S. Basavaraja

Microwave-assisted route for synthesis of nanosized metal oxides

Abstract Microwave-assisted route for the synthesis of nanomaterials has gained importance in the field of synthetic technology because of its faster, cleaner and cost effectiveness than the other conventional and wet chemical methods for the preparation of metal oxide nanoparticles. In the present work, synthesis of metal oxide nanoparticles viz., γ-Fe2O3, NiO, ZnO, CuO and Co-γ-Fe2O3 were carried out by microwave-assisted route through the thermal decomposition of their respective metal oxalate precursors employing polyvinyl alcohol as a fuel. The metal oxide nanoparticles are then characterized for their size and γ to α (in γ-Fe2O3) transition and structure by employing powder X-ray diffraction (XRD) pattern, high-temperature X-ray diffraction (HTXRD) pattern and Fourier transform infrared (FT-IR) spectral studies. The morphology of the samples ranged from nanorods to irregular-shaped particles for different metal oxide samples on the basis of scanning electron microscopy and transmission electron microscopy images. Frequency-dependent dielectric study of the ferrite samples (γ-Fe2O3 and Co-Fe2O3) showed a similar behaviour, where the dielectric constant decreased rapidly with increase in frequency. Possible explanation for this behaviour is given.

Synthesis of MoO3 and its polyvinyl alcohol nanostructured film

The synthesis of ultrafine MoO3 through a self-propagating combustion route employing polyethylene glycol as fuel is reported. The precursor molybdenum oxalate is employed in this study for the conversion of the precursor to ultrafine MoO3 particles. The solvent casting method is adopted for the synthesis of MoO3 dispersed polyvinyl alcohol nanostructured film (MoO3-PVA). These synthesized MoO3 and their composite samples are characterized for their structure, morphology, bonding and thermal behaviour by XRD, SEM, IR and DSC techniques, respectively. The distribution of MoO3 in polyvinyl alcohol gives a crystalline polymer, a compact structure and an increase in glass transition temperature.

Preparation and Characterization of Polypyrrole Silver Nanocomposites via Interfacial Polymerization

Conducting polypyrrole silver (Ppy-AgNC) nanocomposite was synthesized by an interfacial polymerization method. Ag+ ions from the AgNO3 solution were taken in the formation of Ppy-AgNC. The incorporated silver was confirmed by X-ray diffraction (XRD). During the polymerization in a nitrate ion-containing solution, the impregnation leads to the formation of metallic silver. The size distribution of Ag into the polymer is confirmed by transmission electron microscopy (TEM), and proves the formation of a uniform species with spherical particles of Ag (mean diameter of 8-12 nm) branching at the border of Ppy. The thermal behavior of the material was studied by thermogravimetric measurements.

Characterization of γ‐Fe2O3 Nanoparticles Synthesized Through Self‐Propagating Combustion Route

γ‐Fe2O3 nanoparticles of ∼100 nm size were prepared through self‐propagating combustion route using ferrous phthalate precursor employing polyethylene glycol as a fuel. As prepared γ‐Fe2O3 was characterised by employing X‐ray diffraction (XRD), scanning electron micrograph (SEM), Mossbauer spectroscopy, energy dispersive X‐ray microanalysis (EDAX) and X‐ray photoelectron spectroscopy (XPS). From XRD and XPS, we find that the surface of these nanoparticles is α‐Fe2O3 and the core is γ‐Fe2O3 . γ‐Fe2O3 particles were spherical in shape showing a well‐resolved 6 narrow bands in Mossbauer spectrum. No impurities were present, as indicated by EDAX and also no other phase than α and γ was present which substantiates suitability of the synthesis route for γ‐Fe2O3 nanoparticles. The magnetic properties of the γ‐Fe2O3 were also studied by using vibrating sample magnetometer (VSM).

Uses of α-Fe2O3 and fly ash as solid adsorbents

Solid adsorbents have shown great promise for control of particulate and non-particulate matter and as gas sensing devices in recent times. In the present study, adsorption of environmental toxic pollutant such as lead ions on solid adsorbents viz. α-Fe2O3 and fly ash, are reported. Considerable adsorption was observed on fly ash when compared to α-Fe2O3 surface. These studies are characterized by employing solid state and solution studies.

USE OF LIQUID–LIQUID INTERFACE FOR SYNTHESIS OF MAGHEMITE NANOCRYSTALS

Nanocrystals of maghemite (γ-Fe2O3) have been prepared at the interface of organic-aqueous layer by the reaction of ferric acetylacetonate in toluene with sodium hydroxide in aqueous solution. The nanocrystals of γ-Fe2O3 formed at the interface of the organic-aqueous layer have been confirmed by X-ray diffraction (XRD) pattern. The sample has been characterized morphologically by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM) techniques. Magnetic hysteresis loop and zero-field cooling measurements exhibited superparamagnetism behavior for γ-Fe2O3 nanocrystals.