The Experts below are selected from a list of 219 Experts worldwide ranked by ideXlab platform
Robert C Haddon - One of the best experts on this subject based on the ideXlab platform.
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Sidewall functionalization of single-walled carbon nanotubes by addition of Dichlorocarbene.
Journal of the American Chemical Society, 2003Co-Authors: Bin Zhao, Mark A Hamon, Katalin Kamaras, Mikhail E Itkis, Robert C HaddonAbstract:We report the sidewall functionalization of soluble HiPco single-walled carbon nanotubes (SWNTs) by addition of Dichlorocarbene. The Dichlorocarbene-functionalized SWNTs [(s-SWNT)CCl(2)] retain their solubility in organic solvents such as tetrahydrofuran and dichlorobenzene. The degree of Dichlorocarbene functionalization was varied between 12% and 23% by using different amounts of the Dichlorocarbene precursor. Because the addition of Dichlorocarbene saturates the carbon atoms on the sidewall of the SWNTs and effectively replaces the delocalized partial double bonds with a cyclopropane functionality, the optical spectra of the SWNTs change dramatically. We estimate that the saturation of 25% of the pi-network electronic structure of the SWNTs is sufficient to remove all vestiges of the interband transitions in the infrared spectrum. The transitions at the Fermi level in the metallic SWNTs that appear in the far-infrared (FIR) region of the spectrum show a dramatic decrease of intensity on Dichlorocarbene functionalization. The FIR region of the spectrum allows a clear differentiation between the covalent and the ionic chemistry of SWNTs. In contrast with covalent functionalization, we show that reaction of the SWNTs with bromine vapor leads to a strong increase in absorptions at the Fermi level that is observable in the FIR due to hole doping of the semiconducting SWNTs. Thermal treatment of the (s-SWNT)CCl(2) above 300 degrees C resulted in the breakage of C-Cl bonds, but did not restore the original electronic structure of the SWNTs.
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sidewall functionalization of single walled carbon nanotubes by addition of Dichlorocarbene
Journal of the American Chemical Society, 2003Co-Authors: Bin Zhao, Mark A Hamon, Katalin Kamaras, Mikhail E Itkis, Robert C HaddonAbstract:We report the sidewall functionalization of soluble HiPco single-walled carbon nanotubes (SWNTs) by addition of Dichlorocarbene. The Dichlorocarbene-functionalized SWNTs [(s-SWNT)CCl2] retain their solubility in organic solvents such as tetrahydrofuran and dichlorobenzene. The degree of Dichlorocarbene functionalization was varied between 12% and 23% by using different amounts of the Dichlorocarbene precursor. Because the addition of Dichlorocarbene saturates the carbon atoms on the sidewall of the SWNTs and effectively replaces the delocalized partial double bonds with a cyclopropane functionality, the optical spectra of the SWNTs change dramatically. We estimate that the saturation of 25% of the π-network electronic structure of the SWNTs is sufficient to remove all vestiges of the interband transitions in the infrared spectrum. The transitions at the Fermi level in the metallic SWNTs that appear in the far-infrared (FIR) region of the spectrum show a dramatic decrease of intensity on Dichlorocarbene fu...
Bin Zhao - One of the best experts on this subject based on the ideXlab platform.
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Sidewall functionalization of single-walled carbon nanotubes by addition of Dichlorocarbene.
Journal of the American Chemical Society, 2003Co-Authors: Bin Zhao, Mark A Hamon, Katalin Kamaras, Mikhail E Itkis, Robert C HaddonAbstract:We report the sidewall functionalization of soluble HiPco single-walled carbon nanotubes (SWNTs) by addition of Dichlorocarbene. The Dichlorocarbene-functionalized SWNTs [(s-SWNT)CCl(2)] retain their solubility in organic solvents such as tetrahydrofuran and dichlorobenzene. The degree of Dichlorocarbene functionalization was varied between 12% and 23% by using different amounts of the Dichlorocarbene precursor. Because the addition of Dichlorocarbene saturates the carbon atoms on the sidewall of the SWNTs and effectively replaces the delocalized partial double bonds with a cyclopropane functionality, the optical spectra of the SWNTs change dramatically. We estimate that the saturation of 25% of the pi-network electronic structure of the SWNTs is sufficient to remove all vestiges of the interband transitions in the infrared spectrum. The transitions at the Fermi level in the metallic SWNTs that appear in the far-infrared (FIR) region of the spectrum show a dramatic decrease of intensity on Dichlorocarbene functionalization. The FIR region of the spectrum allows a clear differentiation between the covalent and the ionic chemistry of SWNTs. In contrast with covalent functionalization, we show that reaction of the SWNTs with bromine vapor leads to a strong increase in absorptions at the Fermi level that is observable in the FIR due to hole doping of the semiconducting SWNTs. Thermal treatment of the (s-SWNT)CCl(2) above 300 degrees C resulted in the breakage of C-Cl bonds, but did not restore the original electronic structure of the SWNTs.
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sidewall functionalization of single walled carbon nanotubes by addition of Dichlorocarbene
Journal of the American Chemical Society, 2003Co-Authors: Bin Zhao, Mark A Hamon, Katalin Kamaras, Mikhail E Itkis, Robert C HaddonAbstract:We report the sidewall functionalization of soluble HiPco single-walled carbon nanotubes (SWNTs) by addition of Dichlorocarbene. The Dichlorocarbene-functionalized SWNTs [(s-SWNT)CCl2] retain their solubility in organic solvents such as tetrahydrofuran and dichlorobenzene. The degree of Dichlorocarbene functionalization was varied between 12% and 23% by using different amounts of the Dichlorocarbene precursor. Because the addition of Dichlorocarbene saturates the carbon atoms on the sidewall of the SWNTs and effectively replaces the delocalized partial double bonds with a cyclopropane functionality, the optical spectra of the SWNTs change dramatically. We estimate that the saturation of 25% of the π-network electronic structure of the SWNTs is sufficient to remove all vestiges of the interband transitions in the infrared spectrum. The transitions at the Fermi level in the metallic SWNTs that appear in the far-infrared (FIR) region of the spectrum show a dramatic decrease of intensity on Dichlorocarbene fu...
Eagambaram Murugan - One of the best experts on this subject based on the ideXlab platform.
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catalytic activity of novel soluble multi site phase transfer catalyst in Dichlorocarbene addition to α pinene
Journal of Molecular Catalysis A-chemical, 2008Co-Authors: Eagambaram Murugan, Prakash GopinathAbstract:Abstract A novel soluble multi-site phase transfer catalyst (MPTC), viz., 2,4,6-tris(triethylammoniummethylene chloride) mesitylene (TTEAMCM) containing three active sites was synthesized and characterized through FT-IR, 1H NMR, 13C NMR and [chloride ion] analyses. The spectral and [chloride ion] results strongly confirm the presence of three active sites in the catalyst. The catalytic efficacy of this new soluble MPTC was examined by determining the pseudo-first order rate constant for Dichlorocarbene addition to α-pinene reaction using low concentration of NaOH (20%) at 40 °C and comparing the observed rate constant with the rate constant of the same reaction catalyzed by commercially available single-site PTCs under identical reaction conditions. The observed result shows that TTEAMCM has a higher reactivity (≈threefold) than the single-site PTCs in terms of rate constant. Further, a thorough kinetic study was conducted for Dichlorocarbene addition to α-pinene using TTEAMCM by varying the experimental parameters such as stirring speed, [substrate], [NaOH], [catalyst] and temperature and it was found that the rate constants show dependence on all the experimental parameters. The activation energy and thermodynamic parameters viz., enthalpy, entropy and free energy change were also calculated. Based on the observed kinetic and thermodynamic parameters, an interfacial mechanism was proposed for Dichlorocarbene addition to α-pinene.
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synthesis and characterization of novel multi site phase transfer catalyst and its catalytic efficiency for Dichlorocarbene addition to citral
Journal of Molecular Catalysis A-chemical, 2005Co-Authors: Ayyanar Siva, Eagambaram MuruganAbstract:Abstract Novel soluble multi-site phase transfer catalyst was synthesized from low cost starting materials and its catalytic efficiency is assessed by observing the kinetics of Dichlorocarbene addition to citral in the absence of solvents. This new synthesized phase transfer catalyst viz., 1,3,5-tris[4-{2,3-bis(triethylammoniummethylene chloride)}-phenoxymethyl]benzene possesses six active centers. This novel catalyst has higher activity than the commercially available single-site phase transfer catalysts. The Dichlorocarbene addition to citral reaction was carried out at low temperature (40 °C) under pseudo-first order conditions by keeping low concentration of aqueous sodium hydroxide and excess of chloroform and the disappearance of citral were monitored by gas chromatography. The effect of various experimental parameters such as [substrate], [catalyst], [aqueous NaOH], stirring speed and temperature on the rate of the reaction has been studied, and based on the kinetic results obtained, a plausible mechanism is proposed.
Qianer Zhang - One of the best experts on this subject based on the ideXlab platform.
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The 2+1 cycloadditions of Dichlorocarbene, silylene, germylene, and oxycarbonylnitrene onto the sidewall of armchair (5,5) single-wall carbon nanotube
The Journal of Physical Chemistry B, 2003Co-Authors: Feng Tian, Qianer ZhangAbstract:The [2+1] cycloadditions of Dichlorocarbene, silylene, germylene, and oxycarbonylnitrene onto the sidewall of an armchair (5,5) single-wall carbon nanotube (SWNT) have been investigated by means of a two-layered ONIOM (MO:MO) approach. It is shown that (i) the [2+1] cycloaddition on the nanotube sidewall is site-selective, the 1,2-pair site being favored, giving rise to the formation of three-membered ring species, (ii) the additions of Dichlorocarbene and oxycarbonylnitrenes require small activation energies, whereas the additions of silylene and germylene are barrierless, (iii) thermal stability of the as-formed SWNT derivatives follows the order oxycarbonylnitrene ≫ Dichlorocarbene > silylene > germylene, and (iv) among the four reagents concerned, silylene is the best to be used for the functionalization and purification of SWNTs. Finally, we propose that the [2+1] cycloaddition products of SWNTs can be good starting points for further functionalization of SWNTs because the three-membered rings in the...
Mikhail E Itkis - One of the best experts on this subject based on the ideXlab platform.
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Sidewall functionalization of single-walled carbon nanotubes by addition of Dichlorocarbene.
Journal of the American Chemical Society, 2003Co-Authors: Bin Zhao, Mark A Hamon, Katalin Kamaras, Mikhail E Itkis, Robert C HaddonAbstract:We report the sidewall functionalization of soluble HiPco single-walled carbon nanotubes (SWNTs) by addition of Dichlorocarbene. The Dichlorocarbene-functionalized SWNTs [(s-SWNT)CCl(2)] retain their solubility in organic solvents such as tetrahydrofuran and dichlorobenzene. The degree of Dichlorocarbene functionalization was varied between 12% and 23% by using different amounts of the Dichlorocarbene precursor. Because the addition of Dichlorocarbene saturates the carbon atoms on the sidewall of the SWNTs and effectively replaces the delocalized partial double bonds with a cyclopropane functionality, the optical spectra of the SWNTs change dramatically. We estimate that the saturation of 25% of the pi-network electronic structure of the SWNTs is sufficient to remove all vestiges of the interband transitions in the infrared spectrum. The transitions at the Fermi level in the metallic SWNTs that appear in the far-infrared (FIR) region of the spectrum show a dramatic decrease of intensity on Dichlorocarbene functionalization. The FIR region of the spectrum allows a clear differentiation between the covalent and the ionic chemistry of SWNTs. In contrast with covalent functionalization, we show that reaction of the SWNTs with bromine vapor leads to a strong increase in absorptions at the Fermi level that is observable in the FIR due to hole doping of the semiconducting SWNTs. Thermal treatment of the (s-SWNT)CCl(2) above 300 degrees C resulted in the breakage of C-Cl bonds, but did not restore the original electronic structure of the SWNTs.
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sidewall functionalization of single walled carbon nanotubes by addition of Dichlorocarbene
Journal of the American Chemical Society, 2003Co-Authors: Bin Zhao, Mark A Hamon, Katalin Kamaras, Mikhail E Itkis, Robert C HaddonAbstract:We report the sidewall functionalization of soluble HiPco single-walled carbon nanotubes (SWNTs) by addition of Dichlorocarbene. The Dichlorocarbene-functionalized SWNTs [(s-SWNT)CCl2] retain their solubility in organic solvents such as tetrahydrofuran and dichlorobenzene. The degree of Dichlorocarbene functionalization was varied between 12% and 23% by using different amounts of the Dichlorocarbene precursor. Because the addition of Dichlorocarbene saturates the carbon atoms on the sidewall of the SWNTs and effectively replaces the delocalized partial double bonds with a cyclopropane functionality, the optical spectra of the SWNTs change dramatically. We estimate that the saturation of 25% of the π-network electronic structure of the SWNTs is sufficient to remove all vestiges of the interband transitions in the infrared spectrum. The transitions at the Fermi level in the metallic SWNTs that appear in the far-infrared (FIR) region of the spectrum show a dramatic decrease of intensity on Dichlorocarbene fu...