Synthesis and electron microscopy of high entropy alloy nanoparticles

This work provides a methodology for synthesizing isolated multi-component, high entropy alloy nanoparticles. Wet chemical synthesis technique was used to synthesis NiFeCrCuCo nanoparticles. As synthesized nanoparticles were spherical with an average size of 26.7 +/- 3.3 nm. Average composition of the as-synthesized nanoparticle dispersion was 26 +/- 2 at% Cr, 14 +/- 2 at% Fe, 10 +/- 0.6 at% Co, 25 +/- 0.1 at% Ni and 25 +/- 1.1 at% Cu. Compositional analysis of the nanoparticles conducted using the compositional line profile analysis and compositional mapping on a single nanoparticle level revealed a fairly uniform distribution of all the five component elements within the nanoparticle volume. Electron diffraction analysis clearly revealed that the structure of as-synthesized nanoparticles was face centered cubic. (C) 2015 Elsevier B.V. All rights reserved.

Synthesis of Hollow Nanotubes of Zn2SiO4 or SiO2: Mechanistic Understanding and Uranium Adsorption Behavior

We report a facile synthesis of Zn2SiO4 nanotubes using a two-step process consisting of a wet-chemical synthesis of core-shell ZnO@SiO2 nanorods followed by thermal annealing. While annealing in air leads to the formation of hollow Zn2SiO4, annealing under reducing atmosphere leads to the formation of SiO2 nanotubes. We rationalize the formation of the silicate phase at temperatures much lower than the temperatures reported in the literature based on the porous nature of the silica shell on the ZnO nanorods. We present results from in situ transmission electron microscopy experiments to clearly show void nucleation at the interface between ZnO and the silica shell and the growth of the silicate phase by the Kirkendall effect. The porous nature of the silica shell is also responsible for the etching of the ZnO leading to the formation of silica nanotubes under reducing conditions. Both the hollow silica and silicate nanotubes exhibit good uranium sorption at different ranges of pH making them possible candidates for nuclear waste management.

Solution combustion synthesis, structure and luminescence of Y3Al5O12 : Tb3+ phosphors

The synthesis and optical properties of Y3Al5O12:Tb3+ phosphors are reported in this paper. Y3Al5O12:Tb3+ phosphors were synthesized by a facile solution combustion method. Citric acid traps the constituent cations and also acts as a fuel. Y3Al5O12 (YAG) phase can crystallize through sintering at 900 degrees C for 2 h, and there were no intermediate phases such as YAlO3 (YAP) and Y4Al2O9 (YAM) in the sintering process. The excitation spectra of crystalline Y3Al5O12:Tb3+ are different from that of amorphous one due to the crystal field effect. The emission spectra mainly show D-5(4) -> F-7(6) transition under UV excitation. The higher concentration quenching in Y3Al5O12:Tb3+ nanophosphors may be due to the confinement effect on resonant energy transfer of nanocrystalline. It is also indicated that the solution combustion synthesis method provides a good distribution of Tb3+ activators in Y3Al5O12 host. (c) 2005 Published by Elsevier B.V.

Demonstration of GaN/InGaN light emitting diodes on (100) beta-Ga2O3 substrates by metalorganic chemical vapour deposition

The growth and fabrication of GaN/InGaN multiple quantum well (MQW) light emitting diodes ( LEDs) on ( 100) beta-Ga2O3 single crystal substrates by metal-organic chemical vapour deposition (MOCVD) technique are reported. x-ray diffraction (XRD) theta-2 theta. scan spectroscopy is carried out on the GaN buffer layer grown on a ( 100) beta-Ga2O3 substrate. The spectrum presents several sharp peaks corresponding to the ( 100) beta-Ga2O3 and ( 004) GaN. High-quality ( 0002) GaN material is obtained. The emission characteristics of the GaN/InGaN MQW LED are measurement. The first green LED on beta-Ga2O3 with vertical current injection is demonstrated.

Efficient synthesis and utilization of phenyl-substituted heteroaromatic carboxylic acids as aryl diketo acid isosteres in the design of novel HIV-1 integrase inhibitors

Three new types of aryl diketo acid (ADK) isosteres were designed by conversion of the biologically labile 1,3-diketo unit into heteroaromatic motif such as isoxazole, isothiazole, or 1H-pyrazole to improve the physicochemical property of ADK-based HIV-1

Local synthesis and alignment of zinc oxide nanowires in aqueous solution using microheaters

A bottom-up technique for synthesizing transversely suspended zinc oxide nanowires (ZnO NWs) under a zinc nitrate (Zn(NO 3) 2· 6H 2O) and hexamethylenetetramine (HMTA, (CH 2) 6·N 4) solution within a microfabricated device is reported in this paper. The device consists of a microheater which is used to initially create an oxidized ZnO seed layer. ZnO NWs are then locally synthesized by the microheater and electrodes embedded within the devices are used to drive electric field directed horizontal alignment of the nanowires within the device. The entire process is carried out at low temperature. This approach has the potential to considerably simplify the fabrication and assembly of ZnO nanowires on CMOS compatible substrates, allowing for the chemical synthesis to be carried out under near-ambient conditions by locally defining the conditions for nanowire growth on a silicon reactor chip. © 2012 IEEE.

One-pot synthesis of silver nanoplates and charge-transfer complex nanofibers

We describe a facile one-pot process to synthesize Ag nanoplates by reducing silver nitrate with 3,3',5,5'-tetramethylbenzidine (TMB) at room temperature. The silver nanoplates were highly oriented single crystals with (111) planes as the basal planes. TMB can be readily oxidized to charge-transfer (CT) complex between TMB, as a donor, and (TMB)(2+), as an acceptor. The pi-pi interaction of the neutral amine (TMB) and diiminium structure (dication, TMB2+) result in the formation of one-dimensional CT complex nanofiber.

Hydrothermal synthesis of SrCO3 : Eu3+/Tb3+ microneedles and their luminescence properties

SrCO3:Eu3+ /Tb3+ microneedles that grow along the a-axis were successfully prepared through a large-scale and facile hydrothermal method without any template and further annealing treatment. X-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL) spectra as well kinetic decays, were used to characterize the samples. The preferential growth along a-axis for SrCO3:Eu3+/Tb3+ microneedles has been proposed through analysis of the XRD patterns of samples obtained at different hydrothermal treatment time. Under ultraviolet excitation, the SrCO3:Eu3+ and SrCO3:Tb3+ microncedle samples show a strong red and green emission corresponding to the D-5(0)-F-7(j) (J = 1, 2, 3, 4) transitions of Eu3+ and the D-5(4)-(7) F-j (J = 6, 5, 4, 3) transitions of Tb3+, respectively, which have potential applications in lighting fields.

Glycyl glycine templating synthesis of single-crystal silver nanoplates

We describe the small-biomolecule ( glycyl glycine)-directed synthesis of single-crystalline silver nanoplates, and different experimental conditions have been explored for a more thorough understanding of the growth mechanism. The yield of silver nanoplates relative to the total number of nanoparticles formed was as high as similar to 80%. It was found that the ratio of glycyl glycine to AgNO3 was the key to forming Ag nanoplates.

Synthesis of highly faceted multiply twinned gold nanocrystals stabilized by polyoxometalates

A novel and facile chemical synthesis of highly faceted multiply twinned gold nanocrystals is reported. The gold nanocrystals are hexagonal in transmission electron microscopy and icosahedral in scanning electron microscopy. Phosphotungstic acid (PTA), which was previously reduced, serves as a reductant and stabilizer for the synthesis of gold nanocrystals. The PTA-gold nanocomposites are quite stable in aqueous solutions, and electrochemically active towards the hydrogen evolution reaction.

Rapid synthesis of cubic Pt nanoparticies and their use for the preparation of Pt nanoagglomerates

We report the synthesis of hexadecyltrimethylammonium bromide (CTAB)-stabilized cubic Pt nanoparticles by NaBH4 reduction of H2PtCl6 in aqueous CTAB solution. These Pt nanoparticles (average size of 7 nm) were well dispersed in aqueous solution and stable at least for 2 months. Addition of a trace amount of AgNO3 can alter the morphology of these Pt nanoparticles. More interestingly, the as-prepared uniform Pt nanoparticles were further developed into bigger Pt nanoagglomerates (similar to 20 to 47 nm) by a seed-mediate growth process. Dentritic and spherical Pt nanoagglomerates can be synthesized by altering the incubation time and their size can be tuned by controlling the amount of the seeds added.

Chemical Constituents of a Marine-Derived Endophytic Fungus Penicillium commune G2M

Cultivation of the endophytic fungus Penicillium commune, which was isolated from the semi-mangrove plant Hibiscus tiliaceus, afforded one new compound 1-O-(2,4-dihydroxy-6-methylbenzoyl)-glycerol (1) along with thirteen known products, including 1-O-acetylglycerol (2), N-acetyltryptophan (3), 3-indolylacetic acid methyl ester (4), 1-(2,4-dihydroxy-3,5-dimethylphenyl)ethanone (5), 2-(2,5-dihydroxyphenyl)acetic acid (6), (4R,5S)-5-hydroxyhexan-4-olide (7), thymidine (8), uracil (9), thymine (10), ergosterol (11), beta-sitosterol (12), beta-daucosterol (13), and ergosta-7,22-dien-3 beta,5 alpha,6 beta-triol (14). The structures of these compounds were established by detailed NMR spectroscopic analysis, as well as by comparison with literature data or with authentic samples.

Influence of methanol on retention of hydrophobic organic chemicals in soil leaching column chromatography

The influence of methanol in methanol-water mixed eluents on the capacity factor (P), an important parameter which could depict leaching potential of hydrophobic organic chemicals (HOCs) in soil leaching column chromatography (SLCC), was investigated. Two reference soils, GSE 17201 obtained from Bayer Landwirtschaftszentrum, Monheim, Germany and SP 14696 from LUFA, Spencer, Germany, were used as packing materials in soil columns, and isocratic elution with methanol-water mixtures at different volume fractions of methanol (phi) were tested. Shortterm exposure of the column (packed with the GSE 17201 soil) to the eluents increased solute retention by a certain (23% log-unit) degree evaluated through a correlation with the retention on the same soil column but unpreconditioned by methanol-containing eluents. Long-term exposure of soil columns to the eluents did not influence the solute retention. A log-linear equation, log k' = log k'(w) - Sphi, could well and generally describe the retention of HOCs in SLCC. For the compounds of homologous series, logk'(w), had good linear relationship with S, indicating the hydrophobic partition mechanism existing in the retention process. (C) 2002 Elsevier Science Ltd. All rights reserved.

Synthesis and characterization of ZrO2 : Eu nanopowder by EDTA complexing sol-gel method

Nanocrystalline ZrO2:Eu was synthesized by complexing sol-gel method. The effects of heat treatment on structure, grain size and luminescence properties of ZrO2:Eu were studied with X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and photoluminescence measurements. The dependence between the fluorescence emission and the crystalline structure is discussed. (c) 2004 Elsevier B.V. All rights reserved.

A novel approach to Co/CNTs catalyst via chemical vapor deposition of organometallic compounds

A novel approach for attaching well-dispersed cobalt nanoparticles homogeneously onto carbon nanotubes via metal organic chemical vapor deposition technique is reported. The obtained Co/CNTs catalysts feature a narrow size distribution of Co particles centering around 7.5 nm, and show high activity and regioselectivity for hydroformylation of 1-octene.