Hideo Hata

Direct Deposition of Trivalent Rhodium Hydroxide Nanoparticles onto a Semiconducting Layered Calcium Niobate for Photocatalytic Hydrogen Evolution

Well-dispersed Rh(OH)3 nanoparticles were deposited in the interlayer galleries of a Dion-Jacobson type layered perovskite (ACa2Nb3O10: A=H or K). X-ray photoelectron spectra and zeta potential measurements suggest covalent bonding (Rh-O-Nb) between the nanoparticles and the niobate sheets. After calcination of Rh(OH)3/KCa2Nb3O10 at 350 degrees C in air, interlayer Rh(OH)3 nanoparticles were transformed to Rh2O3 and showed higher photocatalytic activity for hydrogen evolution using methanol as a sacrificial electron donor.

RF diamond transistors : Current status and future prospects

RF diamond transistors have been developed on a hydrogen-terminated surface conductive layer. fT and fmax of 23 and 25 GHz, respectively, have been achieved in a diamond MISFET with a 0.2 µm gate length. Utilizing de-embedding and small-signal equivalent circuit analysis, parasitic components are extracted. The intrinsic fT and fmax of the 0.2-µm-gate diamond MISFET are estimated to be 26 and 36 GHz, respectively. In this report, some of the challenging steps in device fabrication processes such as the development of a low-resistivity ohmic layer, a high-quality gate insulator and acceptor density control technology, toward high-power and high-frequency diamond transistors with high reliability, are introduced.

Immobilization of Photosynthetic Pigments into Silica-Surfactant Nanocomposite Films

Highly transparent silica-surfactant nanocomposite films containing photosynthetic pigments have been successfully formed through the solubilization of chlorophyll a (Chl a) into surfactant micelles. The UV-vis absorption spectra indicated that a large amount of Chl a were transformed into pheophytin a in the films. These photosynthetic pigments were well dispersed in the surfactant assemblies and their chlorin rings were exposed to the surface of silica layers. Even under an air atmosphere, the photostability of immobilized pigments was largely improved in comparison with that in a homogeneous Chl a solution. Because both Chl a and pheophytin a molecules are effective for the photosensitive charge separation, the present film system is very suitable for heterogeneous immobilizing media for photosynthetic pigments from the viewpoint of in vitro biomimetic devices for solar energy conversion.

Micropatterning oligonucleotides on single-crystal diamond surface by photolithography

DNA micropatterns have been for the first time fabricated on a single-crystal diamond surface in conjunction with the photolithography technique. A new chemical modification process for producing amine groups inside patterned regions and a passivation layer terminated with fluorine outside patterned regions is demonstrated. The resulting amine groups within patterned areas and fluorine termination outside patterned areas on the single-crystal diamond surface were characterized by spatially resolved X-ray photoelectron spectroscopy. Amine-terminated oligonucleotides were then linked to the amine-patterned regions using a crosslinker. It was revealed that hybridization on DNA-patterned diamond is specific and selective, with a low background outside the patterns and strong binding to complementary probe DNA immobilized inside the patterns but no binding to noncomplementary probe DNA similarly immobilized inside the patterns. These results suggest that DNA micropatterning on a single-crystal diamond may serve as an ideal platform for future biochips and biosensors.

A Scrolled Sheet Precursor Route to Niobium Oxide Nanotubes

Potassium hexaniobate (K 4 Nb 6 O 17 ) is one of the few relatively well-studied oxides which, upon exfoliation, rolls up into scrolls almost quantitatively with monodisperse length (∼300 nm) and diameter (30 nm). The tubes have high surface area (250-300 m 2 /g) and a wall thickness of 2-3 nm. These H 4 Nb 6 O 17 scrolls were converted to Nb 2 O 5 via a thermal dehydration process, yielding high surface area (150-200 m 2 /g) Nb 2 O 5 nanotubes. Despite extensive atomic rearrangement during dehydration at 400-450 °C, little sintering is occurs, and so the tubular morphology is retained. Attempts to conduct further reactions to obtain LiNbO 3 and KNbO 3 nanotubes from reaction with molten alkali salts failed to yield the intended nanotubular oxides.