Browsing by Author "Sandeep Kumar Singh Patel"

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Fabrication, structure, and magnetic properties of pure-phase biFeO3 and MnFe2O4 nanoparticles and their nanocomposites
(Seoul National University 501-321, 2020) Inna Yusnila Khairani; Anindityo Nugra Arifiadi; Jae-Hyeok Lee; Biswanath Bhoi; Sandeep Kumar Singh Patel; Sang-Koog Kim
We fabricated pure-phase BiFeO3 (BFO) and MnFe2O4 (MFO) nanoparticles as well as their nanocomposites (BMFO), and then we studied their structures and magnetic properties. Pristine BFO nanoparticles of 93.3 nm average diameter were successfully synthesized using the sol-gel method by varying the solvent condition and the precursor amount. Pristine MFO nanoparticles with a mean diameter of 70.5 nm were synthesized using the co-precipitation method entailing the optimization of the preheating and aging steps. The fabricated MFO nanoparticles showed mostly nanospheres with few nanocubes. The nanocomposite samples of 50 % MFO and 50 % BFO were fabricated through grinding and pelletization, followed by sintering under an inert atmosphere. The crystal structures of the pristine materials in the nanocomposites were well preserved. The magnetization values (Ms) of the BFO, MFO, and BMFO were 4.9, 52, and 33 emu/g, respectively. This latter Ms value was significantly higher than that of BFO, owing to the coexistence of Fe2+ and Fe3+ in its BFO phase and the incorporation of magnetic MFO. Two synthesis methods and material properties including the structural, morphological, magnetic, and oxidation states of the BFO-MFO nanocomposites were studied in order to achieve a high Ms value of 33 emu/g, which is higher than the bulk values of previously reported BFO-MFO composite samples. © The Korean Magnetics Society.
R3c to P1 phase transition in Nd3+/Gd3+ co-doped BiFeO3 nanoparticles: Enhanced magnetic and photocatalytic properties
(Elsevier Ltd, 2025) Sandeep Kumar Chauhan; Amit A. Kumar; Narendra Kumar Verma; Paramananda Jena; Bani Mahanti; Sandeep Kumar Singh Patel
We successfully synthesized pure and Nd3+/Gd3+ co-doped BiFeO3 nanoparticles (NPs) via the sol–gel route. X-ray diffraction (XRD) and Raman spectroscopy studies indicates that co-doping at the Bi3+ sites triggered a structural phase transition from rhombohedral (R3c) to triclinic (P1). Also resulted in a decrease in particle size from 41 nm to 33 nm. XPS analysis confirmed successful Nd3+/Gd3+ co-doping in BiFeO3 NPs and reveals the presence of Fe2+ ions. The optical band gap of doped NPs decreased significantly from 2.10 to 1.94 eV. Magnetization measurements revealed a significant enhancement in magnetization values under an applied field of 50 kOe, reaching 1.70 emu/g, a 300 % increase compared to pure BiFeO3 due to the suppression of the spiral spin structure, suggests potential application for spintronics. Nd3+/Gd3+ co-doped BiFeO3 NPs showed remarkable photocatalytic activity, degrading 99 % of methylene blue dye under sunlight irradiation in just 90 min as compared to BiFeO3 NPs. © 2025 Elsevier B.V.
Room-temperature dilute magnetic semiconductor behavior in nonmagnetic Ti4+-doped CeO2 nanoflowers for efficient spintronics and photocatalytic applications
(Springer, 2025) Sandeep Kumar Chauhan; Amit A. Kumar; Paramananda Jena; Simant Kumar Srivastav; Sandeep Kumar Singh Patel
This study investigates the synthesis and characterization of Ti-doped CeO2 nanoflowers (Ce1-xTixO2, x = 0, 0.01, 0.03, and 0.05) prepared via a hydrothermal method. Characterization techniques, including XRD, TEM, XPS, and Raman spectroscopy, confirmed the successful incorporation of Ti into the CeO2 lattice, leading to the formation of pure CeO2 nanoflowers with cubic structure and an increase in oxygen vacancies. The optical band gap of the doped nanoflowers decreased from 3.27 to 3.07 eV. Room temperature ferromagnetism was observed in Ce1-xTixO2 nanoflowers (x = 0.01, 0.03, and 0.05). Notably, the x = 0.05 composition exhibited a remarkable 376% increase in ferromagnetism, reaching 55 × 10−3 emug−1 at 15 kOe. This ferromagnetism is likely attributed to the oxygen vacancies created by doping, which trap charges and lead to the formation of F-centers. These F-centers then interact with impurity atoms, enhancing the magnetic properties. Increased Ti-doping resulted in a noticeable quenching of photoluminescence intensity, indicating improved charge carrier separation. This enhanced separation contributed to the photocatalytic activity of the synthesized samples, which was assessed by methylene blue degradation under UV light. The sample with x = 0.05 exhibited the highest photocatalytic activity. These findings suggest that Ti-doped CeO2 based diluted magnetic semiconductors hold promise for applications in spin-based electronics, optoelectronics and photocatalysis. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2025.
Structural and functional enhancements in BiFeO3nanorods: the effect of Nd3+doping on R3c–Pnma phase transition, magnetism, and photocatalysis
(Royal Society of Chemistry, 2025) Sandeep Kumar Singh Patel; Amit A. Kumar; Sandeep Kumar Chauhan
BiFeO3 and Nd3+-doped BiFeO3 nanorods were successfully synthesized using a hydrothermal method. Characterization revealed that Nd3+-doping induced a structural transformation from a rhombohedral (R3c) to an orthorhombic (Pnma) phase. The decrease in Raman modes further confirms the structural changes. These structural changes, along with the nanoscale dimensions (around 50 nm diameter), significantly enhanced both the photocatalytic activity and magnetic properties of the Nd3+-doped BiFeO3 nanorods. XPS analysis confirmed the successful incorporation of Nd3+ into BiFeO3 and revealed the presence of Fe2+ ions. In addition, UV-Vis spectroscopy showed that the material has excellent visible light absorption, which is slightly red-shifted as a result of doping. We observed greater ferromagnetism in Nd3+–BiFeO3, which we attribute to a structural change that breaks down its antiferromagnetic spin cycloid ordering. The improved photocatalytic performance of the Nd3+–BiFeO3 nanorods is attributed to the band bending process and more efficient electron–hole (e−–h+) separation, suggesting their potential for degrading organic pollutants. This journal is © The Royal Society of Chemistry, 2025
Structural and magnetic properties of Dy3+-doped BaTiO3 nanorods: A study of the tetragonal-to-cubic phase transition and emergent diluted magnetism
(Elsevier B.V., 2025) Sandeep Kumar Singh Patel; Sandeep Kumar Chauhan; A. Naga Lakshman Kumar; Simant Kumar Srivastav
Nanocrystalline pristine BaTiO3 (BTO) and Dy3+-doped BaTiO3 (Dy-BTO) nanorods were synthesized via the hydrothermal method. Structural and compositional analyses using XRD, TEM, XPS, and Raman spectroscopy confirmed the successful incorporation of Dy3+ ions into the BaTiO₃ lattice, with the formation of pure-phase nanorods. Dy3+ doping induced a structural phase transition from the tetragonal (P4mm) to the cubic (Pm3¯m) symmetry, as verified by XRD and Raman results. XPS analysis further revealed that the valence mismatch between the dopant Dy3+ and the host Ba2+ leads to the creation of Ti3+ ions and oxygen vacancies in Dy-BTO. Magnetic characterization through M–H measurements showed that Dy-BTO exhibits an unsaturated hysteresis loop, indicating the coexistence of paramagnetic (PM) and ferromagnetic (FM) phases, while pristine BTO displays a combination of diamagnetic (DM) and FM behavior. The magnetic interactions were quantitatively analyzed using the bound magnetic polaron (BMP) model, which suggests that the formation of Dy3+–Vo–Dy3+ and Ti3+–Vo–Dy3+ centers plays a crucial role in mediating and stabilizing FM ordering. These findings highlight Dy-BTO nanorods as promising candidates for spintronic applications. © 2025 Elsevier B.V.
Temperature-programmed nitridation of monodispersed VOxnanoparticles into nanocrystalline superconducting oxygen-doped vanadium nitride
(Royal Society of Chemistry, 2021) Khemchand Dewangan; Dadan Singh; Sandeep Kumar Singh Patel; Kamlesh Shrivas
A two-stage synthesis process was employed to prepare high-quality nanocrystalline vanadium nitride (VN) for superconducting applications. Firstly, monodispersed amorphous VOxnanoparticles were obtainedviathermal-decomposition of the vanadium(iii) acetylacetonate [V(acac)3] precursor in phenyl ether using oleylamine as a surface stabilizing agent. In the second stage, VOxnanoparticles were nitrided using a temperature-programmed reduction reaction at 700 °C under an NH3atmosphere. Finally, at room temperature a nano-sized nitride sample was oxygen passivated by flowing 0.1% O2-containing N2gas before removing from the furnace to avoid bulk-oxidation of nanocrystals. X-ray diffraction (XRD) peak reflection confirms the formation of phase-pure VN. The transmission electron microscopy (TEM) image displays that the particles are non-agglomerated and have a size distribution of 17.71 ± 3.59 nm. X-ray photoelectron spectroscopy (XPS) study provides evidence that the main oxidation state of vanadium lies between (III) and (0) in the sample. However, it also appears that vanadium located on the surface of VN nanocrystals is oxidized during the passivation. Hence, the present synthesis strategy leads to oxygen-doping on the surface of VN nanoparticles that results in the formation of a vanadium oxide/oxynitride thin-layer on the surface. In addition, the temperature-dependent magnetization study of the product exhibits an abrupt decrease in the magnetization susceptibility at a temperature of 7.1 K, which indicates the onset superconducting transition temperature (Tc) of the prepared VN. The exciting feature in this magnetization study is that the observedTcvalue of VN nanocrystals is similar to that of the pure bulk-VN and is not affected by the existence of different atomic arrangements on the surface of nanocrystals. This property makes it a potential candidate for the future development of new superconducting materials. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2021.