Soma Chakraborty

Rice University, Houston, Texas, United States

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Publications (8)56.51 Total impact

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    ABSTRACT: Reduction of graphite by lithium in liquid ammonia yields graphite salts that can be reacted with dodecyl iodide to yield soluble dodecylated graphite. The height of the soluble graphite nanoplatelets was determined by scanning tunneling microscopy (STM) to be 3.5 nm, corresponding to approximately 10 layers of graphene. Solubility in organic solvents was determined to be 20 mg/L in chloroform and 70 mg/L in 1,2,4-trichlorobenzene.
    Carbon 11/2009; 47(13):2945-2949. DOI:10.1016/j.carbon.2009.06.053 · 6.20 Impact Factor
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    ABSTRACT: The large fullerenes that are formed during the synthesis of C60 by the arc discharge technique can be solubilized by reductive alkylation. The mass range of dodecylated large fullerenes determined by laser desorption ionization, time-of-flight mass spectrometry was found to be 650−3500 amu. The solubility of the dodecylated large fullerenes in chloroform is 15.7 g/L as measured by near-infrared spectroscopy. High-resolution transmission electron microscopy images show the expected nontubular, ring-shaped contrast resembling large fullerenes attached to dodecyl groups. The dodecylated large fullerenes have distinctly different behavior than regular organic molecules in dipolar dephasing, magic angle spinning nuclear magnetic resonance (13C MAS NMR) experiments. Thermal gravimetric analysis and 13C MAS NMR experiments indicate that there is 1 dodecyl group for every 23 sp2 fullerene carbon atoms, that the quaternary aliphatic carbons generated upon dodecylation give signals considerably more shielded than those in alkylated C60 and C70 but similar to the quaternary aliphatic signals in dodecylated single-walled carbon nanotubes, and that the dodecyl groups in the dodecylated large fullerenes exhibit widely varying degrees of motional freedom. The last characteristic was unexpected and apparently results from a combination of dodecyl groups in void spaces of varying size and dodecyl groups on molecules that tumble at various rates.
    Chemistry of Materials 08/2008; 20(17). DOI:10.1021/cm800737z · 8.35 Impact Factor
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    ABSTRACT: Oxidation of graphite may be carried out by reaction with meta-chloroperoxybenzoic acid to yield graphite epoxide. Scanning tunneling microscopy (STM) showed that the functionalization occurs at the edges rather than on the basal plane of the graphite. Quantification of the epoxide content is possible through the deepoxidation reaction using MeReO3/PPh3.
    Journal of the American Chemical Society 05/2008; 130(16):5414-5. DOI:10.1021/ja711063f · 12.11 Impact Factor
  • Soma Chakraborty · Wenhua Guo · Robert H. Hauge · W. E. Billups ·
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    ABSTRACT: Fluorinated graphite (CFX) was alkylated reductively to yield functionalized graphite platelets comprised of six to 23 graphene sheets. A free radical mechanism involving a single electron transfer was proposed. The higher level of functionalization that resulted from the fluorinated substrate led to materials that exhibited an enhanced solubility in organic solvents.
    Chemistry of Materials 04/2008; 20(9). DOI:10.1021/cm800060q · 8.35 Impact Factor
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    ABSTRACT: Dispersions of carbon nanotube salts prepared by treating single-walled carbon nanotubes (SWNTs) with lithium in liquid ammonia react with aryl and alkyl sulfides by single electron transfer (SET) to yield transient radical anions that dissociate into carbon-centered free radicals and mercaptide. The free radicals add to the sidewalls of the nanotubes or recombine with SWNT radical anions. AFM images indicate that the derivatized SWNTs are partially debundled. Disulfides react with carbon nanotube salts to yield SWNTs functionalized by sulfur-centered radicals.
    The Journal of Physical Chemistry C 08/2007; 111(48). DOI:10.1021/jp071746n · 4.77 Impact Factor
  • Soma Chakraborty · Jayanta Chattopadhyay · Wenhua Guo · W Edward Billups ·
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    ABSTRACT: PEGged as soluble: Potassium graphite (C 8K) is functionalized to yield derivatives that are soluble in either water or organic solvents. For example, treatment of C 8K with 5-bromovaleric acid followed by amine-terminated poly(ethylene glycol) leads to water-soluble nanoplatelets (see AFM image).
    Angewandte Chemie International Edition 06/2007; 46(24):4486-8. DOI:10.1002/anie.200605175 · 11.26 Impact Factor
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    ABSTRACT: Single-walled carbon nanotubes have been functionalized and the specific surface areas of the functionalized nanotubes measured. Contrary to expectations, functionalization leads to a decrease in specific surface area compared to that of the unfunctionalized nanotubes. Treatment with a concentrated 1:1 nitric/sulfuric acid mixture followed by high-temperature baking at 1000 degrees C was found to increase the specific surface area of the nanotubes. For the unfunctionalized SWNTs, this treatment increases the specific surface area (SSA) by 20%. In the case of SWNTs functionalized by n-butyl groups the increase in the SSA was nearly 2-fold with the value increasing from 410 (drying at 110 degrees C) to 770 m2/gm (acid and bake treatment followed by drying at 110 degrees C). For the ozonized SWNTs, the SSA increases more than 3-fold from 381 (drying at 110 degrees C) to 1068 m2/gm (acid and bake treatment followed by drying at 110 degrees C). SEM images indicate that the nanotubes rebundle in the solid state with an average bundle size of 10-30 nm. AFM studies show that the ozonized tubes have been cut to short bundles after ozonolysis. Hydrogen uptake studies carried out on the baked ozonized tubes led to a 3 wt % hydrogen uptake at 77 K and 30 bar.
    The Journal of Physical Chemistry B 01/2007; 110(49):24812-5. DOI:10.1021/jp065044u · 3.30 Impact Factor
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    ABSTRACT: Carbon nanotube salts prepared by treating single-wall carbon nanotubes (SWNTs) with lithium in liquid ammonia react with ω-bromocarboxylic acids to yield sidewall-derivatized SWNTs. These can be reacted with amine-terminated polyethyleneglycol (PEG) chains (e.g., H2N−mPEG−OMe, MW = 5000 Da) to yield water-soluble PEGylated SWNTs. Short nanotubes (average length 60 nm) functionalized by PEGylation of the carboxylic acid groups at the end of the nanotubes exhibit greater solubility in water than the longer (average length 300 nm) sidewall-PEGylated pristine nanotubes.
    Chemistry of Materials 11/2006; 18(25). DOI:10.1021/cm0611082 · 8.35 Impact Factor