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 1,693 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We demonstrate a simple one-step process for the synthesis of iron oxide nanoparticle aqueous colloids using the multifunctional molecule, dodecylamine (DDA), that electrostatically complexes with aqueous iron ions (one precursor Fe(2+) from FeCl(2)), reduces them, and subsequently caps the nanoparticles. The iron oxide particles thus synthesized are of the face-centered cubic (FCC) phase with high degree of monodispersity with appropriate concentration of amine capping molecular layer. The aqueous magnetic nanocrystalline colloids were characterized by TEM, XRD, XPS, TGA/DTA and FTIR spectroscopy techniques. The relaxivity, stability, and hydrodynamic size of the nanoparticles were investigated for potential application in magnetic resonance imaging (MRI). The magnetic properties were also studied by using a superconducting quantum interference device (SQUID) magnetometer at room temperature. We believe that such simple one-step synthesis of biocompatible aqueous nanomagnetic colloids will have viable applications in biomedical imaging, diagnostics and therapeutics.
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PMID:Synthesis of Amine-stabilized Aqueous Colloidal Iron Oxide Nanoparticles. 1930 47

Physicochemical properties viz., aggregation, molar mass, shape, and size of chicory inulin in solution were determined by fluorimetry, DLS, SLS, TEM, and viscometry methods. The thermal stability of the biopolymer was examined by TGA, DTA, and DSC measurements. The water vapor adsorption of desiccated inulin was also studied by the isopiestic method, and the data were analyzed in the light of the BET equation. On the basis of the obstruction to ion conductance by the inulin aggregates in solution and analysis of the data, the extent of hydration of inulin in solution was estimated. The result was coupled with the intrinsic viscosity, [eta], of inulin to ascertain the shape of the biopolymer aggregates in aqueous solution. The critical aggregation concentration (cac) of inulin in aqueous as well as in salt solution was assessed by fluorimetry. The weight average molar mass, Mw , of inulin monomer and its aggregate was found to be 4468 and 1.03 x 10(6) g/mol, respectively, in aqueous solution. This aggregated mass was 2.4 x 10(6) g/mol in 0.5M NH(4)SCN solution. The [eta] values of the soft supramolecular aggregates in solution (without and with salt) were small and comparable with globular proteins evidencing spherical geometry of the biopolymer aggregates as supported by the TEM results. In DMSO, rod-like aggregates of inulin was found by the TEM study. The [eta] of the biopolymer in the DMSO medium was therefore, higher than that in the aqueous medium. Unlike aqueous medium, the aggregation in DMSO was not associated with a cac.
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PMID:Physicochemical studies on the biopolymer inulin: a critical evaluation of its self-aggregation, aggregate-morphology, interaction with water, and thermal stability. 1935 42

The tetragonal BaTiO(3) nanopowder is synthesized in a solvent-less, efficient process by the thermolysis of a single [Ba(2)Ti(2)(thd)(4)(OnPr)(8)(nPrOH)(2)] precursor in a closed reactor at 700 degrees C under autogenous pressure, followed by combustion. This paper compiles the synthesis of the [Ba(2)Ti(2)(thd)(4)(OnPr)(8)(nPrOH)(2)] precursor, its analysis by mass spectrometry, and implementation for the fabrication of dielectric tetragonal BaTiO(3) nanopowder by controlled efficient thermal decomposition. The as-prepared, intermediate, and final forms of the obtained nanomaterials are systematically analysed by XRD, Raman, and EDS measurements to gain structural and compositional information. Employing HR-SEM, TEM, and HR-TEM techniques, the morphological changes during the structural evolution of all the phases are pursued. The mechanistic elucidation for the fabrication of BaTiO(3) nanopowder is developed on the basis of TGA and DTA data obtained for the initial [Ba(2)Ti(2)(thd)(4)(OnPr)(8)(nPrOH)(2)] reactant as well as the as-prepared BaCO(3) with amorphous Ti phase.
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PMID:Methodical thermolysis of [Ba2Ti2(thd)4(OnPr)8(nPrOH)2] under autogenous pressure followed by combustion for the synthesis of dielectric tetragonal BaTiO3 nanopowder. 1947 29

Nanoparticles of TiO2 were synthesized and characterized by XRD, BET, TG/DTA and TEM measurements. The commercial azo dye Reactive Red 195 (RR195) was selected as a model dye in order to examine the adsorption capacity of TiO2 at room temperature, under dark conditions. It was demonstrated that RR195 could be efficiently adsorbed in aqueous suspension of TiO2. A study on the effects of various parameters like initial pH, concentration of dye and concentration of adsorbent has been carried out in order to find optimum adsorption conditions. The optimum pH of sorption was 3. Substantial reduction of COD, besides removal of colour, was also achieved. The experimental data were analyzed by the Langmuir and Freundlich adsorption models. Equilibrium data fitted very well with the Langmuir model signifying the energetic homogeneity of TiO2 surface adsorption sites. At the temperature of 30 degrees C, the maximum monolayer adsorption capacity obtained from the Langmuir model is approximately 87 mg/g (pH 3.0). Kinetic studies were carried out and showed a rapid sorption of dye in the first 30 min while equilibrium was reached at 1h. Three kinetic adsorption models were used to describe the kinetics data, the pseudo-first-order model, the pseudo-second-order model and the intraparticle diffusion model. The sorption kinetics of dye was best described by the pseudo-second-order kinetic model.
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PMID:Removal of Reactive Red 195 from aqueous solutions by adsorption on the surface of TiO2 nanoparticles. 1954 Jun 70

We report here the synthesis of Ce(x)Zr(1-x)O(2) and (Ce(0.7)Zr(0.3)O(2))(x)(Al(2)O(3))(1-x) core-shell nanopowders in a single step by liquid-feed flame spray pyrolysis (LF-FSP) of the metalloorganic precursors, Ce(O(2)CCH(2)CH(3))(3)(OH), alumatrane [N(CH(2)CH(2)O)(3)Al], and Zr(O(2)CCH(2)CH(3))(2)(OH)(2). Solutions of all three precursors in ethanol with ceramic yields of 2.5 wt% were aerosolized with O(2), combusted at temperatures above 1500 degrees C, and rapidly quenched at approximately 1000 degrees C/ms to form Ce(x)Zr(1-x)O(2) and (Ce(0.7)Zr(0.3)O(2))(x)(Al(2)O(3))(1-x) nanopowders of selected compositions, at rates of 50-100 g/h. The resulting, as-processed, materials are unaggregated nanopowders with average particle sizes (APSs) < 20 nm and corresponding specific surface areas of 30-50 m(2)/g. The as-processed powders were characterized in terms of phase, particle size, specific surface area, compositions, and morphology by XRD, BET, DLS, SEM, TEM, XPS, TGA-DTA, and FT-IR. LF-FSP provides access to binary Ce(x)Zr(1-x)O(2) nanopowders and ternary (Ce(0.7)Zr(0.3)O(2))(x)(Al(2)O(3))(1-x) nanopowders in one step. The obtained Ce(0.7)Zr(0.3)O(2) powders are solid solutions with a cubic phase. In contrast, LF-FSP of mixtures of the three precursors at specific compositions [x = 0.5, 0.7 for (Ce(0.7)Zr(0.3)O(2))(x)@(Al(2)O(3))(1-x)] provide core-shell nanopowders in a single step. The most reasonable explanation is that there are differences in the rates of condensation, nucleation and miscibility between the gas phase ions that form the Ce(x)Zr(1-x)O(2) solid solutions and those that condense to delta-Al(2)O(3) during processing. These as-produced materials are without microporosity at surface areas of > or = 30 m(2)/g. Evidence is presented suggesting the formation of (Ce/Zr)(3+) species in the as-processed (Ce(0.7)Zr(0.3)O(2))(x)(Al(2)O(3))(1-x) core-shell materials. An accompanying paper indicates that these materials offer significant and novel catalytic activities for hydrocarbon oxidation and deNO(x) processes without using platinum as a co-catalyst.
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PMID:One-step synthesis of core-shell (Ce0.7Zr0.3O2)(x)(Al2O3)(1-x) [(Ce0.7Zr0.3O2)@Al2O3] nanopowders via liquid-feed flame spray pyrolysis (LF-FSP). 1956 96

ZrO(2) supported La(2)O(3) catalyst prepared by impregnation method was examined in the transesterification reaction of sunflower oil with methanol to produce biodiesel. It was found that the catalyst with 21 wt% loaded La(2)O(3) and calcined at 600 degrees C showed the optimum activity. The basic property of the catalyst was studied by CO(2)-TPD, and the results showed that the fatty acid methyl ester (FAME) yield was related to their basicity. The catalyst was also characterized by TG-DTA, XRD, FTIR, SEM and TEM, and the mechanism for the formation of basic sites was discussed. It was also found that the crystallite size of support ZrO(2) decreased by loading of La(2)O(3), and the model of the solid-state reaction on the surface of La(2)O(3)/ZrO(2) catalyst was proposed. Besides, the influence of various reaction variables on the conversion was investigated.
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PMID:Transesterification of sunflower oil to biodiesel on ZrO2 supported La2O3 catalyst. 1976 83

Pure and 0.25% Ni(2+) ion doped goethite samples, prepared by the coprecipitation method, were characterized for pH of Point of Zero Charge (pH(pzc)), Surface area, XRD, TG-DTA, FTIR and TEM. Effect of Ni(2+) ions doping on the adsorption of chromate on goethite was investigated at pH-3, -5 and -7 in the temperature range 303-323K. It was found that adsorption of chromate increases with decreasing pH and increasing temperature on both pure and Ni(2+)-doped goethite. Adsorption of chromate was found to increase from 61.4% to 82.92% with Ni(2+) ion doping in goethite matrix at the lowest pH (pH-3) and highest temperature (323K), using 1.02 mmol L(-1) chromate solution. Langmuir isotherm was found applicable to the experimental data. The values of Delta H (isosteric heat of adsorption) calculated for both the samples of goethite were positive, showing endothermic nature of the adsorption process.
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PMID:Effect of Ni2+ ion doping on the physical characteristics and chromate adsorption behavior of goethite. 1989 21

Alumina is the most frequently employed catalyst or catalytic support in the chemical industry. The catalytic performances of alumina-supported catalysts are largely dependent on the textural properties of the alumina supports. Therefore, any improvement of the alumina properties significant for their catalytic applications is extremely challenging. Ordered mesoporous aluminas with high thermal stability have been successfully prepared by a facile synthesis method. Using the ordered mesoporous aluminas as support, V/Ni-catalysts mesoporous materials also have been prepared by vacuum impregnation method and the coprecipitation method. The mesoporous structures are characterized by XRD, TEM, N2 adsorption -desorption and TG-DTA. Preliminary catalytic tests showed that the ordered mesoporous aluminas prepared in such a way exhibited superior performance in the oxidative dehydrogenation of propane to propylene when they were used as the supports for V and Ni catalysts.
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PMID:Synthesis, characterization and catalytic applications in propane dehydrogenation of ordered mesoporous alumina. 1990 92

Ta2O5 nanopowders to be used as sensing electrodes in high temperature electrochemical gas sensors for hydrocarbons detection were synthesized using a sol-gel method and their structural and microstructural properties were investigated. The as-synthesized powders were heated at different temperatures in the range 250-1000 degrees C and characterized by TG-DTA, XRD, SEM, TEM and FT-IR. This investigation allowed to identify the correct thermal treatments to achieve the microstructural, textural and functional stability of materials working at high temperature, preserving their nano-metric grain size. Planar sensors fabricated by using Ta2O5 powders treated at 750 degrees C showed promising results for the selective detection of propylene at high temperature (700 degrees C). The good stability of the sensing response after gas exposure at high temperature was correlated to the stable microstructure the electrodes. Thus, Ta2O5 powders seems good candidate as sensing electrode for sensors for automotive exhausts monitoring.
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PMID:Tailoring the structural and microstructural properties of nanosized tantalum oxide for high temperature electrochemical gas sensors. 1991 69

Y(2)O(3):Eu(3+) nano-powders were synthesized by homogeneous precipitation and the influence of solution acidity was investigated. IR and TG-DTA analysis showed that in different acidic solutions different kinds of sediments were generated. TEM images revealed distinct morphologies of obtained powders. The resultant powders were sintered into ceramics in vacuum and then in N(2) atmosphere without any additives. SEM images indicated that the morphologies of powders have significant impact on the microstructures of sintering-derived ceramics. Low-agglomerated and uniform powders were in favor of production of ceramics with homogeneous microstructures. Excitation and emission spectra of both powders and ceramics were measured and some changes were observed.
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PMID:Effect of acidity on microstructure and spectroscopic properties of Y2O3:Eu3+ powders and ceramics. 2000 9


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