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Investigations on the structural, optical and electronic properties of Nd doped ZnO thin films
Subramanian, M,Thakur, P,Gautam, S,Chae, K H,Tanemura, M,Hihara, T,Vijayalakshmi, S,Soga, T,Kim, S S,Asokan, K,Jayavel, R Institute of Physics [etc.] 2009 Journal of Physics. D, Applied Physics Vol.42 No.10
<P>We report the synthesis and characterization of Nd doped ZnO thin films grown on Si (1 0 0) substrates by the spray pyrolysis method. The surface morphology of these thin films was investigated by scanning electron microscopy and shows the presence of randomly distributed structures of nanorods. Grazing angle x-ray diffraction studies confirm that the doped Nd ions occupied Zn sites and these samples exhibited a wurtzite hexagonal-like crystal structure similar to that of the parent compound, ZnO. The micro-photoluminescence measurement shows a decrease in the near band edge position with Nd doping in the ZnO matrix due to the impurity levels. The near-edge x-ray absorption fine structure (NEXAFS) measurements at the O K edge clearly exhibit a pre-edge spectral feature which evolves with Nd doping, suggesting incorporation of more charge carriers in the ZnO system and the presence of strong hybridization between O 2p–Nd 5d orbitals. The Nd M<SUB>5</SUB> edge NEXAFS spectra reveal that the Nd ions are in the trivalent state.</P>
Bashir, Abida,Ikram, M,Kumar, Ravi,Thakur, P,Chae, K H,Choi, W K,Reddy, V R IOP Pub 2009 Journal of Physics, Condensed Matter Vol.21 No.32
<P>We present here the structural, electronic structure, magnetic and Mossbauer studies of NdFe1-xNixO3 (0 <= x <= 0.3) samples. All the samples exhibit a single-phase orthorhombic structure with space group Pbnm. The near-edge x-ray absorption fine structure (NEXAFS) studies reveal that, with the Ni substitution at Fe sites, a new spectral feature about 1.5 eV lower than the pre-edge structure of NdFeO3 in the O K edge is observed due to the 3d contraction effect and is growing monotonically with the increase of Ni concentration. The Fe L-3,L-2, Ni L-3,L-2 and Nd M-5,M-4 edges confirm the trivalent state of Fe, Ni and Nd ions. The Mossbauer spectra fitted with two Zeeman sextets confirm the different surroundings of Ni around Fe ions. With the increase in Ni concentration, the sextets are broadened. The increase of quadrupole splitting and the decrease of the hyperfine field suggest the change in the ordered regime of the system. The magnetic behaviour at low temperatures is explained in the context of competition among moments of rare earth (Nd) and transition metal ions (Fe/Ni). The strong paramagnetic contribution of the Nd magnetic sublattice and spin flip phenomenon is observed from the temperature dependence of zero-field-cooled and field-cooled magnetization where spin crossover is observed. The isothermal hysteresis loops show a decrease of magnetization and increase of coercivity with the increase in temperature and complements magnetization versus temperature. The results are explained on the basis of the spin reorientation phenomenon.</P>
Bashir, A.,Ikram, M.,Kumar, R.,Lisboa-Filho, P.N.,Thakur, P. Elsevier 2010 Materials science and engineering B. Advanced Func Vol.172 No.3
We present the structural, electronic structure and magnetic studies of Ni doped SmFeO<SUB>3</SUB>. The X-ray diffraction (XRD) studies confirm the single phase nature of the samples having orthorhombic Pbnm structure and the unit-cell volume is decreasing with the increase of Ni concentration. X-ray absorption spectroscopy (XAS) studies on O K, Fe L<SUB>3,2</SUB>, Ni L<SUB>3,2</SUB> and Sm M<SUB>5,4</SUB> edges of SmFe<SUB>1-x</SUB>Ni<SUB>x</SUB>O<SUB>3</SUB> (x@?0.5) samples along with the reference compounds revealed the homo-valence state of Fe and Ni in these materials. From magnetization studies it has been observed the materials exhibit ferromagnetic and antiferromagnetic sub-lattices, which are strongly dependent on the thermo-magnetic state of the system.
In vitro Antioxidant Activity of Ethanolic Extract of Chlorophytum borivilianum
R. Govindarajan1,,N. Sreevidya1,,M. Vijayakumar1,,M. Thakur2,,V.K. Dixit2,,S. Mehrotra*1,,P. Pushpangadan1 한국생약학회 2005 Natural Product Sciences Vol.11 No.3
Chlorophytum borivilianum Baker (Antharicaceae) comonly referred as ‘Safed Musli’ has beenwidely used in the Indian traditional systems of medicine to treat various diseases like rheumatism apart fromaphordisiac properties. C. borivilianum was screened for the first time to determine its antioxidant activity,isolation of the sapogenins and standardization of the isolated sapogenin fraction using HPTLC. Potent antioxidantactivity of ethanolic extract was found by their ability to scavenge DPPH (84.51%), hydroxyl radical (48.95 %),feryl bi-pyridyl complex (84.53%) along with the inhibition of lipid peroxidation (67.17%) at 100g/mlconcentration. The ethanolic extract also exhibited significant inhibition of superoxide anion radical generated byplant in the traditional system especially its use as a Rasayana drug.
Thakur, A.K.,Nisola, G.M.,Limjuco, L.A.,Parohinog, K.J.,Torrejos, R.E.C.,Shahi, V.K.,Chung, W.J. Korean Society of Industrial and Engineering Chemi 2017 Journal of industrial and engineering chemistry Vol.49 No.-
<P>Nano-spherical amine-rich polyethylenimine (PEI) grafted on mesoporous silica (MCM-41) (PEI/MCM-41) was developed for Cd(II) and Ni(II) removal from water. Characterization of PEI/MCM-41 using various techniques confirms its successful fabrication. Adsorption results reveal that pH and adsorbent dosage must be controlled for maximum removal. The adsorption rate was pseudo-second-order, and fitted well with Langmuir and Freundlich isotherms at equilibrium. The adsorption was thermodynamically spontaneous, endothermic and favourable. Adsorption capacities of 156.0 mg g(-1) Cd(II) and 139.7 mg g(-1) Ni(II) were on par with other high performing reported adsorbents. The PEI/MCM-41 was successfully reused demonstrating its potential for heavy metal decontamination application. (C) 2017 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.</P>
Effect of design modification on efficiency enhancement in Sb2S3 absorber based solar cell
Islam M.T.,Thakur A.K. 한국물리학회 2023 Current Applied Physics Vol.49 No.-
The effect of tailored architecture and interfacial engineering on efficiency enhancement ~3.5 times vis-`a-vis experimental value in Sb2S3 absorber based solar cell is reported. It is attributed to design driven lowered interfacial recombination for identical absorber based solar cell. The design modification comprises optimal intrinsic layer insertion, carrier density control, absorber bandgap widening, Fermi level pinning and back surface field at Sb2S3/metal junction. Hole carrier density lowering and band gap engineering near Sb2S3/CdS junction and interfacial recombination lowering improved short circuit current (~90%), open circuit voltage (~67%), fill factor (~15%) and efficiency (~255%). The simulation analysis confirmed that CdS buffer layer donor defects pinned the Fermi level near conduction band edge at Sb2S3/CdS interface causing lower recombination. A high hole concentration thin layer at Sb2S3/metal interface also reduced back contact interfacial recombination. Modified solar cell architecture confirmed possibility of chalcogenide solar cell having enhanced efficiency ~16% vis-`a-vis 4.5% reported in literature.
Ajinkya M Pawar,Bhagyashree Thakur,Anda Kfir,김현철 대한치과보존학회 2019 Restorative Dentistry & Endodontics Vol.44 No.3
Objectives: To compare the formation of dentinal defects using stainless-steel hand K-files (HFs), rotary files, reciprocating files, and Self-Adjusting File (SAF), when used for oval root canals. Materials and Methods: One hundred and forty extracted human mandibular premolar with single root and oval canal were selected for this study. Oval canals were confirmed by exposing to mesio-distal and bucco-lingual radiographs. Teeth with open apices or anatomic irregularities were excluded. All selected teeth were de-coronated perpendicular to the long axis of the tooth, leaving roots segments approximately of 16 mm in length. Twenty teeth were left unprepared (control), and the remaining 120 teeth were divided into 6 groups (n = 20) and instrumented using HF (size 40/0.02), Revo-S (RS; size 40/0.06), ProTaper NEXT (PTN; size 40/0.06), WaveOne (WO; size 40/0.09), RECIPROC (RC; size 40/0.06), and the SAF (2 mm). Roots were then sectioned 3, 6, and 9 mm from the apex, and observed under stereomicroscope, for presence of dentinal defects. “No defect” was defined as root dentin that presented with no visible microcracks or fractures. “Defect” was defined by microcracks or fractures in the root dentin. Results: The control, HF, and SAF did not exhibit any dentinal defects. In roots instrumented by RS, PTN, WO, and RC files exhibited microcracks (incomplete or complete) in 40%, 30%, 55%, and 50%, respectively. Conclusions: The motor-driven root canal instrumentation with rotary and reciprocating files may create microcracks in radicular dentine, whereas the stainless-steel hand file instrumentation, and the SAF produce minimal or less cracks.