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Showing papers on "Nanoparticle published in 1993"


Patent
23 Jul 1993
TL;DR: In this paper, a biodegradable solid core containing a biologically active material and poly(alkylene glycol) moieties on the surface is provided, which can be modified to achieve variable release rates or to target specific cells or organs.
Abstract: Particles are provided that are not rapidly cleared from the blood stream by the macrophages of the reticuloendothelial system, and that can be modified to achieve variable release rates or to target specific cells or organs. The particles have a biodegradable solid core containing a biologically active material and poly(alkylene glycol) moieties on the surface. The terminal hydroxyl group of the poly(alkylene glycol) can be used to covalently attach onto the surface of the particles biologically active molecules, including antibodies targeted to specific cells or organs, or molecules affecting the charge, lipophilicity or hydrophilicity of the particle. The surface of the particle can also be modified by attaching biodegradable polymers of the same structure as those forming the core of the particles.

664 citations


Journal ArticleDOI
15 Jan 1993-Science
TL;DR: Observation of crystals of pure encapsulated α-LaC2 that were exposed to air for several days before analysis indicates that the LaC2 is protected from degradation by the carbon polyhedral shells of the nanoparticles, a new class of materials that can be protected in their pure or carbide forms and may have interesting and useful properties.
Abstract: Single-domain microcrystals of LaC2 encapsulated within nanoscale polyhedral carbon particles have been synthesized in a carbon arc. Typical particle sizes are on the order of 20 to 40 nanometers. The stoichiometry and phase of the La-containing crystals have been assigned from characteristic lattice spacings observed by high-resolution transmission electron microscopy and energy dispersive spectroscopy (EDS). EDS spectra show that La and C are the only elements present. Characteristic interatomic distances of 3.39 and 2.78 angstroms identify the compound inside the nanoparticle cavities as α-LaC2, the phase of LaC2 that is stable at room temperature. Bulk α-LaC2 is metallic and hydrolytic. Observation of crystals of pure encapsulated α-LaC2 that were exposed to air for several days before analysis indicates that the LaC2 is protected from degradation bythe carbon polyhedral shells of the nanoparticles. A high percentage of the carbon nanoparticles have encapsulated LaC2 single crystals. These carbon-coated metal crystals form a new class of materials that can be protected in their pure or carbide forms and may have interesting and useful properties.

609 citations


Patent
11 Jun 1993
TL;DR: Dispersible particles consisting essentially of a crystalline anticancer agent having a surface modifier adsorbed on the surface thereof in an amount sufficient to maintain an effective average particle size of less than about 1000 nm as mentioned in this paper.
Abstract: Dispersible particles consisting essentially of a crystalline anticancer agent having a surface modifier adsorbed on the surface thereof in an amount sufficient to maintain an effective average particle size of less than about 1000 nm. Anticancer compositions comprising the particles exhibit reduced toxicity and/or enhanced efficacy, and can be administered by IV bolus injection.

517 citations


Journal ArticleDOI
TL;DR: In this paper, a microemulsion-mediated synthesis of zinc oxide nanoparticles for varistor studies and possible applications is described, and the microstructure, high density and electrical conductivity of sintered disks of pure and doped ZnO nanoparticles resulting from clean interfaces of particles and scaled down size of grains are found to result in higher critical electric field and a higher coefficient of nonlinearity in the logE versus logJ curve.

191 citations


Journal ArticleDOI
TL;DR: The results suggest that nanoparticles designed for use as injectable drugs or drug carriers should display similar surface characteristics provided by such amphiphilic surface modifiers.

188 citations


Journal ArticleDOI
TL;DR: In this paper, particles with narrow size distributions were produced by CO2 laser pyrolysis of vapor mixtures of Fe(CO)5 and C2H4, and they were observed to be ferromagnetic in this size range.
Abstract: Nanocrystalline α–Fe, Fe3C, and Fe7C3, particles with narrow size distributions were produced by CO2 laser pyrolysis of vapor mixtures of Fe(CO)5 and C2H4. Details of the synthesis procedure are discussed. Mossbauer spectroscopy and x-ray diffraction were used to identify the structural phases and the former was used also to study the magnetism of the nanoparticles. All the nanoparticles were observed to be ferromagnetic in this size range. If excess C2H4 appears in the reactant gas mixture, several monolayers of pyrolytic carbon were observed to form on the particle surface, as deduced from transmission electron microscopy and Raman scattering studies. Results of thermo-gravimetric analysis/mass spectroscopy studies of this carbon coating indicate it is gasified in hydrogen at temperatures T ∼ 250 °C.

141 citations


Journal ArticleDOI
TL;DR: In this article, the synthesis of copper nanoparticles in reverse micelles is described, where it is possible to form metallic particles either surrounded or not surrounded by an oxide layer.

94 citations


Journal ArticleDOI
TL;DR: A HREM study shows well crystallized nanoparticles with good interaction between Pt particles and SnO2 grains, no icosahedral or decahedral morphologies due to multitwinning are observed.

58 citations


Journal ArticleDOI
TL;DR: In this paper, carbon dioxide laser synthesis from gaseous precursors has been successfully applied to produce nanosized Al2O3 particles, which are suitable dispersoids for intermetallic alloy technology.
Abstract: Carbon dioxide laser synthesis from gaseous precursors has been successfully applied to produce nanosized Al2O3 particles. Trimethylaluminum [Al(CH3)3] and nitrous‐oxide (N2O) were used as gas phase reactants. Ethylene (C2H4) was added as sensitizer gas. The as‐synthesized powder particles showed considerable carbon contamination and an amorphouslike structure. After thermal treatment at 1200–1400 °C, the powder transformed to hexagonal α‐Al2O3 with very low carbon contamination, confirmed by x‐ray diffraction, x‐ray photoelectron spectroscopy, and chemical analysis. The thermally treated powder was composed of spherical single‐crystal nanoparticles with a mean size 〈D〉 of 15–20 nm, as determined by x‐ray diffraction, electron microscopy, and Brunauer–Emmett–Teller specific surface measurements. The laser synthesized Al2O3 particles are suitable dispersoids for intermetallic alloy technology.

43 citations


Book ChapterDOI
01 Jan 1993
TL;DR: In this article, functionalized reverse micelles are used to control the size and the polydispersity of the metallic and semiconductor particles, and the size of the particles can be controlled, either by the amount of water solubilized in the droplets, or by the solvent used to form reverse mouselles or by adding macrocyle molecules.
Abstract: Functionalized reverse micelles are used to control the size and the polydispersity of the metallic and semiconductor particles. The size of the particles can be controlled, either by the amount of water solubilized in the droplets, or by the solvent used to form reverse micelles, or by adding macrocyle molecules.

39 citations


Journal ArticleDOI
TL;DR: In this paper, the authors proposed a gas deposition process, where nanoparticles entrained in a tiny carrier gas jet collide and are deposited onto a target substrate, and analyzed the thermal behavior of nanoparticles during the process.
Abstract: Ultrafine particles having diameters in the range larger than 1 nm and less than 1 μm can be called nanoparticles. Chemically pure nanoparticles are usually produced by evaporation and condensation in a controlled environment. Scientific engineers may consider nanoparticles as materials suitable for the fabrication of micrometer-sized elements of macroproducts, while scientists consider the atomic and electronic structure and properties of nanoparticles. We previously proposed a deposition and/or erosionn process called the gas deposition process, where nanoparticles entrained in a tiny carrier gas jet collide and are deposited onto a target substrate ( Jpn. J. Appl. Phys., 23 (1984) L910–L912). The electrical circuit pattern (approximately 40 μm width), the capacitor (BaTiO 3 ), oxide superconducting contacts (yttrium, bismuth) etc. are exapmles of components of the process. Analysis of the thermal behavior of nanoparticles during the process will be discussed. We believe that this process or any other pollution-free and localized process should be developed as a bridging technology between the macro and atomic worlds.

Journal ArticleDOI
TL;DR: In this paper, the spatial distribution of sputtered particle formation using a vertical, linear arrangement of substrates is investigated, and supersaturation occurs qualitatively as a function of the distance from the substrate, sputtering rate, and the mean free path in the vapor.
Abstract: By adjusting the sputtering rate and gas pressure, it is possible to form nanoparticles of different sizes, phases, and materials. We have investigated the spatial distribution of sputtered particle formation using a vertical, linear arrangement of substrates. Collecting the particles soon after they are formed, before they have time to grow and agglomerate, allows one to obtain a narrow size distribution. In the case of molybdenum, a narrow distribution of cubic particles is formed at relatively large distances (8 cm) from the source. These cubic particles collide and self-assemble in the vapor into arrays of larger cubic particles. The particle size histograms are fitted to lognormal distribution functions. How supersaturation occurs is discussed qualitatively as a function of the distance from the substrate, sputtering rate, and the mean free path in the vapor. This method of nanocrystalline particle formation has potential use in magnetic and opto-electronic (quantum dot) applications, where a narrow size distribution is required.

Patent
20 Apr 1993
TL;DR: In this article, a polymer matrix is used for growing and doped semiconductor nanoparticles of a size <100 Å which exhibit quantum effects, and the nanoparticles are then used to produce quantum effects.
Abstract: Doped semiconductor nanoparticles of a size (<100 Å) which exhibit quantum effects. The nanoparticles are grown and doped within a polymer matrix.

Patent
04 Jun 1993
TL;DR: In this article, a method for the preparation and use of polymeric nanoparticles in the coating industry and in biology is presented, which relates to polymer nanoparticles caracterized in that they have a narrow grain size distribution, a size comprised between 10 and 50 nanometres and present at their surfaces identical or different ionogenic or reactive groupings.
Abstract: The present invention relates to polymer nanoparticles caracterized in that they have a narrow grain size distribution, a size comprised between 10 et 50 nanometres and present at their surfaces identical or different ionogenic or reactive groupings. It also relates to the method for the preparation and use of said polymer nanoparticles in the coating industry and in biology.

Journal ArticleDOI
TL;DR: In this paper, a single process was used to synthesize palladium carbide nanoparticles, a metastable phase with carbon atoms on interstitial sites of metallic lattice, which allowed palladium metallic nanoparticles formed by vapor condensation in flowing argon carrier gas to immediately come in contact with acetone vapor.
Abstract: Nanoparticles of palladium carbide, a metastable phase with carbon atoms on interstitial sites of metallic lattice, were synthesized by a single process, which allows palladium metallic nanoparticles formed by vapor condensation in flowing argon carrier gas to immediately come in contact with acetone vapor. The average particle size observed by transmission electron microscopy is 5 nm and the geometric standard deviation of the distribution is 1.5.

Patent
29 Jun 1993
TL;DR: In this article, the authors describe a class of dispersible particles consisting of a crystalline anticancer agent having a surface modifier adsorbed on the surface thereof in an amount sufficient to maintain an effective average particle size of less than about 1000 nm.
Abstract: of EP0577215Dispersible particles consisting essentially of a crystalline anticancer agent having a surface modifier adsorbed on the surface thereof in an amount sufficient to maintain an effective average particle size of less than about 1000 nm. Anticancer compositions comprising the particles exhibit reduced toxicity and/or enhanced efficacy, and can be administered by intravenous injection.

Journal ArticleDOI
TL;DR: In this paper, a fractal structure consisting of an aggregation of nanosized silver particles having diameters of the order of 15 nm was estimated, which showed a lowering of the effective Debye temperature as the particle size is reduced.
Abstract: Fractal growth of metallic silver within a polymer matrix has been induced by chemical reduction of a suitable sol. A fractal dimension of 1.73±0.01 over a length scale 100–10 000 nm has been estimated. The fractal structure consists of an aggregation of nanosized silver particles having diameters of the order of 15 nm. Electrical conductivity of these nanoparticles shows a lowering of the effective Debye temperature as the particle size is reduced.

Journal ArticleDOI
TL;DR: In this article, high-resolution scanning electron microscopy (SEM) was used to study carbon nanotubes and nanoparticles formed by dc arc-discharge evaporation of a carbon composite rod containing scandium oxide.
Abstract: Carbon nanotubes and nanoparticles formed by dc arc-discharge evaporation of a carbon composite rod containing scandium oxide were studied by high-resolution scanning electron microscopy (SEM). Nanotubes obtained from the composite rod were more abundant than those obtained from pure carbon rod. Many fibrous nanotubes were gathered together and bunched to form long bundles. Moreover, a number of nanoparticles whose size was nearly the same as the diameter of nanotubes were attached to the surface of each tube in the bundle. It was found that scandium had the effect of promoting the growth of nanotubes.

Journal ArticleDOI
TL;DR: In this paper, the morphology and sizes of these particles were examined by transmission electron microscopy, while their phase and crystalline nature were probed by electron and x-ray diffraction.
Abstract: Unilamellar vesicles, formed spontaneously by mixing single-tailed cationic (cetyl trimethyl ammonium tosylate, CTAT) and anionic aqueous solutions of (sodium dodecyl benzene sulfonate, SDBS) surfactants have been used as reactors for the aqueous phase precipitation of nanometer sized particles within their inner cores. AlCl3 solution was encapsulated within these vesicles, aluminum ions were replaced with sodium ions in the extravesicular phase, and sodium hydroxide was then added to the extravesicular region. Hydroxyl ions penetrate through the vesicle walls and react with the available aluminum in the intravesicular region to form the product. The morphology and sizes of these particles were examined by transmission electron microscopy, while their phase and crystalline nature were probed by electron and x-ray diffraction. The product particles were nanometer-sized with near spherical morphology. Good control of particle size was achieved by varying the initial concentration of electrolyte. Single particle electron diffraction revealed a symmetric pair of spots, indicating that the particles were either single crystals or polycrystalline with a low number of grain boundaries or defects. Although wide area electron diffraction showed that the product was δ–Al2O3, powder x-ray diffraction revealed that these particles were, in fact, Al(OH)3. It is likely that heating of these nanoparticles by the high energy electron beam in a high vacuum environment causes a phase transformation, resulting in the difference between the electron and x-ray diffraction results. These results represent the first demonstration of precipitation within vesicles produced spontaneously by mixing appropriate ratios of inexpensive single-tailed surfactants, and may potentially make intravesicular precipitation a commercially viable route for making nanometer-sized particles.

Journal ArticleDOI
TL;DR: In this article, the in situ electron beam induced decomposition of binary metal azides within an electron microscope is demonstrated for the generation of nanometer sized particles of an extended range of metals including La, Ce, Ti, Fe(III), Co, Ni, Mn, Ag, Tl, Cd, Sn, Sb, Bi and Te.

Journal ArticleDOI
TL;DR: In this article, two approaches for producing nanometer-sized TiB2 particles for reinforcement in Ti/TiB2 composites are discussed: (I) gas-phase combustion synthesis and (2) low-temperature wet-chemical synthesis.

Journal ArticleDOI
13 Apr 1993
TL;DR: In this article, the magnetic properties of ferrofluids containing polydisperse chemically coprecipitated Mn-Zn ferrite nanoparticles of various composition, as well as the dispersion characteristics and structure of particles, are investigated.
Abstract: The magnetic properties of ferrofluids containing polydisperse chemically coprecipitated Mn-Zn ferrite nanoparticles of various composition, as well as the dispersion characteristics and structure of particles, are investigated. Results of the neutron-activation analysis of particles give a Mn, Zn and Fe ratio different from that of stoichiometrically predicted ones at precipitation. Magnetogranulometric analysis of ferrofluid samples performed by using the Langevin-type magnetization model of noninteracting subdomain particles shows that, instead of the usually observed log-normal particle size distribution curves, there exists a more complex distribution of magnetic moments of particles. Ultracentrifugal separation of samples allows the distribution of two fractions of particles having different magnetic moment values, which are not proportional to the particle mean volumes determined using X-ray diffraction spectra measurements. >

Journal ArticleDOI
TL;DR: In this article, the authors proposed scanning force microscopy (SFM) as a tool to organize logical and other operative nanostructures constructed from prefabricated, 10-nm-sized particles randomly deposited onto suitable substrate materials by a bottom-up technology.

Journal Article
TL;DR: In this paper, a transparent polyurethane-co-polystyrene (PCP) containing silver nanoparticles was synthesized by radical initiated polymerization of amphiphilic urethane acrylate, nonionomer (UAN)/styrene/silver nitrate mixtures.
Abstract: Yellow transparent polyurethane-co-polystyrene films containing silver nanoparticles could be synthesized. Silver nanoparticles and transparent polymer film making up nanocomposite films were formed simultaneously through radical initiated polymerization of amphiphilic urethane acrylate, nonionomer (UAN)/styrene/silver nitrate mixtures. Size of silver nanoparticle could be controlled by varying weight ratio of styrene in UAN/styrene mixtures and chain length of PEO and PPO segment in UAN chain, which are much easier process compared to the synthetic process of nanoparticles using amphiphilic block copolymers. Formation of silver nanoparticles and change of nanoparticle size could be conformed by transmission electron microscopy and characteristic UV absorbance spectra. Tensile modulus and glass transition temperature of polyurethane-co-polystyrene films were drastically increased at 0.45 wt% of silver nanoparticles embedded at their matrix, indicating that silver nanoparticles embedded at polymer films can act as an inorganic nanofiller for improving mechanical property.

Journal ArticleDOI
TL;DR: In this article, the authors describe a scenario where the authors of PVA are: Ag微粒子が凝集分散している膜でSERSの測定を試みた
Abstract: ゲル膜を介して反応液を接触させる対向拡散法により多孔性ポリビニルアルコール (PVA) ゲル膜中にAg微粒子を分散させた. Ag微粒子分散膜はいずれも420nm近辺に単分散微粒子のプラズモンの吸収を示し, 粒子の凝集が進むにつれて長波長側に幅広い吸収を示した. Ag微粒子が凝集分散している膜でSERSの測定を試みたところ吸着種の強いバンドが観測された.

Journal Article
TL;DR: In this article, the synthesis and characterization of carbon-supported PtRu nanoparticles were carried out by impregnation and colloidal methods and products were compared with commercial carbon supported PtRu.
Abstract: The synthesis and characterization of carbon-supported PtRu nanoparticles were carried out by impregnation and colloidal methods and products were compared with commercial carbon-supported PtRu. To confirm the characteristics of the synthesized PtRu nanoparticles, TEM (and EDX), XRD, and electrochemical analysis were performed to evaluate alloy formation, surface structure, chemical composition of the nanoparticles, and the electrocatalytic activity for methanol oxidation. The impregnation method was relatively easy and straightforward but the average particle size was in excess of 3 nm and the size distribution was broad. However, colloidal methods involved more complicated procedures and required a heat treatment to increase activity, resulting in an average particle size of up to 2.2 - 2.3 mn. The heating conditions used, to achieve a higher catalytic activity, were investigated. A simpler nanoparticle synthetic method that results in a small particle size and high activity without a heat treatment would be desirable.


Journal ArticleDOI
TL;DR: In this article, X-ray diffraction (XRD), transmission electron microscopy (TEM), and Raman scattering were used to determine the particle size, crystallite size, and the structural phase of 2H-MoS2 and 3H-WS2 powders.
Abstract: Nanocrystalline powders of 2H-MoS2 and 2H-WS2 with average particle size 5 and 9 nm, respectively, have been produced using C0 2 laser pyrolysis. Typical production rate for these nanoparticles is 2g/hr. Particle size, crystallite size, and the structural phase were determined using X-ray diffraction(XRD), transmission electron microscopy(TEM), and Raman scattering. Particle size effects may have been observed in the Raman-active modes (WS2 and MoS2) and in the band-edge excitons (MoS 2).

Patent
29 Jun 1993
TL;DR: Particles can be dispersed and consisting essentially of an anti-cancer agent CRYSTAL HAVING A surface modifier absorbed SURFACE thereof in an amount sufficient to maintain a particle size less than 1000 average effective nm as mentioned in this paper.
Abstract: Particles can be dispersed and consisting essentially of an anti-cancer agent CRYSTAL HAVING A surface modifier absorbed SURFACE thereof in an amount sufficient to maintain a particle size less than 1000 average effective nm. ANTICANCER COMPOSITIONS CONTAINING THE particles have a reduced toxicity and / or greater efficiency and can be administered by injection intravenously.

Journal ArticleDOI
TL;DR: In this article, the theoretical principles of these techniques and their main applications to the field of nano particle analysis are discussed and a number of transmission electron microscopy techniques that can be used in order to characterize the shape and structure of nano particles are reported.
Abstract: The study of systems with dimensions of the order of a few to a hundred nanometers has attracted great attention. The main reason is the peculiar physical and chemical behavior of these systems; they are specially important in catalysts since metal nano particles are the most common constituents of the supported catalysts. The understanding of the structure of nano particles is a crucial step for the understanding of the catalytic activity. In the present work we report a number of transmission electron microscopy techniques that can be used in order to characterize the shape and structure of nano particles. In the last decade electron microscopy has had a dramatic development and at the present time we have a number of techniques from medium-resolution such as selected zone dark-field (SZDF) and weak beam dark-field (WBDF) as well as direct atom imaging by high resolution. In the present work we discuss the theoretical principles of these techniques and their main applications to the field of na...