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.

Crystalline metal-organic frameworks (MOFs) are formed by reticular synthesis, which creates strong bonds between inorganic and organic units. Careful selection of MOF constituents can yield crystals of ultrahigh porosity and high thermal and chemical stability. These characteristics allow the interior of MOFs to be chemically altered for use in gas separation, gas storage, and catalysis, among other applications. The precision commonly exercised in their chemical modification and the ability to expand their metrics without changing the underlying topology have not been achieved with other solids. MOFs whose chemical composition and shape of building units can be multiply varied within a particular structure already exist and may lead to materials that offer a synergistic combination of properties.

The Chemistry and Applications of Metal-Organic Frameworks

This critical review shows the basis of photocatalytic water splitting and experimental points, and surveys heterogeneous photocatalyst materials for water splitting into H2 and O2, and H2 or O2 evolution from an aqueous solution containing a sacrificial reagent Many oxides consisting of metal cations with d0 and d10 configurations, metal (oxy)sulfide and metal (oxy)nitride photocatalysts have been reported, especially during the latest decade The fruitful photocatalyst library gives important information on factors affecting photocatalytic performances and design of new materials Photocatalytic water splitting and H2 evolution using abundant compounds as electron donors are expected to contribute to construction of a clean and simple system for solar hydrogen production, and a solution of global energy and environmental issues in the future (361 references)

Heterogeneous photocatalyst materials for water splitting

The surface science of titanium dioxide

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.

There is provided a catalyst that exhibits a high denitration efficiency at a relatively low temperature and does not cause oxidation of SO 2 in a selective catalytic reduction reaction that uses ammonia as a reducing agent. A denitration catalyst is obtained by coating a substrate with a catalyst component. The catalyst component contains 43 wt % or more of vanadium pentoxide and has a BET specific surface area of 30 m 2 /g or more. The denitration catalyst is used for denitration at 200° C. or lower.

Denitration catalyst and method for producing the same

Small gold particles deposited on metal oxides exhibit extraordinarly high catalytic activities. For example, Au/{alpha}-Fe{sub 2}O{sub 3} can catalyze the oxidation of CO at a temperature as low as {minus}70{degrees}C. The reaction is not retarded by accelerated by moisture contained in reaction gases. These unique properties of supported gold catalysts show a potential of their applications in a variety of environmental problems. It has been found that the catalytic nature of supported gold depends on the kind of metal oxide supports. Some examples of the suitable supports are: NiFe{sub 2}O{sub 4} for NO{sub x} reduction by CO and the oxidation-decomposition of trimethylamine; Co{sub 3}O{sub 4} for the complete oxidation of CH{sub 4} and C{sub 3}H{sub 8}; ZnO and TiO{sub 2} for CO{sub 2} hydrogenation. It appears that the interfacial perimeter between gold particles and metal oxide support and the size of gold particles play the most important role in determining the catalytic nature and the activity.

Applications of supported gold catalysts in environmental problems

In this paper we describe the optical and electrical gas sensing properties of In/sub x/O/sub y/N/sub z/ films promoted by an ultra-thin gold overlayer. We have fabricated In/sub x/O/sub y/N/sub z/ films with a nanocrystalline porous structure by RF-sputtering in Ar/N/sub 2/ followed by an annealing process. Gold particles with 20-30 nm diameter on top of the In/sub x/O/sub y/N/sub z/ films have been formed by DC-sputtering followed by an annealing process. We have investigated the optical H/sub 2/ and NO/sub 2/ sensing properties (change of absorbance) and also the electrical sensing effect (change of electrical resistance) for these two gases. A combined optical/electrical sensor for H/sub 2//NO/sub 2/ is proposed.

Optical and electrical gas sensing properties of In/sub x/O/sub y/N/sub z/ films

In this paper, we describe the optical and electrical gas-sensing properties of In O N films with an ultrathin gold promoter overlayer. We have fabricated In O N films with a nanocrystalline porous structure by RF-sputtering in Ar N followed by an annealing process. Gold particles with 20-30-nm diameter have been formed on top of the In O N films by dc sputtering and an annealing process. We have investigated the optical H - and NO -sensing properties (change of absorbance) and also the electrical sensing effect (change of electrical resis- tance) for these two gases. A combined optical/electrical sensor for H NO is proposed. Index Terms—Au In O N films, electrical NO sensor, optical H sensor.

Optical and Electrical H - and NO -Sensing Properties of Au In O N Films

HRTEM(High-Resolution Transmission Electron Microscope), HAADF-STEM (High Angle Annular Dark Field Scanning Transmission Electron Microscope) and EELS(Electron Energy Loss Spectroscopy) techniques were applied for the characterization of Au/TiO 2 catalysts. HAADFSTEM provides precise size distributions for Au particles smaller than ∼2nm in diameter. It was observed that many small particles under 2nm were supported on anatase TiO 2 having a large surface area. The HAADF-STEM method was examined as a way to measure the shape of Au particles. EELS measurements were also used to examine the interface between Au and TiO 2 support to study electronic structure effects.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S1946427400190475

Masatake Haruta

Papers

Denitration catalyst and method for producing the same

Applications of supported gold catalysts in environmental problems

Optical and electrical gas sensing properties of In/sub x/O/sub y/N/sub z/ films

Optical and Electrical H - and NO -Sensing Properties of Au In O N Films

Analytical High-Resolution TEM Study on Au/TiO2 Catalysts