The interest in nanoscale materials stems from the fact that new properties are acquired at this length scale and, equally important, that these properties * To whom correspondence should be addressed. Phone, 404-8940292; fax, 404-894-0294; e-mail, mostafa.el-sayed@ chemistry.gatech.edu. † Case Western Reserve UniversitysMillis 2258. ‡ Phone, 216-368-5918; fax, 216-368-3006; e-mail, burda@case.edu. § Georgia Institute of Technology. 1025 Chem. Rev. 2005, 105, 1025−1102

Chemistry and properties of nanocrystals of different shapes.

Monodisperse samples of silver nanocubes were synthesized in large quantities by reducing silver nitrate with ethylene glycol in the presence of poly(vinyl pyrrolidone) (PVP). These cubes were single crystals and were characterized by a slightly truncated shape bounded by {100}, {110}, and {111} facets. The presence of PVP and its molar ratio (in terms of repeating unit) relative to silver nitrate both played important roles in determining the geometric shape and size of the product. The silver cubes could serve as sacrificial templates to generate single-crystalline nanoboxes of gold: hollow polyhedra bounded by six {100} and eight {111} facets. Controlling the size, shape, and structure of metal nanoparticles is technologically important because of the strong correlation between these parameters and optical, electrical, and catalytic properties.

http://science.sciencemag.org/content/sci/298/5601/2176.full.pdf

Shape-Controlled Synthesis of Gold and Silver Nanoparticles

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.

Magnetic nanoparticles: Synthesis, protection, functionalization, and application

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

Nanocrystals are fundamental to modern science and technology. Mastery over the shape of a nanocrystal enables control of its properties and enhancement of its usefulness for a given application. Our aim is to present a comprehensive review of current research activities that center on the shape-controlled synthesis of metal nanocrystals. We begin with a brief introduction to nucleation and growth within the context of metal nanocrystal synthesis, followed by a discussion of the possible shapes that a metal nanocrystal might take under different conditions. We then focus on a variety of experimental parameters that have been explored to manipulate the nucleation and growth of metal nanocrystals in solution-phase syntheses in an effort to generate specific shapes. We then elaborate on these approaches by selecting examples in which there is already reasonable understanding for the observed shape control or at least the protocols have proven to be reproducible and controllable. Finally, we highlight a number of applications that have been enabled and/or enhanced by the shape-controlled synthesis of metal nanocrystals. We conclude this article with personal perspectives on the directions toward which future research in this field might take.

Shape‐Controlled Synthesis of Metal Nanocrystals: Simple Chemistry Meets Complex Physics?

Since its emergence a few decades ago, nanotechnology has been shown to be a perfect example of a crossroad between different fundamentals sciences. In the last 10 years, the continuous progress of classical topdown lithography and the use of alternative bottom-up elaboration methods has allowed new and smaller components to be created. Their combination has led to very complex and innovative architectures. At the same time, flexible, low-cost, and low-ecologicalfootprint devices have emerged. Thus, the diversity and multidisciplinary features present challenges in addressing these issues in educational programs.

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Practical Works on Nanotechnology: Middle School to Undergraduate Students

Le potentiel d'utilisation des nanoparticules magnetiques (stockage de l'information, ferrofluides, inducteurs...) dans divers secteurs industriels et les limitations des methodes physiques courantes d'elaboration motive la recherche de voies de synthese alternatives. Nous allons voir que la synthese organometallique permet l'obtention de nanoparticules isolees ideales pour l'etude fondamentale des proprietes physiques emergeant a l'echelle du nanometre (aimantation et anisotropie accrues, structure cristalline originale) et de la relation proprietes physiques/environnement chimique. Ces etudes, en retour, ont permis le developpement de nouveaux objets nanometriques. Notamment, des nanobâtonnets de cobalt, materiaux bien adaptes pour l'enregistrement magnetique haute densite, ont pu etre synthetises.

Synthèse organométallique de nano-objets magnétiques aux propriétés physiques contrôlées

High magnetic field study of charge-melting in Bi_{1/2}(Sr,Ca)_{1/2}MnO_3 perovskites: unconventional behaviour of Bi-Sr

The integration of high performance energy storage systems on silicon chips is necessary to support the development of portable electronic devices. Electrochemical double layer capacitors (or supercapacitors) are a good candidate for this purpose as they provide high power densities and long cycle life. Nevertheless, the improvement of the energy densities delivered by supercapacitors is required. High areal and volumetric capacitance values could be reached while using carbide-derived carbons (CDCs), thanks to their tunable nanoporous structure. The fabrication of interdigitated micro-supercapacitors from chlorination of sputtered TiC films on silicon wafer is presented here. On-chip CDC film electrodes were successfully prepared and tested in aqueous electrolyte, delivering high volumetric capacitance of 410 F.cm−3. Moreover, the use of ionic liquids/solvent mixtures provided larger potential windows, leading to high energy densities up to 90 μWh.cm−2.

Marc Respaud

Papers

Practical Works on Nanotechnology: Middle School to Undergraduate Students

Synthèse organométallique de nano-objets magnétiques aux propriétés physiques contrôlées

High magnetic field study of charge-melting in Bi_{1/2}(Sr,Ca)_{1/2}MnO_3 perovskites: unconventional behaviour of Bi-Sr

On-chip carbide derived carbon films for high performance micro-supercapacitors

Preparation and Lithium Insertion Properties of Mesoporous Vanadium Oxide