Controlled growth of monodisperse silica spheres in the micron size range
TL;DR: In this article, a system of chemical reactions has been developed which permits the controlled growth of spherical silica particles of uniform size by means of hydrolysis of alkyl silicates and subsequent condensation of silicic acid in alcoholic solutions.
About: This article is published in Journal of Colloid and Interface Science.The article was published on 1968-01-01. It has received 12884 citations till now. The article focuses on the topics: Stöber process & Silicic acid.
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TL;DR: This review focuses on the synthesis, protection, functionalization, and application of magnetic nanoparticles, as well as the magnetic properties of nanostructured systems.
Abstract: This review focuses on the synthesis, protection, functionalization, and application of magnetic nanoparticles, as well as the magnetic properties of nanostructured systems. Substantial progress in the size and shape control of magnetic nanoparticles has been made by developing methods such as co-precipitation, thermal decomposition and/or reduction, micelle synthesis, and hydrothermal synthesis. A major challenge still is protection against corrosion, and therefore suitable protection strategies will be emphasized, for example, surfactant/polymer coating, silica coating and carbon coating of magnetic nanoparticles or embedding them in a matrix/support. Properly protected magnetic nanoparticles can be used as building blocks for the fabrication of various functional systems, and their application in catalysis and biotechnology will be briefly reviewed. Finally, some future trends and perspectives in these research areas will be outlined.
5,956 citations
TL;DR: Practical Interests of Magnetic NuclearRelaxation for the Characterization of Superparamagnetic Colloid, and Use of Nanoparticles as Contrast Agents forMRI20825.
Abstract: 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.
5,915 citations
TL;DR: In vivo studies under magnetic resonance guidance revealed that exposure to low doses of NIR light in solid tumors treated with metal nanoshells reached average maximum temperatures capable of inducing irreversible tissue damage, and found good correlation with histological findings.
Abstract: Metal nanoshells are a class of nanoparticles with tunable optical resonances. In this article, an application of this technology to thermal ablative therapy for cancer is described. By tuning the nanoshells to strongly absorb light in the near infrared, where optical transmission through tissue is optimal, a distribution of nanoshells at depth in tissue can be used to deliver a therapeutic dose of heat by using moderately low exposures of extracorporeally applied near-infrared (NIR) light. Human breast carcinoma cells incubated with nanoshells in vitro were found to have undergone photothermally induced morbidity on exposure to NIR light (820 nm, 35 W/cm2), as determined by using a fluorescent viability stain. Cells without nanoshells displayed no loss in viability after the same periods and conditions of NIR illumination. Likewise, in vivo studies under magnetic resonance guidance revealed that exposure to low doses of NIR light (820 nm, 4 W/cm2) in solid tumors treated with metal nanoshells reached average maximum temperatures capable of inducing irreversible tissue damage (DeltaT = 37.4 +/- 6.6 degrees C) within 4-6 min. Controls treated without nanoshells demonstrated significantly lower average temperatures on exposure to NIR light (DeltaT < 10 degrees C). These findings demonstrated good correlation with histological findings. Tissues heated above the thermal damage threshold displayed coagulation, cell shrinkage, and loss of nuclear staining, which are indicators of irreversible thermal damage. Control tissues appeared undamaged.
3,774 citations
TL;DR: A simple and intuitive picture that describes the plasmon response of complex nanostructures of arbitrary shape is presented, an electromagnetic analog of molecular orbital theory, that can be understood as the interaction or "hybridization" of elementary plasmons supported by nanostructure of elementary geometries.
Abstract: We present a simple and intuitive picture, an electromagnetic analog of molecular orbital theory, that describes the plasmon response of complex nanostructures of arbitrary shape. Our model can be understood as the interaction or "hybridization" of elementary plasmons supported by nanostructures of elementary geometries. As an example, the approach is applied to the important case of a four-layer concentric nanoshell, where the hybridization of the plasmons of the inner and outer nanoshells determines the resonant frequencies of the multilayer nanostructure.
3,587 citations
TL;DR: The atomic force microscope (AFM) is not only used to image the topography of solid surfaces at high resolution but also to measure force-versus-distance curves as discussed by the authors, which provide valuable information on local material properties such as elasticity, hardness, Hamaker constant, adhesion and surface charge densities.
3,281 citations
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TL;DR: In this article, a series of monodisperse polystyrene latexes has been prepared by carefully controlled emulsion polymerizations. The particle diameters of three of these latexes were determined by electron microscopy.
Abstract: A series of monodisperse polystyrene latexes has been prepared by carefully controlled emulsion polymerizations. The particle diameters of three of these latexes were determined by electron microscopy. The latex particles were dispersed on collodion membranes supported by copper grids. The microscopes had previously been calibrated with collodion replicas of a 30 000 line/inch diffraction grating. In general, the reproducibility of measurements from many photographic exposures was good; however, a few exposures yielded particle diameters considerably higher than the averages.An investigation of this technique indicated that: (1) polystyrene latex particle diameters (collodion membranes—copper grid supports) increased considerably on electron irradiation, (2) collodion diffraction grating replicas (copper grid supports) shrank slightly on electron irradiation, and (3) the magnification of the electron microscope varied slightly from exposure to exposure. It was found that variations of particle diameter re...
156 citations
TL;DR: Aerosil, ein sehr reines, koaguliertes Siliciumdioxyd-Aerosol with Teilchen von 10 bis 40 mμ Durchmesser, wird durch Flammenhydrolyse von siliciumtetrachlorid gewonnen as discussed by the authors.
Abstract: Aerosil, ein sehr reines, koaguliertes Siliciumdioxyd-Aerosol mit Teilchen von 10 bis 40 mμ Durchmesser, wird durch Flammenhydrolyse von Siliciumtetrachlorid gewonnen. Seine physikalischen Eigenschaften (z. B. einheitliche Teilchengrose, definierte, porenfreie Oberflache) lassen sich streng reproduzieren. Dispersionsmittel, die mit der Aerosil-Oberflache uberwiegend physikalische Wechselwirkung eingehen (kettenformige, cyclische und halogenierte Kohlenwasserstoffe, konzentrierte Schwefelsaure), bilden weitgehend unabhangig von der mechanischen Einarbeitung mit 5 bis 8% Aerosil Gele. Dispersionsmittel, bei denen eine chemische Wechselwirkung in Form der Wasserstoffbruckenbindung hinzukommt (Wasser, Alkohole usw.), bilden Gele in Abhangigkeit von der beim Einarbeiten angewendeten Scherkraft erst mit 15 bis 40% Aerosil. Durch Zugabe von Basen last sich die Viscositat derartiger Dispersionen erhohen. Die Viscositat von Dispersionen in Losungsmitteln der ersten Gruppe kann durch Zusatz von wasserstoffbrucken-bildenden Losungsmitteln erniedrigt werden. Das pyrogen gewonnene Aerosil unterscheidet sich von aus Flussigkeiten gefallten Kieselsauren durch hohere chemische Reinheit, durch die porenfreie Teilchenoberflache sowie die geringere Anzahl von Silanol-Gruppen pro Oberflacheneinheit.
65 citations