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Synthesis and Local Electronic Structure of Calcite Nanoparticles
Singh, Jitendra Pal,Lim, Weon Cheol,Won, Sung Ok,Kim, Sang Ok,Chae, Keun Hwa American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.11
<P>Calcite nanoparticles were synthesized using modified sol-gel method starting from calcium nitrate. Annealing of precursor at 0, 300, and 400 degrees C leads to the formation of amorphous phase of calcium carbonate. At 500 degrees C, amorphous phase converted into calcite phase of calcium carbonate, which retains at 600 degrees C. At higher temperature, mixed phases of calcium hydroxide and calcium oxide appear along with the calcite phase. Calcite nanoparticles synthesized at 500 and 600 degrees C exhibit particle size of 23 and 43 nm, respectively. X-ray absorption spectroscopy measurements performed on these materials show that electronic structure is sensitive to crystalline and amorphous calcite phase, however it is almost insensitive to mixed calcite phases present in the mixture of CaO and Ca(OH)(2). Moreover, C K-edge spectra infer about the attached water molecules with calcite.</P>
Surface and local electronic structure modification of MgO film using Zn and Fe ion implantation
Singh, Jitendra Pal,Lim, Weon Cheol,Lee, Jihye,Song, Jonghan,Lee, Ik-Jae,Chae, Keun Hwa Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.432 No.2
<P><B>Abstract</B></P> <P>Present work is motivated to investigate the surface and local electronic structure modifications of MgO films implanted with Zn and Fe ions. MgO film was deposited using radio frequency sputtering method. Atomic force microscopy measurements exhibit morphological changes associated with implantation. Implantation of Fe and Zn ions leads to the reduction of co-ordination geometry of Mg<SUP>2+</SUP> ions in host lattice. The effect is dominant at bulk of film rather than surface as the large concentration of implanted ions resides inside bulk. Moreover, the evidences of interaction among implanted ions and oxygen are not being observed using near edge fine structure measurements.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Implanted ions results surface modification. </LI> <LI> Implantation results in the orientation of MgO thin film. </LI> <LI> No interaction of implanted ions with host lattice is observed. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Jitendra Pal Singh,R.C. Srivastava,H.M. Agrawal,Prem Chand,Ravi Kumar 한국물리학회 2011 Current Applied Physics Vol.11 No.3
The present investigation aims to study the swift heavy ion irradiation induced effects in zinc ferrite nanoparticles through X-ray diffractometry, transmission electron microscopy and electron paramagnetic resonance spectroscopy. A series of zinc ferrite nanoparticles having different crystallite sizes ranging from 12 to 62 nm have been synthesized by using the nitrates of cations and the citric acid as the host. These samples were irradiated by 100 MeV oxygen beam with two fluences 1 × 10^13 and 5 × 10^13 ions/cm^2. The XRD patterns show the deterioration of crystalline phase after irradiation. The average crystallite size decreases after irradiation. EPR analyses of the pristine and irradiated samples show that the changes depend on the average crystallite size of the pristine samples. Further, the pristine sample having a crystallite size of 62 nm passes through dominant changes after irradiation. It was observed that the number of magnetic centres decreases in the irradiated samples.
Singh, Jitendra Pal,Kaur, Baljeet,Sharma, Aditya,Kim, So Hee,Gautam, Sanjeev,Srivastava, Ramesh Chandra,Goyal, Navdeep,Lim, Weol Cheol,Lin, H.-J.,Chen, J. M.,Asokan, K.,Kanjilal, D.,Won, Sung Ok,Lee, The Royal Society of Chemistry 2018 Physical Chemistry Chemical Physics Vol.20 No.17
<P>The interactions of energetic ions with multi-cation compounds and their consequences in terms of changes in the local electronic structure, which may facilitate intriguing hybridization between O 2p and metal d orbitals and magnetic ordering, are the subject of debate and require a deep understanding of energy transfer processes and magnetic exchange mechanisms. In this study, nanocrystals of ZnFe2O4 were exposed to O<SUP>7+</SUP> ions with an energy of 100 MeV to understand, qualitatively and quantitatively, the metal-ligand field interactions, cation migration and magnetic exchange interactions by employing X-ray absorption fine structure measurements and X-ray magnetic circular dichroism to get deeper mechanistic insights. Nanosized zinc ferrite nanoparticles (NPs) with a size of ∼16 nm synthesized in the cubic spinel phase exhibited deterioration of the crystalline phase when 100 MeV O<SUP>7+</SUP> ions passed through them. However, the size of these NPs remained almost the same. The behaviour of crystal deterioration is associated with the confinement of heat in this interaction. The energy confined inside the nanoparticles promotes cation redistribution as well as the modification of the local electronic structure. Prior to this interaction, almost 42% of Zn<SUP>2+</SUP> ions occupied AO4 tetrahedra; however, this value increased to 63% after the interaction. An inverse effect was observed for metal ion occupancies in BO6 octahedra. The L-edge spectra of Fe and Zn reveal that the spin and valence states of the metal ions were not affected by this interaction. This effect is also supported by K-edge measurements for Fe and Zn. The t2g/eg intensity ratio in the O K-edge spectra decreased after this interaction, which is associated with detachment of Zn<SUP>2+</SUP> ions from the lattice. The extent of hybridization, as estimated from the ratio of the post-edge to the pre-edge region of the O K-edge spectra, decreased after this interaction. The metal-oxygen and metal-metal bond lengths were modified as a result of this interaction, as determined from extended X-ray absorption fine structure measurements. These measurements further support the observation of cation migration from AO4 tetrahedra to AO6 octahedra and <I>vice versa</I>. The Fe L-edge magnetic circular dichroism spectra indicate that Fe<SUP>3+</SUP> ions occupying sites in AO4 tetrahedra and BO6 octahedra exhibited antiferromagnetic-like ordering prior to this interaction. The NPs that interacted with energetic O ions displayed a different kind of magnetic ordering.</P>
Synthesis and Characterization of Some Alkaline-Earth-Oxide Nanoparticles
Jitendra Pal Singh,임원철,원성옥,송종한,채근화 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.72 No.8
The present work reports the synthesis of MgO and CaO nanoparticles by using the sol-gel autocombustion method. The annealing of the precursor at 1200 °C was observed to lead the formation of MgO nanoparticles having average crystallite size of ~ 31 nm. Annealing the precursor at same temperature produced materials having a CaO phase with a minor impure phase of calcium carbonate (~ 3%). The crystallite size corresponding to the CaO phase was 38 nm. A change of thermal history in the precursor was observed not to result in an improvement of the CaO phase. The change of thermal history in the precursor gave rise to mixed phases of CaCO3 and Ca(OH)2 rather than the phase of CaO. Further, annealing at 1200 °C for 12 h resulted in the formation of the CaO phase along with almost 1 - 5% of calcium hydroxide as an impurity phase. X-ray absorption spectroscopic measurements carried out on these materials revealed that the local electronic/atomic structure of these oxides was not only affected by the impurity phases but also influenced by the carbaneous impurities attached to the crystallites.