Hokkaido University · Energy
Professor Mai Takashima's research lab specializes in the design, characterization, and application of advanced photocatalytic materials, with a strong focus on titania-based systems and their heterostructures. The lab investigates fundamental aspects of photocatalytic activity, including charge transfer dynamics, facet-dependent reactivity, and light-matter interactions, using advanced spectroscopic techniques such as reversed double-beam photoacoustic spectroscopy. Key research directions include the development of structured photocatalysts—such as inverse-opal photonic crystals and core-shell nanostructures—to enhance light absorption and reaction efficiency through precise engineering of electronic and optical properties. The lab also explores multimodal electron transfer processes and interfacial charge transfer at oxide heterojunctions, aiming to clarify structure-activity relationships for sustainable energy and environmental applications.
Figures are computed from collected data and may differ slightly.
We report easily available and highly reliable colorimetric formaldehyde analysis using only a spectrophotometer/colorimeter, which enables the evaluation of the "true" photocatalytic activity induced by photoabsorption of a "photocatalyst", compared with gas-chromatographic analyses of gaseous products, even though the reliability of colorimetric organic-dye analysis is much worse under visible-light irradiation.
The light-intensity dependence (LID) of oxygen evolution using titanium(IV) oxide particles and electron acceptors under intense UV-LED irradiation was multimodal; in general, the LID changed from second to first order, and then fourth order in some cases. Such LID-order switching could reasonably be explained using a kinetic model in which the probability of multiple-electron (positive holes) accumulation in each particle governs the overall rates digitally. The first to fourth-order light inte
Abstract Changes in surface and bulk structures of rutile titania particles induced by braying up to 10 d and post calcination in air at 773 K were analyzed by reversed double-beam photoacoustic spectroscopy. The observed energy-resolved distribution of electron traps indicated that the surface was amorphized by braying to give rutile-core amorphous-shell structure and the amorphous layer was partly recrystallized by post-calcination leaving grain boundaries in the surface layers, both of which
Abstract Here, we report a novel structured material, titania inverse-opal photonic crystal with or without a single gold nanoparticle in each void, to provide a photoabsorption design strategy as enhanced photoreaction rates, only when wavelengths of photoirradiation, photoabsorption (by gold nanoparticles or titania), and photonic-bandgap edge are trebly matched.
Facet-selective gold or platinum-nanoparticle deposition on decahedral-shaped anatase titania particles (DAPs) exposing {001} and {101} facets via photodeposition (PD) from metal-complex sources was reexamined using DAPs prepared with gas-phase reaction of titanium (IV) chloride and oxygen by quantitatively evaluating the area deposition density on {001} and {101} and comparing with the results of deposition from colloidal metal particles in the dark (CDD) or under photoirradiation (CDL). The ob
Abstract Here, we report experimental evidence of interparticle spatial overlapping of orbitals to result in interparticle charge-transfer excitation (ICTE) at an anatase-rutile interface which is expected to be applicable to clarify the relative band position of metal-oxides and mixture homogeneity of mixture samples measured by reversed double-beam photoacoustic spectroscopy.
The effects of surface loading of iridium(II) oxide (IrO<sub>2</sub>), manganese(IV) oxide (MnO<sub>2</sub>), and cobalt(II) phosphate (CoPi) on the rate of photocatalytic oxygen evolution by anatase or rutile titania particles suspended in aqueous solutions of an electron acceptor, iodate ions, were studied by light intensity-dependence (LID) kinetic analyses. Although the role of these deposits has been reported to be a cocatalyst without showing results of any kinetic analysis, the present LI
Diamond-like carbon (DLC) films have many excellent characteristics such as low friction coefficient, wear resistance, gas barrier property and biocompatibility. These many positive characteristics enable DLC coatings to be applied to a lot of fields from metallic materials to polymer materials for overcoatings. However, usual DLC film has a lot of micro-pores or pinholes, and those defects become problems as DLC film is not able to make the best use of abrasion resistance effectively due to the
Wear and fretting fatigue are important technological problems in automotive, railway and aerospace fields. The purpose of this study is to find a method of reducing the wear of cast-iron (FCD)/aluminum components, which are often applied to automotives, and thus extend their lifetime. First, a stainless-steel (SUS) shim was designed, which can be inserted between an FCD plate and an aluminum plate. Second, diamond-like carbon (DLC) coatings were applied to the shim inserts to prevent the FCD an
Segment-structured diamond-like carbon (S-DLC) film, which is separated DLC films into small segments using metal mask, has been developed in order to improve its tribological property or accomplish multi-functionalized surface. Meanwhile, the S-DLC deposition by conventional methods using metal mesh as masks is difficult to apply to the three-dimensional substrates which have complicate curves. The purpose of this study is to develop coating methods for S-DLC deposition on the three-dimensional
Wear and fretting fatigue are important technological problems in many kinds of fields, especially, in automotives. In our recent study, we proposed diamond-like carbon (DLC)-coated shim inserts deposited by Plasma-Based Ion Implantation and Deposition (PBII&D) method as a method of preventing ductile cast-iron (FCD) / aluminum components from fretting wear, which are usually applied to automotive wheels. Then they were evaluated fatigue characteristics by a bending fatigue test up to 1 million
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