ABSTRACT Coalescing carbon nanotubes is a major challenge for designing structures with novel phy... more ABSTRACT Coalescing carbon nanotubes is a major challenge for designing structures with novel physical and chemical properties and for creating three-dimensional carbon networks with improved mechanical and transport properties. We have coalesced adjacent triple walled carbon nanotubes (TWNTs) covalently, using catalytic boron atoms at high temperatures. The two outermost and then the two inner nanotubes of adjacent TWNTs merged in order to create an enlarged flattened double-walled carbon nanotube which encapsulated the two innermost single-walled carbon nanotubes.
We report a novel physicochemical route to produce highly crystalline nitrogen-doped graphene nan... more We report a novel physicochemical route to produce highly crystalline nitrogen-doped graphene nanoribbons. The technique consists of an abrupt N(2) gas expansion within the hollow core of nitrogen-doped multiwalled carbon nanotubes (CN(x)-MWNTs) when exposed to a fast thermal shock. The multiwalled nanotube unzipping mechanism is rationalized using molecular dynamics and density functional theory simulations, which highlight the importance of open-ended nanotubes in promoting the efficient introduction of N(2) molecules by capillary action within tubes and surface defects, thus triggering an efficient and atomically smooth unzipping. The so-produced nanoribbons could be few-layered (from graphene bilayer onward) and could exhibit both crystalline zigzag and armchair edges. In contrast to methods developed previously, our technique presents various advantages: (1) the tubes are not heavily oxidized; (2) the method yields sharp atomic edges within the resulting nanoribbons; (3) the technique could be scaled up for the bulk production of crystalline nanoribbons from available MWNT sources; and (4) this route could eventually be used to unzip other types of carbon nanotubes or intercalated layered materials such as BN, MoS(2), WS(2), etc.
... After sonication the resulting solution was filtered and washed with deionized water and drie... more ... After sonication the resulting solution was filtered and washed with deionized water and dried. ... After the acid treatment (COx-A) this peak splits in two: one located at 445 oC and the other at 595 oC, this clearly ... “Conductance anisotropy in epitaxial graphene sheets generated by ...
ABSTRACT Silicon carbide (SiC) cellular ceramic skeletons based on ceramic pillars of ∼250 μm in ... more ABSTRACT Silicon carbide (SiC) cellular ceramic skeletons based on ceramic pillars of ∼250 μm in diameter and porous micro-channels of ∼700 μm were used as support to grow long and aligned crystalline carboxyl functionalized carbon nanotubes (COx) by floating catalyst chemical vapor deposition. The resulting hybrid COx/SiC material retained water and allowed the flow of oils and gasoline through the specimen, showing, thus, superhydrophobic and superoleophilic properties. In addition, the developed hybrid material exhibited high electrical conductivity with a good ohmic contact at the COx–SiC interface.
Four novel Co(I)-Co(I) binuclear complexes have been synthesized, namely [Co2(IPHTA)(L)4](CIO4)2 ... more Four novel Co(I)-Co(I) binuclear complexes have been synthesized, namely [Co2(IPHTA)(L)4](CIO4)2 (L denotes 2,2′-bipyridine (bpy); 1,10-phenanthroline (phen); 4,4′-dimethyl-2,2′-bipyridine (Me2bpy) and 5-nitro-1,10-phenanthroline (NO2-phen)), where IPHTA is the isophthalate dianion. Based on IR, elemental analyses, conductivity measurements and electronic spectra, it is proposed that these complexes have IPHTA-bridged structures and consist of two cobalt(I) ions in a distorted octahedral environment. The complexes [Co2(IPHTA)(Me2bpy)4](CIO4)2 (1) and [Co2(IPHTA)(phen)4](CIO4)2 (2) were characterized by variable temperature magnetic susceptibility (4∼300 K) and the data could be well fitted by the least-squares method to a susceptibility equation derived from the spin Hamiltonian operator, ˇ= - 2J Š1 · Š2. The exchange integral, J, was found to be - 1. 28 cm for (1) and - 1.46 cm for (2), indicating that weak antiferromagnetic exchange is present in the binuclear Co(¶) complexes.
Naphthalene (N) or naphthalene-derivative (ND) adsorption-treatment evidently varies the electric... more Naphthalene (N) or naphthalene-derivative (ND) adsorption-treatment evidently varies the electrical conductivity of single wall carbon nanotube (SWCNT) bundles over a wide temperature range due to a charge-transfer interaction. The adsorption treatment of SWCNTs with dinitronaphthalene molecules enhances the electrical conductivity of the SWCNT bundles by 50 times. The temperature dependence of the electrical conductivity of N- or ND-adsorbed SWCNT bundles having a superlattice structure suggests metal-semiconductor transition like behavior near 260 K. The ND-adsorbed SWCNT gives a maximum in the logarithm of electrical conductivity vs. T(-1) plot, which may occur after the change to a metallic state and be associated with a partial unravelling of the SWCNT bundle due to an evoked librational motion of the moieties of ND with elevation of the temperature.
Graphene oxide (GO) has recently become an attractive building block for fabricating graphene-bas... more Graphene oxide (GO) has recently become an attractive building block for fabricating graphene-based functional materials. GO films and fibers have been prepared mainly by vacuum filtration and wet spinning. These materials exhibit relatively high Young's moduli but low toughness and a high tendency to tear or break. Here, we report an alternative method, using bar coating and drying of water/GO dispersions, for preparing large-area GO thin films (e.g., 800-1200 cm(2) or larger) with an outstanding mechanical behavior and excellent tear resistance. These dried films were subsequently scrolled to prepare GO fibers with extremely large elongation to fracture (up to 76%), high toughness (up to 17 J/m(3)), and attractive macroscopic properties, such as uniform circular cross section, smooth surface, and great knotability. This method is simple, and after thermal reduction of the GO material, it can render highly electrically conducting graphene-based fibers with values up to 416 S/cm...
ABSTRACT Coalescing carbon nanotubes is a major challenge for designing structures with novel phy... more ABSTRACT Coalescing carbon nanotubes is a major challenge for designing structures with novel physical and chemical properties and for creating three-dimensional carbon networks with improved mechanical and transport properties. We have coalesced adjacent triple walled carbon nanotubes (TWNTs) covalently, using catalytic boron atoms at high temperatures. The two outermost and then the two inner nanotubes of adjacent TWNTs merged in order to create an enlarged flattened double-walled carbon nanotube which encapsulated the two innermost single-walled carbon nanotubes.
We report a novel physicochemical route to produce highly crystalline nitrogen-doped graphene nan... more We report a novel physicochemical route to produce highly crystalline nitrogen-doped graphene nanoribbons. The technique consists of an abrupt N(2) gas expansion within the hollow core of nitrogen-doped multiwalled carbon nanotubes (CN(x)-MWNTs) when exposed to a fast thermal shock. The multiwalled nanotube unzipping mechanism is rationalized using molecular dynamics and density functional theory simulations, which highlight the importance of open-ended nanotubes in promoting the efficient introduction of N(2) molecules by capillary action within tubes and surface defects, thus triggering an efficient and atomically smooth unzipping. The so-produced nanoribbons could be few-layered (from graphene bilayer onward) and could exhibit both crystalline zigzag and armchair edges. In contrast to methods developed previously, our technique presents various advantages: (1) the tubes are not heavily oxidized; (2) the method yields sharp atomic edges within the resulting nanoribbons; (3) the technique could be scaled up for the bulk production of crystalline nanoribbons from available MWNT sources; and (4) this route could eventually be used to unzip other types of carbon nanotubes or intercalated layered materials such as BN, MoS(2), WS(2), etc.
... After sonication the resulting solution was filtered and washed with deionized water and drie... more ... After sonication the resulting solution was filtered and washed with deionized water and dried. ... After the acid treatment (COx-A) this peak splits in two: one located at 445 oC and the other at 595 oC, this clearly ... “Conductance anisotropy in epitaxial graphene sheets generated by ...
ABSTRACT Silicon carbide (SiC) cellular ceramic skeletons based on ceramic pillars of ∼250 μm in ... more ABSTRACT Silicon carbide (SiC) cellular ceramic skeletons based on ceramic pillars of ∼250 μm in diameter and porous micro-channels of ∼700 μm were used as support to grow long and aligned crystalline carboxyl functionalized carbon nanotubes (COx) by floating catalyst chemical vapor deposition. The resulting hybrid COx/SiC material retained water and allowed the flow of oils and gasoline through the specimen, showing, thus, superhydrophobic and superoleophilic properties. In addition, the developed hybrid material exhibited high electrical conductivity with a good ohmic contact at the COx–SiC interface.
Four novel Co(I)-Co(I) binuclear complexes have been synthesized, namely [Co2(IPHTA)(L)4](CIO4)2 ... more Four novel Co(I)-Co(I) binuclear complexes have been synthesized, namely [Co2(IPHTA)(L)4](CIO4)2 (L denotes 2,2′-bipyridine (bpy); 1,10-phenanthroline (phen); 4,4′-dimethyl-2,2′-bipyridine (Me2bpy) and 5-nitro-1,10-phenanthroline (NO2-phen)), where IPHTA is the isophthalate dianion. Based on IR, elemental analyses, conductivity measurements and electronic spectra, it is proposed that these complexes have IPHTA-bridged structures and consist of two cobalt(I) ions in a distorted octahedral environment. The complexes [Co2(IPHTA)(Me2bpy)4](CIO4)2 (1) and [Co2(IPHTA)(phen)4](CIO4)2 (2) were characterized by variable temperature magnetic susceptibility (4∼300 K) and the data could be well fitted by the least-squares method to a susceptibility equation derived from the spin Hamiltonian operator, ˇ= - 2J Š1 · Š2. The exchange integral, J, was found to be - 1. 28 cm for (1) and - 1.46 cm for (2), indicating that weak antiferromagnetic exchange is present in the binuclear Co(¶) complexes.
Naphthalene (N) or naphthalene-derivative (ND) adsorption-treatment evidently varies the electric... more Naphthalene (N) or naphthalene-derivative (ND) adsorption-treatment evidently varies the electrical conductivity of single wall carbon nanotube (SWCNT) bundles over a wide temperature range due to a charge-transfer interaction. The adsorption treatment of SWCNTs with dinitronaphthalene molecules enhances the electrical conductivity of the SWCNT bundles by 50 times. The temperature dependence of the electrical conductivity of N- or ND-adsorbed SWCNT bundles having a superlattice structure suggests metal-semiconductor transition like behavior near 260 K. The ND-adsorbed SWCNT gives a maximum in the logarithm of electrical conductivity vs. T(-1) plot, which may occur after the change to a metallic state and be associated with a partial unravelling of the SWCNT bundle due to an evoked librational motion of the moieties of ND with elevation of the temperature.
Graphene oxide (GO) has recently become an attractive building block for fabricating graphene-bas... more Graphene oxide (GO) has recently become an attractive building block for fabricating graphene-based functional materials. GO films and fibers have been prepared mainly by vacuum filtration and wet spinning. These materials exhibit relatively high Young's moduli but low toughness and a high tendency to tear or break. Here, we report an alternative method, using bar coating and drying of water/GO dispersions, for preparing large-area GO thin films (e.g., 800-1200 cm(2) or larger) with an outstanding mechanical behavior and excellent tear resistance. These dried films were subsequently scrolled to prepare GO fibers with extremely large elongation to fracture (up to 76%), high toughness (up to 17 J/m(3)), and attractive macroscopic properties, such as uniform circular cross section, smooth surface, and great knotability. This method is simple, and after thermal reduction of the GO material, it can render highly electrically conducting graphene-based fibers with values up to 416 S/cm...
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