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CONTENTS
Volume 2, Number 3, September 2014
 

Abstract
Nanomaterials synthesized by natural bioresources such as microorganisms, animals and plants in nature can also be synthesized in laboratories even on large scale. This is considered as an attractive prospect for eco-friendly or so-called green synthesis. Development of eco-friendly synthesis of biocompatible nanoparticles and their potential biomedical applications introduces the concept of nanobiotechnology. The lower cost and lesser side effects as compare to chemical methods of synthesis are the main advantages of biosynthesis. This review article demonstrates the role of various biological resources e.g. bacteria, fungi, actinomycetes, plant leaves, fruits and honey as well as animal tissues for the synthesis of nanoparticles mainly gold and silver with an overview of their potential applications.

Key Words
nanoparticle; nanobiotechnology; microorganism; biosynthesis; biomedical applications; plant extract

Address
Ujjal Kumar Sur: Department of Chemistry, Behala College, Kolkata-700060,West Bengal, India

Abstract
Among the various nanoparticles reported for commercial applications, considerable interest has been generated by the use of silver nanoparticles. Owning to extremely small size, silver nanoparticles exhibit enhanced properties when compared with the bulk material. In this research work, silver nanoparticles were prepared by the reduction of silver salt with a reducing agent by a solvothermal method using different solvent mediums such as ethanol, hexane, toluene and acetone with water. The prepared silver nanoparticles were characterized systematically by X-ray diffraction (XRD), particle size analysis and scanning electron microscope (SEM). The results revealed the formation of pure silver phase and nano-sized particles. Among the different solvent mediums used, the silver nanoparticles prepared by hexane and water as solvent mixture resulted in very low particle size.

Key Words
silver nanoparticles; solvothermal synthesis; characterization

Address
K. Venkateswara Guptha and A. Samson Nesaraj: Department of Chemistry, School of Science and Humanities, Karunya University, (Karunya Institute of Technology and Sciences), Coimbatore – 641 114, Tamil Nadu, India

Abstract
The three-dimensional Nano-Electronic Modeling toolkit (NEMO 3-D) is an open source software package that allows the atomistic calculation of single-particle electronic states and optical response of various semiconductor structures including bulk materials, quantum dots, impurities, quantum wires, quantum wells and nanocrystals containing millions of atoms. This paper, first, describes a software module introduced in the NEMO 3-D toolkit for the calculation of electronic bandstructure and interband optical transitions in nanowires having wurtzite crystal symmetry. The energetics (Hamiltonian) of the quantum system under study is described via the tight-binding (TB) formalism (including sp3, sp3s* and sp3d5s* models as appropriate). Emphasis has been given in the treatment of surface atoms that, if left unpassivated, can lead to the creation of energy states within the bandgap of the sample. Furthermore, the developed software has been validated via the calculation of: a) modulation of the energy bandgap and the effective masses in [0001] oriented wurtzite nanowires as compared to the experimentally reported values in bulk structures, and b) the localization of wavefunctions and the optical anisotropy in GaN/AlN disk-in-wire nanowires.

Key Words
NEMO 3-D; atomistic simulation; tight-binding; Wurtzite nanowire; optical anisotropy; internal fields; electronic structure

Address
Vinay U. Chimalgi, Md Rezaul Karim Nishat, Krishna K. Yalavarthi and Shaikh S. Ahmed: Department of Electrical and Computer Engineering, Southern Illinois University at Carbondale, 1230 Lincoln Drive, Carbondale, IL 62901, USA


Abstract
This study is aimed to the numerical modeling of the surface plasmon-polariton excitation by a layer of active (electrically pumped) quantum dots embedded in a semiconductor, covered with a metal. It is shown that this excitation becomes much more efficient if the metal has a form of a thin (with thickness of several nanometers) film. The cause of this enhancement in comparison with a thick covering metal film is the partial surface plasmon-polariton localized at the metal-semiconductor interface penetration into air. In result the real part of the metal+air half-space effective dielectric function becomes closer (in absolute value) to the real part of the semiconductor dielectric function than in the case of a thick covering metal film. This leads to approaching the point of the surface plasmon-polariton resonance (where absolute values of these parts coincide) and, therefore, the enhancement of the surface plasmon-polariton excitation. The calculations were made for a particular example of InAs quantum dot layer embedded in GaAs matrix covered with an Au film. Its results indicate that for the 10 nm Au film the rate of this excitation becomes by 2.5 times, and for the 5 nm Au film – by 6-7 times larger than in the case of a thick (40 nm or more) Au film.

Key Words
surface plasmon-polaritons; nanometer metal films; quantum dots

Address
Vladimir A. Kukushkin: Department of Plasma Physics and High-Power Electronics, Institute of Applied Physics of the Russian Academy of Science, 46 Ulyanov st., 603950 Nizhny Novgorod, Russia; Nizhny Novgorod State University named after N.I. Lobachevsky, 23 Gagarina pr., 603950 Nizhny Novgorod, Russia
Nikoly V. Baidus: Nizhny Novgorod State University named after N.I. Lobachevsky, 23 Gagarina pr., 603950 Nizhny Novgorod, Russia; 3Research Physico-Technical Institute of the Nizhny Novgorod State University named after N.I. Lobachevsky, 23 Gagarina pr., 603950 Nizhny Novgorod, Russia


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