A. Govindaraj
Jawaharlal Nehru Centre for Advanced Scientific Research
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Publication
Featured researches published by A. Govindaraj.
ACS Nano | 2007
L. S. Panchakarla; A. Govindaraj; C. N. R. Rao
Double-walled carbon nanotubes (DWNTs) doped with nitrogen and boron have been prepared by the decomposition of a CH(4) + Ar mixture along with pyridine (or NH(3)) and diborane, respectively, over a Mo(0.1)Fe(0.9)Mg(13)O catalyst, prepared by the combustion route. The doped DWNTs bave been characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy, electron energy loss spectroscopy, and Raman spectroscopy. The dopant concentration is around 1 atom % for both boron and nitrogen. The radial breathing modes in the Raman spectra have been employed along with TEM to obtain the inner and outer diameters of the DWNTs. The diameter ranges for the undoped, N-doped (pyridine), N-doped (NH(3)), and B-doped DWNTs are 0.73-2.20, 0.74-2.30, 0.73-2.32, and 0.74-2.36 nm, respectively, the boron-doped DWNTs giving rise to a high proportion of the large diameter DWNTs. Besides affecting the G-band in the Raman spectra, N- and B-doping affect the proportion of semiconducting nanotubes.
Journal of Materials Chemistry | 2007
Shrinwantu Pal; S. R. C. Vivekchand; A. Govindaraj; C. N. R. Rao
By interaction with a trialkylamine or trialkylphosphine, BN nanotubes can be dispersed in a hydrocarbon medium with retention of the nanotube structure.
Journal of Materials Chemistry | 2008
Asish Pal; Bhupender S. Chhikara; A. Govindaraj; Santanu Bhattacharya; C. N. R. Rao
For the preparation of novel organogel–carbon nanotube nanocomposites, pristine single-walled carbon nanotubes (SWNT) were incorporated into physical gels formed by an L-alanine based low molecular mass organogelator (LMOG). The gelation process and the properties of the resulting nanocomposites were found to depend on the kind of SWNTs incorporated in the gels. With pristine SWNTs, only a limited amount could be dispersed in the organogels. Attempted incorporation of higher amounts of pristine SWNTs led to precipitation from the gel. To improve their solubility in the gel matrix, a variety of SWNTs functionalized with different aliphatic and aromatic chains were synthesized. Scanning electron microscope images of the nanocomposites showed that the texture and organization of the gel aggregates were altered upon the incorporation of SWNTs. The microstructures of the nanocomposites were found to depend on the kind of SWNTs used. Incorporation of functionalized SWNTs into the organogels depressed the sol to gel transition temperature, with the n-hexadecyl chain functionalized SWNTs being more effective than the n-dodecyl chain functionalized counterpart. Rheological investigations of pristine SWNT containing gels indicated that the flow of nanocomposites became resistant to applied stress at a very low wt% of SWNT incorporation. Again more effective control of flow behavior was achieved with functionalized SWNTs possessing longer hydrocarbon chains. This happens presumably via effective interdigitation of the pendant chains with the fatty acid amides of L-alanine in the gel assembly. Remarkably, using near IR laser irradiation at 1064 nm for a short duration (1 min) at room temperature, it was possible to selectively induce a gel-to-sol phase transition of the nanocomposites, while prolonged irradiation (30 min) of the organogel under identical conditions did not cause gel melting.
International Journal of Nanotechnology | 2007
M. Maaza; T. Mhlungu; M.O. Ndwandwe; N. Cingo; A.C. Beye; A. Govindaraj; C. N. R. Rao
An enhanced interference phenomenon in the IR absorbance-wavenumber profiles of ship-shaped carbon nanotubes powder has been observed by attenuated total reflection at room temperature. This room temperature interference phenomenon was considered as possibly originating from an optical resonance effect and that single carbon nanotubes could act as individual Fabry-Perot or Lummer-Gehrcke resonant cavities. It is demonstrated that this interference phenomenon could be an Anderson type localisation phenomenon due to resonant modes in the semi-disordered ship-shaped carbon nanotubes nanopowder which could form a plausible resonant cavity.
Journal of Chemical Sciences | 2008
S. R. C. Vivekchand; Chandra Sekhar Rout; K. S. Subrahmanyam; A. Govindaraj; C. N. R. Rao
Journal of Physical Chemistry C | 2008
Anupama Ghosh; K. S. Subrahmanyam; Katla Sai Krishna; Sudipta Datta; A. Govindaraj; Swapan K. Pati; C. N. R. Rao
Chemical Engineering Science | 2004
C. N. R. Rao; A. Govindaraj; Gautam Gundiah; S. R. C. Vivekchand
Nanotechnology | 2007
Chandra Sekhar Rout; Manu Hegde; A. Govindaraj; C. N. R. Rao
Physical Review Letters | 2007
Anindya Das; A. K. Sood; A. Govindaraj; A. Marco Saitta; Michele Lazzeri; Francesco Mauri; C. N. R. Rao
Bulletin of Materials Science | 2007
L. S. Panchakarla; A. Govindaraj
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Jawaharlal Nehru Centre for Advanced Scientific Research
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