A high quality BiOCl film with petal-like hierarchical structures and its visible-light photocatalytic property.

BiOCl film with petal-like hierarchical structures is obtained by dipping bismuth film into the mixed solution of H2O2 and HCl. To obtain a high quality BiOCI film, a connecting layer of Chromium is deposited between the substrate and Bismuth film. The product is easy-synthesized, high productive, reusable and environment-friendly. The structural analysis indicates that the BiOCI film is composed by petals with smooth surfaces, and the nanopetals grow along the (101) directions. Raman spectroscopy shows that the film has a good stress-resist feature. The PL spectrum shows that the defect energy levels of BiOCI nanostructure contribute to the excellent photoactivity of degradation the rhodamine B (RhB) under visible-light irradiation (A > 420 nm). This photocatalyst can keep stable photoactivity after it has been reused for 6 rounds. All those properties ensure the photocatalyst a bright future in the application of the pollution treatment.

Topotactic transformations of superstructures: from thin films to two-dimensional networks to nested two-dimensional networks.

Design and synthesis of super-nanostructures is one of the key and prominent topics in nanotechnology. Here we propose a novel methodology for synthesizing complex hierarchical superstructures using sacrificial templates composed of ordered two-dimensional (2D) nanostructures through lattice-directed topotactic transformations. The fabricated superstructures are nested 2D orthogonal Bi(2)S(3) networks composed of nanorods. Further investigation indicates that the lattice matching between the product and sacrificial template is the dominant mechanism for the formation of the superstructures, which agrees well with the simulation results based on an anisotropic nucleation and growth analysis. Our approach may provide a promising way toward a lattice-directed nonlithographic nanofabrication technique for making functional porous nanoarchitectures and electronic devices.

Controllable fabrication of super-resolution nanocrater arrays by laser direct writing.

A super-resolution fabrication technique for highly-ordered nanocrater arrays is reported based on laser direct writing method. Nanocraters with diameters up to 40 nm, which is much smaller than the diffraction limit of laser system, are fabricated on titanium films using a 532 nm laser. The diameters of the craters are tunable from 350 nm to 40 nm, with a rigorous linear relationship versus the writing laser powers and an approximate linear relationship versus pulse widths. Laser ablation and oxidation are involved in formation mechanism and Gaussian distribution of laser energy density is proposed to play a key role of super-resolution structures.

Grayscale photomask fabricated by laser direct writing in metallic nano-films.

The grayscale photomask plays a key role in grayscale lithography for creating 3D microstructures like micro-optical elements and MEMS structures, but how to fabricate grayscale masks in a cost-effective way is still a big challenge. Here we present novel low cost grayscale masks created in a two-step method by laser direct writing on Sn nano-films, which demonstrate continuous-tone gray levels depended on writing powers. The mechanism of the gray levels is due to the coexistence of the metal and the oxides formed in a laser-induced thermal process. The photomasks reveal good technical properties in fabricating 3D microstructures for practical applications.

Laser direct writing of nanoreliefs in Sn nanofilms.

High-resolution (approximately 200 nm) nanoreliefs, which possess a controllable height change (Deltah, up to film thickness) and transmittance or reflectance, have been successfully fabricated in 12-nm-thick Sn films by using 532 nm pulsed laser direct writing. Different from current micro/nanofabrication techniques, the height change of the nanoreliefs is generated by a laser-induced-thickening process. The majority of the height change comes from a balling and coarsening effect rather than oxidation of grains. Because both optical density and Deltah of the nanoreliefs are almost linear to laser power, the optical images can highly resemble the topographic images. This technique is useful for fabricating complicated nanorelief structures and fine images.

A novel BiOCl film with flowerlike hierarchical structures and its optical properties.

A novel BiOCl film with flowerlike hierarchical structures has been fabricated for the first time by dipping Bi film in a mixed solution of H(2)O(2) and HCl. This method presents the advantages of a simple technique, template-free, uniform and controllable morphology, as well as easy mass production. Each flowerlike hierarchical structure is composed of several dozen ultra-thin single-crystal nanopetals which grow along the 110 directions in the tetragonal structure. The layered growth of nanopetals is related to the more marked anion polarization along the c axis and layered stacking of various atoms (Cl-Bi-O-Bi-Cl). The growth mechanism of the BiOCl hierarchical structure is preferred to be a nucleation-dissolution-recrystallization process. A Raman shift originating from laser-induced compressive stress is observed. Photoluminescence (PL) spectra of the BiOCl film show principal green emission, indicating potential applications in optoelectronic devices.

Effect of recorded-dot size on readout signal in nano-optical storage.

In this paper, we study the features on transmittance and reflectance for different diameter and height of recorded bubble dot in a PtOx super-RENS disk, by means of a simulating calculation. Some interesting conclusions are shown, and difference between model adopted in our study and actual structure is also discussed.

Study on readout durability of super-RENS disk.

Characteristics essential for the readout durability of a superresolution near-field structure (super-RENS) disk are studied experimentally by using a home-built optical measuring setup and atomic force microscope, based on a simplified PtOx super-RENS disk. The experimental results show that for a super-RENS disk with constant structure and materials, readout signals including transmittance and reflectance vary with changes in bubble shape and size, indicating that the readout durability of the disk has a strong dependence on bubble stability, which is closely related to the thickness of the cover layer, the recording power and readout power, and the mechanical properties of the dielectric layer. Based on our experimental results, the main direction for improving readout durability is also proposed.

Zinc oxide nanostructures: epitaxially growing from hexagonal zinc nanostructures.

The epitaxial growth of ZnO nanosheets and nanoneedles from a Zn/ZnO core/shell structure is verified by an experiment in which the ZnO nanoneedles and nanosheets are synthesized in air within an ultra-low temperature range from 250 to 400 °C by thermal oxidation of Zn films made up of hexagonal nanodiscs or nanoprisms. The hexagonal Zn structures are oxidized to form a Zn/ZnO core/shell structure with an epitaxial relationship; ZnO nanoneedles and nanosheets are found to grow epitaxially from the ZnO shell, along sixfold symmetric [Formula: see text] directions, showing the same lattice orientation as the Zn core. The stability difference among different facets of hexagonal Zn crystal structures plays a key role in the formation of ZnO nanosheets, nanoneedles and the Zn/ZnO core/shell structure, as well as ZnO hollow structures. A vapor-solid mechanism is suggested to explain the epitaxial growth process of the ZnO products. Photoluminescence properties of the ZnO nanostructures are also explored.