotocatalíticas, investigadas. Os resultados indicaram que estes compostos cristalizam na estrutura do tipo pirocloro, no sistema cúbico, grupo espacial Fd-3m. Os valores estimados dos "band gaps" dos óxidos In 2 BiNbO 7 e Ga 2 BiNbO 7 são 2,52(5) e 2,57(8) eV, respectivamente. A reação fotocatalítica da decomposição de água pura foi estudada na presença dos fotocatalisadores M 2 BiNbO 7 (M = In e Ga) e irradiação no ultravioleta, através do monitoramento da formação de H 2 e de O 2 . A degradação fotocatalítica do corante azul de metileno em água, na presença destes óxidos, foi investigada sob irradiação no visível. Os catalisadores M 2 BiNbO 7 (M = In e Ga) mostraram-se mais ativos do que o P-25, nessas condições. Completa degradação do azul de metileno foi observada após irradiação no visível durante 160 minutos, na presença do fotocatalisador Ga 2 BiNbO 7 , e após 180 minutos na presença de In 2 BiNbO 7 . A diminuição do teor total de carbono (TOC) e a formação dos produtos SO 42-e NO 3 -confirmaram a mineralização do azul de metileno durante o processo fotocatalítico.M 2 BiNbO 7 (M = In and Ga) were synthesized by solid-state reaction method and their structural and photocatalytic properties were investigated. The results indicated that these compounds crystallize in the pyrochlore-type structure, cubic system with space group Fd-3m. In addition, the band gaps of In 2 BiNbO 7 and Ga 2 BiNbO 7 were estimated to be about 2.52(5) and 2.57(8) eV, respectively. For the photocatalytic water splitting reaction, H 2 or O 2 evolution was observed from pure water respectively with M 2 BiNbO 7 (M = In and Ga) as the photocatalysts under ultraviolet light irradiation. Photocatalytic degradation of aqueous methylene blue (MB) dye over these compounds was further investigated under visible light irradiation. M 2 BiNbO 7 (M = In and Ga) showed markedly higher catalytic activity compared to P-25 for MB photocatalytic degradation under visible light irradiation. Complete removal of aqueous MB was observed after visible light irradiation for 160 min with the Ga 2 BiNbO 7 as the photocatalyst and for 180 min with the In 2 BiNbO 7 as the photocatalyst. The decrease of the total organic carbon (TOC) and the formation of inorganic products, SO 4 2-and NO 3 -, demonstrated the continuous mineralization of aqueous MB during the photocatalytic process.Keywords: inorganic photocatalysts, crystal structure, removal of methylene blue dye, band structure, visible light irradiation IntroductionSince Honda and Fujishima first observed the splitting of water on TiO 2 electrode in 1972, 1 the investigation of semiconductor photocatalysts has attracted much attention from both academic and industrial societies. 2,3 The photocatalytic water splitting using solar energy to produce hydrogen gas is crucial owing to the emergent requirement of clean and renewable sources. [2][3][4] Up to now, some photocatalysts with di...

We report in this paper the electric properties of nanostructured copper filament arrays self-organized by a novel electrochemical method. Due to the spontaneous oscillation of the concentration field of [Cu2+ ] in front of the growing interface, crystallites of copper and cuprous oxide appear alternately on the filaments of the electrodeposits. A conducting atomic force microscope (CAFM) and current imaging tunnelling spectroscopy (CITS) were used to characterize the electric properties of the nanostructured copper filaments. By applying a constant voltage across the conducting probe of the CAFM and the sample, an electric current mapping is achieved, in which alternating low and high current regions correspond exactly to the periodic nanostructures on the filaments. The profile of the electric current along the structured filament has been analysed, and no noticeable potential drop has been observed. A typical linear I–V curve for a metal and nonlinear I–V curve for a semiconductor were collected in the high and low current regions respectively. These results suggest that despite the periodic distribution of Cu2O crystallites on the deposited filament, there should exist a metallic core of copper crystallites inside the filament. This type of structured metal–semiconductor filament might have potential application.

In this paper, we report the long-range ordering effect observed in the electro-crystallization of Zn and ZnO from an ultrathin aqueous electrolyte layer of ZnSO4 . The deposition branches are regularly angled, covered with random-looking, scalelike crystalline platelets of ZnO. Although the orientation of each crystalline platelet of ZnO appears random, transmission electron microscopy shows that they essentially possess the same crystallographic orientation as the single-crystalline zinc electrodeposit underneath. Based on the experimental observations, we suggest that this unique long-range ordering effect results from an epitaxial nucleation effect in electrocrystallization.

We report here the electrodeposition of periodically structured single-crystalline zinc branches from an ultrathin aqueous electrolyte layer of ZnSO 4 . The main trunk and side branches of electrodeposits are regularly angled, and each branch is made of periodic bead-like structures. Layered morphology has been observed on each bead. During electrodeposition, spontaneous oscillation of electric current occurs when constant voltage is applied across the electrodes, and the oscillation leads to periodic patterns on deposit branches. According to electron diffraction of transmission electron microscopy (TEM), the whole branch of electrodeposits has the same crystallographic orientation despite the fact that the branch looks like an assembly of beads. We interpret this unique growth behavior to the epitaxial nucleation in the transport-limited growth system.