Spray drying: An alternative synthesis method for polycationic oxide compounds

Synthesis of polycationic compounds by the spray-drying technique is an interesting alternative in the domain of aqueous precursor synthesis methods. Spray drying yields high quality samples with good reproducibility. The possibility of scaling up for production of large quantities with fast processing time is well established by the commercial availability of powders of various compositions. In this paper, we have discussed the advantages and limitations of this method and demonstrated its interest by synthesizing a few polycationic compounds selected for their attractive properties of thermoelectricity [Bi1.68Ca2Co1.69O 8, La0.95A0.05CoO3 (A=Ca, Sr, Ba)] or magnetoresistance [La0.70A0.30MnO3 (A=Sr, Ba)]. We have confirmed the quality of these samples by reporting their structure, magnetic and transport properties. © 2010 Elsevier Ltd All rights reserved.

Porous ZnAl2O4 spinel nanorods doped with Eu3+: synthesis and photoluminescence

Eu3+-doped zinc aluminate (ZnAl2O4) nanorods with a spinel structure were successfully synthesized via an annealing transformation of layered precursors obtained by a homogeneous coprecipitation method combined with surfactant assembly. These spinel nanorods, which consist of much finer nanofibres together with large quantities of irregular mesopores and which possess a large surface area of 93.2 m(2) g(-1) and a relatively narrow pore size distribution in the range of 6 - 20 nm, are an ideal optical host for Eu3+ luminescent centres. In this nanostructure, rather disordered surroundings induce the typical electric-dipole emission (D-5(0) --> F-7(2)) of Eu3+ to predominate and broaden.

Synthesis and random laser application of ZnO nano-walls: a review

This review paper summarises briefly some important achievements of our recent research on the synthesis and novel applications of nanostructure ZnO such as honeycomb shaped 3-D (dimension) nano random-walls. A chemical reaction/vapour transportation deposition technique was employed to fabricate this structure on ZnO/SiO2/Si substrate without any catalyst and additive in a simple tube furnace to aim the low-cost and high qualified samples. Random laser action with strong coherent feedback at the wavelength between 375 nm and 395 nm has been firstly observed under 355 nm optical excitation with threshold pumping intensity of 0.38 MW/cm(2).

Preparation of A-type zeolite membranes on nonporous metal supports by using electrophoretic technique

A-type zeolite membranes were prepared on the nonporous metal supports by using electrophoretic technique. The as-synthesized membranes were characterized by XRD and SEM. The effect of the applied potential on the formation of the A-type zeolite membrane was investigated, and the formation mechanism of zeolite membrane in the electric field was discussed. The results showed that the negative charged zeolite particles could migrate to the anode metal surface homogenously and rapidly under the action of the applied electric field, consequently formed uniform and dense membranes in short time. The applied potential had great effect on the membrane formation, and more uniform and denser zeolite membranes were prepared on the nonporous metal supports with 1 V potential.

Synthesis and surface characteristics of zirconia and modified zirconia: Performance of CO hydrogenation

ZrO2-A and ZrO2-B catalysts were prepared by two different coprecipitation methods and their performance of CO hydrogenation was studied. The results indicated that ZrO2 and Li-, Pd- and Mn-modified ZrO2 catalysts exhibited good selectivity and high STY to higher alcohols. The surface characteristics of ZrO2-A and ZrO2-B samples were investigated by means of BET, NH3-TPD, XRD and UV Raman technique. The tetragonal zirconia on the surface region of ZrO2-A and Li-Pd-Mn/ZrO2-A catalysts may be responsible for the high selectivity towards ethanol, while the monoclinic zirconia on the surface of ZrO2-B and Li-Pd-Mn/ZrO2-B catalysts may be crucial to the high isobutanol selectivity.

A general method for the rapid synthesis of hollow metallic or bimetallic nanoelectrocatalysts with urchinlike morphology

We have reported a facile and general method for the rapid synthesis of hollow nanostructures with urchinlike morphology. In-situ produced Ag nanoparticles can be used as sacrificial templates to rapidly synthesize diverse hollow urchinlike metallic or bimetallic (such as Au/Pt) nanostructures. It has been found that heating the solution at 100 degrees C during the galvanic replacement is very necessary for obtaining urchinlike nanostructures. Through changing the molar ratios of Ag to Pt, the wall thickness of hollow nanospheres can be easily controlled; through changing the diameter of Ag nanoparticles, the size of cavity of hollow nanospheres can be facilely controlled; through changing the morphologies of Ag nanostructures from nanoparticle to nanowire, hollow Pt nanotubes can be easily designed. This one-pot approach can be extended to synthesize other hollow nanospheres such as Pd, Pd/Pt, Au/Pd, and Au/Pt. The features of this technique are that it is facile, quick, economical, and versatile.

Synthesis of carbon nanofibers for mediatorless sensitive detection of NADH

Highly sensitive amperometric detection of dihydronicotinamide adenine dinucleotide (NADH) by using novel synthesized carbon nanofibers (CNFs) without addition of any mediator has been proposed. The CNFs were prepared by combination of electrospinning technique with thermal treatment method and were applied without any oxidation pretreatment to construct the electrochemical sensor. In amperometric detection of NADH, a linear range up to 11.45 mu M with a low detection limit of 20 nM was obtained with the CNF-modified carbon paste electrode (CNF-CPE).

Ionic liquid-based "all-in-one" synthesis and photoluminescence properties of lanthanide fluorides

A facile route to the synthesis of LnF(3) nanocrystals has been accomplished in three ionic liquids (ILs) (OmimPF(6), OmimBF(4), and BmimPF(6)). The partial hydrolysis of PF6- and BF4- was utilized to introduce a new fluoride source. Uniform LnF(3) (Ln = La, Ce, Pr, Nd, Sm, Eu, Er), Tb3+-doped CeF3, and Eu3+-doped LaF3 nanocrystals could be obtained in a large scale, and the products were up to 0.15 g per 10 mL solvents. In the "all-in-one" systems, the ILs acted as solvents, reaction agents, and templates.

Self-assembled 3D Architectures of LuBO3 : Eu3+: Phase-selective synthesis, growth mechanism, and tunable luminescent properties

Rhombohedral-calcite and hexagonal-vaterite types of LuBO:Eu3+ microparticles with various complex self-assembled 3D architectures have been prepared selectively by an efficient surfactant- and template-free hydrothermal process for the first time. X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectrometry, transmission electron microscopy, high-resolution transmission electron microscopy, selected area electron diffraction, photoluminescence, and cathodoluminescence spectra as well as kinetic decays were used to characterize the samples.

Ionic liquid-based "all-in-one" synthesis and photoluminescence properties of lanthanide fluorides

A facile route to the synthesis of LnF(3) nanocrystals has been accomplished in three ionic liquids (ILs) (OmimPF(6), OmimBF(4), and BmimPF(6)). The partial hydrolysis of PF6- and BF4- was utilized to introduce a new fluoride source. Uniform LnF(3) (Ln = La, Ce, Pr, Nd, Sm, Eu, Er), Tb3+-doped CeF3, and Eu3+-doped LaF3 nanocrystals could be obtained in a large scale, and the products were up to 0.15 g per 10 mL solvents. In the "all-in-one" systems, the ILs acted as solvents, reaction agents, and templates.

Synthesis of N-Methylimidazolium Functionalized Strongly Basic Anion Exchange Resins for Adsorption of Cr(VI)

N-Methylimidazolium functionalized strongly basic anion exchange resins in the Cl- form (RCI) and SO46- form (R2SO4) were synthesized and employed for adsorption of Cr(VI) from aqueous solution. FT-IR and elementary analysis proved the structures of anion exchange resins and the content of functional groups. The gel-type strongly basic anion exchange resins had high thermal stability according to TGA and good chemical stability under the experimental conditions. The adsorption behaviors of Cr(VI) on RCI and R2SO4 were studied using the batch technique. It was shown that adsorption equilibrium was reached rapidly within 60 min. The adsorption data for RCI and R2SO4 were consistent with the Langmuir isotherm equation.

Prussian Blue/Multiwalled Carbon Nanotube Hybrids: Synthesis, Assembly and Electrochemical Behavior

Prussian blue/carbon nanotube (PB/CNT) hybrids with excellent dispersibility in aqueous solutions were synthesized by adding CNTs to an acidic solution of Fe3+, [Fe(CN)(6)](3-) and KCl. Fourier transform infrared spectroscopy, UV-vis absorption spectroscopy and scanning electron microscopy were employed to confirm the formation of PB/CNT hybrids. The PB nanoparticles formed on the CNT surfaces exhibit a narrow size distribution and an average size of 40 nm. The present results demonstrate that the selective reduction of Fe3+ to Fe2+ by CNTs is the key step for PB/CNT hybrid formation. The subsequent fabrication of the PB/CNT hybrid films was achieved by layer-by-layer technique. The thus-prepared PB/CNT hybrid films exhibit electrocatalytic activity towards H2O2 reduction.

Design of polymeric stabilizers for size-controlled synthesis of monodisperse gold nanoparticles in water

A new methodology is described for the one-step aqueous preparation of highly monodisperse gold nanoparticles with diameters below 5 nm using thioether- and thiol-functionalized polymer ligands. The particle size and size distribution was controlled by subtle variation of the polymer structure. It was shown that poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA) were the most effective stabilizing polymers in the group studied and that relatively low molar mass ligands (similar to 2500 g/mol) gave rise to the narrowest particle size distributions. Particle uniformity and colloidal stability to changes in ionic strength and pH were strongly affected by the hydrophobicity of the ligand end group. "Multidentate" thiol-terminated ligands were produced by employing dithiols and tetrathiols as chain-transfer agents, and these ligands gave rise to particles with unprecedented control over particle size and enhanced colloidal stability. It was found throughout that dynamic light scattering (DLS) is a very useful corroboratory technique for characterization of these gold nanoparticles in addition to optical spectroscopy and TEM.

Synthesis, structure and photochromic properties of a novel 1,6-hexanediamine trimolybdate supramolecular compound

A novel supramolecular compound 1,6-hexanediamine trimolybdate ((C6H18N2[Mo3O10], denoted as HDAMo) has been synthesized by a hydrothermal method and its structure has been characterized by elemental analyses, Fourier transform infrared (FT-IR) spectra, single-crystal X-ray diffraction (XRD) technique. This single crystal compound consists of protonated 1,6-hexanediamine (HDA) cations and polyoxometalate [Mo3O10](2-) anions. Its crystal structure belongs to monoclinic system (space group P2(1)/n) with a = 7.7508(14), b = 11.467(2), c = 16.167(3) angstrom, beta = 92.689(3)degrees, V = 143 5.3(5) angstrom(3), Z = 4 and D-ealc = 2.619 g cm(-3). The final statistics based on F-2 are GOF = 0.980, R-1 = 0.0261 and wR(2) = 0.0506 for I > 2 sigma(I). XRD analysis revealed that in the crystal structure of HDAMo, novel infinite [Mo3O10](2-) chains parallel to a axis are made up of distorted MoO6 octahedra connected by corners and edges. The protonated HDA cations occupy channels formed by [Mo(3)O3(10)](2-) Chains and exhibit strong hydrogen bond interactions to terminal and bridging oxo groups of the chains. The [Mo3O10](2-) chains linked through protonated HAD cations formed a one-dimensional network. The HDAMo compound shows novel photochromic properties, i.e., its color changes from white to reddish brown gradually under UV irradiation. XRD, FT-IR, ESR spectra and XPS are used to investigate the photochromic behavior of the compound.

Synthesis and properties of a novel isomeric polyimide/SiO2 hybrid material

A novel isomeric polyimide/SiO2 hybrid material was successfully prepared through sol-gel technique, and its structure, thermal properties and nano-indenter properties were investigated. First, 3-[(4-phenylethynyl)phthalimide]propyl triethoxysilane (PEIPTES) was successfully synthesized, its structure was characterized by elemental analysis, FT-IR and C-13 NMR. The researches on solubility and thermal properties of PEIPTES show that it can be used for modifying nano-SiO2 precursor. Nano-SiO2 precursor was synthesized by tetraethoxysilane (TECS) through sol-gel technique. Then the PEIPTES solution and the nano-SiO2 precursor were mixed for 6 h to let the PEIPTES molecules react with the nano-SiO2 precursor, and modified nano-SiO2 precursor was obtained. The modified reaction was confirmed by the analyses of FT-IR. At last, isomeric polyimide/SiO2 hybrid material was produced by using isomeric polyimide resin solution and the modified nano-SiO2 precursor after heat treatment process. The structure analysis by SEM indicated that SiO2 particles dispersed in isomeric polyimide matrix homogeneously with nanoscale. Thermogravimetric analyzer, dynamic mechanical thermal analyzer and nano-indenter XP was employed to detect the properties of the materials, the results demonstrated that isomeric polyimide/SiO2 hybrid material has much better thermal properties and nano-indenter properties than those of isomeric polyimide.