New synthesis approach for low temperature bimetallic nanoparticles: size and composition controlled Sn-Cu nanoparticles

A various size of Sn-Cu nanoparticles were synthesized by using a modified polyol process for low temperature electronic devices. Monodispersive Sn-Cu nanoparticles with diameters of 21 nm, 18 nm and 14 nm were synthesized. In addition, the eutectic composition shift was also observed in nano-sized particles as compared with bulk alloys. By controlling the size and eutectic composition, a significant melting temperature depression of 30.3 degrees C was achieved. These melting temperature depression approaches will reduce adverse thermal effects in electronic devices and provide the synthesis guidelines for bimetallic nanoparticles with a low melting temperature.     

Synthesis and agglomeration of gold nanoparticles in reverse micelles

Reverse micelles prepared in the system water, sodium bis-(2-ethylhexyl) sulfoccinate (AOT), and isooctane were investigated as a templating system for the production of gold nanoparticles from Au(III) and the reducing agent sulfite. A core-shell Mie model was used to describe the optical properties of gold nanoparticles in the reverse micelles. Dynamic light scattering of gold colloids in aqueous media and in reverse micelle solution indicated agglomeration of micelles containing particles. This was verified theoretically with an analysis of the total interaction energy between pairs of particles as a function of particle size. The analysis indicated that particles larger than about 8?nm in diameter should reversibly flocculate. Transmission electron microscopy measurements of gold nanoparticles produced in our reverse micelles showed diameters of 8-10?nm. Evidence of cluster formation was also observed. Time-correlated UV-vis absorption measurements showed a red shift for the peak wavelength. This was interpreted as the result of multiple scattering and plasmon interaction between particles due to agglomeration of micelles with particles larger than 8?nm.     

Sensitized luminescent terbium nanoparticles: preparation and time-resolved fluorescence assay for DNA

A highly luminescent terbium nanoparticle as the biolabel based on the sensitization of a dye molecule was prepared. The luminescent complexes included in the particles were composed of a quinolone-based dye molecule as the light-energy transfer donor and a polyaminocarboxylate-based chelator with excellent water-solubility and a high binding constant for lanthanides. The structure of two functional entities in the single molecule made the complex highly luminescent in aqueous solution. Silica nanoparticles containing terbium complexes were prepared by the reverse microemulsion method. Such a terbium nanoparticle is as bright as about 340 free terbium complexes, and it has a 1.5-ms fluorescence lifetime that enables it to be used in the time-resolved fluorescence assays. The conjugate of the nanoparticle with oligonucleotide was prepared and used to carry out a DNA sandwich hybridization assay based on magnetic microbeads as solid-phase carrier. The experimental results showed that the detection sensitivity with the nanoparticles is more than 100-fold as high as that with dye Fluorescein isothiocyanate (FITC) molecules.     

New approach to synthesis of semimagnetic semiconductor nanoparticles

The technique of colloidal chemistry has been applied for synthesis of nonmagnetic CdS and Cd_1−xMn_xS semimagnetic semiconductor nanocrystals. The Cd_1−xMn_xS nanocrystals have been synthesized by means of substitution reaction. The performed TEM analysis suggests of spherical shape of nanoparticles for the colloidal Cd_1−xMn_xS nanoparticles. The optical properties of the obtained nanocomposite solution have been investigated by absorption and emission spectroscopy. Optical spectra demonstrate features which are associated with confinement effect and change of Mn content x in the Cd_1−xMn_xS nanocrystals. Compositional information have been obtained on the base of the model of weak confinement regime and estimation the energy gap for a given composition of the II_1−xMn_xVI alloys at room temperature.     

New dynamic approach to preparation of vapor and gas mixtures

A new method for verifying the efficiency of gas analyzers based on the use of generators with a linear increase in the tested substance concentration in time is proposed. The controlled parameter is time of increase of gas analyzer data from one preset value to another. The generator structure is described and its application is shown for verification of the efficiency of photoionization gas analyzers.     

Synthesis and characterization of europium(III) nanoparticles for time-resolved fluoroimmunoassay of prostate-specific antigen

Recent advances in the fabrication and bioconjugation of nanometre-sized lanthanide(III) chelate particles have led to robust high specific activity labels. This paper describes the synthesis and characterization of lanthanide(III) nanoparticle labels and the use of a nanoparticle in a bioaffinity assay system. Two europium(III) nanoparticles were prepared using an extremely simple, inexpensive and fast agglomeration strategy. A?silica-stabilized nanoparticle was synthesized from hydrophobic tris(dibenzoylmethane)-mono(phenanthroline) and tris(dibenzoylmethane)-mono(5-aminophenanthroline) europium(III) chelates in aqueous solution. In addition, a naphthoyl trifluoroacetone:tri-n-octylphosphineoxide:sodium dodecyl sulfate europium(III) complex was agglomerated in water. The particle sizes ranged from 62 to 140?nm in diameter. The silica-stabilized particle was further coated with a monoclonal antibody. The analytical performance of the bioconjugated nanoparticle label was evaluated in a model sandwich immunoassay of prostate-specific antigen. The detection limit of human prostate-specific antigen was 28?ng?l(-1), 850?fM, in a microtiter plate format using time-resolved fluorometry. The coefficient of variation ranged from 1 to 9%. The novel nanoparticle label improves the specific activity of existing lanthanide(III) nanoparticle labels and simplifies the preparation route. In addition, prepared high-density nanoparticle labels using lanthanide(III) chelates or other specific fluorochromes have potential applications in a number of other fields.     

Dielectric investigations of pristine and modified ZnO nanoparticles for energy storage devices

Pristine ZnO, Al-doped ZnO, and TiO₂ coated ZnO nanoparticles (NPs) were synthesized by the wet chemical precipitation technique. All the synthesized NPs were characterized using X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy. XRD analysis of pristine ZnO and Al-doped ZnO NPs revealed the hexagonal wurtzite structure with P6₃mc space group with no secondary phases and impurities. FESEM micrographs also depicted hexagonal grains with well-defined grain boundaries. TEM images showed hexagonal polyhedral shape for pure ZnO NPs and spherical shape dominating polyhedral particle for Al-doped ZnO NPs, and pseudospherical particles for TiO₂ coated ZnO NPs. Energy-dispersive X-ray spectroscopy of Al-doped ZnO indicates the eminent exchange of dopant in the lattice site of Zn. Dielectric Studies reveal the highest value of the dielectric constant and lowest value of dielectric loss for Al-doped ZnO as compared to pure and TiO₂-coated ZnO NPs. Suggesting Al-doped ZnO to be used as a dielectric material that can serve as a basic building block of the energy storage devices such as dielectric capacitor. TiO₂-coated ZnO NPs demonstrated higher AC conductivity in comparison to pure ZnO and Al-doped ZnO NPs suggesting their use as a conductive nanofiller materials in a polymer-based nanocomposite to achieve higher energy density.

     

Impact of agglomeration on the relaxometric properties of paramagnetic ultra-small gadolinium oxide nanoparticles

Ultra-small gadolinium oxide nanoparticles (US-Gd(2)O(3)) are used to provide 'positive' contrast effects in magnetic resonance imaging (MRI), and are being considered for molecular and cellular imaging applications. However, these nanoparticles can aggregate over time in aqueous medium, as well as when internalized into cells. This study is aimed at measuring in vitro, in aqueous medium, the impact of aggregation on the relaxometric properties of paramagnetic US-Gd(2)O(3) particles. First, the nanoparticle core size as well as aggregation behaviour was assessed by HRTEM. DLS (hydrodynamic diameter) was used to measure the hydrodynamic diameter of nanoparticles and nanoaggregates. The relaxometric properties were measured by NMRD profiling, as well as with (1)H NMR relaxometers. Then, the positive contrast enhancement effect was assessed by using magnetic resonance scanners (at 1.5 and 7 T). At every magnetic field, the longitudinal relaxivity (r(1)) decreased upon agglomeration, while remaining high enough to provide positive contrast. On the other hand, the transverse relaxivity (r(2)) slightly decreased at 0.47 and 1.41 T, but it was enhanced at higher fields (7 and 11.7 T) upon agglomeration. All NMRD profiles revealed a characteristic relaxivity peak in the range 60-100 MHz, suggesting the possibility to use US-Gd(2)O(3) as an efficient 'positive-T(1)' contrast agent at clinical magnetic fields (1-3 T), in spite of aggregation.     

Synthesis and investigations of rutile phase nanoparticles of TiO2

TiO₂ nanoparticles have been synthesized at room temperature using a simple chemical precipitation route. Particles were further coated with polymer. Detailed structural analysis of the particles has been carried out. Wide-angle X-ray scattering (WAXS) and transmission electron microscopy (TEM) confirm that as-synthesized particles as well as annealed particles are nanoparticles having pure rutile phase. Thermal annealing at 1000 °C of 4.2 nm particles led to an increased size 20 nm in the same phase. The purity and composition of the particles were determined using energy dispersive analysis of X-rays (EDAX) and X-ray photoelectron spectroscopy (XPS), respectively.     

One-step approach for the synthesis and self-assembly of silver nanoparticles

This study demonstrates a facile approach for one-step synthesis and self-assembly of silver nanoparticles at ambient conditions. It was found that pyrogallol acid (PYA) can play multiple roles in the proposed synthesis, including a reducing agent, a stabilizer, and a linking agent for assembly. Silver ions can be readily reduced by PYA at room temperature due to its powerful reducing capability. The capability in shape and size control can be evidenced by TEM images. A third function of PYA in this case is to link the generated silver particles into chains through the action of hydrogen bonding, which leads to a new plasmon resonance emerges in the longer wavelength region centered at approximately 650 nm. These results may be useful for shape-controlled synthesis and self-assembly of other metallic nanoparticles. The self-assembly structures would be imposed more functional applications in the areas of optics, plasmonics, biomedicine labeling and ionic sensing.     

The need for a European Union approach to accident investigations

On 11 June 2003, the Commission decided to create a high-level "Group of Experts to advise the Commission on a strategy for dealing with accidents in the transport sector". The task of the Group is to, inter alia, assist the Commission on the formulation of common European methodological elements for independent technical accident investigations. This article describes the recent developments in the legal framework related to accident investigations in the European Union and presents the keystone elements which should form the basis of an EU approach to accident investigations. It will also explain the rationale behind the setting up the above-mentioned Group of Experts.     

Development of new templating approach for hollow nanoparticles and their applications

This review mainly focuses on simple template routes for hollow particles and introduces their applications. An inorganic template using inorganic particles is a facile technique to obtain hollow particles with various shapes, sizes, from nano to micron, and also different shell microstructures. These structure controls provide wide applications such as superior thermal insulation films, anti-corrosion films, and unexpected “easy-to-grip” volley ball coatings, etc. This technique is also an environmentally friendly route that only requires a mild condition to remove the template, and the generated byproducts can be reused for synthesis of the template. This paper describes the sol–gel synthesis which is useful to form the shell structure of the hollow particle and then how to control the particle structure using various templating routes. In addition to our achievements using hollow silica nanoparticles, the development of applications such as the lithium ion battery, biomedical products, and catalysts, will be outlined.     

General BE approach for three-dimensional dynamic fracture analysis

A general mixed boundary element approach for three-dimensional dynamic fracture mechanics problems is presented in this paper. A mixed traction-displacement integral equation formulation in the frequency domain is used. The hypersingular and strongly singular kernels are regularized by analytical transformations yielding an easy to implement BE approach. Nine-node quadrilateral and six-node triangular continuous quadratic elements are used for external boundaries and crack surfaces. The crack front elements have their mid node at one quarter of the element length allowing for a proper representation of the crack surface displacement. The present approach is intended for the frequency domain analysis of fracture mechanics problems of any general 3D geometry; i.e. boundless or bounded regions, single or multiple, surface or internal cracks. Transient dynamic problems are studied using the FFT algorithm. The numerical results presented show the robustness and accuracy of the approach which requires a reasonable number of elements and degrees of freedom.     

Mixed numerical-analytical approach for dynamic one-point-bend test modelling

Specimen deformation during a one-point-bend impact test is modelled within 2D linear elasticity framework. Using modal superposition technique, the closed-form solutions for the striker force and dynamic stress intensity factor (DSIF) variation with time are derived. Parameters used in these solutions have been determined using plane stress finite element model of the specimen and approximated polynomially for a wide range of the specimen geometry parameters. The efficiency of the method proposed has been verified by comparison of the analytical results with the experimental data available in the literature and with the results of finite element analysis.     

一种机械系统动力学响应分析方法

 为了动力学响应分析的通用性及简便性,提出一种新的动力学响应分析方法.将机械系统分解成有序单开链单元,按其正序首先在约束度小于0的单元进行虚拟赋值,然后在其他单元依次进行运动分析,最后可得到维数最低的运动学方程.基于虚功原理导出动力学响应方程通式,对广义速度与广义加速度特殊赋值后通过序单开链法可求出响应方程的各系数,从而确定动力学响应方程.该动力学响应方程的维数等于机械系统自由度,形式简洁,便于求解,平面三自由度并联机构的实例表明了该方法的有效性.     

Sensitive method for determination of protein and cell concentrations based on competitive adsorption to nanoparticles and time-resolved luminescence resonance energy transfer between labeled proteins

A sensitive mix-and-measure method for the determination of protein and cell concentrations was developed. It is based on the competitive adsorption between the analyte and donor- and acceptor-labeled proteins to carboxylate-modified polystyrene nanoparticles. A high time-resolved luminescence resonance energy transfer (TR-LRET) signal is detected in the absence of the analyte due to the close proximity of the nanoparticle-adsorbed labeled proteins. The increased concentration of the analyte decreases the adsorption of the labeled proteins, leading to the loss of proximity and thus a decrease in the TR-LRET. The detection limit of the assay was 2.6 ng of proteins, which is higher than that of the most sensitive commercial methods. The method was also applied to cell counting, and 200 eukaryotic cells were measured in a microtiter well under the optimized conditions. The average coefficient of variation for both developed assays was approximately 10%, and the protein-to-protein variability for 11 different proteins was no more than 20%. The developed method requires no labeled particles, making the concept optimally applicable to varying targets as the material of the particle may be selected according to the application.