The Experts below are selected from a list of 1710 Experts worldwide ranked by ideXlab platform
Kunichi Miyazawa - One of the best experts on this subject based on the ideXlab platform.
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vortex aligned fullerene Nanowhiskers as a scaffold for orienting cell growth
2015Co-Authors: Venkata Krishnan, M Sathish, Yuki Kasuya, Lok Kumar Shrestha, Shinsuke Ishihara, Kosuke Minami, Hiromi Morita, Tomohiko Yamazaki, Nobutaka Hanagata, Kunichi MiyazawaAbstract:A versatile method for the rapid fabrication of aligned fullerene C60 Nanowhiskers (C60NWs) at the air–water interface is presented. This method is based on the vortex motion of a subphase (water), which directs floating C60NWs to align on the water surface according to the direction of rotational flow. Aligned C60NWs could be transferred onto many different flat substrates, and, in this case, aligned C60NWs on glass substrates were employed as a scaffold for cell culture. Bone forming human osteoblast MG63 cells adhered well to the C60NWs, and their growth was found to be oriented with the axis of the aligned C60NWs. Cells grown on aligned C60NWs were more highly oriented with the axis of alignment than when grown on randomly oriented Nanowhiskers. A study of cell proliferation on the C60NWs revealed their low toxicity, indicating their potential for use in biomedical applications.
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solvent engineering for shape shifter pure fullerene c60
2009Co-Authors: M Sathish, Kunichi Miyazawa, Jonathan P Hill, Katsuhiko ArigaAbstract:As a highly anticipated technique for bottom-up nanotechnology, i.e., shape control of pure functional molecules, we here report controlled formation of two-dimensional (2D) objects such as hexagons and rhombi and their selective shape shifting into one-dimensional (1D) rods through solvent-dependent changes of crystal lattice, all from pure C60. Uniformly shaped rhombi and hexagons were obtained at tert-butyl alcohol/toluene and i-propyl alcohol/CCl4 interfaces, respectively. In addition, exposure of these 2D nanosheets to water induced selective transformation into 1D nanorods. Nanorhombi were converted to short nanorods upon exposure to water. This shape shift is accompanied by changes in crystalline structures from a mixed fcc/hexagonal to pure fcc lattice, the latter of which is almost identical with morphologically similar C60 Nanowhiskers. Metastable nanorhombi which possess a strained mixed crystalline structure metamorphosize into the more stable short nanowhisker (nanorods). In contrast, the sta...
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Fracture surface and correlation of buckling force with aspect ratio of C60 crystalline whiskers
2007Co-Authors: Koji Asaka, Kunichi Miyazawa, Ryoei Kato, Ryozo Yoshizaki, Tomohiro KizukaAbstract:Abstract The structure and mechanical properties of crystalline whiskers with an average diameter of 600 nm, composed of C 60 molecules were studied by transmission electron microscopy combined with nanonewton force measurements used in atomic force microscopy. C 60 Nanowhiskers with a body-centered tetragonal structure are compressed along their long axis. Young's modulus of the C 60 Nanowhiskers was estimated to be 28 ± 5 GPa. The buckling stress was correlated to the aspect ratio of length to diameter of the C 60 Nanowhiskers. The (100) surface was the principal fracture surface of the C 60 Nanowhiskers.
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solvated structure of c60 Nanowhiskers
2005Co-Authors: Junichi Minato, Kunichi MiyazawaAbstract:Abstract This work characterizes the structure of C60 Nanowhiskers prepared by the liquid–liquid interfacial precipitation method in the C60-saturated m-xylene and isopropyl alcohol system. Transmission electron microscopy and X-ray diffraction measurement show that the C60 Nanowhiskers had a hexagonal structure with cell dimensions a = 2.407 nm and c = 1.018 nm which is different from pristine C60. The structure of the C60 Nanowhiskers in solution is different from that of the solvated structure reported for the C60 nanotubes but similar to that reported for the C60 bulk crystal solvated with m-xylene. X-ray diffraction analysis also showed a shift to fcc structure after solvent evaporation. The C60 Nanowhiskers prepared using toluene as solvent also showed a similar solvated structure, and a more rapid structural change into fcc upon drying was again observed.
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c60 Nanowhiskers formed by the liquid liquid interfacial precipitation method
2002Co-Authors: Kunichi Miyazawa, Y Kuwasaki, A Obayashi, Makoto KuwabaraAbstract:Fine needlelike crystals of C60 have been formed by a liquid–liquid interfacial precipitation method which uses an interface of the concentrated toluene solution of C60/isopropyl alcohol. The needlelike crystals of C60 with a diameter of submicrons (“C60 Nanowhiskers”) were found to be single crystalline and composed of thin slabswith a thickness of about 10 nm. The intermolecular distance of the C60 Nanowhiskerswas found to be shortened along the growth axis as compared with the pristine C60crystals, indicating a formation of strong bonding between C60 molecules. TheC60 Nanowhiskers are assumed to be polymerized via the “2 + 2” cycloaddition inthe close-packed [110]c direction.
Makoto Kuwabara - One of the best experts on this subject based on the ideXlab platform.
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c60 Nanowhiskers formed by the liquid liquid interfacial precipitation method
2002Co-Authors: Kunichi Miyazawa, Y Kuwasaki, A Obayashi, Makoto KuwabaraAbstract:Fine needlelike crystals of C60 have been formed by a liquid–liquid interfacial precipitation method which uses an interface of the concentrated toluene solution of C60/isopropyl alcohol. The needlelike crystals of C60 with a diameter of submicrons (“C60 Nanowhiskers”) were found to be single crystalline and composed of thin slabswith a thickness of about 10 nm. The intermolecular distance of the C60 Nanowhiskerswas found to be shortened along the growth axis as compared with the pristine C60crystals, indicating a formation of strong bonding between C60 molecules. TheC60 Nanowhiskers are assumed to be polymerized via the “2 + 2” cycloaddition inthe close-packed [110]c direction.
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c60 Nanowhiskers in a mixture of lead zirconate titanate sol c60 toluene solution
2001Co-Authors: Kunichi Miyazawa, Akio Obayashi, Makoto KuwabaraAbstract:Fine fibrous structures of C60 with a diameter on the order of nanometers were discovered in a lead zirconate titanate sol ultrasonically mixed with a toluene solution of C60. By transmission electron microscopy observations, they were identified as single-crystalline fibers of C60 with submicrometer diameters, i.e., Nanowhiskers of C60. The C60 Nanowhiskers showed thin slablike TEM images, and the growth axis of the Nanowhiskers was parallel to the 〈110〉 close-packed direction of a fcc crystal system of C60.
Philippe Tingaut - One of the best experts on this subject based on the ideXlab platform.
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Supramolecular structure characterization of cellulose II Nanowhiskers produced by acid hydrolysis of cellulose I substrates.
2012Co-Authors: Gilles Sèbe, Frédérique Ham-pichavant, Emmanuel Ibarboure, Akissi Lydie Chantal Koffi, Philippe TingautAbstract:Cellulose II Nanowhiskers (CNW-II) were produced by treatment of microcrystalline cellulose with sulfuric acid by both controlling the amount of H(2)SO(4) introduced and the time of addition during the hydrolysis process. The crystalline structure was confirmed by both XRD and (13)C CP-MAS NMR spectroscopy. When observed between crossed polarizers, the cellulose II suspension displayed flow birefringence and was stable for several months. The CNW-II Nanowhiskers were significantly smaller than the cellulose I Nanowhiskers (CNW-I) and had a rounded shape at the tip. The CNW-II average length and height were estimated by AFM to be 153 ± 66 and 4.2 ± 1.5 nm, respectively. An average width of 6.3 ± 1.7 nm was found by TEM, suggesting a ribbon-shape morphology for these whiskers. The average dimensions of the CNW-II elementary crystallites were estimated from the XRD data, using Scherrer's equation. A tentative cross-sectional geometry consistent with both XRD and NMR data was then proposed and compared with the geometry of the CNW-I Nanowhiskers.
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supramolecular structure characterization of cellulose ii Nanowhiskers produced by acid hydrolysis of cellulose i substrates
2012Co-Authors: Gilles Sèbe, Emmanuel Ibarboure, Akissi Lydie Chantal Koffi, Frederique Hampichavant, Philippe TingautAbstract:Cellulose II Nanowhiskers (CNW-II) were produced by treatment of microcrystalline cellulose with sulfuric acid by both controlling the amount of H2SO4 introduced and the time of addition during the hydrolysis process. The crystalline structure was confirmed by both XRD and 13C CP-MAS NMR spectroscopy. When observed between crossed polarizers, the cellulose II suspension displayed flow birefringence and was stable for several months. The CNW-II Nanowhiskers were significantly smaller than the cellulose I Nanowhiskers (CNW-I) and had a rounded shape at the tip. The CNW-II average length and height were estimated by AFM to be 153 ± 66 and 4.2 ± 1.5 nm, respectively. An average width of 6.3 ± 1.7 nm was found by TEM, suggesting a ribbon-shape morphology for these whiskers. The average dimensions of the CNW-II elementary crystallites were estimated from the XRD data, using Scherrer’s equation. A tentative cross-sectional geometry consistent with both XRD and NMR data was then proposed and compared with the geo...
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acetylation of cellulose Nanowhiskers with vinyl acetate under moderate conditions
2009Co-Authors: Nihat Sami Cetin, Philippe Tingaut, Nilguel Ozmen, Nathan Henry, David P Harper, Mark Dadmun, Gilles SèbeAbstract:A novel and straightforward method for the surface acetylation of cellulose Nanowhiskers by transesterification of vinyl acetate is proposed. The reaction of vinyl acetate with the hydroxyl groups of cellulose Nanowhiskers obtained from cotton linters was examined with potassium carbonate as catalyst. Results indicate that during the first stage of the reaction, only the surface of the Nanowhiskers was modified, while their dimensions and crystallinity remained unchanged. With increasing reaction time, diffusion mechanisms controlled the rate, leading to Nanowhiskers with higher levels of acetylation, smaller dimensions, and lower crystallinity. In THF, a solvent of low polarity, the suspensions from modified Nanowhiskers showed improved stability with increased acetylation.
V M Ustinov - One of the best experts on this subject based on the ideXlab platform.
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diffusion induced growth of gaas Nanowhiskers during molecular beam epitaxy theory and experiment
2005Co-Authors: V G Dubrovskii, G E Cirlin, I P Soshnikov, A A Tonkikh, N V Sibirev, Yu B Samsonenko, V M UstinovAbstract:Mechanisms of nanowhisker formation during molecular beam epitaxy (MBE) are studied theoretically within the frame of a kinetic model that accounts for the adatom diffusion from the surface to the top of Nanowhiskers. It is shown that the adatom diffusion flux may considerably increase the vertical growth rate of Nanowhiskers. The decreasing length/diameter dependence of the MBE grown Nanowhiskers is obtained that explains a number of experimentally observed facts. The results of experimental investigations of GaAs Nanowhiskers grown by MBE on the GaAs(111)B surface activated by Au at different conditions are presented and analyzed. It is shown that the length of thin GaAs Nanowhiskers is several times larger than the effective thickness of deposited GaAs. Theoretical and experimental length/diameter curves are compared to each other and a good correlation between them is demonstrated.
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diffusion induced growth of gaas Nanowhiskers during molecular beam epitaxy theory and experiment
2005Co-Authors: V G Dubrovskii, G E Cirlin, I P Soshnikov, A A Tonkikh, N V Sibirev, Yu B Samsonenko, V M UstinovAbstract:Mechanisms of nanowhisker formation during molecular beam epitaxy sMBEd are studied theoreticallywithin the frame of a kinetic model that accounts for the adatom diffusion from the surface to the top ofNanowhiskers. It is shown that the adatom diffusion flux may considerably increase the vertical growth rate ofNanowhiskers. The decreasing length/diameter dependence of the MBE grown Nanowhiskers is obtained thatexplains a number of experimentally observed facts. The results of experimental investigations of GaAsNanowhiskers grown by MBE on the GaAss111dB surface activated by Au at different conditions are presentedand analyzed. It is shown that the length of thin GaAs Nanowhiskers is several times larger than the effectivethickness of deposited GaAs. Theoretical and experimental length/diameter curves are compared to each otherand a good correlation between them is demonstrated.DOI: 10.1103/PhysRevB.71.205325 PACS numberssd: 68.65.2k, 68.47.Fg, 68.70.1w, 81.10.AjI. INTRODUCTION
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on the non monotonic lateral size dependence of the height of gaas Nanowhiskers grown by molecular beam epitaxy at high temperature
2004Co-Authors: V G Dubrovskii, G E Cirlin, I P Soshnikov, A A Tonkikh, N V Sibirev, Yu B Samsonenko, V M UstinovAbstract:GaAs Nanowhiskers were grown by molecular beam epitaxy on the GaAs(111)B surface activated by Au at the surface temperature of 585 °C. The dependence of nanowhisker height on the size of Au–GaAs alloy drops was investigated. It has been found that the height of GaAs Nanowhiskers is zero at a certain minimum diameter of drop, then increases with size, has a pronounced maximum at a certain size, decreases for thicker whiskers and finally goes to a certain asymptotic value. The theoretical model for the growth kinetics of Nanowhiskers was developed in order to explain the observed size dependence. The results of comparison of theoretical and experimental data for the height of GaAs Nanowhiskers are presented and analyzed. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Gilles Sèbe - One of the best experts on this subject based on the ideXlab platform.
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Supramolecular structure characterization of cellulose II Nanowhiskers produced by acid hydrolysis of cellulose I substrates.
2012Co-Authors: Gilles Sèbe, Frédérique Ham-pichavant, Emmanuel Ibarboure, Akissi Lydie Chantal Koffi, Philippe TingautAbstract:Cellulose II Nanowhiskers (CNW-II) were produced by treatment of microcrystalline cellulose with sulfuric acid by both controlling the amount of H(2)SO(4) introduced and the time of addition during the hydrolysis process. The crystalline structure was confirmed by both XRD and (13)C CP-MAS NMR spectroscopy. When observed between crossed polarizers, the cellulose II suspension displayed flow birefringence and was stable for several months. The CNW-II Nanowhiskers were significantly smaller than the cellulose I Nanowhiskers (CNW-I) and had a rounded shape at the tip. The CNW-II average length and height were estimated by AFM to be 153 ± 66 and 4.2 ± 1.5 nm, respectively. An average width of 6.3 ± 1.7 nm was found by TEM, suggesting a ribbon-shape morphology for these whiskers. The average dimensions of the CNW-II elementary crystallites were estimated from the XRD data, using Scherrer's equation. A tentative cross-sectional geometry consistent with both XRD and NMR data was then proposed and compared with the geometry of the CNW-I Nanowhiskers.
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supramolecular structure characterization of cellulose ii Nanowhiskers produced by acid hydrolysis of cellulose i substrates
2012Co-Authors: Gilles Sèbe, Emmanuel Ibarboure, Akissi Lydie Chantal Koffi, Frederique Hampichavant, Philippe TingautAbstract:Cellulose II Nanowhiskers (CNW-II) were produced by treatment of microcrystalline cellulose with sulfuric acid by both controlling the amount of H2SO4 introduced and the time of addition during the hydrolysis process. The crystalline structure was confirmed by both XRD and 13C CP-MAS NMR spectroscopy. When observed between crossed polarizers, the cellulose II suspension displayed flow birefringence and was stable for several months. The CNW-II Nanowhiskers were significantly smaller than the cellulose I Nanowhiskers (CNW-I) and had a rounded shape at the tip. The CNW-II average length and height were estimated by AFM to be 153 ± 66 and 4.2 ± 1.5 nm, respectively. An average width of 6.3 ± 1.7 nm was found by TEM, suggesting a ribbon-shape morphology for these whiskers. The average dimensions of the CNW-II elementary crystallites were estimated from the XRD data, using Scherrer’s equation. A tentative cross-sectional geometry consistent with both XRD and NMR data was then proposed and compared with the geo...
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acetylation of cellulose Nanowhiskers with vinyl acetate under moderate conditions
2009Co-Authors: Nihat Sami Cetin, Philippe Tingaut, Nilguel Ozmen, Nathan Henry, David P Harper, Mark Dadmun, Gilles SèbeAbstract:A novel and straightforward method for the surface acetylation of cellulose Nanowhiskers by transesterification of vinyl acetate is proposed. The reaction of vinyl acetate with the hydroxyl groups of cellulose Nanowhiskers obtained from cotton linters was examined with potassium carbonate as catalyst. Results indicate that during the first stage of the reaction, only the surface of the Nanowhiskers was modified, while their dimensions and crystallinity remained unchanged. With increasing reaction time, diffusion mechanisms controlled the rate, leading to Nanowhiskers with higher levels of acetylation, smaller dimensions, and lower crystallinity. In THF, a solvent of low polarity, the suspensions from modified Nanowhiskers showed improved stability with increased acetylation.
