Fengqiang Sun

Two-dimensional hierarchical porous silica film and its tunable superhydrophobicity

Base do na monolayer polystyrene (PS) colloidal crystal, large-scale two-dimensional (2D) hierarchical porous silica (orderly arranged macropores and disordered mesopores in its skeleton) with a high specific surface area was fabricated by the sol–gel technique. Such material has demonstrated superhydrophilicity with a water contact angle (CA) of 5 ◦ and superhydrophobicity with a water CA of 154 ◦ after surface modification with fluoroalkylsilane. More interestingly, the water CA can be increased to 165 ◦ using a heat-deformed PS template, which suggests that the superhydrophobicity can be controlled by the template with different heat-deformed extents. Such silica films have applications in fields of adsorbent, catalytic, chromatographic support, microseparator and microfluid devices. (Some figures in this article are in colour only in the electronic version)

Ultraviolet-light-emitting ZnO nanosheets prepared by a chemical bath deposition method

Two-dimensional polar-surface-dominated ZnO nanosheets (nanodiscs) with dimensions of several microns and thickness of tens of nanometres were synthesized in bulk quantity at low temperature (~70??C) by a simple and environmentally benign chemical bath deposition (CBD) method. These ZnO nanosheets are of single-crystal wurtzite structure; they grow along the crystallographic directions within polar {0001} planes. This is different from previous reported films or nanowire arrays prepared by the CBD method. Raman scattering spectrum studies confirm that the as-synthesized nanosheets are of high crystal quality and indicate an optical phonon confinement effect in such ZnO nanosheets. These nanosheets show a sharp intrinsic ultraviolet excitonic emission peak centred at 380?nm at room temperature, have large surface area exposed to the gaseous environment, and could be an ideal ultraviolet light source or objects for the fabrication of nanoscaled devices.

Hetero-apertured micro/nanostructured ordered porous array: layer-by-layered construction and structure-induced sensing parameter controllability.

The double-layer hetero-apertured porous films with hierarchical micro/nanoarchitectures were fabricated on a desired substrate, based on a simple and flexible strategy alternately using the monolayer colloidal crystal with different sizes of colloidal spheres as templates. Such films are of biperiodic ordered structures and can be fully lifted off from the substrate and present a freestanding property. The structures and morphologies of the films can be controlled by combination of the colloidal monolayers with different sphere sizes. The corresponding gas sensing devices were also built. Representatively, the In(2)O(3) hierarchically micro/nanostructured porous film-based sensors have shown both higher sensitivity and much faster response to NH(3) atmosphere than the corresponding conventional nanostructured ones. Importantly, the gas-sensing parameters (i.e., response time and the sensitivity) can be well-controlled separately in a large range simply by changing the pore sizes in different layers of the porous film. Further, for the application, a diagram of gas-sensing parameters (t(R)-S diagram) was presented, which can not only give a measurement of sensing performances but also well guide design and fabrication of the hierarchically structure-based sensors with desired sensing performances. This work is an important step toward the practical application of the nanostructured porous film sensors.

Well-aligned zinc sulfide nanobelt arrays: Excellent field emitters

Large-scale, well-aligned and oriented wurtzite ZnS nanobelt arrays are fabricated by a simple solvothermal reaction and subsequent heat treatment. The nanobelts grow along the [0001] direction perpendicularly on a zinc substrate, which are about 30nm in thickness, several hundreds of nanometers in width, and up to 4μm in length. Importantly, such nanostructured arrays show a good field emission property with low turn-on field (3.8Vμm−1) and high field enhancement factor (∼1800), which is ascribed to the top edges and corners of the freestanding and well aligned nanobelts, and good electric contact with the conducting substrate where they grow.

Morphology-controlled 2D ordered arrays by heating-induced deformation of 2D colloidal monolayer

We develop a strategy to fabricate morphology-controlled two dimensional (2D) ordered arrays by solution-dipping sintered colloidal monolayer template. By heating colloid monolayer templates for different times, the morphology of ordered arrays can be controlled effectively, which is valuable to investigate the morphology-dependent optical, magnetic, electrochemical, catalytic properties of arrays. With increase of the heating time for templates, 2D ordered arrays with different morphologies can be fabricated in turn, such as, spherical pore array, honeycomb-shaped nanowall array, nanopillar array and regular network. Two kinds of morphology-controlled 2D periodic arrays, ferric oxide and silica, have been fabricated successfully by this way. This route is universal for synthesis of other compounds’ ordered arrays with controlled morphology. This strategy has expanded the applications of the colloidal monolayers as templates to prepare ordered nanostructured functional arrays.

Two-dimensional ordered polymer hollow sphere and convex structure arrays based on monolayer pore films

A two-step replication strategy to two-dimensional ordered polymer hollow sphere and convex structure arrays is presented based on polystyrene colloidal monolayer and inverse opal made of FeO(OH). We can control formation of a small hole on top of the hollow spheres by the concentration of polymer precursors, which could be of importance in selective permeability, nutrient and drug deliver, biotechnology, and even study of black-body irradiation in micro or nano space. In addition, the fabrication strategy is suitable for the most soluble polymer materials, which can solidify when they are concentrated.

Substrate dependent surface plasmon resonance evolution of Ag nanoparticles treated in atmospheres

The evolution of surface plasmon resonance (SPR) with alternate air and H2 treatment was investigated for silver nanoparticles on different SiO2-based substrates (soda-lime glass, quartz glass and mesoporous SiO2). It has been shown that evolution behaviours on the three substrates are very different. For silver nanoparticles on the mesoporous SiO2 substrate, alternate air and H2 heat treatment led to the alternate disappearance and appearance of the SPR, showing the reversibility of optical changes. For a soda-lime glass substrate, the SPR absorption also disappeared after the first run heat treatment in air and re-appeared after subsequent H2 heat treatment, but the second run heat treatment in air could not induce the re-disappearance of the SPR. After alternate heating of the sample in air and H2 for four or more cycles, the SPR stayed almost unchanged. For a quartz glass substrate, however, the SPR absorption became negligible after alternate air and H2 heat treatment. Such effects of the substrate on the SPR are explained in terms of the subtle difference of the three SiO2-based substrates in micro-structure or chemical composition, and the redox of silver in the treatment atmospheres. This study could be important for the design and architectonics of new optical devices based on SiO2 materials and could also promote the understanding of the interaction of silver nanoparticles with the environment.

Fabrication of large-scale zinc oxide ordered pore arrays with controllable morphology

The fabrication of large-scale ZnO ordered pore arrays by the potentiostatic electrochemical deposition method based on a two-dimensional ordered colloidal monolayer template is reported. The pore morphology evolves from hemispherical to a well-like structure by controlling the deposition potential.

Micro/nanostructured arrays: fabrication, applications, and devices

1 Institute of Solid State Physics, Chinese Academy of Sciences, Hefei, Anhui 230031, China 2 School of Materials Science and Engineering, University of Jinan, Jinan, Shandong 250022, China 3Department of Material Science and Engineering, South China Normal University, Guangzhou, Guangdong 510631, China 4Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology (KAIST), 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701, Republic of Korea

Mono-, multi-layer nanostructured porous films and gas sensors

A simple and flexible strategy is presented for synthesis of mono or multi-layer nanostructured ordered porous films on any desired substrates with flat or even curved surface, based on the fact that polystyrene sphere colloidal monolayer on glass substrate can lift off and floated on some precursor solutions, which can, in turn, be transferred onto any substrates by picking it up. SnO/sub 2/ ordered nanostructured porous films are thus successfully synthesized on the cylindrical surface, the concave surface and the spherical surface, respectively, just by taking the easily acquired SnCl/sub 4/ solution as precursor. More importantly, the mono and multi-layer porous films are also directly synthesized on commercially supplied ceramic or porcelain tubes which are used for the substrate of gas sensors. And hence, the SnO2 ordered nanostructured porous gas-sensor is constructed. Sensitivity of the sensor can be easily controlled by changing the sizes of polystyrene spheres. Such method is universal and suitable for synthesis of many other oxides or doped porous films, mesoporous/macroporous gas sensor films and even the hetero-multi-layer porous films on the curved surfaces just by changing the compositions of the precursors or alternatively repeating this strategy. This strategy provides a good way to construct nanostructured gas-sensors and practical possibility of the nanostructured devices in the near future.