YIn0.9Mn0.1O3-ZnO nano-pigment exhibiting intense blue color with impressive solar reflectance

The current study reports on the synthesis and characterization of a new inorganic nano-pigment with an intense blue color and high solar radiation reflective properties (70%). The nano-pigment YIn0.9Mn0.1O3-ZnO was synthesized by a sol-gel combustion method and characterized with the aid of X-Ray diffraction, Raman spectroscopy, Magnetic susceptibility, Transmission electron microscopy, UV ndash;vis-NIR diffuse reflectance spectroscopy and CIE-1976 L*a*b* color measurements. The Rietveld refinement of the XRD patterns of the developed nano-pigment disclosed the existence of YIn0.9Mn0.1O3 and ZnO in a 1:1 ratio with hexagonal crystal structures. For comparison, YIn0.9Mn0.1O3 was also synthesized by the sol gel combustion route and its optical properties compared with that of YIn0.9Mn0.1O3-ZnO. It is interesting to note that the developed YIn0.9Mn0.1O3-ZnO nano-pigmeht exhibits superior blue hue (b* = -40.55) and solar reflectance (R* = 70%) values as compared to the YIn0.9Mn0.1O3 nano-pigment (b* = -22.28, R* = 50%). Most importantly, the potential utility of the nano-pigment as a ``Cool Pigment'' was demonstrated by coating onto roofing materials like aluminum roofing sheets. (C) 2015 Elsevier Ltd. All rights reserved.

Photocatalytic properties of KBiO(3) and LiBiO(3) with tunnel structures

In the present study, KBiO(3) is synthesized by a standard oxidation technique while LiBiO(3) is prepared by hydrothermal method. The synthesized catalysts are characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), BET surface area analysis and Diffuse Reflectance Spectroscopy (DRS). The XRD patterns suggest that KBiO(3) crystallizes in the cubic structure while LiBiO(3) crystallizes in orthorhombic structure and both of these adopt the tunnel structure. The SEM images reveal micron size polyhedral shaped KBiO(3) particles and rod-like or prismatic shape particles for LiBiO(3). The band gap is calculated from the diffuse reflectance spectrum and is found to be 2.1 eV and 1.8 eV for KBiO(3) and LiBiO(3), respectively. The band gap and the crystal structure data suggest that these materials can be used as photocatalysts. The photocatalytic activity of KBiO(3) and LiBiO(3) are evaluated for the degradation of anionic and cationic dyes, respectively, under UV and solar radiations.

Photocatalytic degradation of gaseous toluene by using immobilized titania/silica on aluminum sheets

The aim of this study was to prepare a highly active immobilized titania/silica photocatalyst and to test its performance in situ toward degradation of toluene as one of the major toxic indoor contaminants. In this work, two different titania layers immobilized on Al sheets were synthesized via low temperature sol-gel method employing presynthesized highly active titania powders (Degussa P25 and Millennium PC500, mass ratio 1:1): (a) with a silica/titania binder and a protective layer and (b) without the binder. The photocatalysts were characterized by X-ray diffraction, nitrogen sorption measurements, scanning electron microscopy (SEM), infrared spectroscopy, and UV-vis diffuse reflectance spectroscopy (DRS). The in situ photocatalytic degradation of gaseous toluene was selected as a probe reaction to test photocatalytic activity and to verify the potential application of these materials for air remediation. Results show that nontransparent highly photocatalytically active coatings based on the silica/titania binder and homogeneously dispersed TiO2 powders were obtained on the Al sheets. The crystalline structure of titania was not altered upon addition of the binder, which also prevented inhomogeneous agglomeration of particles on the photocatalyst surface. The photoactivity results indicate that the adsorption properties and photocatalytic activity of immobilized photocatalysts with the silica/titania binder and an underlying protective layer were very effective and additionally, they exhibited considerably improved adhesion and uniformity. We present a new highly photocatalytically active immobilized catalyst on a convenient metallic support, which has a potential application in an air cleaning device.

Green colored nano-pigments derived from Y2BaCuO5: NIR reflective coatings

A green colored nano-pigment Y2BaCuO5 with impressive near infra-red (NIR) reflectance (61% at 1100 nm) was synthesized by a nano-emulsion method. The developed nano-crystalline powders were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), UV-vis-NIR diffuse reflectance spectroscopy and CIE-L*a*b* 1976 color scales. The XRD and Rietveld analyses of the designed pigment powders reveal the orthorhombic crystal structure for Y2BaCuO5, where yttrium is coordinated by seven oxygen atoms with the local symmetry of a distorted trigonal prism, barium is coordinated by eleven oxygen atoms, and the coordination polyhedron of copper is a distorted square pyramid CuO5]. The UV-vis spectrum of the nano-pigment exhibits an intense d-d transition associated with CuO5 chromophore between 2.1 and 2.5 eV in the visible domain. Therefore, a green color has been displayed by the developed nano-pigment. The potential utility of the nano-pigments as ``Cool Pigments'' was demonstrated by coating on to a building roofing material like cement slab and PVC coatings. (C) 2014 Elsevier Ltd. All rights reserved.

Conducting polymer-carbon black nanocomposite sensor for volatile organic compounds and correlating sensor response by molecular dynamics

Volatile organic compounds (VOCs) are present in our every day used products such as plastics, cosmetics, air fresheners, paint, etc. The determination of amount of VOC present in atmosphere can be carried out via various sensors. In this work a nanocomposite of a novel thiophene based conducting polymer and carbon black is used as a volatile organic compound sensor. The fabricated 2 lead chemiresistor sensor was tested for vapours of toluene, acetone, cylcohexane, and carbon tetrachloride. The sensor responds to all the vapours, however, exhibit maximum response to toluene vapours. The sensor was evaluated for various concentrations of toluene. The lower limit of detection of the sensor is 15 +/- 10 ppm. The study of the effect of humidity on senor response to toluene showed that the response decreases at higher humidity conditions. The surface morphology of the nanocomposite was characterized by scanning electron microscopy. Diffuse reflectance spectroscopy was used to investigate the absorption of vapours by the nanocomposite film. Contact angle measurements were used to present the effect of water vapour on the toluene response of nanocomposite film. Solubility parameter of the conducting polymer is predicted by molecular dynamics. The sensing behaviour of the conducting polymer is correlated with solubility parameter of the polymer. Dispersion interaction of conducting polymer with toluene is believed to be the reason for the selective response towards toluene. (C) 2014 Elsevier B.V. All rights reserved.

Structural refinement, optical and electrical properties of Ba1-x Sm-2x/3](Zr0.05Ti0.95)O-3 ceramics

Samarium doped barium zirconate titanate ceramics with general formula Ba1-x Sm-2x/3](Zr0.05Ti0.95)O-3 x = 0, 0.01, 0.02, and 0.03] were prepared by high energy ball milling method. X-ray diffraction patterns and micro-Raman spectroscopy confirmed that these ceramics have a single phase with a tetragonal structure. Rietveld refinement data were employed to model BaO12], SmO12], ZrO6], and TiO6] clusters in the lattice. Scanning electron microscopy shows a reduction in average grain size with the increase of Sm3+ ions into lattice. Temperature-dependent dielectric studies indicate a ferroelectric phase transition and the transition temperature decreases with an increase in Sm3+ ion content. The nature of the transition was investigated by the Curie-Weiss law and it is observed that the diffusivity increases with Sm3+ ion content. The ferroelectric hysteresis loop illustrates that the remnant polarization and coercive field increase with an increase in Sm3+ ions content. Optical properties of the ceramics were studied using ultraviolet-visible diffuse reflectance spectroscopy.

Porous wide band gap BiNbO4 ceramic nanopowder synthesised by low temperature solution-based method for gas sensing applications

In this study, we report the gas sensing behavior of BiNbO4 nanopowder prepared by a low temperature simple solution-based method. Before the sensing behaviour study, the as-synthesized nanopowder was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, UV-diffuse reflectance spectroscopy, impedance analysis, and surface area measurement. The NH3 sensing behavior of BiNbO4 was then studied by temperature modulation (50-350 degrees C) as well as concentration modulation (20-140 ppm). At the optimum operating temperature of 325 degrees C, the sensitivity was measured to be 90%. The cross-sensitivity of as-synthesized BiNbO4 sensor was also investigated by assessing the sensing behavior toward other gases such as hydrogen sulphide (H2S), ethanol (C2H5OH), and liquid petroleum gas (LPG). Finally, selectivity of the sensing material toward NH3 was characterized by observing the sensor response with gas concentrations in the range 20-140 ppm. The response and recovery time for NH3 sensing at 120 ppm were about 16 s and about 17 s, respectively.

Fabrication of novel Ag3PO4/BiOBr heterojunction with high stability and enhanced visible-light-driven photocatalytic activity

Herein, we report a facile and effective method to enhance the photocatalytic activity of bismuth oxybromide (BiOBr) semiconductor through the fabrication of heterojunction with Ag3PO4. The as synthesized Ag3PO4/BiOBr microspheres were characterized with transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD) and UV-vis diffuse reflectance spectroscopy (DRS). The new Ag3PO4/BiOBr heterojunctions exhibited wide absorption in the visible-light region and compared to pure BiOBr and Ag3PO4 samples displayed exceptionally high photocatalytic activity for the degradation of typical organic pollutants such as Rhodamine B (RhB) and phenol. The optimal Ag/Bi weight ratio in Ag3PO4/BiOBr microsphere (AB7) was found to be 0.7. The enhanced photocatalytic activity was related to the efficient separation of electron-hole pairs derived from matching band potentials between BiOBr and Ag3PO4 which results into the generation of natural energy bias at heterojunction and subsequent transfer of photoinduced charge carriers. Moreover, the synthesized samples exhibited almost no loss of activity even after 6 recycling runs indicating their high photocatalytic stability. Considering the facile and environment friendly route for the synthesis of Ag3PO4/BiOBr hybrids with enhanced visible-light induced photocatalytic activity, it is possible to widely apply these hybrids in various fields such as waste water treatment. (C) 2015 Elsevier B.V. All rights reserved.

Novel AgBr/Ag3PO4 Decorated Ceria Nanoflake Composites for Enhanced Photocatalytic Activity toward Dyes and Bacteria under Visible Light

The aim of this study was to develop heterogeneous visible light active photocatalysts using AgBr and Ag3PO4 using CeO2 nanoflakes as an efficient substrate. Ascorbic acid was employed as a fuel to synthesize fine ceria nanoflakes by a facile solution combustion process. AgBr and Ag3PO4 were decorated on ceria to prepare AgBr/Ag3PO4/ceria nanocomposites. The structure of the composite was determined by X-ray diffraction analysis. Novel flakelike morphology was revealed using electron microscopy techniques. The nanocomposites exhibit excellent photocatalytic activity under visible light compared to pristine ceria nanoparticles. The nanocomposite catalyst particles degraded both anionic and cationic dyes. It also exhibited efficient antimicrobial activity under visible light. The AgBr/Ag3PO4/ceria nanocomposite was characterized using X-ray diffraction analysis, diffuse reflectance spectroscopy, electron microscopy, BET surface area analysis, and X-ray photoelectron spectroscopy, and the reasons for enhanced photocatalytic activity were elucidated. The presence of silver based semiconductors on ceria has shown to decrease charge recombination through photoluminescence analysis that attributed for enhanced photocatalytic activity. The AgBr/Ag3PO4/ceria nanocomposite has shown a stable performance after many repeated cycles.

Efficient visible light photocatalytic activity and enhanced stability of BiOBr/Cd(OH)(2) heterostructures

Novel BioBr/Cd(OH)(2) heterostructures were synthesized by a facile chemical bath method under ambient conditions. A series of BiOBr/Cd(OH)(2) heterostructures were obtained by tuning the Bi/Cd molar ratios. The obtained heterostructures were characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). Optical properties were studied by UV-visible spectroscopy, diffuse reflectance spectroscopy and photoluminescence (PL). Photocatalytic studies on rhodamine B (RhB) under visible light irradiation showed that the heterostructures are very efficient photocatalysts in mild basic medium. Scavenger test studies confirmed that the photogenerated holes and superoxide radicals (O-2(center dot-)) are the main active species responsible for RhB degradation. Comparison of photoluminescence (PL) intensity suggested that an inhibited charge recombination is crucial for the degradation process over these photocatalysts. Moreover, relative positioning of the valence and conduction band edges of the semiconductors, O-2/O-2(center dot-) and (OH)-O-center dot/H2O redox potentials and HOMO-LUMO levels of RhB appear to be responsible for the hole-specificity of degradation. Photocatalytic recycling experiments indicated the high stability of the catalysts in the reaction medium without any significant loss of activity. This study hence concludes that the heterojunction constructed between Cd(OH)(2) and BiOBr interfaces play a crucial role in influencing the charge carrier dynamics and subsequent photocatalytic activity.

Spotting 2D atomic layers on aluminum nitride thin films

Substrates for 2D materials are important for tailoring their fundamental properties and realizing device applications. Aluminum nitride (AIN) films on silicon are promising large-area substrates for such devices in view of their high surface phonon energies and reasonably large dielectric constants. In this paper epitaxial layers of AlN on 2 `' Si wafers have been investigated as a necessary first step to realize devices from exfoliated or transferred atomic layers. Significant thickness dependent contrast enhancements are both predicted and observed for monolayers of graphene and MoS2 on AlN films as compared to the conventional SiO2 films on silicon, with calculated contrast values approaching 100% for graphene on AlN as compared to 8% for SiO2 at normal incidences. Quantitative estimates of experimentally measured contrast using reflectance spectroscopy show very good agreement with calculated values. Transistors of monolayer graphene on AlN films are demonstrated, indicating the feasibility of complete device fabrication on the identified layers.

Room temperature ferromagnetism and white light emissive CdS:Cr nanoparticles synthesized by chemical co-precipitation method

Undoped and Cr (3% and 5%) doped CdS nanoparticles were synthesized by chemical co-precipitation method. The synthesized nanocrystalline particles are characterized by energy dispersive X-ray analysis (EDAX), scanning electron microscope (SEM), X-ray Diffraction (XRD), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (DRS), photoluminescence (PL), Electron paramagnetic resonance (EPR), vibrating sample magnetometer (VSM) and Raman spectroscopy. XRD studies indicate that Cr doping in host CdS result a structural change from Cubic phase to mixed (cubic + hexagonal) phase. Due to quantum confinement effect, widening of the band gap is observed for undoped and Cr doped CdS nanoparticles compared to bulk CdS. The average particle size calculated from band gap values is in good agreement with the TEM study calculation and it is around 4-5 nm. A strong violet emission band consisting of two emission peaks is observed for undoped CdS nanoparticles, whereas for CdS:Cr nanoparticles, a broad emission band ranging from 420 nm to 730 nm with a maximum at similar to 587 nm is observed. The broad emission band is due to the overlapped emissions from variety of defects. EPR spectra of CdS:Cr samples reveal resonance signal at g = 2.143 corresponding to interacting Cr3+ ions. VSM studies indicate that the diamagnetic CdS nanoparticles are transform to ferromagnetic for 3% Cr3+ doping and the ferromagnetic nature is diminished with increasing the doping concentration to 5%. (C) 2015 Elsevier B.V. All rights reserved.

High-Temperature Phase Transition Studies in a Novel Fast Ion Conductor, Na2Cd(SO4)2, Probed by Raman Spectroscopy

Temperature-dependent Raman spectroscopic studies were carried out on Na2Cd(SO4)(2) from room temperature to 600 degrees C. We observe two transitions at around 280 and 565 degrees C. These transitions are driven by the change in the SO4 ion. On the basis of these studies, one can explain the changes in the conductivity data observed around 280 and 565 degrees C. At 280 degrees C, spontaneous tilting of the SO4 ion leads to restriction of Na+ mobility. Above 565 degrees C, the SO4 ion starts to rotate freely, leading to increased mobility of Na+ ion in the channel.

Studies on glass transition and starch re-crystallization in wheat bread during staling using electrical impedance spectroscopy

Bread staling is a very complex phenomenon that is not yet completely understood. The present work explains how the electrical impedance spectroscopy technique can be utilized to investigate the effect of staling on the physicochemical properties of wheat bread during storage. An instrument based on electrical impedance spectroscopy technique is developed to study the electrical properties of wheat bread both at its crumb and crust with the help of designed multi-channel ring electrodes. Electrical impedance behavior, mainly capacitance and resistance, of wheat bread at crust and crumb during storage (up to 120 h) is investigated. The variation in capacitance showed the glass transition phenomenon at room temperature in bread crust after 96 h of storage with 18% of moisture in it. The resistance changes at bread crumb showed the starch recrystallization during staling.

Identification of the nature of platinum related midgap state in silicon by deep level transient spectroscopy

In this article, we present the detailed investigations on platinum related midgap state corresponding to E-c -0.52 eV probed by deep level transient spectroscopy. By irradiating the platinum doped samples with high-energy (1.1 MeV) gamma rays, we observed that the concentration of the midgap state increases and follows a square dependence with irradiation dose. However, the concentration of the acceptor corresponding to E-c -20.28 eV remained constant. Furthermore, from the studies on passivation by atomic hydrogen and thermal reactivation, we noticed that the E-c -0.52 eV level reappears in the samples annealed at high temperatures after hydrogenation. The interaction of platinum with various defects and the qualitative arguments based on the law of mass action suggest that the platinum related midgap defect might possibly correspond to the interstitial platinum-divacancy complex (V-Pt-V).