Calcination Effect on the Photoluminescence,Optical, Structural,and Magnetic Properties of Polyvinyl Alcohol Doped ZnFe2O4 Nanoparticles

Abstract

Spinel ferrite based nanoparticle material has been at the forefront of contemporary nanotechnology for use in various industrial and biomedical applications. The preparation and characterization of zinc ferrite nanoparticles (ZFNPs) doped with polyvinyl alcohol (PVA) are reported in this work. The formulated ZFNP/PVAs were characterized using powder X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-visible spectroscopy, photoluminescence (PL) and a vibrating sample magnetometer (VSM). The XRD established the cubic spinel crystal structure of the as-prepared and calcined sample with an increase in the crystallite size after the calcination. The SEM analysis showed a spherical morphology within the range of 10-40?nm after calcination. The bandgap energy was enhanced after calcination. The PL analysis revealed a prominent peak in the UV band, which showed the characteristics of the formulated nanostructure. Transformation to a superparamagnetic nature was observed after calcination. It is noteworthy that after calcination of the formulated ZFNP/PVAs, the structural, optical, bandgap energy, morphology, photoluminescence and the magnetic properties were influenced and enhanced for various applications, chiefly for hyperthermia, magnetic resonance imaging, drug delivery and allied disciplines.     

Influence of varying molar concentration on the properties of electrochemically-deposited zirconium-doped ZnSe thin films

The effects of molar concentration on ZnSe and Zr-doped ZnSe thin films were studied after successful synthesis by electrochemical technique. 0.1 M zinc tetraoxosulphate (VI) heptahydrate (ZnSO₄·7H₂O) and 0.1 M selenium powder respectively served as the cationic and anionic precursors while 0.1 mol% of zirconium oxidchlorid (ZrOCl₂·8H₂O) was used as the dopant. The morphology, structure, elemental, light response, and electrical features of the samples were studied. The films exhibited uniform distribution of spherical balls with crystalline peaks at (220), (221), (300), and (310) planes. The elemental composition of the film confirmed the deposition of as-synthesized elements. Improved optical characteristics and reduced band gap energies of the films from 2.4 eV to 2.0 eV were gotten upon the addition of zirconium. Electrical results showed increased material conductivity at increasing dopant percentages. The synthesized materials are potentially applied in optoelectronics and photovoltaics.     

The structure of wholly aromatic polyesters with bulky side chains: Poly(phenylene phenyl-terephthalate)

Abstract

The thermotropic polyester prepared from phenyl-terephthalic acid and hydro-quinone is highly crystalline, despite the probable random 2-and 3-disposition of the phenyl substituents. The x-ray pattern of melt-spun fibers contains 18 Bragg reflections that are indexed by a monoclinic unit cell with dimensions a = 28.0 Å. b = 4.89 Å, c = 12.48 Å (fiber axis), and γ = 114.8°, containing monomer units of four chains. In the ac-plane, the chains are arranged in pairs with the phenyl side chains interdigitated; successive pairs of chains are staggered by about c/2. We have used molecular mechanics modeling to simulate arrays of chains with random 2-and 3-disposition of the side chains on the terephthalic acid units and have compared the results with those for a similar structure in which all the substituents were at the 2-position. The refined model for random substitution is distorted, but the average separations of the monomer units are within experimental error of the observed unit cell dimensions, and their standard deviations are very similar to those derived from the line-broadening data. The potential energy of the random substitution model is only about 1 kcal/mol of monomer higher than that for the model with all 2-substitution, indicating the random substitution is not a problem for the formation of an ordered structure.     

乳液催化剂存在下空气辅助甲酸氧化法使油品脱硫(英文)

Catalytic oxidative desulfurization(ODS) of model oil and commercial oil samples was investigated using an air-assisted performic acid oxidation system with a phase transfer or emulsion catalyst comprising a quaternary ammonium salt-based heteropolyoxometalate.Different emulsion catalysts with a Keggin type heteroployoxometalate anion(containing W,Mo,and V) and cetyltrimethylammonium bromide cation were prepared and characterized by X-ray fluorescence,Fourier transform infrared spectroscopy,and scanning electron microscopy.[C16H33N(CH3)3]3[PW9Mo3O40] was the most effective catalyst in the current oxidation system,which reduced the sulfur content of the model oil from 1275 μg/g to 57 μg/g.The reactivity order of different model sulfur compounds was thiophene < dibenzothiophene < 4,6-dimethyldibenzothiophene. The ODS of model sulfur compounds followed first order kinetics with apparent activation energy from 29 to 27 kJ/mol.The catalysts also performed efficiently in the ODS of the industrial oil samples,including untreated naphtha,light gas oil,heavy gas oil,and Athabasca oil sands derived bitumen,for which sulfur removal rates were 83%,85%,68% and 64%,respectively.     

Constructing carbon nanotube junctions by Ar ion beam irradiation

Carbon nanotubes (CNTs) irradiated by Ar ion beams at elevated temperature were studied. The irradiation-induced defects in CNTs are greatly reduced by elevated temperature. Moreover, the two types of CNT junctions, the crossing junction and the parallel junction, were formed. And the CNT networks may be fabricated by the two types of CNT junctions. The formation process and the corresponding mechanism of CNT networks are discussed.     

Electrochemical and spectroscopic characterization of organic compound uptake in silica core-shell nanocapsules

Oil-filled silica nanocapsules consisting of a hydrophobic liquid core and a silicate shell have been shown to efficiently extract hydrophobic compounds from aqueous media. With a view toward quantifying the selectivity of these systems, a series of electrochemical and spectroscopic measurements was performed. Uptake and kinetics experiments were carried out through electrochemical measurements by using solutions of lipophilic electroactive molecules of different sizes and with different affinities for silica. Other solutions with fluorescent probes were used for spectrophotometry measurements. In this work we report the environment where the lipophilic compounds studied end up after absorption and the kinetics of their uptake by the oil-filled silica nanocapsules with different shell thicknesses.     

Influence of clay modification on the properties of aramid-layered silicate nanocomposites

Nanocomposites from organoclay and aromatic polyamide were prepared using solution intercalation method. Aramid chains were synthesised by reacting 4-aminophenylsulfone with isophthaloyl chloride in dimethylacetamide. Dodecylamine was used as a modifier to change the hydrophilic nature of montmorillonite into organophilic. Suitable quantities of organoclay were mixed in the aramid solution with high-speed stirring for homogeneous dispersion of the clay. Thin films cast from these materials after evaporating the solvent were characterised. The morphology of nanocomposites was determined by X-ray diffraction and TEM. Results revealed the formation of delaminated and disordered intercalated clay platelets in the aramid matrix. Mechanical data indicated improvement in the tensile strength and modulus with clay loading up to 6 wt.%. The glass transition temperature increased up to 20 wt.% organoclay, suggesting better cohesion between the two phases and thermal stability augmented with increasing clay loading. The water uptake reduced gradually as a function of organoclay showing decreased permeability.     

Effect of surface modification of montmorillonite on the properties of aromatic polyamide/clay nanocomposites

The surface modification of montmorillonite clay was carried out through ion‐ exchange reaction using p‐phenylenediamine as a modifier. This modified clay was employed to prepare aromatic polyamide/organoclay nanocomposite materials. The dispersion behavior of clay was examined in the polyamide matrix. Polyamide chains were synthesized from 4‐aminophenyl sulfone and isophthaloyl chloride (IPC) in dimethylacetamide. These amide chains were suitably end‐capped with carbonyl chloride end groups to interact chemically with modified montmorillonite clay. The resulting nanocomposite films containing 2–20 wt% of organoclay were characterized by TEM, X‐ray diffraction (XRD), thin‐film tensile testing; thermogravimetric analysis (TGA), differential scanning calorimetric (DSC) and water absorption measurements. Mechanical testing revealed that modulus and strength improved up to 6 wt% organoclay loading while elongation and toughness of nanocomposites decreased with the addition of clay content in the matrix. Thermal decomposition temperatures of the nanocomposites were in the range 225–450 °C. These nanocomposites expressed increase in the glass‐transition temperature values relative to pure polyamide describing interfacial interactions among the phases. The percent water uptake of these composites reduced upon the addition of modified layered silicate depicting improved barrier properties. Copyright © 2008 John Wiley & Sons, Ltd.