The historical notion regarding the inability of gold to catalyze reactions has been discarded in view of recent studies, which have clearly demonstrated the high catalytic efficiency of supported nano-gold catalysts. Although nano-Au catalysts are known to catalyze a variety of reactions, the major focus has been on CO oxidation catalysis. In this work we focus on the important aspects related to the CO oxidation reaction. Special emphasis is placed on the studies undertaken on model nano-Au systems as these studies have considerably enhanced the understanding of the oxidation process. Pure Nano gold powder in a highly dispersed state can selectively oxidize CO in the presence of excess hydrogen (of tremendous interest to state-of-the-art low-temperature fuel cells); related studies are addressed in this review. The nano-gold catalysts have also been investigated for the direct vapor-phase oxidation of propylene to propylene oxide in the presence of molecular oxygen; these investigations are highlighted in this work.
Gold nano-particles confined in the walls of mesoporous silica (GMS) catalysts were successfully prepared by a novel and simple technique utilizing thioether functional groups in the walls of mesoporous silica to anchor HAuCl4. Calcination of the materials removed organic moieties and reduced the gold salt to gold nano-particles. In this procedure, the thioether groups were introduced into the silica wall via a co-condensation of tetraethyl orthosilicate (TEOS) with 1,4-bis(triethoxysily)propane tetrasulfide. These gold containing mesoporous catalysts have unusually high surface area and pore volume.
The catalysts were evaluated for the solvent free liquid phase oxidation of benzyl alcohol by molecular oxygen. High selectivity to benzaldehyde was obtained under the reaction conditions of 403 K, 15 atm and 5 h in an autoclave. The 1.5% GMS catalyst was also evaluated for oxidation of alcohols using toluene as solvent under flowing oxygen at atmospheric pressure at 353 K in a two-necked flask. Under these conditions the conversion of benzyl alcohol reached 100% after 2 h and it was demonstrated that the catalyst can be recycled three times without significant loss of activity.
Chromium nanoparticles and morphology
Several concentrations of adsorbent and adsorbate were tested, trying to cover a large range of possible real conditions. Results showed that the Freundlich isotherm represented well the adsorption equilibrium reached between nanoparticles and chromium, whereas adsorption kinetics could be modeled by a pseudo-second-order expression. The separation of chromium–cerium nanoparticles from the medium and the desorption of chromium using sodium hydroxide without cerium losses was obtained. Nanoparticles agglomeration and morphological changes during the adsorption–desorption process were observed by TEM.
Chromium nanoparticles and morphology changes during the process
In this study, suspended cerium oxide nanoparticles stabilized with hexamethylenetetramine were used for the removal of dissolved chromium VI in pure water.
Another remarkable result obtained in this study is the low toxicity in the water treated by nanoparticles measured by the Microtox® commercial method. These results can be used to propose this treatment sequence for a clean and simple removal of drinking water or wastewater re-use when a high toxicity heavy metal such as chromium VI is the responsible for water pollution.
ZnO and Cr doped ZnO nanoparticles were synthesized by chemical vapor synthesis (CVS) which is a modified chemical vapor deposition (CVD) process. The resulting powders consist of nanocrystalline particles and were characterized by X-ray diffraction (XRD), nitrogen adsorption (BET), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX), element analysis, and extended X-ray absorption fine structure (EXAFS) spectroscopy. The grain size decreases with increasing dopant concentration. The lattice constants extracted by the Rietveld method from XRD data vary slightly with doping concentration. XRD and EXAFS data analysis show that the Chromium dopant atoms are incorporated into the wurtzite host lattice.
Synthesis of Metal Alloy Nanoparticles
A simple, convenient, and general method for the synthesis of metal and metal alloy nanoparticles is presented. Irradiation of metal powders in suspension in either aqueous or organic solutions by unfocused 532 nm laser radiation produces nanoparticles with a homogeneous composition proportional to the composition of the starting metal powder mixture. This is demonstrated using UV−vis absorption spectroscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and modelization. The mechanism of alloy formation is discussed.
This Review is focused on the recent progresses in the synthetic approaches to the precise control of structure, size, shape, composition and multi-functionality of metal and metal alloy nanoparticles. Many of these strategies have been developed based on colloidal methods, and to limited extent, the galvanic and other methods.
Synthesis of Metal Alloy Nanoparticles in Solution by Laser Irradiation of a Metal Powder Suspension. The shape, size and composition often govern the chemical and catalytic properties that are important for electrochemical energy applications. The structure–property relationship and the design in controllable structures and morphologies for specific reactions such as oxygen reduction reaction (ORR) are emphasized.Magnetic nanoparticles have potential applications in high-density memory devices, but their complicated synthesis often requires high temperatures, expensive reagents, and postsynthesis annealing to achieve the desired magnetic properties. Current synthetic methods for magnetic nanoparticles often require post-synthetic modifications, suggesting that the practical application of magnetic nanoparticles will depend on the development of alternative synthetic strategies.
We report a biological template to directly grow magnetic nanoparticles of desired material composition and phase under ambient conditions. A phage display methodology was adapted to identify peptide sequences that both specifically bind to the ferromagnetic L10 phase of FePt and control the crystallization of FePt nanoparticles using a modified arrested precipitation technique.
Nano Element Particles on Dispersing in ODS Steel
From the irradiation resistance and high-temperature strength, oxide dispersion strengthened (ODS) ferritic steels are candidate materials for advanced and fusion reactors. For the development of advanced steels the key issue is to homogenize nano-particles into matrix. Recent studies have indicated that Ti addition can homogenize Y-Ti complex particles into ferrite matrix, but the reason of the effect of additional elements has not been clarified. In this model study, we focus on the effect of additional elements, such as IV and V families and other oxide formers, which can control potentially the distribution of the oxide particles.
The materials used in this study were based on Fe-9Cr-Y2O3 alloys which were mechanical alloyed (MA) from the powder of Fe, Cr and Y2O3, which was added systematically with the element of Ti, Zr, Ta, V, Nb, Hf, Al, Si and others. Usually ODS fabrication process is required for hot extrusion, but we annealed up to 1150 C for simplify the microstructure. To evaluate the distribution of ODS Nano Element Particles ; we used TEM equipped with EDS after electro-polishing or FIB techniques.
(1) In the case of Si or Al addition, oxides were disappeared after MA process, which means Y2O3 and other elements should be in solution at non-equilibrium condition. Two types of oxides of Y2O3 and Al2O3 or SiO2 developed after the annealing at 850 C,b> developed after the annealing at 850 C, but only complex oxides were developed after the annealing at 1150 C. This result suggests that the oxide formation is independent process for Y and Si or Al. (2) In the case of Ti addition, oxides also were disappeared after MA process, but developed after annealing at 1150 C. This means that Ti can stabilize complex oxides of Y and Ti, and enhance the fine distribution of the oxides comparing with simple Fe-9Cr-Y2O3 alloy.
Microwave hybrid synthesis of silicon carbide nanopowders
Nanosized silicon carbide powders were synthesised from a mixture of silica gel and carbon through both the conventional and microwave heating methods. Reaction kinetics of SiC formation were found to exhibit notable differences for the samples heated in microwave field and furnace. In the conventional method SiC nanopowders can be synthesised after 105 min heating at 1500 °C in a coke-bed using an electrical tube furnace. Electron microscopy studies of these powders showed the existence of equiaxed SiC nanopowders with an average particle size of 8.2 nm. In the microwave heating process, SiC powders formed after 60 min; the powder consisted of a mixture of SiC nanopowders (with two average particle sizes of 13.6 and 58.2 nm) and particles in the shape of long strands (with an average diameter of 330 nm).
The powders were prepared by a sol-gel process. Dielectric constants (ϵ′) and dielectric loss tangents (tanδ) were measured within the microwave frequency range from 4 to18 GHz. Both ϵ′ and tanδ of pure SiC nanopowder are much higher (ϵ′=40–50, tanδ=0.6–0.7) than for the doped ones over the frequency range. The dielectric parameters decreased with increasing aluminum and nitrogen contents. Infrared (IR) spectra were measured in the range from 500 to 4000 cm−1, showing that the background of pure SiC nanopowder is also much higher than for the doped ones. The possible mechanisms of these promising features of undoped SiC nanopowder are discussed.
By a simple and controlled method, that is, by electroless plating, nickel has been deposited on the surfaces of Silicon Carbide Nanopowders Energy dispersive spectrometry (EDS) spectra show that pre-treatments of the silicon carbide nanoparticles have an important influence on the effect of electroless nickel plating. Transmission electron microscopy images and EDS spectra of silicon carbide nanoparticles before and after electroless nickel plating reveal that nickel has been deposited on the surface of silicon carbide nanoparticles and the deposited nickel and silicon carbide nanoparticles are bound tightly.
The Extinction Spectra of Silver Nanopowders Arrays
Influence of Array Structure on Plasmon Resonance Wavelength and Width
We use high-quality electrodynamics methods to study the extinction spectra of one-dimensional linear chains and two-dimensional planar arrays of spherical Silver Nanopowders, placing emphasis on the variation of the plasmon resonance wavelength and width with array structure (spacing, symmetry), particle size, and polarization direction. Two levels of theory have been considered, coupled dipoles with fully retarded interactions and T-matrix theory that includes a converged multipole expansion on each particle. We find that the most important array effects for particles having a radius of 30 nm or smaller are captured by the couple dipole approach.
Our calculations demonstrate several surprising effects that run counter to conventional wisdom in which the particle interactions are assumed to be governed by electrostatic dipolar interactions. In particular, we find that for planar arrays of particles with polarization parallel to the plane the plasmon resonance blue shifts as array spacing D decreases for D larger than about 75 nm and then it red shifts for smaller spacings. In addition, we find that the plasmon narrows for D > 180 nm but broadens for smaller spacings.
The results can be rationalized using a simple analytical model, which demonstrates that the plasmon wavelength shift is determined by the real part of the retarded dipole sum while the width is determined by the imaginary part of this sum. The optimal blue shifts and narrowing are found when the particle spacing is slightly smaller than the plasmon wavelength, while red shifts and broadening can be found for spacings much smaller than the plasmon wavelength at which electrostatic interactions are dominant. We also find that the array spectrum does not change significantly with array symmetry (square or hexagonal) or irradiated spot size (i.e., constant array size or constant particle number).
The application of metal nanowires
Metal nanowires can have a variety of forms. Sometimes they appear in the order to non crystal, such as five symmetrical or helix. Electronic in the Pentagon pipe and spiral pipe winding.
This lack of crystal order is because the nanotubes in only one dimension (Zhou Xiang) reflect cyclical, while in other dimensions can have any order to the law of energy. For example, in some cases, nanowires can show five fold symmetry, this symmetry cannot be observed in nature, but can be found in a small amount of atoms contributing to clusters. The five fold symmetry equivalent atoms cluster twenty fold symmetry: Twenty surface body is low energy states of a cluster of atoms, but because the surface of the body twenty can not be repeated indefinitely in all directions and fill the whole space, this order is not observed in the crystal.
In electronic, optoelectronic and nano electronic and mechanical devices, nano wires may play an important role. It also can be used as in the synthesis of additives, quantum devices in the line, field emitters and biological molecular nano sensor.
Metal nanowires can be natural sunlight came together in a very small area in the crystal, light gathering ability is 15 times the average light intensity. Because of the wavelength diameter is smaller than the incident solar light nanowire crystals, can cause the nanowires inside the crystal and the surrounding light intensity of resonance. The study participants, just to get the doctor degree of research on Niels Pohl Peter Klogstrup explained that the photons through resonance emit more concentrated (solar energy conversion is realized in the process of dissemination in the photon), which helps to improve the conversion efficiency of solar energy, so that the solar cell technology nanowires get real ascension based on the.
Nano silicon semiconductor light-emitting materials research
By changing the quantity of silicon rich, annealing conditions, size and density control oxidation of silicon in silicon Silicon Carbide Nanopowders. Literature that the critical temperature of silicon nanocrystals is 1000oC, and we tested to determine the critical annealing temperature for 900oC nanocrystals. On the right is via the 900oC annealing silicon rich silicon was about high resolution electron microscopy images of 30% silicon rich silicon oxide. Can clear the silicon nanocrystals. On the left corner of the electron diffraction pattern it is.
First observed by Au/ (Ge/SiO2) /p-Si superlattice structure electroluminescence. Right out of high resolution electron microscopy figure four cycle Ge/SiO2 superlattices. The bright line for the SiO2, 2.0nm thickness, Ge thickness of 2.4nm.
The growth of nano SiO2/Si/SiO2 double barrier by magnetron sputtering technique on silicon substrate (NDB) single well potential sandwich structure, the first realization of visible photoluminescence of Au/NDB/p-Si structure. Discovery of electroluminescence peak position, intensity with the nanometer silicon layer thickness (W) changes as synchronous oscillations, as shown on the right. Further tests and analyses show that the oscillation period is equal to the deBroglie wavelength of 1/2 carrier. Lighting model is explained by our group proposed electroluminescence.
For the first time based on SiO2:Si:Er film growth by magnetron sputtering has been achieved on the 1.54 m wavelength as (optical communication window) Er electroluminescence.
The wide application of nanotechnology
Nanometer and meters, micrometers and other units, is a unit of length, and a nanometer is equal to ten-nine meters, about an order of magnitude than chemical bonds grew up. Nanotechnology is the study by between 0.1 and 100 nm in size the system motion laws of matter and interactions as well as possible technical problems in the practical application of science and technology. Can be derived from nano-electronics, mechanical, biological, materials processing and so on.
Nano-materials refers to at least three dimensional spatial scale of one-dimensional nanoscale materials, it is made between the size of atoms, molecules and the macroscopic system of next-generation materials composed of nanoparticles. Due to its small scale units, interface takes up a fair amount of ingredients. Therefore, nano-materials with a variety of features, which lead to different system of nano-particles from mostly large chunks of the macro-system of many of the special nature of the material. Nano system makes people awareness natural and entered a new of levels, it is contact Atomic, and molecular and macro system of link, is people past never exploration had of new field, actually by nano particles composition of material to macro system evolution process in the, in structure Shang ordered degrees of changes, in State Shang of non-balance nature, makes system of nature produced is big of difference, on Nano material of research will makes people from micro to macro of transition has more in-depth of awareness. Characteristics of nanomaterials?
When the particle size down to the nanoscale, will lead to sound, light, electricity, magnetism, and thermal performance of new features. For example: is a wide research of II-VI semiconductor cadmium sulfide, the absorption band edge and luminescence spectra of peak position will significantly blue shift as the grain size decreases. According to this principle, can control the grain size to get different energy gap in cadmium sulfide, which greatly enriched material for content and is expected to get new use. We know the type of material is limited, micro-and nano-CDs are made of cadmium and sulfur, but by controlling production, band gap and luminescent properties of different materials can be obtained. In other words, through nano-technology is a new material. Nano Element Particles Often has a large surface area per gram surface area of the solid can reach hundreds of thousands of square meters, which makes them available as a highly active adsorbents and catalysts, hydrogen storage, organic synthesis and has important applications in areas such as environmental protection.
Nano-effects means that nano-materials with traditional materials do not have the exotic or unusual physical, chemical characteristics, such as conductive copper to a Nano-grade boundaries are not conductive, insulating silicon dioxide, crystals, and began conducting at a Nano line.
Development of nanometer drug carrier
Common nano drug carriers include inorganic and polymeric nano-drug delivery nano drug carriers. Among them, the polymeric nanoparticles as drug delivery research earlier, has a small amount of polymer-based drug of nano carrier got some European and American countries the drug agency approved for clinical treatment. This is because the polymer nanoparticles good biocompatibility, toxicity, drug coated through physical or chemical bonding in its polymer nanoparticles, excreted polymeric carrier via degradation after their release. Common inorganic nano-drug delivery system include magnetic nanoparticles, mesoporous silica, Nano-carbon materials, quantum dots, and the inorganic nano-drug delivery system, in achieving the targeted drug delivery, controlled-release and sustained-release drugs, as well as targeted cancer therapy is a good prospect
And Nano Element Particles compared to, inorganic nano particles not only size, and morphology can controlled sex like surface area big, and unique of light, and electric, and magnetic nature gives its has potential of imaging developer, and target to conveying and collaborative drug treatment, function, makes its more for in cell within for drug conveying. main introduced Fe3O4 magnetic Nano grain, and contains drug Nano hydroxy apatite, and quantum points several new contains drug nano particles of typical preparation process and the exists of problem, And looks forward to the prospect of drug-loaded nanoparticles.
Biomedical uses of magnetic nano-particles is mainly due to its special magnetic properties, it is usually based on magnetic nano-particles for nuclear, organic or inorganic shell by surface modification coating formed by assembling composite particles with unique features. Nano magnetic target to drug carrier as a new drug carrier, can in specific of oriented mechanism Xia, will drug efficient of transport to target organ, makes drug in local played role, greatly to reduced has drug on body of HIV side effects. magnetic nano particles due to its good of Super Shun magnetic can makes its outside magnetic field of role Xia convenient to for magnetic separation and oriented, and due to magnetic nano particles can in magnetic field in the not was permanent magnetization, so in body both security and easily control. In addition, the magnetic nanoparticles also has suspension stability, functional group characteristics and biocompatibility, biodegradability and magnetic fluorescent double-functional advantages.
There are many kinds of magnetic materials, including Tungsten Carbide Cobalt Powder, chromium oxide, iron oxide, ferrite and iron nitride, including magnetic particles of Fe3O4 is the most widely used. Magnetic Fe3O4 nanoparticle size distribution around 1-100 nm, Nano-size particles with different from atoms is also different from the physical and chemical properties of the bulk materials [6], magnetic nanoparticles of quantum size effect and surface effects causes significant changes in magnetic properties. Nano-particle size d<16 NM, anisotropic thermal motion reduced and compared, easy magnetization direction without the law change, they generate superparamagnetic. And Fe3O4 has was proved nontoxic and has bio compatible sex, based on unique of physical, and chemical, and thermal and magnetic performance, Super Shun magnetic iron oxide nano particles has is big of potential application Yu variety bio medicine field, as cell mark, and target to and the as cell ecological research of tool for cell separation and purification, cell treatment; organization repair; drug transmission; NMR Imaging; cancer of fever treatment,. Fe3O4 become most biomedical research in the field and also the most promising Nano magnetic material.