High-density gold nanoparticles supported on a [Ru(bpy)(3)](2+)-doped silica/Fe3O4 nanocomposite: Facile preparation, magnetically induced immobilization, and applications in ECL detection

A large-scale process combined sonication with self-assembly techniques for the preparation of high-density gold nanoparticles supported on a [Ru(bpy)(3)](2+)-doped silica/Fe3O4 nanocomposite (GNRSF) is provided. The obtained hybrid nanomaterials containing Fe3O4 spheres have high saturation magnetization, which leads to their effective immobilization on the surface of an ITO electrode through simple manipulation by an external magnetic field (without the need of a special immobilization apparatus). Furthermore, this hybrid nanomaterial film exhibits a good and very stable electrochemiluminescence (ECL) behavior, which gives a linear response for tripropylamine (TPA) concentrations between 5 mu m and 0.21 mM, with a detection limit in the micromolar range. The sensitivity of this ECL sensor can be easily controlled by the amount of [Ru(bpy)(3)](2+) immobilized on the hybrid nanomaterials (that is, varying the amount of [Ru(bpy)(3)](2+) during GNRSF synthesis).

Bifunctional nanostructure of magnetic core luminescent shell and its application as solid-state electrochemiluminescence sensor material

Bifunctional nanoarchitecture has been developed by combining the magnetic iron oxide and the luminescent Ru(bpy)(3)(2+) encapsulated in silica. First, the iron oxide nanoparticles were synthesized and coated with silica, which was used to isolate the magnetic nanoparticles from the outer-shell encapsulated Ru(bpy)(3)(2+) to prevent luminescence quenching. Then onto this core an outer shell of silica containing encapsulated Ru(bpy)(3)(2+) was grown through the Stober method. Highly luminescent Ru(bpy)(3)(2+) serves as a luminescent marker, while magnetic Fe3O4 nanoparticles allow external manipulation by a magnetic field. Since Ru(bpy)(3)(2+) is a typical electrochemiluminescence (ECL) reagent and it could still maintain such property when encapsulated in the bifunctional nanoparticle, we explored the feasibility of applying the as-prepared nanostructure to fabricating an ECL sensor; such method is simple and effective. We applied the prepared ECL sensor not only to the typical Ru(bpy)(3)(2+) co-reactant tripropylamine (TPA), but also to the practically important polyamines. Consequently, the ECL sensor shows a wide linear range, high sensitivity, and good stability.

Vapor phase beckmann rearrangement of cyclohexanone oxime over rare earth pyrophosphates

A new application of rare earth pyrophosphates in vapor phase Beckmann rearrangement of cyclohexanone oxime was investigated. The rare earth phosphates were characterized by means of XRD, FT-IR, NH3-TPD and water contact angle measurement. It was found that the weak surface acidity and appropriate surface hydrophobicity should be two key factors in the excellent performance of these catalysts.

Fabrication of magnetic luminescent nanocomposites by a layer-by-layer self-assembly approach

Magnetic luminescent nanocomposites were prepared via a layer-by-layer (LbL) assembly approach. The Fe3O4 magnetic nanoparticles of 8.5 nm were used as a template for the deposition of the CdTe quantum dots (QDs)/polyelectrolyte (PE) multilayers. The number of polyelectrolyte multilayers separating the nanoparticle layers and the number of QDs/ polyelectrolyte deposition cycles were varied to obtain two kinds of magnetic luminescent nanocomposites, Fe3O4/PEn/CdTe and Fe3O4/(PE3/CdTe)(n), respectively. The assembly processes were monitored through microelectrophoresis and UV-vis spectra. The topography and the size of the nanocomposites were studied by transmission electron microscopy. The LbL technique for fabricating magnetic luminescent nanocomposites has some advantages to tune their properties. It was found that the selection of a certain number of the inserted polyelectrolyte interlayers and the CdTe QDs loading on the nanocomposites could optimize the photoluminescence properties of the nanocomposites. Furthermore, the nanocomposites could be easily separated and collected in an external magnetic field.

In situ synthesis and characterization of multiwalled carbon nanotube/Au nanoparticle composite materials

An effective and facile in Situ reduction approach for the fabrication of carbon nanotube-supported Au nanoparticle (CNT/Au NP) composite nanomaterials is demonstrated in this article. Linear polyethyleneimine (PEI) is ingeniously used as both a functionalizing agent for the multiwalled carbon nanotubes (MWNTs) and a reducing agent for the formation of An NPs. This method involves a simple mixing process followed by a mild heating process. This approach does not need the exhaustive surface oxidation process of CNTs. The coverage of Au NPs on CNTs is tunable by varying the experimental parameters, such as the initial molar ratio of PEI to HAuCl4, the relative concentration of PEI and HAUCl(4) to MWNTs, and the temperature and duration of the heat treatment. More importantly, even the heterogeneous CNT/Au composite nanowires are obtainable through this method. TEM, XPS, and XRD are all used to characterize the CNT/Au composite materials. In addition, the optical and electrocatalytic properties are investigated.

Cupric hexacyanoferrate nanoparticle modified carbon ceramic composite electrodes

Graphite powder-supported cupric hexacyanoferrate (CuHCF) nanoparticles were dispersed into methyltrimethoxysilane based gels to produce a conducting carbon ceramic Composite, which was used as electrode material to fabricate surface- renewable CuHCF-modified electrodes. Electrochemical behavior of the CuHCF-modifled carbon ceramic composite electrodes was characterized using cyclic and square-wave voltammetry. Cyclic voltammograms at various scan rates indicated that peak currents were surface-confined at low scan rates. In the presence of glutathione, a clear electrocatalytic response was observed at the CuHCF-modified composite electrodes. In addition, the electrodes exhibited a distinct advantage of reproducible surface-renewal by simple mechanical polishing on emery paper, as well as ease of preparation, and good chemical and mechanical stability in a flowing stream.

Factors influencing the catalytic activity of SBA-15-supported copper nanoparticles in CO oxidation

Copper nanoparticles were deposited onto mesoporous SBA-15 support via two different routes: post-grafting method and incipient wet impregnation method. Both XRD and TEM reveal that the post-grafting can make Cu particles very small in size and highly dispersed into channels of SBA-15, while the impregnation method mainly forms large Cu particles on the external surface of SBA-15. TPR experiments show that CuO species formed by the post-grafting method is more reducible than that prepared by the impregnation method. The catalytic activity tests for CO oxidation manifests that the sample prepared by the post-grafting method has a much higher activity than that prepared by the impregnation method, with a lowering of 50 degrees C for T-50, showing a strong dependence of catalytic activity on the size and dispersion of Cu particles. Besides the preparation procedure, other factors including calcination temperature, reduction treatment, copper loading as well as the feed composition, have an important effect on the catalytic activity. The best performance was obtained when the catalyst was calcined at 500 degrees C and reduced at 550 degrees C. The calcination and reduction treatment at high temperature have been found to be necessary to completely remove the organic residue and to generate active metallic copper particles. (c) 2005 Elsevier B.V. All rights reserved.

Evidence for the tongue of ionization under northward interplanetary magnetic field conditions

Pryse, Sian; Middleton, H. R.; Kersley, L.; Bust, G. S., 'Evidence for the tongue of ionization under northward interplanetary magnetic field conditions', Journal of Geophysical Research (2005) 110(A7) pp.A07301 RAE2008

Low-loss directional cloaks without superluminal velocity or magnetic response.

The possibility of making an optically large (many wavelengths in diameter) object appear invisible has been a subject of many recent studies. Exact invisibility scenarios for large (relative to the wavelength) objects involve (meta)materials with superluminal phase velocity [refractive index (RI) less than unity] and/or magnetic response. We introduce a new approximation applicable to certain device geometries in the eikonal limit: piecewise-uniform scaling of the RI. This transformation preserves the ray trajectories but leads to a uniform phase delay. We show how to take advantage of phase delays to achieve a limited (directional and wavelength-dependent) form of invisibility that does not require loss-ridden (meta)materials with superluminal phase velocities.

Self-focusing and envelope pulse generation in nonlinear magnetic metamaterials

The self-modulation of waves propagating in nonlinear magnetic metamaterials is investigated. Considering the propagation of a modulated amplitude magnetic field in such a medium, we show that the self-modulation of the carrier wave leads to a spontaneous energy localization via the generation of localized envelope structures (envelope solitons), whose form and properties are discussed. These results are also supported by numerical calculations.

Remarkable stability of ionic gold supported on sulfated lanthanum oxide

Isolated cationic gold deposited on sulfated lanthanum oxide has been shown to exhibit remarkable stability opening a promising way of stabilising ionic gold for catalytic reactions.

Highly selective and efficient hydrogenation of carboxylic acids to alcohols using titania supported Pt catalysts

Selective hydrogenation of carboxylic acids to alcohols and alkanes has been achieved under remarkably mild reaction temperatures and H-2 pressures (333 K, 0.5 MPa) using Pt/TiO2 catalyst.

Electromagnetic interaction between a metallic nanoparticle and surface in tunnelling proximity-modelling and experiment

We simulate the localized surface plasmon resonances of an Au nanoparticle within tunnelling proximity of an Au substrate. The results demonstrate that the calculated resonance energies can be identified with those experimentally detected for light emission from the tip-sample junction of a scanning tunnelling microscope. Relative to the modes of an isolated nanoparticle these modes show significant red-shifting, extending further into the infrared with increasing radius, primarily due to a proximity-induced lowering of the effective bulk plasmon frequency. Spatial mapping of the field enhancement factor shows an oscillatory variation of the field, absent in the case of a dielectric substrate; also the degree of localization of the modes, and thus the resolution achievable electromagnetically, is shown to depend primarily on the nanoparticle radius, which is only weakly dependent on wavelength.

Energy Dependence of Gold Nanoparticle Radiosensitization in Plasmid DNA

Gold nanoparticles (GNPs) are of considerable interest for use as a radiosensitizer, because of their biocompatibility and their ability to increase dose deposited because of their high mass energy absorption coefficient. Their sensitizing properties have been verified experimentally, but a discrepancy between the experimental results and theoretical predictions suggests that the sensitizing effect does not depend solely on gold's superior absorption of energetic photons. This work presents the results of three sets of experiments that independently mapped out the energy dependence of the radiosensitizing effects of GNPs on plasmid DNA suspended in water. Incident photon energy was varied from 11.8 to 80 keV through the use of monochromatic synchrotron and broadband X-rays. These results depart significantly from the theoretical predictions in two ways: First, the sensitization is significantly larger than would be predicted; second, it does not vary with energy as would be predicted from energy absorption coefficients. These results clearly demonstrate that the effects of GNP-enhanced therapies cannot be predicted by considering additional dose alone and that a greater understanding of the processes involved is necessary for the development of future therapeutics.

New Cu-Based Catalysts Supported on TiO2 Films for Ullmann SNAr-Type C-O Coupling Reactions

New routes for the preparation of highly active TiO2-supported Cu and CuZn catalysts have been developed for C-O coupling reactions. Slurries of a titania precursor were dip-coated onto glass beads to obtain either structured mesoporous or non-porous titania thin films. The Cu and CuZn nanoparticles, synthesized using a reduction by solvent method, were deposited onto calcined films to obtain a Cu loading of 2 wt%. The catalysts were characterized by inductively coupled plasma (ICP) spectroscopy, temperature-programmed oxidation/reduction (TPO/TPR) techniques, Cu-63 nuclear magnetic resonance (NMR) spectroscopy, X-ray diffraction (XRD), scanning and transmission electron microscopy (S/TEM-EDX) and X-ray photo-electron spectroscopy (XPS). The activity and stability of the catalysts obtained have been studied in the C-O Ullmann coupling of 4-chloropyridine and potassium phenolate. The titania-supported nanoparticles retained catalyst activity for up to 12 h. However, catalyst deactivation was observed for longer operation times due to oxidation of the Cu nanoparticles. The oxidation rate could be significantly reduced over the CuZn/TiO2 catalytic films due to the presence of Zn. The 4-phenoxypyridine yield was 64% on the Cu/nonporous TiO2 at 120 degrees C. The highest product yield of 84% was obtained on the Cu/mesoporous TiO2 at 140 degrees C, corresponding to an initial reaction rate of 104 mmol g(cat)(-1) s(-1). The activation energy on the Cu/mesoporous TiO2 catalyst was found to be (144 +/- 5) kJ mol(-1), which is close to the value obtained for the reaction over unsupported CuZn nanoparticles (123 +/- 3 kJ mol(-1)) and almost twice the value observed over the catalysts deposited onto the non-porous TiO2 support (75 +/- 2 kJ mol(-1)).