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>

A study of glass and carbon fibers in FRAC utilizing machine learning approach

Ankita Upadhya,M. S. Thakur,Nitisha Sharma,Fadi H. Almohammed,Parveen Sihag Techno-Press 2024 Advances in materials research Vol.13 No.1

Asphalt concrete (AC), is a mixture of bitumen and aggregates, which is very sensitive in the design of flexible pavement. In this study, the Marshall stability of the glass and carbon fiber bituminous concrete was predicted by using Artificial Neural Network (ANN), Support Vector Machine (SVM), Random Forest (RF), and M5P Tree machine learning algorithms. To predict the Marshall stability, nine inputs parameters i.e., Bitumen, Glass and Carbon fibers mixed in 100:0, 75:25, 50:50, 25:75, 0:100 percentage (designated as 100GF:0CF, 75GF:25CF, 50GF:50 CF, 25GF:75CF, 0GF:100CF), Bitumen grade (VG), Fiber length (FL), and Fiber diameter (FD) were utilized from the experimental and literary data. Seven statistical indices i.e., coefficient of correlation (CC), mean absolute error (MAE), root mean squared error (RMSE), relative absolute error (RAE), root relative squared error (RRSE), Scattering index (SI), and BIAS were applied to assess the effectiveness of the developed models. According to the performance evaluation results, Artificial neural network (ANN) was outperforming among other models with CC values as 0.9147 and 0.8648, MAE values as 1.3757 and 1.978, RMSE values as 1.843 and 2.6951, RAE values as 39.88 and 49.31, RRSE values as 40.62 and 50.50, SI values as 0.1379 and 0.2027 and BIAS value as -0.1 290 and -0.2357 in training and testing stage respectively. The Taylor diagram (testing stage) also confirmed that the ANN-based model outperforms the other models. Results of sensitivity analysis showed that the fiber length is the most influential in all nine input parameters whereas the fiber combination of 25GF:75CF was the most effective among all the fiber mixes in Marshall stability.

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.

Electronic structure studies of nanoferrite Cu(x)Co(1-x)Fe2O4 by X-ray absorption spectroscopy.

Gautam, S,Muthurani, S,Balaji, M,Thakur, P,Padiyan, D Pathinettam,Chae, K H,Kim, S S,Asokan, K American Scientific Publishers 2011 Journal of Nanoscience and Nanotechnology Vol.11 No.1

<P>Pure and mixed cobalt copper ferrites are of great interest due to their widespread application in electronics and medicine. We report on the electronic structure of a nanoferrite Cu(x)Co(1-x)Fe2O4 (0.0 < or = x < or = 1.0) system studied by X-ray absorption spectroscopy. These magnetic nanoferrites (average crystallite size approximately 31-43 nm) were synthesized by an auto combustion method and are characterized by high resolution X-ray diffraction and near edge X-ray absorption fine structure measurements at the O K and Co, Cu, and Fe L-edges. The O K-edge spectra suggest that there is a strong hybridization between O 2p and 3d electrons of Co, Cu and Fe cations and Fe L3,2-edge spectra indicate that Fe ions coexist in mixed valence states (Fe3+ and Fe2+) at tetrahedral and octahedral sites of the spinel structure. Copper and cobalt ions are distributed in the divalent state in octahedral sites of the spinel structure. The origin of high saturation magnetization and coercivity in cobalt-copper ferrites are explained in light of these results.</P>

Electronic structure of Cu-doped ZnO thin films by x-ray absorption, magnetic circular dichroism, and resonant inelastic x-ray scattering

Thakur, P.,Bisogni, V.,Cezar, J. C.,Brookes, N. B.,Ghiringhelli, G.,Gautam, S.,Chae, K. H.,Subramanian, M.,Jayavel, R.,Asokan, K. American Institute of Physics 2010 JOURNAL OF APPLIED PHYSICS - Vol.107 No.10

Electronic Structure of Co-doped ZnO Thin Films by X-ray Absorption and Emission Spectroscopy

S. Gautam,P. Thakur,K. H. Chae,G. S. Chang,M. Subramanain,R. Jayavel,K. Asokan 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.1

The electronic structure of Co-doped ZnO thin films, synthesized with a nominal composition of Zn1−xCoxO (x = 0.03, 0.05, 0.7, 0.10, and 0.15) by using spray pyrolysis method, has been investigated using near edge X-ray absorption fine structure (NEXAFS) measurements at the O K- and the Co L3,2-edges and using resonant inelastic X-ray scattering (RIXS) measurements at Co L3,2-edge. All the prepared Zn1−xCoxO thin films showed ferromagnetic behavior at room temperature, as measured by using an alternating gradient force magnetometer (AGFM). The intensity of the pre-edge spectral feature at the O K-edge increases with the Co concentration, which clearly reveals that there is strong hybridization of O 2p − Co 3d atoms in the ZnO matrix. Spectral features of the Co L3,2-edge NEXAFS exhibit multiple absorption peaks and are similar to those of Co2+ ions coordinated in tetrahedral symmetry by four oxygen atoms. These results clearly demonstrate that Co is in a 2+ state, substituting at the Zn site. Co L3,2-edge RIXS measurements show that the substitution by Co atoms can explain the magnetic interaction in Co-doped ZnO. The electronic structure of Co-doped ZnO thin films, synthesized with a nominal composition of Zn1−xCoxO (x = 0.03, 0.05, 0.7, 0.10, and 0.15) by using spray pyrolysis method, has been investigated using near edge X-ray absorption fine structure (NEXAFS) measurements at the O K- and the Co L3,2-edges and using resonant inelastic X-ray scattering (RIXS) measurements at Co L3,2-edge. All the prepared Zn1−xCoxO thin films showed ferromagnetic behavior at room temperature, as measured by using an alternating gradient force magnetometer (AGFM). The intensity of the pre-edge spectral feature at the O K-edge increases with the Co concentration, which clearly reveals that there is strong hybridization of O 2p − Co 3d atoms in the ZnO matrix. Spectral features of the Co L3,2-edge NEXAFS exhibit multiple absorption peaks and are similar to those of Co2+ ions coordinated in tetrahedral symmetry by four oxygen atoms. These results clearly demonstrate that Co is in a 2+ state, substituting at the Zn site. Co L3,2-edge RIXS measurements show that the substitution by Co atoms can explain the magnetic interaction in Co-doped ZnO.

Screen Slant Lightlike Submanifolds of Indefinite Sasakian Manifolds

Haider, S.M. Khursheed,Advin, Advin,Thakur, Mamta Department of Mathematics 2012 Kyungpook mathematical journal Vol.52 No.4

In this paper, we introduce screen slant lightlike submanifold of an indefinite Sasakian manifold and give examples. We prove a characterization theorem for the existence of screen slant lightlike submanifolds. We also obtain integrability conditions of both screen and radical distributions, prove characterization theorems on the existence of minimal screen slant lightlike submanifolds and give an example of proper minimal screen slant lightlike submanifolds of $R_2^9$.

Influence of Diet on Methane and Nitrous Oxide Emissions from Cattle Manure

Vinu M. Nampoothiri,Madhu Mohini,S. S. Thakur,Goutham Mondal 한국대기환경학회 2015 Asian Journal of Atmospheric Environment (AJAE) Vol.9 No.3

Livestock is one of the major contributors of greenhouse gases (GHGs). It accounts for 14.5% of the global GHGs emissions like methane (CH4) from enteric fermentation and manure, nitrous oxide (N2O) from manure and fertilizer. Since enteric emissions are a major contributor of CH4 than that of manure emissions hence primary efforts were made on reducing enteric emissions, with minor attention to dung emissions. Many researches were conducted by dietary manipulation to mitigate enteric CH4 emission. However dietary manipulation also had significant effects on manure GHGs emissions too. Several works proved that manure CH4 emissions were increased with high level of concentrate supplementation despite reduction in enteric CH4. Fat and CP content of the diet has shown inconsistent results on manure CH4 emissions. Amount of concentrate in the diet has shown little effect whereas dietary CP content exhibited conflicting effects on manure N2O emissions.

X-ray Absorption and Emission Studies of Mn-doped ZnO Thin Films

P. Thakur,S. Gautam,K. H. Chae,M. Subramanain,R. Jayavel,K. Asokan 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.1

The electronic structure of Mn-doped ZnO thin films, a dilute magnetic semiconductor (DMS) having possible room temperature (RT) ferromagnetism, synthesized with nominal compositions of Zn1−xMnxO (x = 0.03, 0.05, 0.07, 0.10, and 0.15) by using the spray pyrolysis method are investigated using soft X-ray absorption and emission spectroscopy. The intensity of the pre-edge spectral feature at the O K-edge increases with Mn concentration, which clearly reveals that there is a strong hybridization of Mn ions with the ZnO matrix. The near-edge X-ray absorption fine structure (NEXAFS) measurements at the Mn K- and L3,2-edges show a mixed valence nature for the Mn ions, with Mn2+ and Mn3+/Mn4+ states, and the Mn3+/Mn4+ states are observed to increase with the Mn-concentration. Mn L2,3 resonant inelastic X-ray scattering (RIXS) measurements show that the excess Mn interstitials appear in the sample and that direct exchange interactions with substitutional Mn atoms may explain the magnetic interaction in Mn-doped ZnO. The electronic structure of Mn-doped ZnO thin films, a dilute magnetic semiconductor (DMS) having possible room temperature (RT) ferromagnetism, synthesized with nominal compositions of Zn1−xMnxO (x = 0.03, 0.05, 0.07, 0.10, and 0.15) by using the spray pyrolysis method are investigated using soft X-ray absorption and emission spectroscopy. The intensity of the pre-edge spectral feature at the O K-edge increases with Mn concentration, which clearly reveals that there is a strong hybridization of Mn ions with the ZnO matrix. The near-edge X-ray absorption fine structure (NEXAFS) measurements at the Mn K- and L3,2-edges show a mixed valence nature for the Mn ions, with Mn2+ and Mn3+/Mn4+ states, and the Mn3+/Mn4+ states are observed to increase with the Mn-concentration. Mn L2,3 resonant inelastic X-ray scattering (RIXS) measurements show that the excess Mn interstitials appear in the sample and that direct exchange interactions with substitutional Mn atoms may explain the magnetic interaction in Mn-doped ZnO.

Technological Role of Indium in Nickel-zinc Nano Ferrites Synthesized Via Oil-in-water Micelle Technique

Sangeeta Thakur,S.C. Katyal,Patrick Queffelec,Jean Loaec,M. Singh 한국자기학회 2008 한국자기학회 학술연구발표회 논문개요집 Vol.- No.-