Uncapped silver nanoparticles synthesized by DC arc thermal plasma technique for conductor paste formulation

Uncapped silver nanoparticles were synthesized by DC arc thermal plasma technique. The synthesized nanoparticles were structurally cubic and showed wide particle size variation (between 20–150 nm). Thick film paste formulated from such uncapped silver nanoparticles was screen-printed on alumina substrates and the resultant ‘green’ films were fired at different firing temperatures. The films fired at 600 °C revealed better microstructure properties and also yielded the lowest value of sheet resistance in comparison to those corresponding to conventional peak firing temperature of 850 °C. Our findings directly support the role of silver nanoparticles in substantially depressing the operative peak firing temperature involved in traditional conductor thick films technology.     

Time-varied synthesis of hierarchical ZnO microspheres and their applications in dye-sensitized solar cells

Journal of Solid State Electrochemistry - Hierarchically nano-structured ZnO microspheres have been synthesized solvothermally at variable reaction times (6, 12, 36, and 48 h) by using...     

Exploring Antagonistic Metabolites of Established Biocontrol Agent of Marine Origin

Biocontrol ability of Pseudomonas aeruginosa ID 4365, a biocontrol agent of groundnut phytopathogens from marine origin, was previously attributed to the production of pyoverdin type of siderophores. However, pyoverdin-rich supernatants of this organism showed better antifungal activity compared to equivalent amount of purified pyoverdin indicating presence of undetected metabolite(s) in pyoverdin rich supernatants. On the basis of observation that antagonistic activity was iron-dependent and iron-independent, an attempt was made to detect the presence of additional metabolites. In addition to pyoverdin, strain produced additional siderophores, viz. pyochelin and salicylic acid. Two broad spectrum antifungal compounds, viz. pyocyanin and phenazine-1-carboxylic acid, were detected, characterized, and activity against phytopathogens was demonstrated. Iron- and phosphate-dependent co-production of siderophores and phenazines was confirmed. Strain showed additional features like production of hydrogen cyanide, indol-3-acetic acid, and phosphate solubilization.     

Energetics of model compounds of water oxidizing complex containing quinone cofactors

To reveal reaction mechanism of PS-II, the reaction products of photolysis may be compared with their thermolytic products. According to required molecular assemblies in manganese clusters at WOC of PS-II, we have strategically synthesized dimers (M-1, M-2), trimers (M-3A, M-3B) and tetramer (M-4) using spin carrier imino-phenol functionalized ligands viz. Lawsone Oxime (L-1) and Phthiocol Oxime (L-2) of naturally occurring quinones .These are characterized by elemental analyses, thermogravimetric analyses, differential thermal analyses, powder X-ray diffraction and infrared spectroscopy. Stabilization energies for molecular associations of ligands in various redox and stereoisomeric forms via hydrogen bondings are compared with thermal energies required for their expulsion from the coordination polymers calculated with the help of Coats and Redfern’s relation of rising temperatures. Activation energy required for establishing tetramer (M-4) and dimer (M-2) in coordination sphere by counter ion using same synthetic route is found to be comparable (~37.48±1 kJ mol^-1). Quantitized energies from TG-DTA data for valence tautomers of redox active ligands play significant role in formation of resultant model compound. viz. tetramer, dimer of dimer and trimer. The role of oxo, acetato and spin carrier ligands in model cluster compounds are proposed with respect to their expulsion energies.     

Effect of γ-radiation on TL,ESR and evaluation of trapping parameters of K2Ca(SO4)2:X (X = Dy or Eu) phosphors

ABSTRACT

The present phosphor K₂Ca(SO₄)_2, doped by dysprosium and europium, is synthesized by the solid-state diffusion method. The doping concentration varied from 0.1 to 0.5?mol% by weight. A phosphor is studied for X-ray powder diffraction, surface morphology analytical scanning electron microscopy and analyzed by energy-dispersive X-ray spectroscopy. The prepared phosphor K₂Ca(SO₄)_2, doped by Dy and Eu, has been characterized for thermoluminescence (TL) glow curve, showing maximum peak temperatures at 176°C and at 200°C, respectively. TL peak intensity of K₂Ca(SO₄)₂: Dy and Eu was compared with the standard TLD CaSO₄:Dy phosphor. Both phosphors show the dose linearity ranging from 20 to 240?Gy doses of γ-rays of ⁶⁰Co source at room temperature. Negligible fading has been observed when irradiated with γ-rays and stored for 60 days without taking any care from sunlight. The TL materials were used in powder forms. The linearity of ESR response with dose for powder forms of K₂Ca(SO₄)₂: Dy was also studied using the signals at g?=?2:0039 (SO₃^?) and at g?=?2:02282 (SO₄^?). It was observed that the range of linearity of dose response extended between 20 and 240?Gy. Kinetic parameters have been calculated using three different methods: Chen's peak shape method, various heating rate method and initial rise method. To study the heating rate method, the glow curve was recorded for the heating rate as 1°C, 3°C, 5°C, 7°C, 9°C each time. Electron spin resonance (ESR) shows the ionic radical formation during γ-irradiation, which is responsible for TL. The effect of temperature and microwave power on the ESR signal was also studied.     

Calculation of pressure using the virtual-volume-variation method and the virial method from chain conformations obtained by Monte Carlo simulations on the second nearest neighbor diamond lattice

For a model system of polyethylene of chain lengths 40 and 100 carbon atoms, we calculated the pressure at different densities and compared them with the experimental values. The simulation was conducted on the second nearest neighbor diamond lattice, and the pressure was calculated using the virtual-volume-variation method after the system was reverse mapped to its fully atomistic form in continuous space and energy minimized. In addition, the pressure was also calculated from the virial route by conducting a short molecular dynamics simulation starting from the energy minimized structure. We show that the pressure obtained from our simulations is quite reasonable in the length of simulation time (in Monte Carlo steps) normally employed in our group. These results provide additional evidence for the equilibration of our model systems, and methodology to calculate the pressure in our lattice models.     

Reactions of cobalt resacetophenone oximate with heterocyclic nitrogen bases

Summary Adduct formation constants of the pyridine adducts of the cobalt(II) chelate of resacetophenone oxime in cyclohexanone have been determined spectrophotometrically. Spectral changes in the absorbance were observed in visible range. The stability of the cobalt adducts increases in the following order of the bases: pyridine<4-picoline<3,5-lutidine<1,10-phenanthroline<2,9-neocuproin<2,2-bipyridyl.     

Electric field gradient at100Rh in HCP zirconium and gadolinium

The measurement of QI frequencies at¹⁰⁰Rh in Zr and Gd reveal that the electronic contribution to the EFG is quite large. The value of ¦K¦ is 8 for¹⁰⁰RhZr whereas it is 45 for¹⁰⁰RhGd. The temperature variation of¹⁰⁰RhZr neither follows T^1.5 nor has a linear T dependence.     

Asymmetric synthesis of (6R)-4-hydroxy-6-substituted-δ-lactones

A novel approach for the asymmetric synthesis of (6R)-4-hydroxy-6-substituted-δ-lactones has been achieved using asymmetric reduction of a prochiral ketone in the presence of (S)-(?)-diphenyl-prolinol/borane as a key step. The enantiomeric purity of the products was determined by chiral GC.     

Hydrogen bonding motif in 2-hydroxy-1,4-naphthoquinone

Self-assemblies of 2-hydroxy-1,4-naphthoquinone (HNQ) have been investigated using the (HNQ)_n (n=1–4) series as modeled systems employing ab initio Hartree–Fock calculations. The energetics and charge distribution in these molecular systems are presented. As revealed from the electron density in the highest occupied molecular orbital of the lowest energy conformers of (HNQ)_n (n=1–4) the charge percolates to the end unit of the assembly. This has been supported by the molecular electrostatic potential topography.