Browsing by Author "Mahapatro, Ajit Kumar"

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    Annealing influence on the magnetic and thermal stability of FeNi3 nanoparticles for magnetic hyperthermia applications
    (Elsevier Ltd, 2025) Mahapatro, Ajit Kumar; Kadian, Ankit; Dev, Kapil
    Metallic magnetic nanoparticles having excellent magnetic properties are potential candidate for biomedical applications like magnetic hyperthermia and drug delivery, however their long-term stability remains a critical challenge, limiting their utility for such applications. Monodisperse spherical FeNi3 permalloy nanoparticles (NPs) were synthesized by surfactant free polyol method and their magnetic and thermal stability was tested for magnetic hyperthermia. The synthesized NPs possessed FCC phase and spherical morphology with average diameter of ∼155 nm. The structural ordering and morphology were improved upon annealing treatment at 300 ˚C resulting in enhanced magnetic properties where the saturation magnetization increased from 54 emu/g to 78 emu/g. The magnetic properties were retained over a long period in ambient conditions. Further, the thermogravimetric measurements in ambient conditions established the thermal stability of the nanoparticles up to 350 ˚C. Transmission electron microscopy revealed a protective amorphous coating all over the NP surface, which shield them from corrosion in ambient conditions. These highly stable NPs showed excellent magnetic hyperthermia response in water as well as ethylene glycol medium. The specific absorption rate of the NPs was improved upon annealing from 268 W/g to 299 W/g in water. The long-term magnetic and thermal stability of these NPs and their excellent SAR values makes them a suitable candidate for magnetic hyperthermia-based cancer therapy.
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    Effect of calcination on morphology of zinc oxide nanoparticles
    (Taylor and Francis Ltd., 2025) Mahapatro, Ajit Kumar; Tandona, Ram Pal; Kumara, Subodh
    Zinc oxide (ZnO) nanoparticles are synthesized using the sol-gel method by considering zinc acetate dihydrate as a precursor, and the morphology and crystalline structure of the as-synthesized ZnO nanoparticles are understood using materials characterization techniques. The effect of calcination temperature and time on the morphology of ZnO powder is studied thoroughly and systematically. The recipe for preparing highly pure ZnO powders is optimized at minimal calcination temperature and time. The powder X-ray diffraction analysis reveals a wurtzite crystal structure for ZnO nanoparticles (ZnO-NPs). From the diffraction patterns, it is evident that the powders calcined at 700 °C for 3 h closely match the JCPDS standard for minimal calcination temperature and time. The peak at 364.48 cm−1 in the Fourier transform infrared spectroscopy provides information about the bonding interaction between Zn and O in ZnO-NPs. The UV-Visible absorption spectra of ZnO-NPs indicate a shifting of peak from 374.37 to 378.49 nm, and the corresponding Tauc plot estimates a change in band gap from 2.461 eV to 2.847 eV for ZnO prepared with calcined at 700 °C for 3 h and 6 h, respectively, due to change in morphology and particle size. The field emission scanning electron microscopy (FESEM) images indicate the formation of spherical-shaped nanoparticles with smooth surfaces and EDAX spectra reveal compositions of zinc and oxygen-only ZnO-NPs. Noticeable changes in the particle size and morphology are observed with increasing calcination temperature. The Raman spectra of the ZnO-NPs recorded using a 514 nm excitation wavelength indicate E2(high) mode at 437.5 cm−1 in Zno-NPs prepared by calcining at 700 °C for 3 h. The optimal condition for achieving high pure ZnO-NPs with well-defined morphology is concluded by calcining the ZnO powder at 700 °C for a duration of 3 h.