@article { ISI:000260776800015, title = {Structure and microbial synthesis of sub-10 nm Bi2O3 nanocrystals}, journal = {Journal of Nanoscience and Nanotechnology}, volume = {8}, number = {8}, year = {2008}, month = {AUG}, pages = {3909-3913}, publisher = {AMER SCIENTIFIC PUBLISHERS}, address = {25650 NORTH LEWIS WAY, STEVENSON RANCH, CA 91381-1439 USA}, abstract = {

After the advent of novel chemical and microbial techniques, providing control over grain size and shape of the nanomaterials, several binary-oxide materials have been explored in size less than 10 nm for their tunable physical properties. Bi2O3 nanoparticles have also redrawn attention due to their excellent properties, mostly as optoelectronic material. Here, we report the room-temperature biosynthesis of Bi2O3 nanoparticles in a size range of 5-8 nm by extra-cellularly challenging the plant pathogenic fungus-Fusarium oxysporum with the bismuth nitrate as precursor. The as-synthesized particle-surfaces are inherently functionalized by a robust layer of proteins which provides them very good stability in the aqueous medium. Structural investigation using selected area electron diffraction, high resolution transmission electron microscopy and powder XRD shows that particles are almost perfectly single crystalline and primarily crystallize in alpha-phase with monoclinic structure.

}, keywords = {Biosynthesis, fungi, High Refractive Index, High Resolution TEM, Nanoparticles}, issn = {1533-4880}, doi = {10.1166/jnn.2008.179}, author = {Uddin, Imran and Adyanthaya, Suguna D. and Syed, Asad and Selvaraj, K. and Ahmad, Absar and Poddar, Pankaj} } @article { ISI:000273689600061, title = {Magnetic and dielectric properties and Raman spectroscopy of GdCrO3 nanoparticles}, journal = {Journal of Applied Physics}, volume = {107}, number = {1}, year = {2010}, month = {JAN}, pages = {013912}, publisher = {AMER INST PHYSICS}, address = {CIRCULATION \& FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USA}, abstract = {

The rare earth orthochromites are extremely interesting due to the richness of their optical, dielectric, and magnetic properties as well as due to their multiferroic properties which make them suitable materials to study in the nanoregime. However, the wet-chemical synthesis of these materials in nanosize is nontrivial. Here, we report for the first time, the detailed Raman spectra as well as magnetic and dielectric properties of chemically synthesized GdCrO3 nanoparticles of size ranging from 40 to 60 nm. The magnetic properties are dictated by competing Cr3+-Cr3+, Gd3+-Cr3+, and Gd3+-Gd3+ superexchange interactions in different temperature regions, resulting into an antiferromagnetic ordering at 167 K due to the Cr3+-Cr3+ followed by weak ferromagnetic ordering due to the onset of Cr3+-Gd3+ interactions. At lower temperature, it shows weak antiferromagnetic ordering due to Gd3+-Gd3+ interaction. Below 95 K, GdCrO3 nanoparticles showed the presence of negative magnetization due to Gd3+ and Cr3+ interactions resulting into weak ferromagnetic coupling. The Raman spectroscopy shows the characteristic Raman shifts indicating that below 450 cm(-1), Gd3+ ions play a dominant role in determining the phonon frequencies of GdCrO3, and above 450 cm(-1), the Cr+3 ions dominate. We also present for the first time the low temperature dielectric constant and loss tangent data for GdCrO3 in a broad temperature and frequency range. The dielectric constant shows a decrease in comparison to the bulk values due to the size dependent effects. It also shows a peak centered at around 320 K above which it shows a sharp decrease. The dielectric loss value in GdCrO3 nanoparticles is quite small and shows an interesting frequency dependent anomaly at lower temperature which might be due to the coupling between magnetic and dielectric order parameters.

}, keywords = {dielectric losses, gadolinium compounds, Magnetisation, Multiferroics, nanofabrication, Nanoparticles, permittivity, phonons, Raman spectra, superexchange interactions}, issn = {0021-8979}, doi = {10.1063/1.3275926}, author = {Jaiswal, Adhish and Das, Raja and Vivekanand, K. and Maity, Tuhin and Abraham, Priya Mary and Adyanthaya, Suguna D. and Poddar, Pankaj} } @article { ISI:000290015600029, title = {Field emission studies of silver nanoparticles synthesized by electron cyclotron resonance plasma}, journal = {Applied Surface Science}, volume = {257}, number = {16}, year = {2011}, month = {JUN}, pages = {7184-7189}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Field emission has been studied for silver nanoparticles (25-200 nm), deposited within a cylindrical silver target in an electron cyclotron resonance (ECR) plasma. Particle size distribution was controlled by optimum biasing voltages between the chamber and the target. Presence of non-oxidized silver was confirmed from the X-Ray diffraction analysis; however, thin protective layer of oxide was identified from the selective area electron diffraction pattern obtained with transmission electron microscopy. The silver nanoparticles were seen to exhibit hilly pointed like structures when viewed under the atomic force microscopy (AFM). The emissive properties of these particles were investigated by field emission microscopy. It is found that this technique of deposition is ideal for formation of nanoparticles films on different substrate geometries with size controllability as well as its application to emission devices. (C) 2011 Elsevier B.V. All rights reserved.

}, keywords = {Cold plasma, field emission, Nanoparticles, thin film}, issn = {0169-4332}, doi = {10.1016/j.apsusc.2011.03.088}, author = {Purohit, Vishwas and Mazumder, Baishakhi and Bhise, Ashok B. and Poddar, Pankaj and Joag, Dilip S. and Bhoraskar, S. V.} } @article { ISI:000289003000012, title = {Synthesis and optical studies of GdCrO3 nanoparticles}, journal = {Journal of Nanoparticle Research}, volume = {13}, number = {3}, year = {2011}, month = {MAR}, pages = {1019-1027}, publisher = {SPRINGER}, address = {VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS}, abstract = {

{Here we report for the first time, a detailed synthesis mechanism of GdCrO3 nanoparticles using a surfactant-less hydrothermal method. We also report a detailed study of their structural and optical properties. The selected area electron diffraction and powder X-ray diffraction studies of GdCrO3 nanoparticles show pure phase and excellent crystallinity with average particle size around 50-60 nm. The structural analysis indicates a distorted perovskite crystal structure with lattice parameter values of a = 5.3099 +/- A 0.0022

}, keywords = {hydrothermal, Nanoparticles, Rare earth orthochromites}, issn = {1388-0764}, doi = {10.1007/s11051-010-0090-4}, author = {Jaiswal, Adhish and Das, Raja and Adyanthaya, Suguna D. and Poddar, Pankaj} } @article { ISI:000300606400030, title = {Green approach towards size controlled synthesis of biocompatible antibacterial metal nanoparticles in aqueous phase using lysozyme}, journal = {Current Nanoscience}, volume = {8}, number = {1}, year = {2012}, month = {FEB}, pages = {130-140}, publisher = {BENTHAM SCIENCE PUBL LTD}, address = {EXECUTIVE STE Y-2, PO BOX 7917, SAIF ZONE, 1200 BR SHARJAH, U ARAB EMIRATES}, abstract = {

Inspired by array of proteins present in nature, we choose lysozyme (hen egg protein) as a model system to synthesize nanoparticles of noble metals to understand the mechanism of interaction as well as to use them for potential applications such as potent antibacterial agents. Lysozyme is a very well studied biomolecule containing aromatic amino acids like tryptophan and tyrosine. Tyrosine has phenoxy group which is considered to be responsible for interacting with the metal ions. Lysozyme can be suitably modified by treatment with N-bromosuccinimide/N-acetylimidazole to obtain tight control over size distribution of nanoparticles. Here we report the direct synthesis of nanocrystals of gold and silver at controlled pH and light conditions without using any known reducing agents. Out of these, synthesis of gold nanoparticles is assisted by the presence of low concentration of Ag+ ions through the galvanic exchange. It is remarkable to note that the structure of protein is not changed drastically as seen by the FTIR studies. As-synthesized lysozyme capped nanoparticles prepared by this method are biocompatible and retain antibacterial property.

}, keywords = {Antibacterial, Biocompatible, Gold, lysozyme, Nanoparticles, Silver}, issn = {1573-4137}, author = {Kumar, Umesh and Ranjan, Amaresh K. and Sharan, Chandrashekhar and Hardikar, Anandwardhan A. and Pundle, Archana and Poddar, Pankaj} } @article { ISI:000337521700013, title = {Large magnetocaloric effect, moment, and coercivity enhancement after coating Ni nanoparticles with Ag}, journal = {ChemPhysChem}, volume = {15}, number = {8}, year = {2014}, month = {JUN}, pages = {1619-1623}, publisher = {WILEY-V C H VERLAG GMBH}, address = {BOSCHSTRASSE 12, D-69469 WEINHEIM, GERMANY}, abstract = {

We observe a large magnetocaloric effect in monodisperse Ni and NicoreAgshell nanoparticles in the superparamagnetic region. The organically passivated Ni nanospheres show a large magnetic entropy change of 0.9 J kg(-1)K for a 3 T magnetic field change. In comparison to the surfactant-coated Ni nanoparticles, the NicoreAgshell nanoparticles show an enhanced coercivity, magnetization, and magnetocaloric effect (1.3 kgK for a 3 T magnetic field change). The coercivity at 10 K increases from 360 Oe for Ni nanoparticles to nearly 610 Oe for NicoreAgshell particles. This large enhancement is attributed to the enhanced inter-particle interaction, which is mediated by the metallic shell, over the relatively weaker dipolar interaction in the surfactant-coated Ni nanoparticles, and to modification of the surface spin structure.

}, keywords = {anisotropy, core-shell, magnetic properties, Nanoparticles, superparamagnetic}, issn = {1439-4235}, doi = {10.1002/cphc.201300886}, author = {Srinath, Sanyadanam and Poddar, Pankaj and Das, Raja and Sidhaye, Deepti and Bhagavatula L. V. Prasad and Gass, James and Srikanth, Hariharan} }