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Sornadurai D.,Materials Science Group | Ravindran T.R.,Materials Science Group | Paul V.T.,Metallurgy and Materials Group | Sastry V.S.,Indira Gandhi Center for Atomic Research
AIP Conference Proceedings | Year: 2012

Synthesis parameters are optimized in order to grow single crystals of multiferroic BiFeO3. 2 to 3 mm size pyramid (tetrahedron) shaped single crystals were successfully obtained by solvothermal method. Scanning electron microscopy with EDAX confirmed the phase formation. Raman scattering spectra of bulk BiFeO3 single crystals have been measured which match well with reported spectra. © 2012 American Institute of Physics.

Pati S.S.,Metallurgy and Materials Group | Kalyani S.,Metallurgy and Materials Group | Mahendran V.,Metallurgy and Materials Group | Philip J.,Metallurgy and Materials Group
Journal of Nanoscience and Nanotechnology | Year: 2014

Magnetite nanoparticles of size ranging from 7-10 nm are prepared from aqueous solutions of Fe2+ and Fe3+ by microwave irradiation at different reaction temperatures ranging from 50 to 200 °C. The effect of reaction temperature on the structural and magnetic properties of nanoparticles is studied using X-ray diffraction (XRD), Transmission electron microscopy (TEM), Small angle X-ray scattering (SAXS), Thermo gravimetry (TGA), Differential scanning calorimetry (DSC), Vibrating sample magnetometer (VSM) and Fourier transform infrared spectroscopy (FTIR) techniques. The average size of the prepared particles, obtained from SAXS, is found to vary from 11 to 15±1 nm as the reaction temperature is increased from 50 to 200 °C. The weight gain curves under an external magnetic field show slope changes at 300 and 596 °C because of the magnetite to maghemite phase transition and ferri to paramagnetic phase transitions, respectively. The ferromagnetic α-Fe2 O3 to antiferromagnetic γ-Fe2 O3 phase transition temperature is found to be enhanced by 154 °C for the nanoparticles prepared at 200 °C, due to an enhanced activation energy for the cubic to a more compact hexagonal transition. The increase in the phase stability of nanoparticles prepared at elevated temperature is attributed to the diffusion of Na+ in the spinel structure. These results are useful to tailor magnetic particles with enhanced thermal stability for practical applications. Copyright © 2014 American Scientific Publishers.

Sangeetha J.,Metallurgy and Materials Group | Philip J.,Metallurgy and Materials Group
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2012

The interaction of iron oxide nanoparticles with casein micelles was studied using Dynamic Light Scattering (DLS) size measurement, Ultraviolet-visible (UV-vis) spectroscopy, Fourier Transform InfraRed (FTIR) spectroscopy, ThermoGravimetric Analysis (TGA), rheology and phase contrast microscopy. The whole milk and skimmed milk treated nanocomplex show an absorption peak at 196nm, due to the peptide bond of casein. The DLS studies show that the milk treated nanocomplex of average primary particle size ∼38nm form hydroclusters of size ∼615nm that disintegrate into smaller clusters upon sonication. The FTIR spectrum of skimmed milk treated nanocomplex shows the characteristic peaks of casein and the nanoparticles. The peaks at 3365cm -1, 1722cm -1, 1652cm -1 and 1585cm -1 (of casein) and a broad peak at 585cm -1 (of FeO bond vibration of Fe 3O 4) were observed for the nanocomplex. The TGA results of skimmed milk treated nanocomplex show a weight loss of ∼13.3%. The rheological studies show that skimmed milk treated nanocomplex exhibit good mechanical stability, whereas the uncoated nanoparticles exhibit poor mechanical stability. The response of uncoated nanoparticles and milk treated nanocomplex to an applied magnetic field shows that iron oxide-casein nanocomplexes reversibly self assemble to form one dimensional chains along the direction of applied magnetic field when the dipolar interaction energy exceeds the thermal energy. Since casein is non-toxic and inexpensive, iron oxide nanoparticle-casein nanocomplexes may find applications in controlled release drug delivery systems. © 2012 Elsevier B.V.

Sangeetha J.,Metallurgy and Materials Group | Philip J.,Metallurgy and Materials Group
RSC Advances | Year: 2013

Lawsone, (2-hydroxy-1,4-naphthoquinone or HNQ), is known for its antimicrobial activity, corrosion inhibition and metal chelation properties. We describe here a simple methodology to functionalize Fe3O4 nanoparticles with lawsone to produce Fe3O4-Cysteine-HNQ nanocomplex, using cysteine as a linker. The characterization of the nanocomplex is done using Fourier Transform Infrared (FTIR) spectroscopy, Thermogravimetric Analysis (TGA), Dynamic Light Scattering size measurement, zeta potential and contact angle measurement. The zeta potential of uncoated nanoparticles and Fe3O4-Cysteine-HNQ nanocomplex is found to be +48 mV and -38 mV respectively. The reversal of surface charge from positive to negative corroborates the presence of lawsone monolayer at particle interface. Further, TGA result shows a weight loss of 32% for these nanocomplexes due to the decomposition of lawsone and cysteine present on the nanoparticles. The FTIR spectrum of the nanocomplex exhibits CC and CO stretching bands of lawsone, with a slight shift in their position, which confirms the interaction of lawsone with the cysteine coated nanoparticles. Fe3O4-Cysteine-HNQ nanocomplexes exhibit interesting properties such as increased wettability (contact angle ∼20°) on stainless steel substrate and antimicrobial activity against Staphylococcus aureus, with a minimum inhibitory concentration of 700 μg mL-1. These results show that lawsone functionalized magnetite nanoparticles can be used as response stimulus antimicrobial agents. © 2013 The Royal Society of Chemistry.

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