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Sumio Iijima - One of the best experts on this subject based on the ideXlab platform.
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selective diameter control of single walled carbon nanotubes in the Gas Phase Synthesis
Journal of Nanoscience and Nanotechnology, 2008Co-Authors: Takeshi Saito, Satoshi Ohshima, Motoo Yumura, Toshiya Okazaki, Shigekazu Ohmori, Sumio IijimaAbstract:A novel approach for selective diameter control of single-walled carbon nanotubes (SWNTs) is performed in the Gas-Phase growth using two kinds of carbon sources with different decomposition properties; the one carbon source (1st carbon source) is the organic solvent which is difficult to decompose in the reactor and the another carbon source (2nd carbon source) is facile to decompose. The diameter distributions of SWNTs synthesized with various conditions of the flow rate of the 2nd carbon source were investigated by resonant Raman scattering, optical absorption, and photoluminescence (PL) mapping measurements. It was found that increasing the flow rate of the ethylene tends to decrease the diameter of synthesized SWNTs, probably due to the earlier nucleation of SWNTs induced by the ethylene addition. The controlling the flow rate of the ethylene used as a 2nd carbon source can selectively tune the diameter distribution of SWNTs in our growth system.
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supramolecular catalysts for the Gas Phase Synthesis of single walled carbon nanotubes
Journal of Physical Chemistry B, 2006Co-Authors: Takeshi Saito, Satoshi Ohshima, Hiroki Ago, Motoo Yumura, Sumio IijimaAbstract:Reversed micelles containing metallic ions have been used as precursors of novel catalysts for the Gas-Phase Synthesis of single-walled carbon nanotubes (SWNTs). This technique possesses the following advantages: (i) excellent solubility in organic solvents, which are used as reactants and (ii) facile preparation of multicomponent catalysts enabling systematic screening of catalyst compositions for the Synthesis of SWNTs. In this study, we report the results of the screening study on the catalytic behavior of Fe-Mo binary catalysts during the Synthesis of SWNTs. The results suggested that the catalytic ability was closely related to the strain of the crystal structure of Fe-Mo catalysts formed in the reaction and/or the Phase transition caused by dissolution of the Mo atoms. The addition of lithium to the Fe-Mo binary catalysts has revealed an increase in the yield of SWNTs.
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size control of metal nanoparticle catalysts for the Gas Phase Synthesis of single walled carbon nanotubes
Journal of Physical Chemistry B, 2005Co-Authors: Takeshi Saito, Satoshi Ohshima, Hiroki Ago, Motoo Yumura, Sumio IijimaAbstract:Nanoparticle catalysts are essential and indispensable for all syntheses of single-walled carbon nanotubes (SWCNTs). We have prepared size-controlled Co, Co-Mo, and Fe-Mo nanoparticles by the reversed micelle method as the catalysts for the Gas-Phase pyrolytic Synthesis of SWCNTs. From the investigation of the relation between the sizes of the nanoparticles and the alkyl-chain lengths of the cationic surfactants, dialkyldimethylammonium bromides, it has been found that the alkyl groups of the surfactants could play a role in controlling the sizes of the nanoparticles and that the alkyl chain of the surfactant should be preferably less than 10 carbon atoms at most to prepare smaller-size nanoparticles with a narrow size distribution. The reduction of the particle size increases the number of nanoparticles in the colloidal solution and leads to a higher yield of SWCNTs.
Motoo Yumura - One of the best experts on this subject based on the ideXlab platform.
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selective diameter control of single walled carbon nanotubes in the Gas Phase Synthesis
Journal of Nanoscience and Nanotechnology, 2008Co-Authors: Takeshi Saito, Satoshi Ohshima, Motoo Yumura, Toshiya Okazaki, Shigekazu Ohmori, Sumio IijimaAbstract:A novel approach for selective diameter control of single-walled carbon nanotubes (SWNTs) is performed in the Gas-Phase growth using two kinds of carbon sources with different decomposition properties; the one carbon source (1st carbon source) is the organic solvent which is difficult to decompose in the reactor and the another carbon source (2nd carbon source) is facile to decompose. The diameter distributions of SWNTs synthesized with various conditions of the flow rate of the 2nd carbon source were investigated by resonant Raman scattering, optical absorption, and photoluminescence (PL) mapping measurements. It was found that increasing the flow rate of the ethylene tends to decrease the diameter of synthesized SWNTs, probably due to the earlier nucleation of SWNTs induced by the ethylene addition. The controlling the flow rate of the ethylene used as a 2nd carbon source can selectively tune the diameter distribution of SWNTs in our growth system.
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supramolecular catalysts for the Gas Phase Synthesis of single walled carbon nanotubes
Journal of Physical Chemistry B, 2006Co-Authors: Takeshi Saito, Satoshi Ohshima, Hiroki Ago, Motoo Yumura, Sumio IijimaAbstract:Reversed micelles containing metallic ions have been used as precursors of novel catalysts for the Gas-Phase Synthesis of single-walled carbon nanotubes (SWNTs). This technique possesses the following advantages: (i) excellent solubility in organic solvents, which are used as reactants and (ii) facile preparation of multicomponent catalysts enabling systematic screening of catalyst compositions for the Synthesis of SWNTs. In this study, we report the results of the screening study on the catalytic behavior of Fe-Mo binary catalysts during the Synthesis of SWNTs. The results suggested that the catalytic ability was closely related to the strain of the crystal structure of Fe-Mo catalysts formed in the reaction and/or the Phase transition caused by dissolution of the Mo atoms. The addition of lithium to the Fe-Mo binary catalysts has revealed an increase in the yield of SWNTs.
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size control of metal nanoparticle catalysts for the Gas Phase Synthesis of single walled carbon nanotubes
Journal of Physical Chemistry B, 2005Co-Authors: Takeshi Saito, Satoshi Ohshima, Hiroki Ago, Motoo Yumura, Sumio IijimaAbstract:Nanoparticle catalysts are essential and indispensable for all syntheses of single-walled carbon nanotubes (SWCNTs). We have prepared size-controlled Co, Co-Mo, and Fe-Mo nanoparticles by the reversed micelle method as the catalysts for the Gas-Phase pyrolytic Synthesis of SWCNTs. From the investigation of the relation between the sizes of the nanoparticles and the alkyl-chain lengths of the cationic surfactants, dialkyldimethylammonium bromides, it has been found that the alkyl groups of the surfactants could play a role in controlling the sizes of the nanoparticles and that the alkyl chain of the surfactant should be preferably less than 10 carbon atoms at most to prepare smaller-size nanoparticles with a narrow size distribution. The reduction of the particle size increases the number of nanoparticles in the colloidal solution and leads to a higher yield of SWCNTs.
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Gas Phase Synthesis of single wall carbon nanotubes from colloidal solution of metal nanoparticles
Journal of Physical Chemistry B, 2001Co-Authors: Hiroki Ago, Satoshi Ohshima, And Kunio Uchida, Motoo YumuraAbstract:Metal nanoparticles play an important role in chemical vapor deposition (CVD) Synthesis of carbon nanotubes because nanoparticles not only catalyze the nanotube growth but also determine the structural characteristics of the nanotubes. We report on the Synthesis of single-wall carbon nanotubes (SWNTs) on the basis of the Gas-Phase reaction of colloidal solutions of metal nanoparticles containing Co and Mo. The colloidal solution of the nanoparticles is prepared by a reverse micelle method and injected into a furnace, where the solvent serves as the carbon source while the nanoparticles act as the catalyst. We have found that addition of a small amount of thiophene leads to formation of the SWNTs. The formation mechanism of the SWNTs is discussed by comparing the present CVD and laser-ablation methods.
Mukhles Sowwan - One of the best experts on this subject based on the ideXlab platform.
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Site‐Specific Wetting of Iron Nanocubes by Gold Atoms in Gas‐Phase Synthesis
'Wiley', 2019Co-Authors: Jerome Vernieres, Panagiotis Grammatikopoulos, Stephan Steinhauer, Junlei Zhao, Flyura Djurabekova, Kai Nordlund, Riccardo Ferrando, Mukhles SowwanAbstract:A key challenge in nanotechnology is the rational design of multicomponent materials that beat the properties of their elemental counterparts. At the same time, when considering the material composition of such hybrid nanostructures and the fabrication process to obtain them, one should favor the use of nontoxic, abundant elements in view of the limited availability of critical metals and sustainability. Cluster beam deposition offers a solvent‐ and, therefore, effluent‐free physical Synthesis method to achieve nanomaterials with tailored characteristics. However, the simultaneous control of size, shape, and elemental distribution within a single nanoparticle in a small‐size regime (sub‐10 nm) is still a major challenge, equally limiting physical and chemical approaches. Here, a single‐step nanoparticle fabrication method based on magnetron‐sputtering inert‐Gas condensation is reported, which relies on selective wetting of specific surface sites on precondensed iron nanocubes by gold atoms. Using a newly developed Fe–Au interatomic potential, the growth mechanism is decomposed into a multistage model implemented in a molecular dynamics simulation framework. The importance of growth kinetics is emphasized through differences between structures obtained either experimentally or computationally, and thermodynamically favorable configurations determined via global optimization techniques. These results provide a roadmap for engineering complex nanoalloys toward targeted applications
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nanoparticle design by Gas Phase Synthesis
Advances in Physics: X, 2016Co-Authors: Panagiotis Grammatikopoulos, Stephan Steinhauer, Jerome Vernieres, Vidyadhar Singh, Mukhles SowwanAbstract:AbstractGas-Phase Synthesis characterizes a class of bottom-up methods for producing multifunctional nanoparticles (NPs) from individual atoms or molecules. This review aims to summarize recent achievements using this approach, and compare its potential to other physical or chemical NP fabrication techniques. More specifically, emphasis is given to magnetron-sputter Gas-Phase condensation, since it allows for flexible growth of complex, sophisticated NPs, owing to the fast kinetics and non-equilibrium processes it entails. Nanoparticle Synthesis is decomposed into four stages, i.e. aggregation, shell-coating, mass-filtration, and deposition. We present the formation of NPs of various functionalities for different applications, such as magnetic, plasmonic, catalytic and, Gas-sensing, emphasizing on the primary dependence of each type on a different stage of the fabrication process, and their resultant physical and chemical properties.
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engineering high performance pd core mgo porous shell nanocatalysts via heterogeneous Gas Phase Synthesis
Nanoscale, 2015Co-Authors: Vidyadhar Singh, Cathal Cassidy, Frank Abildpedersen, Kengo Aranishi, Sushant Kumar, Christian Gspan, Werner Grogger, Mukhles SowwanAbstract:We report on the design and Synthesis of high performance catalytic nanoparticles with a robust geometry via magnetron-sputter inert-Gas condensation. Sputtering of Pd and Mg from two independent neighbouring targets enabled heterogeneous condensation and growth of nanoparticles with controlled Pd core–MgO porous shell structure. The thickness of the shell and the number of cores within each nanoparticle could be tailored by adjusting the respective sputtering powers. The nanoparticles were directly deposited on glassy carbon electrodes, and their catalytic activity towards methanol oxidation was examined by cyclic voltammetry. The measurements indicated that the catalytic activity was superior to conventional bare Pd nanoparticles. As confirmed by electron microscopy imaging and supported by density-functional theory (DFT) calculations, we attribute the improved catalytic performance primarily to inhibition of Pd core sintering during the catalytic process by the metal-oxide shell.
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heterogeneous Gas Phase Synthesis and molecular dynamics modeling of janus and core satellite si ag nanoparticles
Journal of Physical Chemistry C, 2014Co-Authors: Vidyadhar Singh, Panagiotis Grammatikopoulos, Mukhles Sowwan, K Nordlund, Flyura Djurabekova, Cathal CassidyAbstract:Heterogeneous Gas-Phase condensation is a promising method of producing hybrid multifunctional nanoparticles with tailored composition and microstructure but also intrinsically introduces greater complexity to the nucleation process and growth kinetics. Herein, we report on the Synthesis and growth modeling of silicon–silver (Si–Ag) hybrid nanoparticles using Gas-aggregated cosputtering from elemental Si and Ag source targets. The final Si–Ag ensemble size was manipulated in the range 5–15 nm by appropriate tuning of the deposition parameters, while variations in the Si–Ag sputtering power ratio, from 1.8 to 2.25, allowed distinctive Janus and core–satellite structures, respectively, to be produced. Molecular dynamics simulations indicate that the individual species first form independent clusters of Si and Ag without significant intermixing. Collisions between unlike species are unstable in the early stages of growth (<100 ns), with large temperature differences resulting in rapid energy exchange and sep...
Albert G. Nasibulin - One of the best experts on this subject based on the ideXlab platform.
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Gas-Phase Synthesis and Control of Structure and Thickness of Graphene Layers on Copper Substrates
Metal Science and Heat Treatment, 2016Co-Authors: A. I. Rudskoy, T. S. Kol’tsova, T. V. Larionova, E. S. Vasil’eva, A. N. Smirnov, Albert G. NasibulinAbstract:The process of formation of graphene layers on a copper substrate is studied as a function of the pressure in the growth chamber. It is shown that the graphene layers form by nucleation and growth of graphene nuclei that later combine into a continuous layer. Growth in the pressure is accompanied by thickening of the synthesized graphene, intensification of compressive stresses, and appearance of structure defects.
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Gas Phase Synthesis of non bundled small diameter single walled carbon nanotubes with near armchair chiralities
arXiv: Mesoscale and Nanoscale Physics, 2016Co-Authors: Kimmo Mustonen, Patrik Laiho, Hua Jiang, Antti Kaskela, Zhen Zhu, Olivier Reynaud, Nikolay Houbenov, Ying Tian, Toma Susi, Albert G. NasibulinAbstract:We present a novel floating catalyst Synthesis route for individual, i.e. non-bundled, small diameter single-walled carbon nanotubes (SWCNTs) with a narrow chiral angle distribution peaking at high chiralities near the armchair species. An ex situ spark discharge generator was used to form iron particles with geometric number mean diameters of 3-4 nm and fed into a laminar flow chemical vapour deposition reactor for the continuous Synthesis of long and high-quality SWCNTs from ambient pressure carbon monoxide. The intensity ratio of G/D peaks in Raman spectra up to 48 and mean tube lengths up to 4 microns were observed. The chiral distributions, as directly determined by electron diffraction in the transmission electron microscope, clustered around the (n,m) indices (7,6), (8,6), (8,7) and (9,6), with up to 70% of tubes having chiral angles over 20°. The mean diameter of SWCNTs was reduced from 1.10 to 1.04 nm by decreasing the growth temperature from 880 to 750 °C, which simultaneously increased the fraction of semiconducting tubes from 67 to 80%. Limiting the nanotube Gas Phase number concentration to approx. 100 000 per cubic centimetre successfully prevented nanotube bundle formation that is due to collisions induced by Brownian diffusion. Up to 80 % of 500 as-deposited tubes observed by atomic force and transmission electron microscopy were individual. Transparent conducting films deposited from these SWCNTs exhibited record low sheet resistances of 63 Ohms/sq. at 90 % transparency for 550 nm light.
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Gas Phase Synthesis of non bundled small diameter single walled carbon nanotubes with near armchair chiralities
Applied Physics Letters, 2015Co-Authors: Kimmo Mustonen, Patrik Laiho, Hua Jiang, Antti Kaskela, Zhen Zhu, Olivier Reynaud, Nikolay Houbenov, Ying Tian, Toma Susi, Albert G. NasibulinAbstract:We present a floating catalyst Synthesis route for individual, i.e., non-bundled, small diameter single-walled carbon nanotubes (SWCNTs) with a narrow chiral angle distribution peaking at high chiralities near the armchair species. An ex situ spark discharge generator was used to form iron particles with geometric number mean diameters of 3–4 nm and fed into a laminar flow chemical vapour deposition reactor for the continuous Synthesis of long and high-quality SWCNTs from ambient pressure carbon monoxide. The intensity ratio of G/D peaks in Raman spectra up to 48 and mean tube lengths up to 4 μm were observed. The chiral distributions, as directly determined by electron diffraction in the transmission electron microscope, clustered around the (n,m) indices (7,6), (8,6), (8,7), and (9,6), with up to 70% of tubes having chiral angles over 20°. The mean diameter of SWCNTs was reduced from 1.10 to 1.04 nm by decreasing the growth temperature from 880 to 750 °C, which simultaneously increased the fraction of s...
Hiroki Ago - One of the best experts on this subject based on the ideXlab platform.
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supramolecular catalysts for the Gas Phase Synthesis of single walled carbon nanotubes
Journal of Physical Chemistry B, 2006Co-Authors: Takeshi Saito, Satoshi Ohshima, Hiroki Ago, Motoo Yumura, Sumio IijimaAbstract:Reversed micelles containing metallic ions have been used as precursors of novel catalysts for the Gas-Phase Synthesis of single-walled carbon nanotubes (SWNTs). This technique possesses the following advantages: (i) excellent solubility in organic solvents, which are used as reactants and (ii) facile preparation of multicomponent catalysts enabling systematic screening of catalyst compositions for the Synthesis of SWNTs. In this study, we report the results of the screening study on the catalytic behavior of Fe-Mo binary catalysts during the Synthesis of SWNTs. The results suggested that the catalytic ability was closely related to the strain of the crystal structure of Fe-Mo catalysts formed in the reaction and/or the Phase transition caused by dissolution of the Mo atoms. The addition of lithium to the Fe-Mo binary catalysts has revealed an increase in the yield of SWNTs.
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size control of metal nanoparticle catalysts for the Gas Phase Synthesis of single walled carbon nanotubes
Journal of Physical Chemistry B, 2005Co-Authors: Takeshi Saito, Satoshi Ohshima, Hiroki Ago, Motoo Yumura, Sumio IijimaAbstract:Nanoparticle catalysts are essential and indispensable for all syntheses of single-walled carbon nanotubes (SWCNTs). We have prepared size-controlled Co, Co-Mo, and Fe-Mo nanoparticles by the reversed micelle method as the catalysts for the Gas-Phase pyrolytic Synthesis of SWCNTs. From the investigation of the relation between the sizes of the nanoparticles and the alkyl-chain lengths of the cationic surfactants, dialkyldimethylammonium bromides, it has been found that the alkyl groups of the surfactants could play a role in controlling the sizes of the nanoparticles and that the alkyl chain of the surfactant should be preferably less than 10 carbon atoms at most to prepare smaller-size nanoparticles with a narrow size distribution. The reduction of the particle size increases the number of nanoparticles in the colloidal solution and leads to a higher yield of SWCNTs.
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Gas Phase Synthesis of single wall carbon nanotubes from colloidal solution of metal nanoparticles
Journal of Physical Chemistry B, 2001Co-Authors: Hiroki Ago, Satoshi Ohshima, And Kunio Uchida, Motoo YumuraAbstract:Metal nanoparticles play an important role in chemical vapor deposition (CVD) Synthesis of carbon nanotubes because nanoparticles not only catalyze the nanotube growth but also determine the structural characteristics of the nanotubes. We report on the Synthesis of single-wall carbon nanotubes (SWNTs) on the basis of the Gas-Phase reaction of colloidal solutions of metal nanoparticles containing Co and Mo. The colloidal solution of the nanoparticles is prepared by a reverse micelle method and injected into a furnace, where the solvent serves as the carbon source while the nanoparticles act as the catalyst. We have found that addition of a small amount of thiophene leads to formation of the SWNTs. The formation mechanism of the SWNTs is discussed by comparing the present CVD and laser-ablation methods.
