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Since the discovery of carbon nanotubes, there has been great interest in the synthesis and characterization of other one-dimensional materials. A variety of inorganic materials have been prepared in the form of nanowires with a diameter of a few nm and lengths going up to several microns. In order to produce the nanowires, both vapor-growth and solution-growth processes have been made use of. Besides physical methods, such as thermal evaporation and laser ablation, chemical methods including solvothermal, hydrothermal and carbothermal reactions have been employed for their synthesis. In this article, we describe the synthesis, structure and properties of nanowires of various inorganic materials, which include elements, oxides, nitrides, carbides and chalcogenides. Wherever possible, we have also included the relevant information on related one-dimensional materials, such as nanobelts.
No abstract is provided for this article.
The interface between water and an organic liquid has been exploited to prepare nanocrystals of CdS. The technique involves introducing an appropriate precursor of cadmium in the organic layer and the sulfiding reagent in the aqueous layer. The size distribution of the nanocrystals formed at the interface can be controlled by varying parameters such as the reactant concentration, temperature, viscosity of the medium, reaction time and the choice of the reagents. The CdS nanocrystals have been characterized by TEM, electronic absorption and emission spectroscopy. Nanocrystaline γ-Fe2O3 and ZnO can be prepared by taking cupferron complex of the metals in the organic layer and NaOH in the aqueous layer.
Multi-walled as well as single-walled carbon nanotubes are conveniently prepared by the pyrolysis of organometallic precursors, such as metallocenes and phthalocyanines, in a reducing atmosphere. Pyrolysis of organometallics alone or in mixture with hydrocarbons also yields aligned nanotube bundles with useful field emission properties. By pyrolyzing organometallics in the presence of thiophene, Y-junction nanotubes are obtained in large quantities. The junction nanotubes have a good potential in nanoelectronics. Carbon nano-tubes prepared from organometallics are useful for preparing nanowires and nanotubes of materials such as BN, GaN, SiC, and Si 3 N 4 .
A Monte Carlo simulation study has been carried out on the glassy crystalline phases of methane obtained by annealing or quenching the plastic (orientationally disordered) phase. Different cooling rates lead to different states of the glass. Temperature variation of the reorientational parameter suggests the presence of a transition between the plastic and glassy crystalline phases.
A simple n-state configurational excitation model which takes into account the presence of weakly connected pentamer units in liquid water is proposed. The model has features of both the “continuum” and “mixture” models. Calculations based on this model satisfactorily account for the important, diagnostic thermodynamic properties of water such as the density maximum, fraction of monomers and so on.
No abstract is provided for this article.
Electron spectroscopic studies clearly demonstrate that modification of the surfaces of Mn, Fe and Ni metals by chlorine significantly decreases the strength of interaction between the metal and adsorbed molecules such as CO and N2. This is in contrast to the effect of electropositive additives such as Ba and Al which increase the adsorption bond strength significantly.
No abstract is provided for this article.
