Browsing by Author "Amit A. Kumar"

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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 mechanistic insights into an Fe3+-triggered quinazoline based molecular rotor
(2014) Rampal R. Pandey; Gábor G. Méhes; Amit A. Kumar; Rakesh R. Kumar Gupta; Chihaya C. Adachi; Daya D. Shankar Pandey
Highly fluorescent, multifunctional and thermoreversible conformational switching (1) has been designed and developed by embedding two imidazo[1,2-c]quinazoline (IQ) units in the pyridyl scaffold. The origin of the conformational and optical switching of 1 to 1’ has been established by various studies and by developing a model compound. © 2014 The Partner Organisations.