High Aspect‐Ratio Cylindrical Nanopore Arrays and Their Use for Templating Titania Nanoposts

We have designed a two-dimensional photonic crystal in electro-optic materials that can actively control the superprism effect. By applying an electric field to the photonic crystal, the electro-optic effect will change the dielectric constant of the material, which modifies both the band structure and the dispersion surfaces. In the proposed structures, we show that electric fields of up to 6 V/μm in (Pb0.09La0.91)(Zr0.65Ti0.35)O3-based photonic crystals can deflect light up to 49°. This device concept can be used for a class of optical modulation devices that can provide a local control of dispersion surfaces within a photonic crystal.

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Electro-optic control of the superprism effect in photonic crystals

Carbon nanotube-supported ZrO2 and Pt (Pt–ZrO2/CNT) catalysts with various Pt/ZrO2 molar ratios were prepared by sol–gel and ethylene glycol reduction methods. X-ray diffraction and transmission electron microscopy showed that ZrO2 nanocrystallites tend to grow gradually with the increase of ZrO2 ratio, whereas the size of Pt crystallites decreases and they disperse uniformly on the surface of carbon nanotube-supported ZrO2. The composite catalyst activities were examined by cyclic voltammetry, potentiostatic polarization and CO stripping voltammetry in acidic solutions. The results demonstrated that the addition of ZrO2 significantly increased the catalytic activity of Pt for methanol and ethanol oxidation. However, the promotion degree varied with the increase of ZrO2 content. The maximum catalytic activity for methanol and ethanol oxidation was observed at Pt–ZrO2/CNTs (1:1) and Pt–ZrO2/CNTs (1:3), respectively. This difference was ascribed to the dissimilar catalytic mechanism of Pt–ZrO2/CNTs for methanol and for ethanol electro-oxidation.

Promotion of carbon nanotube-supported Pt catalyst for methanol and ethanol electro-oxidation by ZrO2 in acidic media

Hybrid organic–inorganic materials based on TiO2 gels demonstrate high photosensitivity. Associated with their stable photochromic behavior, these make them suitable for laser-induced photopatterning. We show that the electronic coupling along the extended interface between the inorganic, TiO2-based gel, and the organic, poly(hydroxyethyl methacrylate) networks allows (i) a rapid scavenging of the photo-excited holes by the polymer, (ii) an efficient trapping of the photo-exited electrons as small polarons (Ti3+) that develop “dark” absorption continuum covering the spectral range from 350 nm (UV) to 2.5 μm (IR), and (iii) long-term (over months) conservation of trapped charges at high number density. Furthermore, we give the proof that the electron transfer depends on the material microstructure, which can be affected by the material chemistry and processing. Undeniably, a delay between the gelation of the system and the organic polymerization step allows tuning the photochromic responses of the resulting nanocomposites. A comparison is made between the prepared gel-based samples and a reference sample, which is obtained by the organic copolymerization of functional precondensed inorganic building units, titanium oxo-clusters, Ti16O16(OEt)24(OEMA)8 with hydroxyethyl methacrylate. The experiments show the highest values of quantum yield (12%) and Ti3+ concentration (1.7 × 1020 cm−3 or 14% of titanium atoms) attained in samples where the organic polymerization is induced after gelation. This behavior is explained by a strong coupling between the organic and the inorganic components of the hybrid towards the hole exchange and a poor coupling towards the electron exchange.

Laser-induced photopatterning of organic-inorganic TiO2-based hybrid materials with tunable interfacial electron transfer.

We have deposited titanium dioxide (TiO2) thin films on glass using titanium (IV) isopropoxide (Ti[OCH(CH3)2]4, 97%) by sol–gel processing. In order to elevate photocatalytic activity of the as-grown TiO2 films, argon and oxygen plasmas ignited by radio-frequency (RF) and microwave (MW) under both vacuum and atmosphere conditions were also used in the range of 50–200 W within 30 min at room temperature. Photocatalytic activity was evaluated by the measurements of the contact angle, UV/vis irradiation, and toluene removal test. In this work, the effect of the plasma with photocatalyst (TiO2) on the improvement of hydrophilic properties has mainly been investigated. A superhydrophilic property and surface morphology change appeared in the light irradiation with O2 plasma treatment. Based on this work, we confirmed that the plasma treatment method was very reliable method for the synthesis of TiO2 thin films with high catalytic performance.

F. Chiba

Papers

Photosensitive gel films prepared by the chemical modification and their application to surface-relief gratings