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.

Nanomaterials are engineered structures with at least one dimension of 100 nanometers or less. These materials are increasingly being used for commercial purposes such as fillers, opacifiers, catalysts, semiconductors, cosmetics, microelectronics, and drug carriers. Materials in this size range may approach the length scale at which some specific physical or chemical interactions with their environment can occur. As a result, their properties differ substantially from those bulk materials of the same composition, allowing them to perform exceptional feats of conductivity, reactivity, and optical sensitivity. Possible undesirable results of these capabilities are harmful interactions with biological systems and the environment, with the potential to generate toxicity. The establishment of principles and test procedures to ensure safe manufacture and use of nanomaterials in the marketplace is urgently required and achievable.

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Toxic Potential of Materials at the Nanolevel

Synthesis and surface engineering of iron oxide nanoparticles for biomedical applications

Rapid growth in nanotechnology is increasing the likelihood of engineered nanomaterials coming into contact with humans and the environment. Nanoparticles interacting with proteins, membranes, cells, DNA and organelles establish a series of nanoparticle/biological interfaces that depend on colloidal forces as well as dynamic biophysicochemical interactions. These interactions lead to the formation of protein coronas, particle wrapping, intracellular uptake and biocatalytic processes that could have biocompatible or bioadverse outcomes. For their part, the biomolecules may induce phase transformations, free energy releases, restructuring and dissolution at the nanomaterial surface. Probing these various interfaces allows the development of predictive relationships between structure and activity that are determined by nanomaterial properties such as size, shape, surface chemistry, roughness and surface coatings. This knowledge is important from the perspective of safe use of nanomaterials.

Understanding biophysicochemical interactions at the nano–bio interface

http://sistemas.eel.usp.br/docentes/arquivos/2166002/1234Nb/Geetha-review2009.pdf

Ti based biomaterials, the ultimate choice for orthopaedic implants – A review

Polymer resins incorporating nanoparticles having a particle size in the range of 1-100 nm and a narrow particle size distribution have improved tensile properties and scratch resistance.

Nanoparticle-filled polymers

We report a simple and effective approach to disperse CdSe quantum dots (QDs) into a high molecular weight silicone matrix and prepare highly transparent luminescent CdSe–silicone nanocomposites. The CdSe QDs were synthesized via a room temperature injection method and were subsequently grafted with organophosphate-terminated poly(dimethyl siloxane) (PDMS) brushes. It was found that the bimodal PDMS-brush-grafted QDs demonstrate a homogeneous dispersion within the high molecular weight silicone matrix, enabling the preparation of thick transparent CdSe–silicone nanocomposites. The good dispersion also benefits the uniformity and long-term stability of the photoluminescence of the CdSe–silicone nanocomposites against thermal annealing. The prepared CdSe–silicone nanocomposites would have potential applications as color-conversion materials on light emitting diodes. This dispersing strategy could be broadly applicable and provides valuable guidelines for dispersing other functional nanoparticles in silicones.

Transparent luminescent silicone nanocomposites filled with bimodal PDMS-brush-grafted CdSe quantum dots

Synthesis, sintering, and magnetic properties of nanophase Cr2O3

The role of TiO2 nanoparticle surfaces in affecting the crystalline structure of low-density polyethylene (LDPE) has been investigated by varying the nanoparticle surface from hydrophilic (as-received) to less hydrophilic (dried) or more hydrophilic (polar silane treated). Differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WXRD) were used to determine the degree of crystallinity and crystalline structure. The impact of nanoparticle aggregates on the nanometer to micrometer organization of LDPE crystals was studied with atomic force microscopy (AFM) and small-angle light scattering (SALS). This characterization showed that the presence of the TiO2 nanoparticles, with the various different surface conditions investigated, did not alter the degree of LDPE crystallinity, the unit cell dimensions, the average lamellar thickness, or the average spherulite size. However, the nanoparticles did affect the internal arrangement of intraspherulitic crystalline aggregates by decreasing the relative optic axis orientation of these crystals, usually referred to as internal spherulite disorder. The LDPE filled with the nanoparticles treated with a polar silane (N-(2-aminoethyl) 3-aminopropyl-trimethoxysilane (AEAPS)) showed the highest internal spherulitic disorder and exhibited the most poorly developed spherulite structure. The combination of SALS with AFM has allowed a detailed characterization of the morphology of the semicrystalline polymer nanocomposites. Information on the internal organization of the spherulites, the size of the nanoparticle aggregates, and the location of the nanoparticle aggregates can be uniquely obtained when both techniques are used. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 488–497, 2005

Effect of titania nanoparticles on the morphology of low density polyethylene

Exposing osteoblasts on an electrically conducting nanocomposite, which may be an orthopaedic/dental implant, to electrical stimulation enhances osteoblast proliferation thereon. The electrically conducting nanoscale material includes an electrically conducting nanoscale material and a biocompatible polymer and/or a biocompatible ceramic; carbon nanotubes may be used as the electrically conducting nanoscale material.

Richard W. Siegel

Papers

Nanoparticle-filled polymers

Transparent luminescent silicone nanocomposites filled with bimodal PDMS-brush-grafted CdSe quantum dots

Synthesis, sintering, and magnetic properties of nanophase Cr2O3

Effect of titania nanoparticles on the morphology of low density polyethylene

Electrically conducting nanocomposite materials for biomedical applications