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.

COLLOIDAL particles of metals and semiconductors have potentially useful optical, optoelectronic and material properties1–4 that derive from their small (nanoscopic) size. These properties might lead to applications including chemical sensors, spectro-scopic enhancers, quantum dot and nanostructure fabrication, and microimaging methods2–4. A great deal of control can now be exercised over the chemical composition, size and polydis-persity1,2 of colloidal particles, and many methods have been developed for assembling them into useful aggregates and materials. Here we describe a method for assembling colloidal gold nanoparticles rationally and reversibly into macroscopic aggregates. The method involves attaching to the surfaces of two batches of 13-nm gold particles non-complementary DNA oligo-nucleotides capped with thiol groups, which bind to gold. When we add to the solution an oligonucleotide duplex with 'sticky ends' that are complementary to the two grafted sequences, the nanoparticles self-assemble into aggregates. This assembly process can be reversed by thermal denaturation. This strategy should now make it possible to tailor the optical, electronic and structural properties of the colloidal aggregates by using the specificity of DNA interactions to direct the interactions between particles of different size and composition.

A DNA-based Method for Rationally Assembling Nanoparticles Into Macroscopic Materials

Diamond-like carbon (DLC) is a metastable form of amorphous carbon with significant sp3 bonding. DLC is a semiconductor with a high mechanical hardness, chemical inertness, and optical transparency. This review will describe the deposition methods, deposition mechanisms, characterisation methods, electronic structure, gap states, defects, doping, luminescence, field emission, mechanical properties and some applications of DLCs. The films have widespread applications as protective coatings in areas, such as magnetic storage disks, optical windows and micro-electromechanical devices (MEMs).

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Diamond-like amorphous carbon

The oxidation of 1,4-butanediol and butyrolactone have been investigated by using supported gold, palladium and gold–palladium nanoparticles. The products of such reactions are valuable chemical intermediates and, for example, can present a viable pathway for the sustainable production of polymers. If both gold and palladium were present, a significant synergistic effect on the selective formation of dimethyl succinate was observed. The support played a significant role in the reaction, with magnesium hydroxide leading to the highest yield of dimethyl succinate. Based on structural characterisation of the fresh and used catalysts, it was determined that small gold–palladium nanoalloys supported on a basic Mg(OH)2 support provided the best catalysts for this reaction.

Gold‐Nanoparticle‐Based Catalysts for the Oxidative Esterification of 1,4‐Butanediol into Dimethyl Succinate

A hexagonal raft of monodisperse alkane-thiol-stabilized Au nanoparticles has been self-assembled from solution on to an amorphous C substrate and then subsequently a second layer of monodisperse but differently sized gold nanoparticles deposited on top of the first. Detailed analysis of electron micrographs obtained from various regions of this bilayer revealed the presence of several distinct epitaxial interface structures. A simple near-coincident-site lattice model is used to rationalize the existence of the observed characteristic nanoparticle interface structures.

Adoption of near-coincident-site lattice orientations by contacting monolayer rafts of metallic nanoparticles with different superlattice periodicities

In the version of this Article originally published online, in Fig. 2b, the y axis unit incorrectly included superscript –1 on Ni; it should have been just Ni. In the PDF only, in Fig. 2d–f, the label ‘Particle size (nm)’ was missing from the x axes. All of these corrections have now been made.

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Publisher Correction: Unravelling structure sensitivity in CO 2 hydrogenation over nickel

A commercial sputtered neutral mass spectrometer, using a rf‐generated plasma for both sputtering and postionization of sputtered particles, has been modified to improve sensitivity for trace analysis The modified instrument has been used to depth profile zinc‐implanted gallium arsenide A detection limit of 20 ppma was attained for zinc under conditions of maximum depth resolution from an analyzed sample area of 02 cm2 with a useful yield of 5 to 7×10−10  The results have been compared with those of secondary ion mass spectrometry Sputtered neutral mass spectrometry (SNMS) depth profiles revealed zinc redistribution in one heavily implanted sample, leading to the discovery of unusual structural damage through transmission electron microscopy This investigation is discussed as an example of the usefulness of the SNMS technique in practical applications

Christopher J. Kiely

Papers

Gold‐Nanoparticle‐Based Catalysts for the Oxidative Esterification of 1,4‐Butanediol into Dimethyl Succinate

Adoption of near-coincident-site lattice orientations by contacting monolayer rafts of metallic nanoparticles with different superlattice periodicities

Publisher Correction: Unravelling structure sensitivity in CO 2 hydrogenation over nickel

High‐sensitivity plasma‐based sputtered neutral mass spectrometry depth profiling of zinc‐implanted GaAs

Comment on “Unit Cell Information for δ- and γ-VOPO4” by Z. G. Li, R. L. Harlow, N. Herron III, H. S. Horowitz, and E. M. McCarron