Although gold is the subject of one of the most ancient themes of investigation in science, its renaissance now leads to an exponentially increasing number of publications, especially in the context of emerging nanoscience and nanotechnology with nanoparticles and self-assembled monolayers (SAMs). We will limit the present review to gold nanoparticles (AuNPs), also called gold colloids. AuNPs are the most stable metal nanoparticles, and they present fascinating aspects such as their assembly of multiple types involving materials science, the behavior of the individual particles, size-related electronic, magnetic and optical properties (quantum size effect), and their applications to catalysis and biology. Their promises are in these fields as well as in the bottom-up approach of nanotechnology, and they will be key materials and building block in the 21st century. Whereas the extraction of gold started in the 5th millennium B.C. near Varna (Bulgaria) and reached 10 tons per year in Egypt around 1200-1300 B.C. when the marvelous statue of Touthankamon was constructed, it is probable that “soluble” gold appeared around the 5th or 4th century B.C. in Egypt and China. In antiquity, materials were used in an ecological sense for both aesthetic and curative purposes. Colloidal gold was used to make ruby glass 293 Chem. Rev. 2004, 104, 293−346

Gold nanoparticles: assembly, supramolecular chemistry, quantum-size-related properties, and applications toward biology, catalysis, and nanotechnology.

Synthesis and surface engineering of iron oxide nanoparticles for biomedical applications

1. Introduction 20642. Synthesis of Magnetic Nanoparticles 20662.1. Classical Synthesis by Coprecipitation 20662.2. Reactions in Constrained Environments 20682.3. Hydrothermal and High-TemperatureReactions20692.4. Sol-Gel Reactions 20702.5. Polyol Methods 20712.6. Flow Injection Syntheses 20712.7. Electrochemical Methods 20712.8. Aerosol/Vapor Methods 20712.9. Sonolysis 20723. Stabilization of Magnetic Particles 20723.1. Monomeric Stabilizers 20723.1.1. Carboxylates 20733.1.2. Phosphates 20733.2. Inorganic Materials 20733.2.1. Silica 20733.2.2. Gold 20743.3. Polymer Stabilizers 20743.3.1. Dextran 20743.3.2. Polyethylene Glycol (PEG) 20753.3.3. Polyvinyl Alcohol (PVA) 20753.3.4. Alginate 20753.3.5. Chitosan 20753.3.6. Other Polymers 20753.4. Other Strategies for Stabilization 20764. Methods of Vectorization of the Particles 20765. Structural and Physicochemical Characterization 20785.1. Size, Polydispersity, Shape, and SurfaceCharacterization20795.2. Structure of Ferro- or FerrimagneticNanoparticles20805.2.1. Ferro- and Ferrimagnetic Nanoparticles 20805.3. Use of Nanoparticles as Contrast Agents forMRI20825.3.1. High Anisotropy Model 20845.3.2. Small Crystal and Low Anisotropy EnergyLimit20855.3.3. Practical Interests of Magnetic NuclearRelaxation for the Characterization ofSuperparamagnetic Colloid20855.3.4. Relaxation of Agglomerated Systems 20856. Applications 20866.1. MRI: Cellular Labeling, Molecular Imaging(Inﬂammation, Apoptose, etc.)20866.2.

Magnetic Iron Oxide Nanoparticles: Synthesis, Stabilization, Vectorization, Physicochemical Characterizations, and Biological Applications

Polymer nanocomposites with layered silicates as the inorganic phase (reinforcement) are discussed. The materials design and synthesis rely on the ability of layered silicates to intercalate in the galleries between their layers a wide range of monomers and polymers. Special emphasis is placed on a new, versatile and environmentally benign synthesis approach by polymer melt intercalation. In contrast to in-situ polymerization and solution intercalation, melt intercalation involves mixing the layered silicate with the polymer and heating the mixture above the softening point of the polymer. Compatibility with various polymers is accomplished by derivatizing the silicates with alkyl ammonium cations via an ion exchange reaction. By fine-tuning the surface characteristics nanodispersion (i. e. intercalation or delamination) can be accomplished. The resulting polymer layered silicate (PLS) nanocomposites exhibit properties dramatically different from their more conventional counterparts. For example, PLS nanocomposites can attain a particular degree of stiffness, strength and barrier properties with far less inorganic content than comparable glass- or mineral reinforced polymers and, therefore, they are far lighter in weight. In addition, PLS nanocomposites exhibit significant increase in thermal stability as well as self-extinguishing characteristics. The combination of improved properties, convenient processing and low cost has already led to a few commercial applications with more currently under development.

Polymer Layered Silicate Nanocomposites

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...

http://www.geocities.ws/nandwana_vikas/Synthesis_of_Highly_Crystalline_and_Monodisperse_Maghemite.pdf

Synthesis of highly crystalline and monodisperse maghemite nanocrystallites without a size-selection process.

A new magnetic material with appreciable optical transmission in the visible region at room temperature has been isolated as a gamma-Fe(2)O(3)/polymer nanocomposite. The synthesis is carried out in an ion-exchange resin at 60 degrees C. Magnetization and susceptibility data demonstrate loading-dependent saturation moments as high as 46 electromagnetic units per gram and superparamagnetism for lower loadings where particle sizes are less than 100 angstroms. Optical absorption studies show that the small-particle form of gamma-Fe(2)O(3) is considerably more transparent to visible light than the single-crystal form. The difference in absorption ranges from nearly an order of magnitude in the "red" spectral region to a factor of 3 at 5400 angstroms. The magnetization of the nanocomposite is greater by more than an order of magnitude than those of the strongest room-temperature transparent magnets, FeBO(3) and FeF(3).

https://science.sciencemag.org/content/sci/257/5067/219.full.pdf

Matrix-Mediated Synthesis of Nanocrystalline γ-Fe2O3: A New Optically Transparent Magnetic Material

An ink jet ink includes a colorant and a liquid component containing at least one of an epoxy and a vinyl ether. Water may also be dissolved in the liquid component. Preferably, the vinyl ether is ethylene glycol monovinyl ether. An ink jet recording process includes the steps of ejecting an ink jet ink, such as the inks of the present invention, from an orifice to form an image on a recording medium.

Ink jet compositions and recording processes

Electrostatographic carrier materials having low bulk densities and high magnetic permeabilities are obtained by providing an alumino-boro-silicate glass particle containing from between about 10 to about 15 molar percent Fe 2 O 3 in which superparamagnetic ferrite crystallites having an average particle size of up to about 500A have been precipitated by heat treatment. The magnetic behavior of the glass carrier particles which is dependent on the number present and size of the ferrite crystallites can be closely controlled by heat treatment at temperatures in the range of between about 600° C and 800° C. When mixed with toner particles, these magnetic glass carrier materials experience significantly reduced toner impaction levels.

Magnetic glass carrier materials

Mossbauer and magnetization measurements have been made on a [(SiO2)45(Ca0)55]65[Fe2O3]35 glass equilibrated at 1550 °C in a variable oxygen partial pressure atmosphere. The concentration of Fe2+ cations, as determined by Mossbauer analysis, is observed to increase with lower pO2 pressures at the expense of the fraction of Fe3+ cations tetrahedrally coordinated. The Fe2+ doublet is found to display the largest isomer shift and quadrupole splitting. For the two types of ferric cations there appears to be a general tendency for the Fe3+ cations with lower coordination to have a lower isomer shift but a substantially larger quadrupole splitting. Room temperature magnetization data indicate all the samples to contain superparamagnetic particles which increase in abundance with lower pO2 pressures. The superparamagnetic behavior is attributed to the formation of ferrite precipitates which occur during quenching.

Michael P. O'Horo

Papers

Matrix-Mediated Synthesis of Nanocrystalline γ-Fe2O3: A New Optically Transparent Magnetic Material

Ink jet compositions and recording processes

Magnetic glass carrier materials

Effect of melt atmosphere on the magnetic properties of a [(SiO2)45(CaO)55]65[Fe2O3]35 glass

FeBO3 solid solutions: Synthesis, crystal chemistry, and magnetic properties☆