Showing papers on "Nanoparticle published in 2001"
TL;DR: In this paper, it was shown that a "nanofluid" consisting of copper nanometer-sized particles dispersed in ethylene glycol has a much higher effective thermal conductivity than either pure or pure glycol or even polyethylene glycol containing the same volume fraction of dispersed oxide nanoparticles.
Abstract: It is shown that a “nanofluid” consisting of copper nanometer-sized particles dispersed in ethylene glycol has a much higher effective thermal conductivity than either pure ethylene glycol or ethylene glycol containing the same volume fraction of dispersed oxide nanoparticles. The effective thermal conductivity of ethylene glycol is shown to be increased by up to 40% for a nanofluid consisting of ethylene glycol containing approximately 0.3 vol % Cu nanoparticles of mean diameter <10 nm. The results are anomalous based on previous theoretical calculations that had predicted a strong effect of particle shape on effective nanofluid thermal conductivity, but no effect of either particle size or particle thermal conductivity.
3,551 citations
TL;DR: This light-driven process results in a colloid with distinctive optical properties that directly relate to the nanoprism shape of the particles, which could be useful in developing multicolor diagnostic labels on the basis of nanoparticle composition and size but also of shape.
Abstract: A photoinduced method for converting large quantities of silver nanospheres into triangular nanoprisms is reported. The photo-process has been characterized by time-dependent ultraviolet-visible spectroscopy and transmission electron microscopy, allowing for the observation of several key intermediates in and characteristics of the conversion process. This light-driven process results in a colloid with distinctive optical properties that directly relate to the nanoprism shape of the particles. Theoretical calculations coupled with experimental observations allow for the assignment of the nanoprism plasmon bands and for the first identification of two distinct quadrupole plasmon resonances for a nanoparticle. Unlike the spherical particles they are derived from that Rayleigh light-scatter in the blue, these nanoprisms exhibit scattering in the red, which could be useful in developing multicolor diagnostic labels on the basis not only of nanoparticle composition and size but also of shape.
3,256 citations
TL;DR: This review is focused on current approaches emerging at the intersection of materials research, nanosciences, and molecular biotechnology, which is closely associated with both the physical and chemical properties of organic and inorganic nanoparticles.
Abstract: Based on fundamental chemistry, biotechnology and materials science have developed over the past three decades into today's powerful disciplines which allow the engineering of advanced technical devices and the industrial production of active substances for pharmaceutical and biomedical applications. This review is focused on current approaches emerging at the intersection of materials research, nanosciences, and molecular biotechnology. This novel and highly interdisciplinary field of chemistry is closely associated with both the physical and chemical properties of organic and inorganic nanoparticles, as well as to the various aspects of molecular cloning, recombinant DNA and protein technology, and immunology. Evolutionary optimized biomolecules such as nucleic acids, proteins, and supramolecular complexes of these components, are utilized in the production of nanostructured and mesoscopic architectures from organic and inorganic materials. The highly developed instruments and techniques of today's materials research are used for basic and applied studies of fundamental biological processes.
2,268 citations
TL;DR: Intradendrimer hydrogenation and carbon-carbon coupling reactions in water, organic solvents, biphasic fluorous/organic solvent, and supercritical CO2 are also described.
Abstract: This Account reports the synthesis and characterization of dendrimer-encapsulated metal nanoparticles and their applications to catalysis. These materials are prepared by sequestering metal ions within dendrimers followed by chemical reduction to yield the corresponding zerovalent metal nanoparticle. The size of such particles depends on the number of metal ions initially loaded into the dendrimer. Intradendrimer hydrogenation and carbon−carbon coupling reactions in water, organic solvents, biphasic fluorous/organic solvents, and supercritical CO2 are also described.
1,925 citations
TL;DR: High-temperature (300 degrees C) aging of iron-oleic acid metal complex, which was prepared by the thermal decomposition of iron pentacarbonyl in the presence of oleic acid at 100 degrees C, was found to generate monodisperse iron nanoparticles.
Abstract: The synthesis of highly crystalline and monodisperse γ-Fe2O3 nanocrystallites is reported. High-temperature (300 °C) aging of iron−oleic acid metal complex, which was prepared by the thermal decomposition of iron pentacarbonyl in the presence of oleic acid at 100 °C, was found to generate monodisperse iron nanoparticles. The resulting iron nanoparticles were transformed to monodisperse γ-Fe2O3 nanocrystallites by controlled oxidation by using trimethylamine oxide as a mild oxidant. Particle size can be varied from 4 to 16 nm by controlling the experimental parameters. Transmission electron microscopic images of the particles showed 2-dimensional and 3-dimensional assembly of particles, demonstrating the uniformity of these nanoparticles. Electron diffraction, X-ray diffraction, and high-resolution transmission electron microscopic (TEM) images of the nanoparticles showed the highly crystalline nature of the γ-Fe2O3 structures. Monodisperse γ-Fe2O3 nanocrystallites with a particle size of 13 nm also can be...
1,893 citations
23 Aug 2001
TL;DR: Nanomaterials in energy storage systems have been studied extensively in the literature (see as mentioned in this paper for an overview of the applications of nanomaterial materials in the field of energy storage.
Abstract: CONTRIBUTORS PART I INTRODUCTION TO NANOMATERIALS 1 Introduction to Nanoscale Materials in Chemistry, Edition II ( Ryan M Richards ) 2 Unique Bonding in Nanomaterials and Powders ( Keith P McKenna ) 3 Particles as Molecules ( C M Sorensen ) PART II NEW SYNTHETIC METHODS TO NANOMATERIALS 4 Microwave Preparation of Metal Fluorides and their Biological Application ( David S Jacob, Jonathan Lellouche, Ehud Banin, and Aharon Gedanken ) 5 Transition Metal Nitrides and Carbides ( Piotr Krawiec and Stefan Kaskel ) 6 Kinetics of Colloidal Chemical Synthesis of Monodisperse Spherical Nanocrystals ( Soon Gu Kwon and Taeghwan Hyeon) 7 Nanorods ( P Jeevanandam ) PART III NANOSTRUCTURED SOLIDS: MICRO- AND MESOPOROUS MATERIALS AND POLYMER NANOCOMPOSITES 8 Aerogels: Disordered, Porous Nanostructures ( Stephanie L Brock ) 9 Ordered Microporous and Mesoporous Materials ( Freddy Kleitz ) 10 Applications of Microporous and Mesoporous Materials ( Anirban Ghosh, Edgar Jordan, and Daniel F Shantz ) PART IV ORGANIZED TWO- AND THREE-DIMENSIONAL NANOCRYSTALS 11 Inorganic-Organic Composites ( Warren T Ford ) 12 DNA-Modified Nanoparticles: Gold and Silver ( Abigail K R Lytton-Jean and Jae-Seung Lee ) PART V NANOTUBES, RIBBONS, AND SHEETS 13 Carbon Nanotubes and Related Structures ( Daniel E Resasco ) PART VI NANOCATALYSTS, SORBENTS, AND ENERGY APPLICATIONS 14 Reaction of Nanoparticles with Gases ( Ken-Ichi Aika ) 15 Nanomaterials in Energy Storage Systems ( Winny Dong and Bruce Dunn ) PART VII UNIQUE PHYSICAL PROPERTIES OF NANOMATERIALS 16 Optical and Electronic Properties of Metal and Semiconductor Nanostructures ( Mausam Kalita, Matthew T Basel, Katherine Janik, and Stefan H Bossmann ) PART VIII PHOTOCHEMISTRY OF NANOMATERIALS 17 Photocatalytic Purification of Water and Air over Nanoparticulate TiO2 ( Igor N Martyanov and Kenneth J Klabunde ) 18 Photofunctional Zeolites and Mesoporous Materials Incorporating Single-Site Heterogeneous Catalysts ( Masakazu Anpo, Masaya Matsuoka, and Masato Takeuchi ) 19 Photocatalytic Remediation ( Shalini Rodrigues ) PART IX BIOLOGICAL AND ENVIRONMENTAL ASPECTS OF NANOMATERIALS 20 Nanomaterials for Environmental Remediation ( Angela Iseli, HaiDoo Kwen, and Shyamala Rajagopalan ) 21 Nanoscience and Nanotechnology: Environmental and Health Impacts ( Sherrie Elzey, Russell G Larsen, Courtney Howe, and Vicki H Grassian ) 22 Toxicity of Inhaled Nanomaterials ( John A Pickrell, L E Erickson, K Dhakal, and Kenneth J Klabunde ) INDEX
1,274 citations
TL;DR: In this article, the synthesis and study of so-called "nanoparticles" with diameters in the range of 1−20 nm, has become a major interdisciplinary area of research over the past 10 years.
Abstract: The synthesis and study of so-called “nanoparticles”, particles with diameters in the range of 1−20 nm, has become a major interdisciplinary area of research over the past 10 years. Semiconductor nanoparticles promise to play a major role in several new technologies. The intense interest in this area derives from their unique chemical and electronic properties, which gives rise to their potential use in the fields of nonlinear optics, luminescence, electronics, catalysis, solar energy conversion, and optoelectronics, as well as other areas. The small dimensions of these particles result in different physical properties from those observed in the corresponding macrocrystalline, “bulk”, material. As particle sizes become smaller, the ratio of surface atoms to those in the interior increase, leading to the surface properties playing an important role in the properties of the material. Semiconductor nanoparticles also exhibit a change in their electronic properties relative to that of the bulk material; as th...
1,213 citations
TL;DR: Electron microscopy analysis of thin sections of the fungal cells indicated that the silver particles were formed below the cell wall surface, possibly due to reduction of the metal ions by enzymes present in the cell walls membrane.
Abstract: A novel biological method for the synthesis of silver nanoparticles using the fungus Verticillium is reported. Exposure of the fungal biomass to aqueous Ag+ ions resulted in the intracellular reduction of the metal ions and formation of silver nanoparticles of dimensions 25 ± 12 nm. Electron microscopy analysis of thin sections of the fungal cells indicated that the silver particles were formed below the cell wall surface, possibly due to reduction of the metal ions by enzymes present in the cell wall membrane. The metal ions were not toxic to the fungal cells and the cells continued to multiply after biosynthesis of the silver nanoparticles.
1,207 citations
TL;DR: Mesoporous semiconducting films consisting of preferentially orientated monoclinic-phase nanocrystals of tungsten trioxide have been prepared using a novel version of the sol-gel method, combining excellent photoresponse to the blue region of the solar spectrum, up to 500 nm, with good transparency at wavelengths larger than 550 nm.
Abstract: Mesoporous semiconducting films consisting of preferentially orientated monoclinic-phase nanocrystals of tungsten trioxide have been prepared using a novel version of the sol−gel method. Transformations undergone by a colloidal solution of tungstic acid, stabilized by an organic additive such as poly(ethylene glycol) (PEG) 300, as a function of the annealing temperature have been followed by means of a confocal Raman microscope. The shape and size of WO3 nanoparticles, the porosity, and the properties of the films depend critically on preparation parameters, such as the tungstic acid/PEG ratio, the PEG chain length, and the annealing conditions. Well-crystallized WO3 films combine excellent photoresponse to the blue region of the solar spectrum, up to 500 nm, with good transparency at wavelengths larger than 550 nm. Particular applications of these nanocrystalline WO3 films include photoelectrochemical and electrochromic devices.
961 citations
TL;DR: The current state of knowledge of the fundamentals of particle formation from homogeneous solution and the effect of solvent and polymer additives on the morphology and supramolecular structure of the nanoparticle will be discussed and the practical implementation of this new formulation technology will be explored in detail.
Abstract: Many active organic compounds and organic effect materials are poorly soluble in water, or even insoluble. Aqueous forms of application thus require special formulation techniques to utilize or optimize the physiological (pharmaceuticals, cosmetics, plant protection, nutrition) or technical (varnishes, printing inks, toners) action. The most interesting properties of nanodispersions of active organic compounds and effect materials include the impressive increase in solubility, the improvement in biological resorption, and the modification of optical, electrooptical, and other physical properties which are achievable only with particle sizes in the middle or lower nanometer range (50-500 nm). Hence in addition to economic and ecological constraints there are also technical demands which appear to urgently require the development of new processes for the production of organic nanoparticles as alternatives to the established mechanical milling processes. In this context attention is drawn to the recent increase in research activities which have as their objective the continuous, automatic preparation of nanodispersed systems by precipitation from molecular solution. In this review the current state of knowledge of the fundamentals of particle formation from homogeneous solution and the effect of solvent and polymer additives on the morphology and supramolecular structure of the nanoparticle will be discussed. The practical implementation of this new formulation technology will be explored in detail for the carotenoids, a class of compounds of both physiological and technical interest.
950 citations
TL;DR: In this paper, the combined effects of strain and phonon confinement are seen to explain why the Raman peak near $464{cm} in nanoparticles shifts to progressively lower energies and the lineshape of this feature gets progressively broader and asymmetric as the particle size gets smaller.
Abstract: The combined effects of strain and phonon confinement are seen to explain why the Raman peak near $464{\mathrm{cm}}^{\ensuremath{-}1}$ in ${\mathrm{CeO}}_{2\ensuremath{-}y}$ nanoparticles shifts to progressively lower energies and the lineshape of this feature gets progressively broader and asymmetric (on the low-energy side) as the particle size gets smaller. The increasing lattice constant measured for decreasing particle size explains this Raman shift well. The linewidth change is fairly well explained by the inhomogenous strain broadening associated with the small dispersion in particle size and by phonon confinement. The spectra are also likely to be directly affected by the presence of oxygen vacancies. Comparison of the temperature dependence of the Raman lineshape in the nanoparticles and the bulk shows that phonon coupling is no faster in the nanoparticles, so size-dependent phonon coupling does not contribute to the large nanoparticle peak red shifts and broadening at room temperature. Irreversible thermally induced changes are observed in the Raman peak position of the nanoparticles.
TL;DR: In this article, the diameters of single-walled carbon nanotubes are determined by their diameters in the cores of catalytic nanoparticles with diameters between 1−2 nm and 3−5 nm.
Abstract: Discrete catalytic nanoparticles with diameters in the range of 1−2 nm and 3−5 nm respectively are obtained by placing controllable numbers of metal atoms into the cores of apoferritin, and used for growth of single-walled carbon nanotube (SWNTs) on substrates by chemical vapor deposition (CVD). Atomic force microscopy (AFM), transmission electron microscopy (TEM), and micro-Raman spectroscopy are used to characterize isolated nanotubes grown from the discrete nanoparticles. The characterizations, carried out at single-tube and single-particle level, obtain clear evidence that the diameters of nanotubes are determined by the diameters of catalytic nanoparticles. With nanoparticles placed on ultrathin alumina membranes, isolated SWNTs are grown and directly examined by transmission electron microscopy. For the first time, both ends of an as-grown single-walled nanotube are imaged by TEM, leading to a microscopic picture of nanotube growth mechanism. It is shown that controlling the structures of catalytic ...
Book•
26 Oct 2001TL;DR: In this article, a solution-phase nanocluster synthesis and mechanisms of formation magic number metal clusters electrochemical synthesis of high aspect ratio gold particles template synthesis of metal nanostructures using dendrimer templates nanosphere lithography electrochemistry of monolayer protected gold clusters modelling of nanoparticle optical properties hyper-Raleigh scattering of nanoparticles nanoparticle single electron devices DNA detection using gold nanoparticles conductance-based nanoparticle chemical sensors surface plasmon resonance detection of biomolecules synthesis of conductive polymer-gold particle composites optical properties of complex metal nan
Abstract: Introduction to particle synthesis, optical, and electronic properties solution-phase nanocluster synthesis and mechanisms of formation magic number metal clusters electrochemical synthesis of high aspect ratio gold particles template synthesis of metal nanostructures synthesis of metal nanoclusters using dendrimer templates nanosphere lithography electrochemistry of monolayer protected gold clusters modelling of nanoparticle optical properties hyper-Raleigh scattering of nanoparticles nanoparticle single electron devices DNA detection using gold nanoparticles conductance-based nanoparticle chemical sensors surface plasmon resonance detection of biomolecules synthesis of conductive polymer-gold particle composites optical properties of complex metal nanostructures si-coated nanoparticles nanoparticle arrays mixed particle arrays nanoparticles in electronic devices.
TL;DR: In this article, the authors present a synopsis of the wet chemical syntheses of colloidal particles and survey potential applications in catalysis and materials science, but their methods for the characterization of these particles and their surfaces are not reviewed.
Abstract: Mono- and bimetallic colloidal particles have gained increasing attention in science and application throughout the last several years. In this contribution, we present a synopsis of the wet chemical syntheses of these materials and survey potential applications in catalysis and materials science. Methods for the characterization of these particles and their surfaces are not reviewed here.
TL;DR: In this article, the synthesis and coating of superparamagnetic monodispersed iron oxide nanoparticles was carried out by chemical solution method and controlled co-precipitation technique was used to prevent undesirable critical oxidation of Fe.
TL;DR: Although blinking and characteristic emission patterns demonstrate single-nanoparticle observation, large-scale dynamic color changes were also observed, even from the same nanoparticle, in oxidized thin silver films that enable Ag2O particles to grow at high density from silver islands.
Abstract: Fluorescence microscopy of nanoscale silver oxide (Ag2O) reveals strong photoactivated emission for excitation wavelengths shorter than 520 nanometers. Although blinking and characteristic emission patterns demonstrate single-nanoparticle observation, large-scale dynamic color changes were also observed, even from the same nanoparticle. Identical behavior was observed in oxidized thin silver films that enable Ag2O particles to grow at high density from silver islands. Data were readily written to these films with blue excitation; stored data could be nondestructively read with the strong red fluorescence resulting from green (wavelengths longer than 520 nanometers) excitation. The individual luminescent species are thought to be silver nanoclusters that are photochemically generated from the oxide.
TL;DR: In this paper, the authors examined the seed-mediated growth of gold nanoparticles by transmission electron microscopy and electronic absorption spectroscopy and found that changing the seed concentration does affect the size of the product nanoparticles, but the method of reagent addition drastically affects the outcome even more.
Abstract: Central to the concept of seed-mediated growth of nanoparticles is that small nanoparticle seeds serve as nucleation centers to grow nanoparticles to a desired size. We have examined this common assumption in a model system, the wet chemical synthesis of gold nanoparticles via reduction of a gold salt, by transmission electron microscopy and electronic absorption spectroscopy. We find that changing the seed concentration does affect the size of the product nanoparticles, but the method of reagent addition drastically affects the outcome even more. For fast addition of reducing agent, the presence of seeds appears to promote the formation of more seeds instead of growth. The observed nucleations are drastically enhanced (99%) compared to particle growth. For slow addition of reducing agent, the seeds do grow, but the product nanoparticle's degree of homogeneity in shape is compromised. For higher concentrations of seeds, nanoparticle growth is better controlled for slow addition of reducing agent compared ...
TL;DR: In this paper, gold nanoparticles were produced by laser ablation of a gold metal plate in an aqueous solution of sodium dodecyl sulfate, and the size distribution of the nanoparticles thus produced was measured by an electron microscope and was found to shift to a smaller size with an increase in surfactant concentration.
Abstract: Gold nanoparticles were produced by laser ablation of a gold metal plate in an aqueous solution of sodium dodecyl sulfate. The absorption spectrum of the gold nanoparticles was essentially same as that of gold nanoparticles chemically prepared in a solution. The size distribution of the nanoparticles thus produced was measured by an electron microscope and was found to shift to a smaller size with an increase in surfactant concentration. This behavior is explained in terms of the dynamic formation model. Dependence of the nanoparticle abundance on surfactant concentration in the solution shows that stable gold nanoparticles tend to be formed as the surfactant concentration exceeds 10-5 M. The gold nanoparticles having diameters larger than 5 nm were pulverized into those having diameters of 1−5 nm by a 532-nm laser.
TL;DR: The fabrication of magnetic composite core−shell particles and hollow spheres with tailored dimensions and compositions has been accomplished by a multistep (layer-by-layer) strategy as discussed by the authors.
Abstract: The fabrication of magnetic composite core−shell particles and hollow spheres with tailored dimensions and compositions has been accomplished by a multistep (layer-by-layer) strategy. Composite particles were prepared by coating submicrometer-sized anionic polystyrene (PS) latices with magnetite (Fe3O4) nanoparticle layers alternately adsorbed with polyelectrolyte from aqueous solution. The thickness of the deposited multilayers could be finely tuned with nanoscale precision, either by selection of the number of adsorption cycles performed or by the number of polyelectrolyte layers deposited between each nanoparticle layer (i.e., interlayer). As demonstrated by transmission electron microscopy, a marked improvement in the growth, uniformity, and regularity of the composite multilayers was achieved when the number of polyelectrolyte interlayers was increased from one [(poly(diallyldimethylammonium chloride) (PDADMAC)] to three [(PDADMAC/poly(styrenesulfonate) (PSS)/PDADMAC)]. Hollow, intact magnetic sphere...
TL;DR: A new class of microwires can be assembled by dielectrophoresis from suspensions of metallic nanoparticles that have good ohmic conductance and automatically form electrical connections to conductive islands or particles.
Abstract: A new class of microwires can be assembled by dielectrophoresis from suspensions of metallic nanoparticles. The wires are formed in the gaps between planar electrodes and can grow faster than 50 micrometers per second to lengths exceeding 5 millimeters. They have good ohmic conductance and automatically form electrical connections to conductive islands or particles. The thickness and the fractal dimension of the wires can be controlled, and composite wires with a metallic core surrounded by a latex shell can be assembled. The simple assembly process and their high surface-to-volume ratio make these structures promising for wet electronic and bioelectronic circuits.
TL;DR: In this article, an irradiation grafting method was applied for the modification of nanoparticles so that the latter can be added to polymeric materials for improving their mechanical performance, using existing compounding techniques.
TL;DR: The applicability of the layer-by-layer (LbL) technique for the formation of a range of polymer-core inorganic-shell particles and inorganic hollow spheres is demonstrated Titanium dioxide, silica, and Laponite nanoparticles were used as the inorganic building blocks for multilayer formation on polystyrene (PS) sphere templates Composite organic−inorganic particles were formed by the controlled assembly of the preformed nanoparticles in alternation with oppositely charged polyelectrolytes onto PS microspheres as discussed by the authors.
Abstract: The applicability of the layer-by-layer (LbL) technique for the formation of a range of polymer-core inorganic-shell particles and inorganic hollow spheres is demonstrated Titanium dioxide, silica, and Laponite nanoparticles were used as the inorganic building blocks for multilayer formation on polystyrene (PS) sphere templates Composite organic−inorganic particles were formed by the controlled assembly of the preformed nanoparticles in alternation with oppositely charged polyelectrolytes onto PS microspheres The influence of nanoparticle type, shape (spherical to sheetlike), and size (3−100 nm), and the diameter of the PS sphere templates (210−640 nm) on the formation of multilayer shells was examined by transmission and scanning electron microscopy In addition, the LbL technique for coating polymer spheres has been shown to be adaptable with small variations in the coating steps used to optimize the nanoparticle coatings of the different materials For example, the number of polyelectrolyte multilay
TL;DR: In this article, the size-tunable monodisperse magnetic nanoparticles with controlled internal structures have been studied to separate the role of defects from intrinsic, finite size effects.
Abstract: Magnetic colloids, or ferrofluids, have been studied to probe the fundamental size-dependent properties of magnetic particles and have been harnessed in a variety of applications. The magnetorheological properties of magnetic colloids have been exploited in high-performance bearings and seals. The deposition of magnetic dispersions on platters and tapes marked the earliest embodiments of magnet information storage. Magnetic particles enhance contrast in magnetic resonance imaging and promise future diagnostic and drug delivery applications. The need to explore the scaling limits of magnetic storage technology has motivated the preparation of size-tunable monodisperse magnetic nanoparticles with controlled internal structures. The study of these nanoparticles is critical to efforts to separate the role of defects from intrinsic, finite size effects.
TL;DR: In this paper, a 6-8 nm average diameter of magnetite nanoparticles with a 6−8 nm diameter were prepared and the surfactants used to stabilize the nanoparticles and disperse them in organic solvents were oleic acid (OA), lauric acid, dodecyl phosphonate, hexadecyl phosphonates, and dihexadecyl phosphate.
Abstract: Coated magnetite nanoparticles with a 6−8 nm average diameter were prepared. The surfactants used to stabilize the nanoparticles and disperse them in organic solvents were oleic acid (OA), lauric acid , dodecyl phosphonate, hexadecyl phosphonate, and dihexadecyl phosphate. Transmission electron microscopy analyses of the aggregation of the coated particles suggest that carboxylate surfactants provide the particles with better isolation and dispersibility as compared with phosphonate surfactants. However, Fourier transform infrared spectra of the phosphonate and phosphate coated particles suggest that these surfactants cover the surface of the nanoparticles in islands of high packing density. The thermogravimetric and differential scanning calorimetry measurements suggest that there is a quasi-bilayer of these surfactants covering the surface of the nanoparticles, with varying amounts of surfactant in the outer layer and with the second layer weakly bound to the primary layer through hydrophobic interactio...
TL;DR: In this article, a core-shell assembled gold or alloy nanoparticles for electrocatalytic oxidation of carbon monoxide and methanol is studied, based on recent insights in coreshell reactivities and, in part, surprising findings of catalytic activities of oxide-supported gold nanoparticles.
Abstract: The deliberate tailoring of nanoparticles supported on oxides, dispersed in dendrimers and encapsulated in monolayer shells could lead to novel catalytic applications. The study of core–shell assembled gold or alloy nanoparticles for electrocatalytic oxidation of carbon monoxide and methanol stems, in part, from recent insights in core–shell reactivities and, in part, from surprising findings of catalytic activities of oxide-supported gold nanoparticles. Monolayer-encapsulated metallic nanoparticles serve as intriguing model building blocks towards catalysts. Whether such core–shell nanoparticles can in general be developed into aggregation- and poison-resistant catalysts of high catalytic activities rests with our capabilities in catalytic activation and structural manipulation.
TL;DR: In this article, a tunable shape has been synthesized in THF, in the presence of hexadecylamine (HDA) or trioctylphosphineoxide (TOPO), in mild conditions and characterized by HREM and SQUID measurements.
Abstract: Nickel nanoparticles of tunable shape have been synthesized in THF, in the presence of hexadecylamine (HDA) or trioctylphosphineoxide (TOPO), in mild conditions and characterized by HREM and SQUID measurements. The formation of nanorods is promoted by a high amine content in the reaction medium. In contrast to what is observed for TOPO-protected nickel particles, the saturation magnetization of HDA-capped nanoparticles is comparable to that of bulk nickel, which demonstrates that the coordination of an amine ligand does not alter the magnetic properties of nickel.
Patent•
12 Nov 2001
TL;DR: An electrophoretic display comprises a fluid and a plurality of nanoparticles having diameters substantially less the wavelengths of visible light such that, when the nanoparticles are in a dispersed state and uniformly dispersed throughout the fluid, the fluid presents a first optical characteristic, but when the aggregated particles are in an aggregated state in which they are gathered into aggregates substantially larger than the individual nanoparticles.
Abstract: An electrophoretic display comprises a fluid and a plurality of nanoparticles having diameters substantially less the wavelengths of visible light such that, when the nanoparticles are in a dispersed state and uniformly dispersed throughout the fluid, the fluid presents a first optical characteristic, but when the nanoparticles are in an aggregated state in which they are gathered into aggregates substantially larger than the individual nanoparticles, the fluid presents a second optical characteristic different from the first optical characteristic. The electrophoretic display further comprises at least one electrode arranged to apply an electric field to the nanoparticle-containing fluid and thereby move the nanoparticles between their dispersed and aggregated states. Various compound particles comprising multiple nanoparticles, alone or in combination with larger objects, and processes for the preparation of such compound particles, are also described.
TL;DR: In this article, an extended charge transfer (CT) state stemming from PDDP molecules closely stacking in nanoparticles and observed its shift to the high-energy side with decreasing nanoparticle size due to exciton confinement.
Abstract: Nanoparticles of 1-phenyl-3-((dimethylamino)styryl)-5-((dimethylamino)phenyl)-2-pyrazoline (PDDP) ranging from tens to hundreds of nanometers were prepared by using the reprecipitation method. Their excitonic transitions responsible for absorption and emission, as compared with those of dilute solution, have been investigated as a function of nanoparticle size. We found that PDDP nanoparticles possess a special size dependence in their optical properties. We identified an extended charge-transfer (CT) state stemming from PDDP molecules closely stacking in nanoparticles and observed its shift to the high-energy side with decreasing nanoparticle size due to exciton confinement. At the same time, the molecular π−π* absorption of the nanoparticles was also blue-shifted, accompanied by an almost unchanging n−π* absorption as a result of the reduced overlap of the pyrazoline ring π orbital and decreased intermolecular interactions. Moreover, S1 and CT states were in equilibrium in the nanoparticles, and the pro...
TL;DR: In this paper, the role of the gold layer in promoting the photocatalytic charge transfer has been probed using thiocyanate oxidation at a rate constant of 1.25 × 109 s-1.
Abstract: Semiconductor/metal composite nanoparticles have been synthesized by chemically reducing HAuCl4 on the surface of preformed TiO2 nanoparticles. These gold-capped TiO2 nanoparticles (particle diameter 10−40 nm) were stable in acidic (pH 2−4) aqueous solutions. At low [TiO2]:[Au] ratio (<1:1), these composite nanoparticles are bigger in size (20−40 nm) and readily undergo aggregation. The TiO2/Au nanoparticles with TiO2:Au ratio ≥1:10 were relatively stable to 532 nm laser irradiation. On the other hand 532 nm laser pulse excitation of aggregated nanoparticles ([TiO2]:[Au] ≤ 1:1) led to morphological changes as they fused to produce large-size particles. Laser-induced melting/fusion was confirmed from the growth in the particle size as well as the disappearance of the aggregation absorption band. The process of melting and fusion occurred with an apparent rate constant of 1.25 × 109 s-1. The role of the gold layer in promoting the photocatalytic charge transfer has been probed using thiocyanate oxidation at...
TL;DR: The nanoparticle surface biochemical functionalization demonstrates the feasibility of using nanoparticles for biosensing and biomarking applications and shows that the silica nanoparticles are a good biocompatible solid support for enzyme immobilization.
Abstract: In this report, we demonstrate the biochemical modification of silica based nanoparticles. Both pure and dye-doped silica nanoparticles were prepared, and their surfaces were modified with enzymes and biocompatible chemical reagents that allow them to function as biosensors and biomarkers. The nanoparticles produced in this work are uniform in size with a 1.6% relative standard deviation. They have a pure silica surface and can thus be modified easily with many biomolecules for added biochemical functionality. Specifically, we have modified the nanoparticle surfaces with enzyme molecules (glutamate dehydrogenase (GDH) and lactate dehydrogenase (LDH)) and a biocompatible reagent for cell membrane staining. Experimental results show that the silica nanoparticles are a good biocompatible solid support for enzyme immobilization. The immobilized enzyme molecules on the nanoparticle surface have shown excellent enzymatic activity in their respective enzymatic reactions. The nanoparticle surface biochemical functionalization demonstrates the feasibility of using nanoparticles for biosensing and biomarking applications.