Hierarchical Nanoporous Silica Films for Wear Resistant Antireflection Coatings.

High-performance antireflection (AR) layers were prepared by depositing hierarchical nanoporous silica films on glass substrates. We designed a composite layer consisting of mesoporous silica nanoparticles (MSNs) and a mesoporous silica matrix. The introduction of bimodal nanoporous structures, i.

Enzyme-enabled responsive surfaces for anti-contamination materials.

Many real-life stains have origins from biological matters including proteins, lipids, and carbohydrates that act as gluing agents binding along with other particulates or microbes to exposed surfaces of automobiles, furniture, and fabrics. Mimicking naturally occurring self-defensive processes, we demonstrate in this work that a solid surface carrying partially exposed enzyme granules protected the surface in situ from contamination by biological stains and fingerprints. Attributed to the activities of enzymes which can be made compatible with a wide range of materials, such anti-contamination and self-cleaning functionalities are highly selective and efficient toward sticky chemicals.

Biobased polymers: synthesis of graft copolymers and comb polymers using lactic acid macromonomer and properties of the product polymers.

For developing broader application of biobased polymers, graft copolymers and comb polymers having poly(lactic acid) (PLA) side chains have been synthesized by using a macromonomer technique. PLA macromonomers (MMm) having a methacryloyl polymerizable group with different PLA chain length with an average length m = 4, 6, 8, 12, 18, and 30 were prepared via ring-opening polymerization of l-lactide using hydroxyethyl methacrylate (HEMA) initiator catalyzed by Sn(Oct)(2). Radical polymerization behaviors of these macromonomers were examined.

Artificial black opal fabricated from nanoporous carbon spheres.

A nanocasting method via chemical vapor deposition of acetonitrile was successfully employed to fabricate porous carbon colloidal crystal using colloidal crystal from monodispersed mesoporous silica spheres (MMSS) as a sacrificial scaffold. The mesostructure as well as periodic arrays within (111) plane of MMSS were replicated for the carbon colloidal crystal (black opal) with the length scale in the centimeter range. Brilliant iridescent colors were clearly observed for the first time on the black carbon colloidal crystal fabricated from porous carbon spheres, and they changed dramatically in accordance with the observation angle, like natural black opals.

Structural colored liquid membrane without angle dependence.

We have demonstrated for the first time that condensed gel particle suspensions in amorphous-like states display structural color with low angle dependence. This finding is in contrast to the common understanding that a periodic dielectric structure is fundamental to photonic band gap (PBG) production, and it validates the theory that a "tight bonding model" that is applicable to semiconductor systems can also be applied to photonic systems. More practically, this structural colored suspension represents a promising new material for the manufacture of reflective full-color displays with a wide viewing angle and nonfading color materials.

Biobased polymer system: miniemulsion of poly(alkyl methacrylate-graft-lactic acid)s.

To broaden the application scope of lactic acid polymers, a new miniemulsion of poly(alkyl methacrylate-graft-lactic acid)s has been developed. The graft copolymer synthesis was based on a poly(lactic acid) macromonomer having a methacryloyl polymerizable group. The macromonomer and a comonomer of n-butyl methacrylate together with a suitable surfactant formed a miniemulsion of the comonomers in water.

Transparent CoAl2O4 hybrid nano pigment by organic ligand-assisted supercritical water.

Transparent types of inorganic pigments are important as they can be used in a variety of applications, such as metallic finishing, contrast enhancing luminescent pigments, high-end optical filters, and so on. Currently, the difficulty in producing monodisperse and stable binary metal oxide nano pigments at low temperature hampers the applicability and realization of transparent blue nano pigments. Here, for the first time, we report organic ligand capped CoAl2O4 hybrid transparent nano pigment, which has a particle size less than 8 nm with well-stabilized single nanocrystals, using organic ligand-assisted supercritical water as the reaction medium.

In situ observations of the self-assembling process of colloidal crystalline arrays.

Growth processes of colloidal crystalline arrays in a fluidic glass cell were observed by confocal laser scanning microscopy. The results showed that the growth direction varied with the growth rate. At an extremely low growth rate, the array grew toward the 112 direction of the face-centered-cubic lattice.

Photonic band structures of colloidal crystals measured with angle-resolved reflection spectroscopy.

We acquired angle- and polarization-resolved reflection spectra from a colloidal crystal made of polystyrene spheres along the two perpendicular directions corresponding to the LU and LW directions in the first Brillouin zone of an fcc lattice. Dispersion relations between the reflection peak positions and the wave vectors of the incident light were obtained from the measured spectra and compared with calculated photonic band structures. For the first stop band region in the spectra, the behavior of the reflection peak due to Bragg diffraction agreed with the calculated band structure and revealed some differences induced by the polarization and crystalline orientations.

Optically induced melting of colloidal crystals and their recrystallization.

Colloidal crystals melt by applying focused light of optical tweezers and recrystallize after removing it. The disturbed zone by the light grows radially from the focus point and the ordering starts from the interface with the crystal. Although the larger disturbed zone is observed for the higher power optical tweezers, a master curve is extracted by normalization of the disturbed zone.

Close-packed colloidal crystalline arrays composed of silica spheres coated with titania.

Titania coated monodisperse silica spheres have been synthesized and fabricated as a close-packed colloidal crystalline array. We have demonstrated that the coated colloidal sphere can be used to control the peak position of the optical stop band through variation of the coating thickness. The titania coated silica spheres were prepared by the layer-by-layer assembly coating process, which reciprocally laminates the cationic polyelectrolyte and the anionic titania nanosheets on a monodisperse silica spheres, and were sintered to change the titania nanosheets to anatase.

Effects of compression and shearing on the microstructure of polymer-immobilized non-close-packed colloidal crystalline arrays.

We have examined the changes in the optical properties and microstructure of polymer-immobilized non-close-packed colloidal crystalline arrays with compression and shearing stress. The optical properties and microstructures of the arrays were measured by angle-resolved reflection spectroscopy. The spectra indicate an increase in the refractive index and a decrease in the interplane spacing with compression, however, indicating an increase in the interplane spacing with shearing stress.

Close-packed colloidal crystalline arrays composed of polystyrene latex coated with titania nanosheets.

We have demonstrated that polystyrene latex coated with titania nanosheets can be fabricated into a close-packed colloidal crystalline array, and that these coated colloidal spheres can be used to control the peak position of optical stop bands through the coating. The titania-nanosheets-coated polystyrene latex was prepared by the layer-by-layer (LBL) assembly coating process, involving alternating lamination of cationic polyelectrolytes and anionic titania nanosheets on monodisperse polystyrene latex particles. The Bragg diffraction peak of the colloidal crystalline array shifted to longer wavelengths with the coating of titania nanosheets.

Stepwise controlled immobilization of colloidal crystals formed by polymer-grafted silica particles.

Colloidal crystals formed by polymer-grafted silica particles were immobilized by a stepwise procedure consisting of gelation by radical copolymerization followed by solidification by ring-opening radical polymerization. In the first step, the poly(methyl methacrylate) (PMMA)-grafted silica colloidal crystal suspension was incorporated into the gel without altering the crystal structure by copolymerization of cross-linker, 1,2-dimethylacryloyloxyethane (DME) and methyl methacrylate (MMA). In the second step, ring-opening radical polymerization was performed after substituting the solvent with vinylidene-1,3-dioxolane.

Preparation and structure of novel siloxene nanosheets.

We demonstrate the two-dimensional silicon backbone structure of siloxene nanosheets, which produces relatively monodisperse nanosheets with a thickness of 0.7 nm and lengths in the range 100-200 nm; the thickness is an order of magnitude smaller than that of previously reported silicon nanoparticles prepared by a variety of other methods.

Large-domain colloidal crystal films fabricated using a fluidic cell.

The growth of colloidal crystal films from a dispersion of monodispersed silica spheres using a simple cell with one opening was investigated. Colloidal crystal films with large domain sizes were successfully fabricated almost over the cell (approximately 10 cm2) without applying any external force at room temperature. During the drying process, three distinct conditions were observed, in each of which the films exhibited different optical properties.