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In this study, we demonstrate the surfactant-assisted synthesis of uniform-sized titania microspheres and their clusters for highly responsive optical materials. Monodisperse titanium glycolate microspheres were produced by controlled hydrolysis of glycolated titanium butoxide in acetone using surfactant as a stabilizer. The diameter of as-prepared particles ranged from 230 to 650 nm and was finely controlled by changing the concentrations of titanium butoxide and surfactant. In particular, the tunable range of the particle size was at a few tens of nanometers scale by the surfactant concentration, which was much finer than that by the concentration of titanium butoxide. Then, as-prepared titanium glycolate microspheres were transformed into monodisperse titania microspheres of anatase phase by heat treatment. Pure clusters of titania microspheres with an identical configuration were obtained by encapsulating a certain number of microspheres in emulsion droplets and subsequently evaporating the emulsion p...

Multi-faceted microstructures of titanium glycolate have been produced by room-temperature polyol process in which titanium alkoxide and polymethylene glycol were mixed rigorously and then the mixture was aged to settle down as white precipitate. Depending on types of titanium alkoxides and polymethylene glycols, stirring time, and composition, a variety of polygonal microrods were generated. Unlike unidentified structures produced from polyol process at elevated temperature, the titanium glycolate products obtained at room temperature revealed well-defined rod-like or plate-like structures with polygonal cross sections. Then, as-prepared titanium glycolate microstructures were transformed into higher refractive index titania of anatase or rutile phase by annealing. The characterization of as-prepared and annealed structures was conducted using scanning and transmission electron microscopes, X-ray diffractomer, and thermal analyzer for thermogravimetry and differential scanning calorimetry.

In this paper, we demonstrated a unique and simple method for fabricating colloidal particles of complex structures using oil-in-water emulsion droplets as confined geometries. A variety of structural motifs were produced using binary colloids of microspheres of polystyrene (PS) or silica and nanosized particles as the second component. When PS or silica microspheres and PS macromolecules were dispersed in oil-in-water emulsion droplets, particles with well-coordinated patches were obtained because the PS macromolecules partially covered the microsphere clusters. When silica or gold nanoparticles were dispersed together with the PS microspheres in oil-in-water emulsion droplets instead of PS macromolecules, composite particles with patches were obtained. In this case, silica or gold shell structures with well-coordinated windows were produced by selectively removing the large PS microspheres from the organic−inorganic composite clusters.

We demonstrate the scattering superlens using elastic scattering to obtain sub-diffraction resolution. Scattering from disordered nanoparticles enables to reconstruct the sub-wavelength image of the target through time-reversal and transmission matrix.

Colloidal lithography is a recently emerging field; the evolution of this simple technique is still in progress. Recent advances in this area have developed a variety of practical routes of colloidal lithography, which have great potential to replace, at least partially, complex and high-cost advanced lithographic techniques. This Review presents the state of the art of colloidal lithography and consists of three main parts, beginning with synthetic routes to monodisperse colloids and their self-assembly with low defect concentrations, which are used as lithographic masks. Then, we will introduce the modification of the colloidal masks using reactive ion etching (RIE), which produces a variety of nanoscopic features and multifaceted particles. Finally, a few prospective applications of colloidal lithography will be discussed.

Mixture of Ni(OH)(2)-Mg(OH)(2) as precursor of the catalyst used to synthesize carbon nanofibers (CNFs) was treated by mechanochemical (MC) and hand-grinding process. It was found that catalyst particle size decreased sharply under grinding for 60 min, and crystallinity of catalyst particle decreased under grinding. CNFs were synthesized by pyrolysising C2H2 using catalyst treated with MC process (labeled as ground catalyst) and hand ground (labeled as unground catalyst). CNFs with thin and uniform diameter were synthesized using catalyst treated with the MC process, which could be controlled by tuning the grinding time. In addition to tailor size and uniformity of as-grown CNFs, CNFs with bundle and twisted conformation were synthesized using catalyst treated with the MC process. After purification of CNFs and loading with Pt, they were used in fuel cell as the cathode catalyst support. The performance with CNFs synthesized using catalyst treated with the MC process was found to be better than that with CNFs synthesized using unground catalyst. (C) 2004 Elsevier Ltd. All rights reserved.

In this work, we fabricated a designed 2D polymer pattern by embossing and replica molding using colloidal stamps that were prepared from self-assembled particle arrays in a soft, patterned PDMS mold. For a successful pattern transfer, polymer infiltration at the interstices between the silica spheres of the colloidal stamp was controlled by depositing a thin gold layer.

We report here a novel colloidal lithographic approach to the fabrication of nonspherical colloidal particle arrays with a long-range order by selective reactive ion etching (RIE) of multilayered spherical colloidal particles. First, layered colloidal crystals with different crystal structures (or orientations) were self-organized onto substrates. Then, during the RIE, the upper layer in the colloidal multilayer acted as a mask for the lower layer and the resulting anisotropic etching created nonspherical particle arrays and new patterns. The new patterns have shapes that are different from the original as a result of the relative shadowing of the RIE process by the top layer and the lower layers. The shape and size of the particles and patterns were dependent on the crystal orientation relative to the etchant flow, the number of colloidal layers, and the RIE conditions. The various colloidal patterns can be used as masks for two-dimensional (2-D) nanopatterns. In addition, the resulting nonspherical particles can be used as novel building blocks for colloidal photonic crystals.

In this work, we fabricated various 2D hybrid patterns with the feature resolution from micrometer to nanometer scale by using soft lithography and block copolymer lithography. Composite molds for the high-resolution with feature sizes from 135 nm to 50 μm were composed of a hard layer supported by soft PDMS layer. Polymer (PU) replica holes were made from the composite mold by replica molding. Block copolymers (PS-b-PMMA and PS-b-PI) were used as ink materials for the pattern smaller than 100 nm. UV and ozone etching was used for the selective removal of one block in the block copolymer.

Carbon nanomaterials have been prepared by the thermal chemical vapor deposition (CVD) method in which C2H2 gas was deposited on the Ni–Al(OH)3 mixture pretreated by mechanochemical treatment with a high-energy mill. As the duration time of grinding for the Ni–Al(OH)3 mixture by the mixer mill is increased, amorphous Al(OH)3 and smaller Ni particles agglomerated into spheres. With unground and 120-min ground mixture of Ni–Al(OH)3, carbon nanomaterials were prepared at 500 and 600 °C. As a result, carbon nanomaterials prepared on a ground mixture have more uniform morphologies than those of the unground mixture. The characterization of Ni–Al(OH)3 mixture and as-prepared carbon samples was done by X-ray diffractometer (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), Raman spectroscopy and current–voltage (I–V) measurement.

As an pretreatment, a Fe(NO 3 ) 3 .9H 2 O-Al(OH)3 mixture was ground by a high energy mill and used as a supported catalyst for the growth of carbon nanotubes by a thermal CVD. The crystal structure of the catalyst disordered by the grinding influenced significantly the synthesis of carbon nanotubes in a thermal CVD.

A novel method was developed for the assembly of patterned binary and ternary particle arrays and their inverted pore structures onto V-shaped microchannels that were fabricated by soft lithography. For the ternary particle arrays and their inverted pore structures, a dip-coating of binary particle mixture with a controlled size ratio and subsequent O2 RIE were used.

The present paper highlights on the need to understand the correlation of the characteristics of the catalyst layer with the performance of the polymer electrolyte membrane fuel cell (PEMFC). This paper deals with the correlation of the platinum loading in the catalyst layer and the performance of the polymer electrolyte membrane fuel cell and also the correlation of the required hydrophilicity/hydrophobicity in the catalyst layer to get the optimum performance under given operating conditions.

Incubation of polyelectrolyte multilayer coated polystyrene particles in a mixture of water and tetrahydrofuran leads to rapid protrusion of the polystyrene through the polyelectrolyte coating and thus to formation of anisotropic particles, which is independent of the polystyrene core size and the polyelectrolyte coating composition.

Microstructured titanium glycolates such as spheres and rods have been prepared from the mixture of titanium butoxide and ethylene glycol. The synthesized titanium complexes were transformed into high refractive index titania. The obtained titania structures are of practical importance for optical applications in light scattering and stimulated emission.

Titania glycolate microstructures of the spheres and rods have been synthesized from titanium tetrabutoxide (TBT)-ethylene glycol (EG) mixture. As-prepared structures are transformed into anatase-type titania by calcination. Their potential for the photonic and photocatalytic applications can be expected.

Various morphologies of carbon nanotubes (CNTs) grown on the Fe(NO/sub 3/)/sub 3/-Al(OH)/sub 3/ mixtures have been observed. Fe(NO/sub 3/)/sub 3/-Al(OH)/sub 3/ mixtures prepared by impregnation method have been mechanochemically treated by the high energy grinding process using a mixer mill. Long grinding duration of Fe-Al(OH)/sub 3/ induced Al(OH)/sub 3/ to amorphous form and promoted both Fe(NO/sub 3/)/sub 3/ and Al(OH)/sub 3/ to agglomerate into spheres. With as-prepared unground and ground mixtures, CNTs were grown by thermal CVD under C/sub 2/H/sub 2/ and H/sub 2/ gases at 700/spl square/. As a result, CNTs grown on ground mixtures have a more uniform diameter than those of unground mixture. In addition to this, morphological changes of CNTs grown on unground and ground mixtures show that mechanochemical treatment for supported catalyst can act as the factor of growth control.