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Antifungal Activity of Methanolic of Centella asiatica and Andrographis panicuiata
Singh, Pratibha,Singh, U. P.,Singh, J. S. 한국균학회 2000 韓國菌學會誌 Vol.28 No.4
The antifungal activity of methanolic extracts of Centella asiatica and Andrographis panicullata leaves was observed against fourteen fungi, viz., Alternaria alternata, A. brassicae, A. brassicicola, A. solani, A. tenuissima, Cercospora blumae, Curvularia lunata, C. penniseti, and Drechslera monocems, D. oryzae, D. turitica, Fusarium albizziae and F. udum. Different concentrations of the methanolic extract (1000, 2000, 3000, 5000, 7000, 10000ppm) were used. The effect of mixed leaf extract (1500 ppm of C. asiatica + 1500 ppm of A. paniculada) and its 1:2 ad 1:4 dilutions were also studied. The individual extracts of both the plants showed significant inhibitory effect on spore germination of all the fungi tested. F. udum, F. albizzae, D. oryzae, D. turtica, and D. monocems were particularly sensitive to these extracts. In general, the extract of C. asiatica showed a higher inhibitory effect in all concentrations against all the fungi as compared to A. paniculata, except for A. brassicae A. solani, D. oryzae, D. penniseti and Curvularia sp. The inhibitory effect of extracts increased when they were used in combination with or without dilutions against A. brassicicola, A. solani A. brassicae, A. alternata, A. tenussima, C blumae, C. lunata, C. penniseti and Curvularia species. Higher efficacy of active ingredient of these extracts under field condition is envisaged against plant pathogens.
Investigation of ultraviolet emitting Gd doped Sr<sub>2</sub>MgSi<sub>2</sub>O<sub>7</sub> phosphors
Singh, Vijay,Sivaramaiah, G.,Singh, N.,Pathak, M.S.,Rao, J.L.,Jirimali, H.D.,Natarajan, V. Elsevier 2018 Optik Vol.169 No.-
<P><B>Abstract</B></P> <P>This article deals with the ultraviolet (UV)-emitting gadolinium (Gd)-doped strontium magnesium disilicate (Sr<SUB>2</SUB>MgSi<SUB>2</SUB>O<SUB>7</SUB>) phosphors. A series of the Gd-doped Sr<SUB>2</SUB>MgSi<SUB>2</SUB>O<SUB>7</SUB> phosphors were prepared using a sol-gel method. The powders were well characterized using the X-ray powder diffraction (XRPD) and scanning electron microscope (SEM) techniques. The emission measurements upon a specific UV-light excitation (273 nm) showed the emission characteristics of the Gd<SUP>3+</SUP> that are due to the <SUP>6</SUP>P<SUB>J/2</SUB> → <SUP>8</SUP>S<SUB>7/2</SUB> transition. EPR spectra of the prepared samples indicated the presence of Gd<SUP>3+</SUP> ions in low symmetry sites in this sample.</P>
Singh, B.,Kim, J.H.,Parkash, O.,Song, S.J. Ceramurgica ; Elsevier Science Ltd 2016 CERAMICS INTERNATIONAL Vol.42 No.2
The poor sintering-ability of tetravalent metal pyrophosphates MP<SUB>2</SUB>O<SUB>7</SUB> (M=Sn, Zr, Ce) has restricted their application as electrolyte in proton-conducting ceramic-electrolyte fuel cells (PCFCs). In this work, the effect of doping of MnO on the sinterability and ionic conductivity of MP<SUB>2</SUB>O<SUB>7</SUB> is analyzed. MnO-doped MP<SUB>2</SUB>O<SUB>7</SUB> is synthesized via a solid state reaction method. The phase composition and microstructure of MnO-doped MP<SUB>2</SUB>O<SUB>7</SUB> are studied with X-ray diffraction (XRD) and scanning electron microscopy (SEM) and the ionic conductivity of the sintered sample is measured by electrochemical impedance spectroscopy (EIS). It is observed that, compared to the undoped sintered samples, the porosity of the MnO-doped sintered samples is greatly decreased and the ionic conductivity is significantly improved.
Singh, J.,Lingamdinne, L.P.,Yang, J.K.,Chang, Y.Y.,Lee, B.K.,Koduru, J.R. Institution of Chemical Engineers ; Hemisphere Pub 2017 PROCESS SAFETY AND ENVIRONMENTAL PROTECTION Vol.105 No.-
Nano particles (NPs) were synthesized from leachate of fine fraction (<0.25mm) of automobile shredder residue (ASR) at pH levels of 3, 5, 7, 9 and 12. The removal of phenol using NPs in water was investigated to determine whether applying NPs for phenol removal from wastewater would be feasible. The recovered NPs were analyzed by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). In this research, phenol degradation was studied with hydrogen peroxide to assess the potential applicability of NPs for the treatment of wastewater. The results of the SEM and TEM analyses show that the separated NPs were <50nm in size. The FTIR spectra indicate the presence of C?O and O?H bonds in the NPs. The XRD results show the presence of metals oxides of Fe, Zn, and Cu, among others, on the surfaces of the NPs. The results of the XPS analyses show that various elements (e.g., C, O, Zn, and Fe) existed in the recovered NPs. The degree of phenol degradation by NPs in the presence of hydrogen peroxide was significant. Phenol degradation was found to be 100% for NPs synthesized at pH levels of 3 and 7 at a reaction time of 210min. A pseudo-first-order kinetic model showed a very good fit to the phenol degradation results. The probable mechanism for the removal of phenol by NPs was the degradation of phenol by hydroxyl radicals which were produced during the reaction between H<SUB>2</SUB>O<SUB>2</SUB> and NPs in a liquid medium. The results of the present study indicate that NPs recovered from low-grade ASR can be applied for the removal of phenolic compounds from water.
Singh, Vijay,Sivaramaiah, G.,Singh, N.,Rao, J. L.,Dubey, Vikas,Singh, Pramod K. Springer-Verlag 2018 Journal of materials science. Materials in electro Vol.29 No.8
<P>Fe-doped CaAl12O19 was prepared via a simple combustion route. The formation of the as-prepared and post-heated combustion products was confirmed using an XRD analysis. The EPR spectrum of this sample exhibited a number of resonance signals. The paramagnetic centers have been quantified at different g factors in the range of 19.3-1.14. These resonance signals are attributed to pairs of Fe3+ ions. The resonance signal at a g value of similar to 4.2 is attributed to the axial-symmetry tetrahedral site. The resonance signal at a g value of similar to 2.0 is attributed to the presence of Fe3+ ions in an axial-symmetry octahedral site. The EPR parameters of the post-heated CaAl12O19:Fe3+ sample at room temperature and 110 K were calculated and compared.</P>
Singh, J.P.,Gautam, S.,Kumar, P.,Tripathi, A.,Chen, J.M.,Chae, K.H.,Asokan, K. Elsevier Sequoia 2013 Journal of alloys and compounds Vol.572 No.-
Copper-doped calcium titanate (Cu<SUB>x</SUB>Ca<SUB>1-x</SUB>TiO<SUB>3</SUB>, x=0.0, 0.01, 0.02 and 0.03) ceramic system was synthesized using solid state reaction method. X-ray diffraction and Raman spectroscopic studies reveal the presence of Pbnm space group in the samples. The particle size estimated from scanning electron micrograph changes from 235nm to 6.5μm with copper doping, however crystallite size remain almost constant within experimental error. The dielectric study performed on these samples indicates an increase in the value of dielectric constant with Cu doping. The drastic change in the value of dielectric constant of the samples has been attributed to the change in microstructure. Local electronic structure deduced from X-ray absorption near edge structure reveals no distortion at TiO<SUB>6</SUB> octahedra and reduction in O(2p) and Ca(4sp) hybridized states with increase of Cu<SUP>2+</SUP> doping.
Atomic diffusion processes in MgO/Fe/MgO multilayer
Singh, J.P.,Lim, W.C.,Chae, K.H. Academic Press 2015 Superlattices and microstructures Vol.88 No.-
In present work, atomic diffusion processes in MgO/Fe/MgO structure is investigated. This structure is deposited by using e-beam evaporation method in ultra-high vacuum (10<SUP>-7</SUP> Torr). X-ray diffraction pattern exhibits amorphous nature of MgO layer, however, Au and Fe layers are polycrystalline in nature. Structural quality investigated using transmission electron microscopy shows the presence of short-ranged crystalline ordering in MgO layer. Oxygen atoms of this layer exhibit its interaction with Mg to form MgO, however, Fe layer exists in metal form with onset of oxidation at interface. Rutherford backscattering study shows the diffusion of atoms from upper layers to the layers underneath and to the substrate. Au atoms exhibit exponential diffusion profile in the structure, however, the compositional variation of Fe atoms is described using the combination of exponential decay and exponential growth functions.
Eu2+ and Mn2+ Co-doped BaMgAl10O17 Blue- and Green-Emitting Phosphor: A Luminescence and EPR Study
Singh, V.,Sivaramaiah, G.,Rao, J. L.,Singh, N.,Srivastava, A. K.,Jirimali, H. D.,Li, J.,Gao, H.,Kumaran, R. S.,Singh, P. K. Springer Science + Business Media 2016 Journal of electronic materials Vol.45 No.6
<P>Eu2+ and Mn2+ co-doped BaMgAl10O17 phosphor has been prepared by a solution combustion method. The structural, morphological and compositional analysis of the BaMgAl10O17:Eu2+ and Mn2+ powders have been studied by x-ray diffraction, scanning electron microscopy and energy dispersive x-ray spectroscopy. The electron paramagnetic resonance (EPR) spectrum exhibited resonance signals with the effective g values of g a parts per thousand 4.88 and g a parts per thousand 1.98. The resonance signal with the effective g value of g a parts per thousand 4.88 is characteristic of Eu2+ ions whereas g a parts per thousand 1.98 is due to Mn2+ ions. The number of spins participating in resonance, Gibbs free energy, magnetic susceptibility, Curie constant, effective magnetic moment, zero-field splitting parameter and hyperfine splitting constant have been evaluated. From optical and EPR correlation, it is inferred that Eu2+ and Mn2+ are present in the BaMgAl10O17 matrix.</P>
Cr3+-Doped Yb3Ga5O12 Nanophosphor: Synthesis, Optical, EPR, Studies
Singh, V.,Sivaramaiah, G.,Rao, J. L.,Singh, N.,Pathak, M. S.,Jirimali, H. D.,Singh, P. K.,Srivastava, A. K.,Dhoble, S. J.,Mohapatra, M. Springer Science + Business Media 2016 Journal of electronic materials Vol.45 No.8
<P>Gallium garnets of lanthanides are multifunctional materials especially known for their complicated structure and magnetic properties. In addition, with a suitable transition metal dopant ion, these matrices have been proved to be excellent materials for lasers. In particular, gallium garnet of ytterbium (Yb3Ga5O12) is known to possess excellent properties with regards to these applications. In this connection, Yb3Ga5O12 doped with Cr3+ nanophosphors were synthesized by a solution combustion route. The synthesized material was characterized by powder x-ray diffraction and scanning electron microscopy for phase purity and homogenous morphology. In order to ascertain the oxidation state of the doped ion, diffuse reflectance (DRF), photoluminescence (PL) and electron paramagnetic resonance (EPR) experiments were performed on the sample. The DRF and PL data suggested the stabilisation of the trivalent Cr ion in the matrix. The EPR spectra exhibited two resonance signals with effective g values at g approximate to 7.6 and 4. The EPR data corroborated the DRF and PL results, suggesting the stabilisation of Cr3+ in the matrix at octahedral-type geometries.</P>