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.

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Self-assembled monolayers of thiolates on metals as a form of nanotechnology.

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.

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

Although wide variety of molecular precursors have been used for carbonization-based synthesis of fluorescent carbon nanoparticle, biomolecule-derived carbon nanoparticle with tunable fluorescence is difficult to synthesize. Here, we report a generalized approach for the preparation of fluorescent carbon nanoparticle from various biomolecules, such as lactose, ascorbic acid, tyrosine and sucrose. The method involves controlled carbonization of molecular precursor in ethylene glycol at 190°C in the presence of Na3PO4. The presented synthetic method can produce 20–30 mg of nanoparticles in one batch with fluorescence quantum yield in the range of 1–10% and nanoparticles can be conjugated with primary amine-terminated chemical/biochemical by simple incubation. These fluorescent carbon nanoparticles can be transformed into different nanobioconjugates for various biomedical applications.

Generalized synthesis of biomolecule-derived and functionalized fluorescent carbon nanoparticle

Hemin is a protoporphyrin complex of ferric iron ion that acts as catalyst for hydrogen peroxide degradation in catalase and peroxidase enzymes. However, poor water solubility and hemin dimerization inhibits...

Hemin-based cell therapy via nanoparticle-assisted uptake, intracellular reactive oxygen species generation and autophagy induction

Plasmonic‐Fluorescent and Magnetic‐Fluorescent Composite Nanoparticle as Multifunctional Cellular Probe

Biological applications of carbon-based nanomaterials have emerged in the past few years due to their unique optical, electronic, mechanical, and chemical properties. Several classes of carbon nanomaterials are carbon nanotubes; graphene and its derivatives; carbon dots; and graphene quantum dots, as well as some other forms of carbon-based nanomaterials such as fullerene, carbon nanohorns, and carbon nanoonions. In this chapter we will focus on the bioimaging applications of those carbon nanomaterials.

Application of Carbon-Based Nanomaterials as Bioimaging Probe

Piezoelectric nanomaterials offer a green and environmentally friendly approach for water purification where ultrasound or water/air flow can be used for degradation of toxic organics and bacterial disinfection. The principle involves the generation of reactive oxygen species at the piezoelectric nanoparticle surface via external pressure-induced transient local charge generation followed by electrochemical reaction that initiates the oxidative degradation processes. However, coupling of a highly piezoelectric material with an appropriate water purification platform is little explored. Here, we have designed a highly piezoelectric material-based composite and coupled with a commercially available ultrasound platform for water purification application. In particular, the piezoelectric BaTiO3 nanorod is chemically conjugated with silica gel and used for ultrasound-based degradation of toxic chemicals and destruction of cells. The designed materials and methods can be used as a promising alternative approach for water purification application. 

Nikhil R. Jana

Papers

Generalized synthesis of biomolecule-derived and functionalized fluorescent carbon nanoparticle

Hemin-based cell therapy via nanoparticle-assisted uptake, intracellular reactive oxygen species generation and autophagy induction

Plasmonic‐Fluorescent and Magnetic‐Fluorescent Composite Nanoparticle as Multifunctional Cellular Probe

Application of Carbon-Based Nanomaterials as Bioimaging Probe

BaTiO3 Nanorod-Conjugated Silica Gel for Ultrasonic Water Purification via Piezocatalytic Generation of Reactive Oxygen Species