Showing papers by "Takehiko Sasaki published in 2010"
TL;DR: An insight into the origin of the efficient catalysis for selective epoxidation of alkenes with IBA/O(2) is given, resulting in the preferential coordination of trans-stilbene to the Ru-complex at the surface.
Abstract: We have prepared a novel Ru-mononer complex supported on a SiO2 surface by using a Ru-monomer complex precursor with a p-cymene ligand, which was found to be highly active for the selective oxidation of aldehydes and the epoxidation of alkenes using O2 The structure of the supported Ru catalyst was characterized by means of FT-IR, solid-state NMR, diffuse-reflectance UV/vis, XPS, Ru K-edge EXAFS, and DFT calculations, which demonstrated the formation of isolatedly located, unsaturated Ru centers behind a p-cymene ligand of the Ru-complex precursor The site-isolated Ru-monomer complex on SiO2 achieved tremendous TONs (turnover numbers) for the selective oxidation of aldehydes and alkenes; eg TONs of 38,800,000 for selective isobutyraldehyde (IBA) oxidation and 2,100,000 for trans-stilbene epoxidation at ambient temperature, which are among the highest TONs in metal-complex catalyzes to our knowledge We also found that the IBA sole oxidation with an activation energy of 48 kJ mol−1 much more facile tha
59 citations
TL;DR: In this paper, the specific interactions between changed capping agents and crystal planes of Co3O4 led to the selective formation of cubes with {100} orientation and rhombododecahedrons with {110} orientation, respectively.
Abstract: Single-crystalline Co3O4 crystals such as spheres, nanocubes, and rhombododecahedrons were obtained hydrothermally by employing differently charged surfactants and solvents. On the basis of calculations (charge density, atom density, and dipolar moment) on involved charged crystal planes of {100} for the cubes and {110} for the rhombododecahedrons, we proposed that the specific interactions between changed capping agents and crystal planes of Co3O4 led to the selective formation of cubes with {100} orientation and rhombododecahedrons with {110} orientation, respectively. It was also found that the intrinsic structure of charged planes affected possibly not only the crystallization processes and final morphologies of Co3O4 crystals but also the assembly behaviors of Co3O4 particles. Being in a typical spinel structure, the crystallization habits of Co3O4 crystals based on intrinsic structure directed by capping agents are possibly extended to other crystal systems in a similar structure, to get an optimize...
44 citations
TL;DR: This is the first synthesis of Co(OH)(3) with tunable shapes and sizes, which may find important applications as gas sensors, catalysts, and electrode materials, owing to the specific large surface-to-volume ratio and other unique properties endowed by typical 1D nanobelts.
Abstract: In this paper, we demonstrated a facile hydrothermal route leading to the generation of a new cobalt hydroxide, Co(OH)3, nanobelt. This new product of Co(OH)3 nanobelts was well characterized and identified by SEM, TEM, XRD, EDX, XPS, EXAFS, Raman, TGA and SQUID. Additionally, through systematic investigations on morphological evolution, it was found that the size and shape of Co(OH)3 nanobelts were adjustable in large scale, e.g. from 50 to 1.5 µm in length and 5 µm to 20 nm in width, by means of fine experimental parameter control. Furthermore, the unique pseudo-single-crystalline Co3O4 nanobelts were produced from Co(OH)3 precursors via heating treatment. This is the first synthesis of Co(OH)3 with tunable shapes and sizes, which may find important applications as gas sensors, catalysts, and electrode materials, owing to the specific large surface-to-volume ratio and other unique properties endowed by typical 1D nanobelts.
25 citations
TL;DR: In this article, a pulsed laser ablation (532 nm; 52 J/cm2; 7 ns; 10 Hz) was used to synthesize diamantane from pyrolytic graphite in adamantane-dissolved supercritical xenon at a temperature T = 290.2 K and pressure p = 5.86 MPa.
Abstract: Nanocarbon materials have been synthesized by pulsed laser ablation (532 nm; 52 J/cm2; 7 ns; 10 Hz) of highly oriented pyrolytic graphite in adamantane-dissolved supercritical xenon at a temperature T = 290.2 K and pressure p = 5.86 MPa. Micro-Raman spectroscopy of the products revealed the presence of hydrocarbons possessing sp3 hybridized bonds also found in diamond structures. The synthesis of diamantane was confirmed by gas chromatography-mass spectrometry. The same measurements also indicate the possible synthesis of other diamondoids up to octamantane. Thus, laser ablation in supercritical fluids is proposed as one practical method of synthesizing diamondoids.
22 citations
TL;DR: In this article, a diamondoid was synthesized from adamantane (C10H16) using low-temperature plasmas generated in supercritical xenon and the carbon content of the synthesized materials was verified by energy dispersive X-ray spectroscopy.
Abstract: Diamondoid molecules were synthesized from adamantane (C10H16) using low-temperature plasmas generated in supercritical xenon. The carbon content of the synthesized materials was verified by energy dispersive X-ray spectroscopy, while micro-Raman spectroscopy measurements confirmed that the synthesized materials contained sp3 bonds, the features in the Raman spectra being similar to those found in the Raman spectra of higher order diamondoids. Mass peaks at m/z = 396 were most abundant and might be attributed to C30H36 isomers of hexamantane. The synthesis of this particular type of diamondoid is explained by the fewer necessary cleavages of C–C bonds or C–H occurring to form the diamondoid.
14 citations
TL;DR: In this article, a sheet-like dielectric barrier discharge microplasma that can be generated in supercritical fluids was developed, where nanocrystalline diamonds and diamondoid-like sp 3 bonded nano-hydrocarbons were synthesized by using adamantane as a precursor and seed.
Abstract: A two-dimensional, sheet-like dielectric barrier discharge microplasma that can be generated in supercritical fluids was developed. With this type of plasma, generated in supercritical xenon, nanocrystalline diamonds and diamondoid-like sp 3 bonded nano-hydrocarbons were synthesized by using adamantane as a precursor and seed. Pressure and temperature were set close to the critical point of xenon at 6.3 MPa and 290.2 K, respectively. The peak-to-peak voltage for microplasma generation was between 3.4 and 7.1 kV, at a frequency of 10 kHz and the power consumption of the microplasma determined from the I – V measurements reached about 30 mW. Transmission electron microscopy analysis of the lattice of the synthesized particles revealed crystal structures similar to those observed in nanodiamonds, while micro-Raman spectra yielded features also found in Raman and ab initio computational studies of diamondoids.
13 citations
TL;DR: In this paper, the authors measured both fluorescent and phosphorescent organic light emitting diodes (OLEDs) in high magnetic field up to 9 T and reported that the current efficiency steeply increased below 100mT as reported but gradually decreased when the field was larger.
8 citations
TL;DR: In this article, a Ru-monomer complex supported on a SiO2 surface was proposed for the selective oxidation of aldehydes and the epoxidation of alkenes using O2.
Abstract: We have prepared a novel Ru-mononer complex supported on a SiO2 surface by using a Ru-monomer complex precursor with a p-cymene ligand, which was found to be highly active for the selective oxidation of aldehydes and the epoxidation of alkenes using O2. The structure of the supported Ru catalyst was characterized by means of FT-IR, solid-state NMR, diffuse-reflectance UV/vis, XPS, Ru K-edge EXAFS, and DFT calculations, which demonstrated the formation of isolatedly located, unsaturated Ru centers behind a p-cymene ligand of the Ru-complex precursor. The site-isolated Ru-monomer complex on SiO2 achieved tremendous TONs (turnover numbers) for the selective oxidation of aldehydes and alkenes; e.g. TONs of 38,800,000 for selective isobutyraldehyde (IBA) oxidation and 2,100,000 for trans-stilbene epoxidation at ambient temperature, which are among the highest TONs in metal-complex catalyzes to our knowledge. We also found that the IBA sole oxidation with an activation energy of 48 kJ mol−1 much more facile tha...
3 citations
TL;DR: In this paper, density functional theory calculations for NO adsorption and NO-CO reaction were conducted to understand two new aspects of the increases in the amount and reduction rate of adsorbed NO by gas phase CO molecules which are undetectable at the Co2+-ensemble/γ-Al2O3 catalyst surface.
1 citations