An investigation of flower shaped NiO nanostructures by microwave and hydrothermal route
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The face centered cubic phase of NiO nanostructures were successfully synthesized from microwave and hydrothermal methods. The structural properties of the synthesized material were analyzed by X-ray diffraction (XRD) studies. The thermal analysis revealed the transformation of Ni(OH)2 into NiO at about 380 °C. The obtained scanning electron microscopy images exhibited less agglomerated flowers for hydrothermal reacted NiO than the microwave processed samples. The sheet like morphologies of NiO nanostructures were confirmed by transmission electron microscope and the obtained particles sizes were comparable to the calculated values from XRD data. The UV–Vis and photoluminescence spectra results showed that the absorption edges of the NiO nanoflowers have a blue-shift due to quantum confinement effect. The Raman spectrum exhibited the transformation of antiferromagnetic to superparamagnetic transition confirmed from the absence of magnon peak. The XPS spectrum presented the observation of Ni 2p and O 1s levels with higher intense peak nature for hydrothermal treated NiO than microwave. The hysteresis loops of the NiO samples prepared by both hydrothermal and microwave heating methods revealed the weak ferromagnetic behaviors at room temperature. Based on the experimental observations and analysis, a possible hydrothermal reaction mechanism is proposed to synthesize flower shaped NiO nanostructured materials with improved structural, optical, morphological and magnetic properties compared to microwave synthesis.
KeywordsCetyl Trimethyl Ammonium Bromide Quantum Confinement Effect Field Cool Zero Field Cool Small Hysteresis Loop
One of the authors G. Anandha babu gratefully acknowledges DST, India for the financial support under the scheme of INSPIRE Fellowship (Grant No. IF110040) to carry out this work.
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