Nanomaterials properties Chemical reactivity

We have been interested in investigating the size-dependent electronic structure and reactivity of metal clusters deposited on solid substrates. Thus, we have shown that when the cluster size is small (SI nm), an energy gap opens up. Bimetallic clusters show additive effects due to alloying and cluster size in their electronic properties. Small metal clusters of Cu, Ni and Pd show enhanced chemical reactivity with respect to CO and other molecules. Metal clusters and colloids, especially those with protective ligands, have been reviewed in relation to nanomaterials. We have recently developed methods of preparing nanoparticles of various metals as well as nanocrystalline arrays of thiolized nanoparticles of Au, Ag and Pt. In Fig. 16, we show the TEM image of thiol-derivatized Au... 

For example, BSl in its 2005 documenting 71 2005. Vocabulary. Nanoparticules defines a nanomaterial as a material with one or several external dimensions, or an internal structure interne, at the nanometric scale, and which exhibits new properties that differ from those of the same material without nanoscale features. Note the new characteristics may include improved resistance, chemical reactivity or conductivity (translation by author). SCENIHR in a 2007 opinion on The scientific aspects of the existing and proposed definitions relating to products of nanosciences and nanotechnologies specifies that a nanomaterial was any kind of material that is composed of distinct functional parts, many of which with one or several dimensions of approximately 100 nm or less (translation by author). 

Properties directly affected by the surface chemistry include the wetting behavior, adsorption/ attraction, surface charges, basicity/addity, and chemical reactivity. Examples include the increased biocompatibility of CNTs with increasing water solubility, a property which can be achieved by PEGylating (PEG polyethylenglycol) CNTs [122] the covalent incorporation of nanomaterials into a polymer matrix, which results in good dispersions and direct uptake of loads by the reinforcement material [123] and the transformation of nanoporous carbons to solid acids upon sulfonation (e.g., with 4-benzenediazoniumsulfonate) and its use in catalysis [124],... 

The surface properties of nanomaterials include their chemical reactivity, water solubility, charge, functional groups and biocompatibility, In general, the surface properhes of nanomaterials have a profound effect on their toxicity. Pure silica nanomaterials show low levels of toxicity as ... 

One of the major breakthroughs in nanotechnology is the use of nanomaterials as catalysts for environmental applications [149]. Nanomaterials have been developed to improve the properties of catalysts, enhance reactivity towards pollutants, and improve their mobility in various environmental media [150]. Nanomaterials offer applications to pollution prevention through improved catalytic processes that reduce the use of toxic chemicals and eliminate wastes. Nanomaterials also offer applications in environmental remediation and, in the near future, opportunities to create better sensors for process controls. 

Surface functionality and oxygen concentration can influence chemical properties of carbon-based materials in aquatic environments, including surface potential, pH, surface reactivity, and sorption properties (60). Since most of the atoms in CNTs are surface atoms the effects of surface chemistry can be expected to have a large impact on the fate and transport of CNTs in aqueous environments. Smface chemistry is thought to be the primary factor regulating biological toxicity and compatibility of nanomaterials (61), and many potential appHcalions of CNTs are in the biomedical field. 

Along with research on the physical and chemical properties of nanomaterials, simnltaneous and coordinated research is needed on their physiological properties, and any associated enviromnental, health, and safety risks. At the nanoscale, research must address the correlation between factors such as particle size, shape, surface charge, area, and reactivity and potential toxicological risks. 

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