Showing papers by "Toshiharu Teranishi published in 2003"
TL;DR: In this paper, a simple method is proposed to control the size of alkanethiol-protected Au nanoparticles by heat treatment in the solid state, and the size evolution mechanism is discussed on the basis of the thermodynamic model.
Abstract: A simple method is proposed to control the size of alkanethiol-protected Au nanoparticles by heat treatment in the solid state. The mean diameter of the Au nanoparticles prepared by Brust's two-phase method (∼1.5 nm) was evolved to 3.4−9.7 nm by heating to 150−250 °C in air. The uniform growth of nanoparticles was not observed when tetraoctylammonium bromide (TOAB), which was used as a phase-transfer agent during the preparation of Au nanoparticles, was removed before the particle growth process. The crystal structures of Au nanoparticles and alkanethiol ligand structures on Au nanoparticles were characterized before and after the heat treatment. The size-evolution mechanism was discussed on the basis of the thermodynamic model. The heat-treated Au nanoparticles easily formed self-assembled 2D superlattices with hexagonal packing, where the alkanethiol protective agents with an all-trans conformation were estimated to interpenetrate each other.
304 citations
TL;DR: The demonstrated a self-assembly of two different kinds of nanoparticles simultaneously directed on a monolayer film of diblock copolymer micelles via physical and chemical arrangements as an example of controlled fabrication of nanometer-sized building blocks.
Abstract: We demonstrated a self-assembly of two different kinds of nanoparticles simultaneously directed on a monolayer film of diblock copolymer micelles via physical and chemical arrangements. We first incorporated gold nanoparticles physically around the micelles of a monolayer film of PS-PVP micelles having a short-range hexagonal order. Iron oxide nanoparticles were then synthesized chemically in the PVP core area of the ordered micelles, resulting in a mosaic nanopattern of magnetic iron oxide nanoparticles surrounded by metallic gold nanoparticles. Thus, we were able to direct two kinds of nanoparticles to self-assemble in the specific positions as an example of controlled fabrication of nanometer-sized building blocks.
241 citations
TL;DR: An isomeric 0+ state at E x = 2.24 MeV in 12Be was found in the projectile fragmentation of 18O at 100 A MeV on a Be target as discussed by the authors, where the excitation energy and the spin assignment were deduced by measurements of the energies and the angular correlation function of the coincident two γ-rays corresponding to the 0+ → 2+ → 0+ decay.
73 citations
TL;DR: The results strongly suggest that the different types of 2D or 3D superlattices can be constructed by simple addition of proper acid to nanoparticles functionalized with amino groups.
Abstract: In the present work, a novel method was developed for the fabrication of 2D superlattices with different symmetries. Same-surface amino-functionalized Au nanoparticles as building blocks were self-assembled to form different 2D superlattices using surface modification with organic acids. The 2D superlattices of quasi-honeycomb and square structures were obtained by neutralizing amino-functionalized Au nanoparticles with 1,3,5-tribenzenecarboxylic acid and acetic acid, respectively. These results strongly suggest that the different types of 2D or 3D superlattices can be constructed by simple addition of proper acid to nanoparticles functionalized with amino groups. This method will allow us to obtain various desired metal superlattices without fully synthesizing the ligands.
51 citations
TL;DR: In this article, a planar 1D chains and 2D superlattices of gold nanoparticles in the 1.5-9.7 nm range were successfully fabricated by a self-assembly technique.
44 citations
TL;DR: In this paper, the diameter dependences of the magnetizations were measured and the superparamagnetic behavior in the magnetization process and enhanced magnetization was observed compared to the paramagnetic moments in the bulk state.
Abstract: Platinum metal nanoparticles having diameter ranging from 2.3 to 3.8 nm with quite narrow diameter distribution have been synthesized by chemical reaction method, and their diameter dependences of the magnetizations were measured. Pt nanoparticles having the diameter below 3.8 nm exhibited superparamagnetic behavior in the magnetization process and enhanced magnetization was observed compared to the paramagnetic moments in the bulk state. With decreasing the diameter, the magnetic moment increases and reaches 5.0μB/Pt particle at 2.3 nm .
38 citations
TL;DR: In this paper, the direct crystallization of high-silica mordenite (MOR) zeolite using tetraethylammonium and fluoride ions was investigated by varying the primary variables of the hydrothermal synthesis such as Si∶Al and H2O∶SiO2 ratios in the starting synthesis mixture.
Abstract: The direct crystallization of high-silica mordenite (MOR) zeolite using both tetraethylammonium and fluoride ions was investigated by varying the primary variables of the hydrothermal synthesis such as Si∶Al and H2O∶SiO2 ratios in the starting synthesis mixture. Under well-optimized conditions, highly crystalline MOR zeolites with a Si∶Al ratio of approximately 25 were successfully prepared. From evaluation of the thermal stabilities of the MOR zeolites obtained, it was also found that there is a good relationship between the thermal stability and the bulk Si∶Al ratio of MOR zeolites and that any NaF remaining in the zeolite crystals considerably reduces the thermal stability.
35 citations
TL;DR: In this article, a polypropylene (PP)/Ti-MCM-41 nanocomposites were prepared by isospe- cific propylene polymerization with Al(i-C4H9)3 catalyst and the cross polarization/magic angle spinning (CP/MAS) 13 C NMR spectrum of the composite was similar to that of the conventional isotactic PP, and the decrease in the pore volume of the nanocomposition, as measured by N2 adsorption, was consistent with the value calculated from the weight loss in the therm
Abstract: Polypropylene (PP)/Ti-MCM-41 nanocomposites were prepared by isospe- cific propylene polymerization with Ti-MCM-41/Al(i-C4H9)3 catalyst. The cross polar- ization/magic angle spinning (CP/MAS) 13 C NMR spectrum of the composite was similar to that of the conventional isotactic PP, and the decrease in the pore volume of Ti-MCM-41 in the nanocomposites, as measured by N2 adsorption, was consistent with the value calculated from the weight loss in the thermogravimetric analysis (TGA) curve; both these facts attest to propylene polymerization within the mesopores of Ti-MCM-41. Alkali treatment followed by extraction with o-dichlorobenzene allows us to extract the confined PP out of the Ti-MCM-41 mesopores. Although the PP/Ti- MCM-41 nanocomposites do not exhibit a crystalline melting point, the same PP when extracted from the mesopores showed a clear melting point at 154.7 °C; this indicates that the crystallization of PP confined in mesopores is strongly hindered. For the PP polymerized within the confinement, the molecular weight (Mw) and molecular weight distribution (Mw/Mn) were 84,000 and 4.3, respectively; these values were considerably smaller than those of the PP polymerized concurrently outside the Ti-MCM-41 meso- pores (Mw 200,000 - 450,000, Mw/Mn 40 -75). Therefore, the confinement also has a marked effect on the molecular weight of the PP. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3324 -3332, 2003
32 citations
TL;DR: In this article, the influence of aliphatic alcohols on the synthesis of mordenite type zeolite was investigated using a starting synthesis mixture with the chemical compositions (0 −3 ROH∶0.005 −0.035 Na2O∶ 0.01 Al2O3∶SiO2∶40 H2O).
Abstract: The influences of aliphatic alcohols (ROH) on the synthesis of mordenite (MOR) type zeolite were investigated using a starting synthesis mixture with the chemical compositions (0–3 ROH∶0.035 Na2O∶0.005–0.01 Al2O3∶SiO2∶40 H2O). Highly crystalline single crystals of MOR were successfully synthesized using ethanol, 1-propanol and 1-butanol. Under well-optimized conditions, pure uniform and large single crystals up to ca. 50 μm in length were obtained. From sorption experiments of nitrogen, water, benzene and Se, it was found that the single large MOR obtained is not the large-port type MOR and that the effective sorption capacity is markedly influenced by the carbon chain length of aliphatic alcohol used in the crystallization.
28 citations
TL;DR: In this paper, the authors investigated the dealumination-realumination processes of MOR, MFI, FER and BEA zeolites by means of XRD, 27 Al MAS NMR, FT-IR and N2 adsorption.
25 citations
TL;DR: In this paper, a series of supported catalysts were prepared by combining ( n BuCp) 2 ZrCl 2 and Cp 2 ZRCl 2 sequentially grafted on silica in different ratio (1:1 and 1:3) and immobilization order.
Abstract: A series of supported catalysts were prepared by combining ( n BuCp) 2 ZrCl 2 and Cp 2 ZrCl 2 sequentially grafted on silica in different ratio (1:1 and 1:3) and immobilization order. Catalyst systems were characterized by Rutherford backscattering spectrometry (RBS), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). Grafted metal content remained comprised between 0.37 and 0.53 wt.% Zr/SiO 2 . All the systems were shown to be active in ethylene homopolymerization having methylaluminoxane as co-catalyst. Catalyst activity was shown to be dependent on the metallocene nature, but not on the addition order or molar ratio. The highest activity was achieved with Cp 2 ZrCl 2 /( n BuCp) 2 ZrCl 2 (1:3) catalyst system (ca. 4.26 kg PE (mmol Zr h) −1 ). Resulting polymers were characterized by GPC and DSC. In spite of bearing two catalyst centers, no bimodality was observed in the resulting polymers.
TL;DR: In this article, the coincorporation of Al and Ga atoms into the framework of BEA zeolite by the pH control method was investigated by the means of XRD, XRF, 27Al MAS NMR, 71Ga MAS NMRI, XPS, FT-IR and nitrogen adsorption.
TL;DR: In this paper, the post-synthesis method was used to obtain isotactic polypropylenes with wide molecular mass distributions using various Metal-MCM-41 prepared by the post synthesis method.
Abstract: Polymerizations of propylene were conducted using various Metal-MCM-41 prepared by the post-synthesis method. Ti-, Zr-, Hf-, Mn- and Zn-MCM-41 combined with alkylaluminiums were found to give isotactic polypropylenes with wide molecular mass distributions.
01 Jan 2003
TL;DR: In this article, the Coulomb breakup technique was applied to determine the E1 strength of excited levels in 12N and 13O, which dominate the low-energy cross sections of the 11C(p,γ)12N and 12N(pγ)13O reactions, respectively.
Abstract: The Coulomb breakup technique was applied to determine the E1 strength of excited levels in 12N and 13O, which dominate the low-energy cross sections of the 11C(p,γ)12N and 12N(p,γ)13O reactions, respectively. These reactions are important in the hot pp mode nuclear burning in hydrogen-rich massive objects [1]. Under a high-temperature and high-density condition, these capture reactions become faster than the β + decay of 11C and 12N. However, these 11C(p,γ)12N and 12N(p,γ)13O reactions are difficult to study experimentally because the life times of 11C and 12N are too short to prepare them as targets.
TL;DR: Mesoporous silica fibers were prepared by varying primary variables of the synthesis conditions in the static two-phase acidic system such as the hexane/Si (OR)4 and HCl/Si(OR) 4 ratios as well as the alkyl chain length of silicon alkoxide.
Abstract: Mesoporous silica fibers were prepared by varying primary variables of the synthesis conditions in the static two-phase acidic system such as the hexane/Si(OR)4 and HCl/Si(OR)4 ratios as well as the alkyl chain length of silicon alkoxide. The morphological and structural features of the mesoporous silica materials were strongly dependent upon the hydrolysis rate of silica source used. Namely, the high fraction of well-ordered mesoporous silica fibers was achieved by a delicate balance of the hydrolysis rate of silicon alkoxide and the condensation rate of silicate species. The obtained mesoporous silica fibers consisted of hexagonally organized channels running circularly around the fiber axis. The fibers prepared with Si(OC4H9)4 showed the high thermal stability because of the lower content of structural defects within the framework.
TL;DR: In this paper, a large enhancement of the 13 C(α,n) 16 O reaction cross section at low energy limit due to the sub-threshold state in 17 O has been predicted, explaining the neutron source of s-process nucleosynthesis.
01 Jan 2003
TL;DR: In this paper, the authors studied the low-lying E1 and E2 transitions of 12Be via inelastic scattering and found that the effects of shell quenching are most likely to be manifested.
Abstract: In the neutron-rich region around N = 8, experimental evidence is being to accumulate that several neutron-rich nuclei, such as 11Li and 11Be, are strongly influenced by lowlying intruder orbitals [1,2]. In this neighborhood, 12Be is a typical neutron-rich nucleus with N = 8 , where the effects of shell quenching are most likely to be manifested. Since properties of low-lying states in even-even nuclei are sensitive to the modification of the nuclear shell structure, we have studied the low-lying E1 and E2 transitions of 12Be via inelastic scattering.
01 Jan 2003
TL;DR: In this article, the 6He + 6He and 6He+ 8He breakup channels in the two-neutron removal and the inelastic scattering of an exotic 14Be beam were studied.
Abstract: Excited states in 12Be and 14Be were studied by measuring the 6He + 6He and 6He + 8He breakup channels in the two-neutron removal and the inelastic scattering of an exotic 14Be beam, respectively.