Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

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Vapor-phase clusters from ethanol-water liquid mixtures of varying compositions, generated by sampling the binary vapor in equilibrium with the liquid mixture, were examined with the aid of a time-of-flight mass spectrometer. The variation of the mole fraction of the alcohol in the cluster beam with the liquid mole fraction was found to be identical to that of the surface concentration obtained from surface tension measurements. The results also compare well with those obtained from neutron reflection. The mass spectrometric method of determining surface compositions of liquid mixtures is more direct and model independent and is applicable over the entire range of compositions. © 2001 Elsevier Science B.V.

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International Journal of Mass Spectrometry

Mass spectrometric determination of the surface compositions of ethanol-water mixtures

Molecular beams generated from the vapors above the surfaces of alcohol-water mixtures have been examined by mass spectrometry. The alcohols examined are methanol, ethanol, n-propanol, and n-butanol. The variation of the vapor-phase mole fraction of the alcohol, estimated from the cluster populations in the molecular beam, with the liquid mole fraction is found to be identical to that of the surface concentration of the alcohol in the liquid obtained from surface-tension measurements. The populations of the neat alcohol clusters, as distinct from those of alcohol-water clusters, also exhibit a comparable trend. Surface enrichment is considerably more pronounced in the case of n-butanol and n-propanol compared to that of ethanol.

Journal of Physical Chemistry A

Surface enrichment in alcohol-water mixtures

The design and fabrication of a Smalley-type cluster source in combination with a reflcctron based time-of-flight (TOP) mass spectrometer are reported. The generation of clusters is based on supersonic jet expansion of the sampling plume. Sample cells for both liquid and solid targets developed for this purpose are described. Two pulsed Nd-YAG lasers are used in tandem, one (532 nm) for target vapourization and the other (355 nm) for cluster ionization. Methanol clusters of nuclearity up to 14 (mass 500 amu) were produced from liquid methanol as the test sample. The clusters were detected with a mass resolution of ∼ 2500 in the R-TOF geometry. Carbon clusters up to a nuclearity of 28 were obtained using a polyimide target. The utility of the instrument is demonstrated by carrying out experiments to generate mixed clusters from alcohol mixtures. Keywords. Mass spectrometer; cluster source; instrumentation. © Indian Academy of Sciences.

Fulltext

Proceedings of the Indian Academy of Sciences: Chemical Sciences

An indigenous cluster beam apparatus with a reflectron time-of-flight mass spectrometer

B-C-N, C-N and B-N nanotubes, prepared by the pyrolysis of the appropriate precursor compounds around 1000°C in an atmosphere of argon, have been examined by electron microscopy and other techniques. The compositions of the nanotubes have been analysed by electron energy loss spectroscopy and X-ray photoelectron spectroscopy. There is significant compositional variation in B-C-N and C-N nanotubes. Properties of the B-C-N and C-N nanotubes have been compared with those of carbon nanotubes, particularly with respect to the I-V characteristics as obtained from UHV-STM studies. The near absence of B-N nanotubes on pyrolysing the appropriate precursor compound, and other observations made in the present study, indicate the crucial role played by carbon in the initial nucleation and growth of nanotubes.

Chemical Physics Letters

B-C-N, C-N and B-N nanotubes produced by the pyrolysis of precursor molecules over Co catalysts

In the light of the finding that carbon nanotubes get functionalized on reaction with acid and other oxidizing agents, the structures and shapes of nanotube derivatives resulting from possible reaction between functionalized nanotubes, are obtained by an energy minimization procedure and the structures, so obtained, are compared with the observed microscopic images. The shapes of fullerene - like and nanotube - like structures containing seven - membered rings, in addition to six and five - membered rings, are depicted along with the structures of bent nanotubes containing similar ring systems. Diamond - graphite hybrid structures which constitute an important class of carbon materials are also investigated.

Fullerene Science and Technology

Structures and images of novel derivatives of carbon nanotubes, fullerenes and related new carbon forms

Carbon onions are found along with carbon nanotubes and other carbon nanoparticles in the cathodic deposit in the arc-vaporization of graphite. Atomic force microscopy has been used to characterize these particles on the basis of their sizes and shapes. Onion-like particles have three-dimensional, near spherical structure and are distinct from two-dimensional graphitic particles. The spherical shape and height to diameter ratios obtained using atomic force microscope, afford a distinction between onion-like structures and other carbon nanoparticles.

Bulletin of Materials Science

An atomic force microscope study of carbon onions and related nanoparticles

A simple procedure has been developed to prepare thiol-derivatized nanoparticles of metals. The procedure involves the transfer of well-characterized metal hydrosols to a hydrocarbon medium containing the thiol. Thiol-derivatized nanoparticles Au, Ag, and Pt of near spherical shape forming nanocrystalline arrays have been characterized by X-ray diffraction, transmission electron microscopy (TEM), and other techniques. Thiol-derivatized Au particles of mean diameters of 1.0, 2.1, and 4.2 nm from nanocrystalline arrays show characteristic X-ray diffraction patterns. The nanoparticles exhibit Moiré fringes when deposited on a flake of MoSe2, showing that each particle is in itself crystalline. Besides spherical nanoparticles, thiol-derivatized particles of other shapes have been prepared, hexagonal Pt nanoparticles being particularly novel. Scanning tunneling microscopy images not only confirm the size and shape of nanoparticles revealed by TEM, but also show evidence for thiol molecules on the surface.

Journal of Physical Chemistry B

Thiol-derivatized nanocrystalline arrays of gold, silver, and platinum

A scanning tunneling microscopy study of carbon nanocapsules (onions) is reported for the first time. Spherulitic graphite is shown to be purely crystalline graphite based on X-ray diffraction and electron microscopy studies. © 1995, Taylor & Francis Group, LLC. All rights reserved.