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Investigation of nonlinear optical and photocatalytic properties of sol-gel derived KBiFe2O5
No full textKBiFe2O5 polycrystalline powder was synthesized via citrate assisted sol-gel route. Its structural, microstructural, linear, nonlinear optical and photocatalytic properties were investigated. X-ray diffraction analysis revealed its structure to be monoclinic phase at room temperature. Nonlinear optical absorption of this material was investigated using open aperture z-scan technique. A three-photon type absorption mechanism fitted well with the experimental data, and the corresponding nonlinear absorption coefficient was calculated to be 4x10(-23)m(3)/W-2. The band gap of this material as determined by diffuse reflectance spectroscopy was found to be 1.75eV. This makes it suitable for visible light driven photocatalytic applications. The photocatalytic property of KBiFe2O5 was investigated by degradation of methylene blue under visible light irradiation at different pH. The degradation rate constant was found to be 0.031min(-1) at a pH of 11
Circular fringe projection technique for out-of-plane deformation measurements
No full textFringe projection is,a widely used technique for measurement of out-of-plane deformation of diffusely reflecting objects. Among the various fringe patterns employed for projection, usage of linear fringes is most common. However, the phase function of linear fringes has 2 pi periodicity, thereby leading to ambiguity in determining whole-field out-of-plane deformation of dynamic objects. This paper presents a new method of measurement of whole-field out-of-plane deformation of targets by projecting a circular fringe pattern. New technique of fringe analysis is introduced to estimate the underlying phase distribution of the fringe pattern from a single image. In this technique, the fringe pattern is coordinate transformed into polar coordinates, and then Fourier fringe analysis technique is employed to obtain its phase. Subsequent to unwrapping, the phase map is re-transformed to Cartesian coordinates. The phase map obtained after coordinate transformation is converted to out-of-plane deformation map using camera calibration parameters. Simulations are carried out to establish the analysis method. Experimental validation is performed with the development of circular grating based fringe projection system
Expanding Interlayer Spacing in MoS2 for Realizing an Advanced Supercapacitor
No full textCharge-storage mechanism of free-standing MoS2/r-GO (r-GO = reduced graphene oxide) hybrid nanoflakes on molybdenum (Mo) foil in Na2SO4 solution is elucidated for realizing a high-performance asymmetric supercapacitor (ASC). Thiourea that acts primarily as sulfur source also helps intercalating ammonium ions, which along with r-GO facilitate in situ exfoliation of MoS2, producing hierarchical MoS2 with expanded interlayer spacing. This interlayer expansion in MoS2 facilitates Nations intercalation/deintercalation and ensures enhanced capacitance, rate capability, and cycling stability of the capacitor. Besides exhibiting attractive energy-cum-power traits, the 2 V MoS2/r-GO//Fe2O3/MnO2 ASC shows compelling cycling performance for over 20 000 cycles in an aqueous electrolyte
Pick Interpolation on the Polydisc: Small Families of Sufficient Kernels
No full textWe address Pick's interpolation problem on the unit polydisc in Cn, n >= 2, by characterizing all interpolation data that admit a D-valued interpolant in terms of a family of positive-definite kernels parametrized by a class of polynomials. This uses a duality approach that has been associated with Pick interpolation, together with some approximation theory. Furthermore, we use duality methods to understand the set of points on the n-torus at which the boundary values of a given solution to an extremal interpolation problem are not unimodular
Sodium Cobalt Metaphosphate as an Efficient Oxygen Evolution Reaction Catalyst in Alkaline Solution
No full textSodium cobalt metaphosphate NaCo(PO3)(3)] has CoO octahedra (CoO6) and shows superior oxygen evolution reaction (OER) activity in alkaline solution, comparable with the state-of-the-art precious-metal RuO2 catalyst. OER catalysts of this metaphosphate are prepared by combustion (Cb) and solid-state (SS) methods. The combustion-assisted method offers a facile synthesis and one-step carbon composite formation. Unusually high catalytic activity was observed in NCoM-Cb-Ar and could be due to chemical coupling effects between NaCo(PO3)(3) and partially graphitized carbon. This novel electrocatalyst exhibits very small overpotential of 340mV with high mass activity of 532Ag(-1). Good charge transfer abilities and chemical coupling between NaCo(PO3)(3) and amorphous carbon gives the OER activity in NCoM-Cb-Ar
The ridA gene of E. coli is indirectly regulated by BglG through the transcriptional regulator Lrp in stationary phase
No full textRegulators encoded by the beta-glucoside (bgl) operon of Escherichia coli are known to influence the expression of downstream target genes that confer a fitness advantage in stationary phase. We have examined the role of bglG in the regulation of ridA that encodes an enamine/imine deaminase essential for the elimination of reactive intermediates generated during the catabolism of amino acids such as serine. We report here that ridA is positively regulated by leucine responsive regulatory protein (Lrp) and leucine antagonizes the activation by Lrp. We also show that Lrp itself is under the indirect regulation of BglG, which brings about the overexpression of ridA in Bgl(+) strains during stationary phase. Loss of ridA function in a Bgl(+) background results in a significant growth retardation in serine-containing media compared to that in a Bgl-background. We propose that overexpression of ridA in Bgl(+) background during stationary phase is physiologically relevant to eliminate toxic metabolites generated by the catabolism of serine-containing peptides as a result of elevated levels of their uptake
Engineering a 3D MoS2 foam using keratin exfoliated nanosheets
No full textOwing to their exceptional optical and electronic properties; two-dimensional transition metal dichalcogenides (TMDs) such as molybdenum disulfide (MoS2) have attracted immense research interest. However, the lack of an efficient route for large-scale production of nano-layered sheets with long shelf-life and colloidal stability to avoid their restacking upon drying poses a significant bottleneck in their widespread use limiting their utility in device fabrication especially in functional electronics. Here, we report a facile method to obtain the high-quality dispersion of nano-layered MoS2 nanosheets with exceptionally high yield of similar to 56%, long shelf life and excellent electronic properties, which was confirmed by the high conductivity values of 5 x 10(-4) S cm(-1) (much higher than the best reports) measured on the as-casted film. Moreover, we subsequently show that the exfoliated material can be transformed into a 3D MoS2 foam with intact optical properties confirmed from the presence of the band gap at similar to 2.1 eV, and photothermal behavior showing the increase of similar to 40 degrees C within 2 min of NIR irradiation making this material an attractive substrate for applications in catalysis, sensing and functional electronics
Effect of supercooling on the microstructural development and optimization of physical properties of melt grown SnSe crystals
No full textThe microstructural development of stoichiometric tin monoselenide (SnSe) crystals grown by vertical Bridgman-Stockbarger method using an indigenously fabricated furnace has been investigated under high vacuum (similar to 10(-6) mbar). The ampoule translation rate (t(r)) and supercooling, Delta T (= T-m - T, where T-m is the melting point and T is the crystallization temperature) were varied in the range, 12-2 mm/h and 20-100 degrees C respectively. Enhancement of Delta T and t(r) led to constitutional supercooling, inducing compositional changes and non-stoichiometry. Low Delta T (20-40 degrees C) and high t(r) (12-10 mm/h) resulted in globules, flakes and cavities. When Delta T = 60 degrees C and t(r) = 9 to 7 mm/h, mounds were formed with closed contours and ripples, due to atomically rough liquid-solid (l-beta) interface. Fine tuning of Delta T (60 degrees C) and t(r) (2 mm/h) enabled smooth planar interface, so as to yield good quality crystalline structures with periodic atomic deposition promoting crystal growth, layer-by-layer. Energy dispersive analysis by X-rays and powder X-ray diffraction studies revealed appreciable crystallinity, chemical homogeneity and phase purity. The density of crystals estimated from crystallographic data (6.183 g/cm(3)) corroborates with that obtained utilizing Archimedes principle. Thermogravimetric and microindentation analyses established thermal and mechanical stability. The low etch pit density (similar to 10(2) cm(-2)) manifests nearly perfect growth of crystals than their melt counterparts. UV-Vis-NIR and PL spectra reflected direct transition with an energy gap of 1.32 eV, validating immense potential of the grown crystals for photovoltaic applications
Mixing the immiscible through high-velocity mechanical impacts: an experimental and theoretical study
No full textIn two-component metallic systems, thermodynamic immiscibility leads to phase separation such as in two-phase eutectic compositional alloys. The limit of the immiscibility of component elements under non-equilibrium conditions have been explored, but achieving complete miscibility and formation of single phase microstructures in eutectic alloys would be unprecedented. Here, we report that during the low-temperature ball milling that provides high energy impact, complete mixing of phases can occur in immiscible Ag-Cu eutectic alloys. From combined theoretical and experimental studies, we show that impact can produce solid solutions of Ag-Cu nanoparticles of eutectic composition. Our results show that phase diagrams of low dimensional materials under non-equilibrium conditions remain unexplored and could lead to new alloy microstructures drastically different from their bulk counterparts
An investigation on the performance of Di-isopropyl benzyl derivative of Poly (3, 4-propylene dioxythiophene) thin film based electrochromic pixels displays
No full textElectrochromic (EC) smart pixel display was designed and fabricated using a novel monomer di-4-isopropyl benzyl substituted (3, 4-propylene dioxythiophene) (ProDOT-IPBz(2)). The polymer thin film showed absorption between 450 and 650 nm at a fully reduced state. The absorption peak narrowed down slightly towards longer wavelength region (850-900 nm) at the oxidation states. Siju et al has reported the coloration efficiency (CE) of the thin film as similar to 305 cm(2) C-1. The ProDot-IPBZ(2) thin film was used to fabricate EC pixel display of 2 x 2 pixel array on a patterned ITO coated glass. The optical color contrast of the EC pixel display is 40% at 600 nm, with a switching time of about 2 s and 2.5 s respectively. The CE of EC pixel was found to be 555 cm(2) C-1 at 600 nm in the fully doped state. This EC pixel switched for more than 1000 cycles with good color contrast (< 5% T). EC pixel displays showed transmissive, magenta and violet colored states at applied potentials of 1.5, -1.0 and -2.0 V respectively. This EC pixel display is efficient with faster response time and better color contrast