Effect of cobalt doping on structural, thermo and photoluminescent properties of ZnO nanopowders

Nanocrystalline cobalt doped zinc oxide nanoparticles are synthesized by solution combustion method using sucrose as a fuel. The synthesized samples are characterized by XRD, SEM, FTIR, Micro-Raman, UV�Visible techniques. XRD studies confirm that both undoped and Co doped samples exhibit hexagonal wurtzite structure with crystallite size ~30 nm for undoped ZnO and 25�18 nm for Co doped ZnO samples. Both undoped and Co doped samples exhibit Raman peaks at 432, 502, 578, 681, 766, 865, 967 and 1175 cm�1. Intensity of E2 (high) mode of ZnO appeared at 432 cm�1 and decreases drastically with increase in cobalt concentration. Photoluminescence (PL) of all the samples shows violet emission peaks at 361, 398 nm, blue emission peaks at 468,492 nm and weak green emission peaks at 517 and 567 nm. PL intensity is found to decrease with the increase in Co2+ doping. Thermoluminescence (TL) glow curves of Co doped ZnO nano crystalline phosphors are γ-irradiated in the dose range 0.1�5.0 kGy. Prominent glow peaks at 412 and 575 K are observed for all the exposed doses without changing its glow peak structure. TL intensity increases linearly with γ-dose up to 4 kGy. The Kinetic parameters of TL glow are calculated by deconvolution technique. Activation energy and frequency factor are found to be 1.35 eV and 2.10�1011 s�1 respectively. © 201

PHYTOCHEMISTRY AND ETHNOPHARMACOLOGY OF THE SEA GRASS CYMODOCEACEA FAMILY– A REVIEW

Cymodoceaceae is a family of flowering plants, sometimes known as the manatee-grass family,†the family Cymodoceaceae includes only marine species. The angiosperm phylogeny II system, of 2003 (unchanged from the APG system, of 1998), does recognize Cymodoceaceae and places it in the order Alismatales, in the clade monocots. They are marine hydrophytes that grow and complete their life cycle in a submerged condition, in a saline environment. Like terrestrial plant they obtain their energy from light through photosynthesis thus, they grow only in clear and shallow water, and at the suitable condition, they form beds or meadows. The family includes five genera, totalling 16 species of marine plants occurring in tropical seas and oceans (so-called seagrasses). Cymodoceaceae consist of five genera such as Amphibolis, Cymodocea, Halodule, Syringodium, and Thalassodendron. In this genera Cymodocea rotundata Ehrenb. and Hempr. Ex Asch. Cymodocea serrulata, (R.Br.) Asch. and Magnus, Halodule pinifolia (Miki) Hartog, Halodule uninervis (Forssk.) Asch and Syringodium isoetifolium (Asch.) are the species mostly adopted in Indian coastal region. These seagrass species have unique nature and wide application to the environment including human being. In this article botanical aspects, phytochemistry and ethnopharmacology of these five seagrass species belong to Cymodoceaceae family will be discussed

Luminescence properties of La2O3:Eu3+ nanophosphor prepared by sol-​gel method

Undoped and Eu3+ doped La2O3 nanophosphor are synthesized by low temp. sol-​gel technique. The synthesized samples are characterized by X-​ray diffraction (XRD) and av. crystallite size is found to be ∼18 nm and ∼23 nm for undoped and Eu3+ doped La2O3 resp. Gamma ray irradiated undoped La2O3 shows high intense thermoluminescence (TL) glow peak at 640 K and weak TL glow peak at 443 K and the high intense peak intensity is sub linear increase with γ-​dose. Whereas Eu3+ doped La2O3 nanophosphor show a prominent TL glow peak at 640 K and its TL intensity linearly increases up to 1 kGy. The kinetic parameters are estd. using glow curve deconvoluted (GCD) technique. TL emission of γ-​ray irradiated Eu3+ doped La2O3 show peaks at 508, 586, 619 and 706 nm are attributed to Eu3+ transition peaks

Spin and exchange coupling for Ti embedded in a surface dipolar network

We have studied the spin and exchange coupling of Ti atoms on a Cu$_2$N/Cu(100) surface using density functional theory. We find that individual Ti have a spin of 1.0 (i.e., 2 Bohr Magneton) on the Cu$_2$N/Cu(100) surface instead of spin-1/2 as found by Scanning Tunneling Microscope. We suggest an explanation for this difference, a two-stage Kondo effect, which can be verified by experiments. By calculating the exchange coupling for Ti dimers on the Cu$_2$N/Cu(100) surface, we find that the exchange coupling across a `void' of 3.6\AA\ is antiferromagnetic, whereas indirect (superexchange) coupling through a N atom is ferromagnetic. We confirm the existence of superexchange interactions by varying the Ti-N angle in a model trimer calculation. For a square lattice of Ti on Cu$_2$N/Cu(100), we find a novel spin striped phase

Thermoluminescence Studies of γ-Irradiated ZnO:Mg2+ Nanoparticles

Pure and Mg2+ doped ZnO nanoparticles are synthesized by solution combustion method. X-ray diffraction studies of the samples confirm hexagonal phase. Crystallite size is calculated using Scherer formula and found to be ∼30 nm for undoped ZnO and 34–38 nm for Mg2+ doped ZnO. A broad PL emission in the range 400–600 nm with peaks at 400, 450, 468, 483, 492, 517, 553 nm are observed in both pure and Mg2+ doped nanoparticles. Near band edge emission of ZnO is observed at 400 nm. The broad band emissions are due to surface defects. PL emission intensity is found to increase with Mg2+ concentration up to 1.5 mol% and then decreases due to concentration quenching. Samples are irradiated with γ-rays in a dose range 0.05–8 kGy. Gamma irradiation doesn’t affect PL properties. Undoped samples exhibit unstructured low intense TL glow with peak at 720 K. Whereas Mg2+ doped samples exhibit well structured TL glow curves with peak at ∼618 K. TL glow peak intensity of Mg2+ doped samples increases with Mg2+ concentration up to 2 mol%, thereafter decreases. TL curves of Mg2+ (2 mol%) doped ZnO exhibit two glows, a high intense peak at 618 K and a weak one with peak at ∼485 K. TL intensity of Mg2+ (2 mol%) doped ZnO samples increases with gamma dose up to 1 kGy and then decreases. Kinetic parameters of TL glows are calculated by deconvolution technique. Activation energy and frequency factor are found to be 1.5 eV and 3.38 × 1011 s−1 respectively

Reconstruction of the second layer of Ag on Pt(111)

The reconstruction of an Ag monolayer on Ag/Pt(111) is analyzed theoretically, employing a vertically extended Frenkel-Kontorova model whose parameters are derived from density functional theory. Energy minimization is carried out using simulated quantum annealing techniques. Our results are compatible with the STM experiments, where a striped pattern is initially found which transforms into a triangular reconstruction upon annealing. In our model we recognize the first structure as a metastable state, while the second one is the true energy minimum

Robust recognition technique for handwritten Kannada character recognition using capsule networks

Automated reading of handwritten Kannada documents is highly challenging due to the presence of vowels, consonants and its modifiers. The variable nature of handwriting styles aggravates the complexity of machine based reading of handwritten vowels and consonants. In this paper, our investigation is inclined towards design of a deep convolution network with capsule and routing layers to efficiently recognize  Kannada handwritten characters.  Capsule network architecture is built of an input layer,  two convolution layers, primary capsule, routing capsule layers followed by tri-level dense convolution layer and an output layer.  For experimentation, datasets are collected from more than 100 users for creation of training data samples of about 7769 comprising of 49 classes. Test samples of all the 49 classes are again collected separately from 3 to 5 users creating a total of 245 samples for novel patterns. It is inferred from performance evaluation; a loss of 0.66% is obtained in the classification process and for 43 classes precision of 100% is achieved with an accuracy of 99%. An average accuracy of 95% is achieved for all remaining 6 classes with an average precision of 89%

Phytochemical screening and in vitro antioxidant activity of the seagrass Cymodocea serrulata

1216-1221The seagrass Cymodocea serrulata was collected from Ramanathapuram coastal region and its antioxidant potential was determined. The ethanol extract showed the highest phenolic content of 284.94 mg/ml gallic acid equivalence and the ethyl acetate extract showed the highest flavonoids content of 40.18 mg/ml quercetin equivalence. The tannin content was higher at 264.71 mg/ml tannic acid equivalence in aqueous extract. The ethanol extract exhibited the highest 2,2 diphenyl-1-picrylhydrazyl (DPPH) and 2,2¢-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical scavenging activity with IC50 values of 44.47 µg and 2.5 µg, respectively. The ferric reducing ability and nitric oxide scavenging activity were efficient in both ethanol and aqueous extracts. The superoxide scavenging activity was high in hexane extract. The comparative antioxidant study of the subsequent extract of C. serrulata showed that the ethanol extract possesses the highest free radical scavenging property compared to other extracts. This may be due to the presence of high phenolic compounds. The study brings out the medicinal value of C. serrulata which can be used as a nutraceutical compound in various food and pharmaceutical industries

Spill-water recycling

Spill-water recyclin

The influence of radiation on the electrical characteristics of MOSFET and its revival by different annealing techniques

Defects originate in N-channel MOSFETs by exposing them to high-energy ions and 60Co gamma radiation separately to different radiation doses. The electrical variations in MOSFETs are characterized systematically before and after the influence of radiation on MOSFETs. The impact of 60Co gamma radiation on threshold voltage (VTH) and mobility (µ) characteristics of MOSFETs is more than the impact of high energy ions on MOSFETs. The annealing of electrical characteristics in the irradiated MOSFETs is studied systematically by isothermal and isochronal annealing techniques. The isochronal annealing technique is more preferable due to its high recovery rate than the isothermal annealing technique