Templated synthesis and catalytic properties of an Rh/ceria-zirconia catalyst

Ceria-zirconia nanophase with structural defects and high thermal stability was synthesized by a surfactant-templated method. The 0.5 wt.% Rh/ceria-zirconia catalyst shows high activity for NO reduction by CO under an oxygen-rich condition, and the selectivity to 100% N₂ below 200°C was achieved.     

Flame propagation over liquid alcohols

The different spreading regimes above liquid fuels have been experimentally characterized for surface temperatures close to the flash-point temperature. Two different spreading regimes are observed: for temperatures larger than some critical value, flame spreading velocity is well described by the De Ris solid fuel-like model. For temperature values lower than the critical one, a preheating thermocapillary region has been observed in the fuel, which can be described by a purely thermodynamic non-reactive model. The critical transition temperature has shown to present common characteristics for the four alcohols used in the experiments.     

Flame propagation over liquid alcohols

Summary The different spreading regimes above liquid fuels have been experimentally described for a wide range of initial surface temperatures. Five different spreading regimes are observed. The flame spreading driving parameter has been found. The critical transition temperatures between these regimes have been characterized; they present common characteristics for the four alcohols (methanol, ethanol, propanol and butanol) used in the experiments. A preheating zone ahead of the flame (produced by thermocapillarity) has been observed. The initial surface temperature of the liquid fuel results to be a control parameter of flame spreading; therefore, it can be applied to improve fire safety conditions in fuel containers.     

Bacterial aerobic synthesis of nanocrystalline magnetite

The synthesis of iron oxide nanoparticles of the predominantly magnetite phase by the reaction of aqueous iron complexes with the bacterium, Actinobacter spp., is described. This reaction occurs at room temperature and under aerobic conditions, resulting in the formation of superparamagnetic magnetite.     

Detection of carrier information in heterojunctions of nanocrystalline/crystalline Si

Hall effect measurements on heterojunctions of nanocrystalline Si:H (nc-Si:H) film with crystalline Si wafer fabricated by plasma enhanced chemical vapor deposition technique were made as a function of temperature (20–300 K) and magnetic field (0–15 T). Magnetic field-dependent resistivity and Hall data were interpreted with the quantitative mobility spectrum analysis (QMSA) method, which successfully separated the two-dimensional electron gases (2DEGs) at the nc-Si:H/c-Si interface from 3D carriers appearing in the films and substrates. Mobilities and densities of 2DEGs for the specimens were measured. Detail analyses about influences of interface and epitaxial layer quality including doping, film thickness and mean size of nanocrystals on the mobilities and densities of 2DEGs at interfaces were carried out. The important role of the amorphous buffer layer within the junction was identified. Origin of high mobility observed in the prepared films was revealed. Forward and reverse current mechanisms as well as the dependence of breakdown voltages on temperature in the operated nc-Si:H/c-Si heterostructure were elucidated.     

Urease-mediated room-temperature synthesis of nanocrystalline titanium dioxide

Enzymes are an important class of biological molecules whose specific functionalities can be exploited to perform tasks beyond the reach of conventional chemistry. Because they are operational under environmentally friendly, ambient conditions, the adaptation of these biomacromolecules can potentially be used to replace current energy-intensive and environmentally harsh synthesis methods for materials. Here we used a hydrolytic enzyme, urease, to modify the solution environment around a water-soluble and stable TiO(2) precursor to synthesize nanocrystalline titanium dioxide under environmentally benign conditions. This urease-mediated synthesis yields nearly monodisperse TiO(2) nanostructures with high surface area that can be utilized for numerous energy-based applications such as low-cost photovoltaics and photocatalysts.     

Flame synthesis of calcium carbonate nanoparticles

Calcium carbonate nanoparticles of 20-50 nm size were obtained from a flame spray process where combustion of specific calcium-containing precursors results in amorphous or crystalline calcium carbonate particles depending on the spray flow conditions.     

High yield method for nanocrystalline zeolite synthesis

Nanocrystalline zeolites, such as silicalite-1 and zeolite Y, were synthesized in high yield by periodically removing nanocrystals from the synthesis solution and recycling the unused reagents, including the template and T-atom sources.     

Cell penetrable peptoid carrier vehicles: synthesis and evaluation

Using a highly efficient solid-phase route a series of fluorescein conjugated peptoid oligomers were synthesised and observed to display remarkable cell penetrating properties, offering the possibility of highly efficient cellular targeting.     

Combustion synthesis and properties of nanocrystalline zirconium oxide

Nanocrystalline tetragonal zirconia powders have been synthesized by aqueous combustion using glycine (Gly) as a fuel and zirconyl nitrate (ZN) as an oxidizer. The effect of the fuel-to-oxidant molar ratio on the structural and morphological properties of nanocrystalline zirconia powders was studied. Thermodynamic modeling of the combustion reaction showed that the increase in the Gly:ZN molar ratio leads to the increase in theoretical combustion temperature, heat of combustion and amount of produced gases. Powder properties were correlated with the nature of combustion and results of thermodynamic modelling. The increase in the Gly:ZN molar ratio produces more agglomerated powders characterized by a lower degree of uniformity, a lower specific surface area and a slightly bigger crystallite size. On the other hand, the presence of hard agglomerates suppresses the volume expansion, stabilizing tetragonal zirconia, as confirmed by Rietveld refinement. The absence of cubic zirconia was confirmed by FTIR and Raman Spectroscopy. The increase in the calcination temperature led to more agglomerated, compact and less uniform powders. The nanocrystalline nature of zirconia is the reason for the formation of bigger crystallites, the increase in the relative amount of monoclinic phase and sample sintering after calcination at high temperature. The highest measured specific surface area of zirconia was 45.8 m²·g⁻¹, obtained using a fuel-lean precursor.     

Electrodeposition of nanocrystalline aluminium from a chloroaluminate ionic liquid

In this letter we show that nanocrystalline aluminium can be electrodeposited in the Lewis acidic ionic liquid based on AlCl₃ (60 mol%) and 1-(2-methoxyethyl)-3-methylimidazolium chloride ([MoeMIm]Cl) (40 mol%). The study comprised cyclic voltammetry, potentiostatic polarization, and SEM and XRD measurements. The methoxy group in the side chain of the imidazolium cation significantly influences the electrodeposition pathway of Al in comparison to [EMIm]Cl/AlCl₃. Cyclic voltammetry shows a significant current loop attributed to nucleation. Shiny Al layers are obtained with an average crystallite size of about 40 nm.     

Combustion synthesis and characterization of nanocrystalline WO3

The energy payback time associated with the semiconductor active material is an important parameter in a photovoltaic solar cell device. Thus lowering the energy requirements for the semiconductor synthesis step or making it more energy-efficient is critical toward making the overall device economics more competitive relative to other nonpolluting energy options. In this communication, combustion synthesis is demonstrated to be a versatile and energy-efficient method for preparing inorganic oxide semiconductors such as tungsten trioxide (WO3) for photovoltaic or photocatalytic solar energy conversion. The energy efficiency of combustion synthesis accrues from the fact that high process temperatures are self-sustained by the exothermicity of the combustion process, and the only external thermal energy input needed is for dehydration of the fuel/oxidizer precursor mixture and bringing it to ignition. Importantly, we show that, in this approach, it is also possible to tune the optical characteristics of the oxide semiconductor (i.e., shift its response toward the visible range of the electromagnetic spectrum) in situ by doping the host semiconductor during the formative stage itself. As a bonus, the resultant material shows enhanced surface properties such as markedly improved organic dye uptake relative to benchmark samples obtained from commercial sources. Finally, this synthesis approach requires only very simple equipment, a feature that it shares with other "mild" inorganic semiconductor synthesis routes such as sol-gel chemistry, chemical bath deposition, and electrodeposition. The present study constitutes the first use of combustion synthesis for preparing WO3 powder comprising nanosized particles.     

The effect of manganese on the structural and surface properties of nanocrystalline cobalt catalyst for ammonia synthesis

Based on the active surface model of the iron catalyst for ammonia synthesis, the assumptions which led to obtaining the cobalt catalyst for ammonia synthesis were described. The incorporation into the system small amounts of manganese, an element which binds oxygen stronger than cobalt, has influence the development of the catalyst’s specific surface area. The activity of manganese modified catalysts is higher than that of cobalt catalyst without manganese addition. The obtained catalysts were characterized with the following methods: ICP-OES, XRD, BET      

Interfacial rheology of an ultrathin nanocrystalline film formed at the liquid/liquid interface

We report the interfacial properties of monolayers of Ag nanoparticles 10-50 nm in diameter formed at the toluene-water interface under steady as well as oscillatory shear. Strain amplitude sweep measurements carried out on the film reveal a shear thickening peak in the loss moduli (G") at large amplitudes followed by a power law decay of the storage (G') and loss moduli with exponents in the ratio 2:1. In the frequency sweep measurements at low frequencies, the storage modulus remains nearly independent of the angular frequency, whereas G" reveals a power law dependence with a negative slope, a behavior reminiscent of soft glassy systems. Under steady shear, a finite yield stress is observed in the limit of shear rate .gamma going to zero. However, for .gamma > 1 s-1, the shear stress increases gradually. In addition, a significant deviation from the Cox-Merz rule confirms that the monolayer of Ag nanoparticles at the toluene-water interface forms a soft two-dimensional colloidal glass.     

Immobilization of ionic liquid with polyelectrolyte as carrier

An all-purpose approach to immobilize ionic liquids onto solid supports is proposed by chemical grafting on a polyelectrolyte carrier.     

燃烧合成法制备稀土氧化物纳米粉

本文采用硝酸盐 甘氨酸体系合成Ｙ2 Ｏ3、ＣｅＯ2 、Ｎｄ2 Ｏ3、Ｐｒ6 Ｏ11、Ｓｍ2 Ｏ3纳米粉 ,并研究了后三者在潮湿空气中的化学稳定性。其ＩＲ谱随着颗粒尺寸的减少 ,Ｙ Ｏ振动峰发生红移 ,同时谱峰强烈展宽[1,2 ] 。1　仪器及实验ＲｉｇａｋｕＤ/ｍａｘγＡ转靶衍射仪 ,ＨｉｔａｃｈｉＨ 80 0ＴＥＭＳＸ 1 70ＦＴＩＲ光谱仪 ,ＲｉｇａｋｕＰＴＣ 1 0ＡＴＧ ＤＲＡ分析仪。制备时所用前驱物均为水合稀土硝酸盐 ,其中Ｃｅ(ＮＯ3) 3·6Ｈ2 Ｏ为分析纯商用试剂 (纯度为99 99% ) ,其他水合稀土硝酸盐则参照文献[3,4 ] 分别由高纯稀土氧化物…     

Solid-phase synthesis of nanocrystalline lanthanum zirconate using mechanical activation

Nanocrystalline lanthanum zirconate La₂Zr₂O₇ was synthesized by the solid-phase method using preliminary mechanical activation of a La₂O₃ and ZrO₂ mixture. Processes occurring during heating the mixture of mechanoactivated lanthanum and zirconium oxides were studied using the X-ray phase analysis, IR spectroscopy, and complex thermal analysis. Synthesized lanthanum zirconate was characterized by the X-ray phase analysis and transmission electron microscopy methods.