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.

低温触媒燃焼は, メタノールとその分解生成物である水素, 一酸化炭素, ギ酸, ホルムアルデヒドを燃料または酸化除去の主な対象とするもので, クリーンで快適な暖房, 空気の浄化, 中毒•火災の防止, 工業用ガスの精製等に利用される。上記のガスに対する酸化触媒の活性序列を概観した上で, CO酸化触媒に関する研究の現状と応用について筆者らの研究を中心に紹介する。低温CO酸化では, ひ(卑)金属酸化物の方が貴金属およびそれらの酸化物より触媒活性が高く, 白金族金属は金属状態の方が酸化物状態より活性が高い。金属酸化物の場合, 触媒活性は金属と酸素との結合エネルギーに対してM字型の関係を示し, この傾向に着目して新しく開発したAg-Mn-Co系複合酸化物は活性, 耐久性に最も優れている。しかし, 湿分存在下でも室温で実用的に使用できるのは, Pt/SnO2やAu/α-Fe2O3などに代表される貴金属と半導性金属酸化物との複合系である。これらの触媒特性は, 両者の接合界面の酸素に対する反応性が顕著に向上されたことにより発現すると考えられ, 今後の触媒開発の重要な方向の一つを示唆している。

https://www.jstage.jst.go.jp/article/jpi1958/37/5/37_5_480/_pdf

Low-temperature Combustion Catalysts Mainly for CO Oxidation

Gold (Au) can be deposited as nanoparticles (NPs) smaller than 10 nm in diameter on a variety of metal oxide (MOx) NPs. Au/MOx have high catalytic performance and selective oxidation capacity which could have implications in terms of biological activity, and more specifically in modulation of the inflammatory reaction. Therefore, the aim of this study was to examine the effect of Au/TiO2, Au/ZrO2 and Au/CeO2 on viability, phagocytic capacity and inflammatory profile (TNF-α and IL-1β secretion) of murine macrophages. The most important result of this study is an anti-inflammatory effect of Au/MOx depending on the MOx nature with particle internalization and no alteration of cell viability and phagocytosis. The effect was dependent on the MOx NPs chemical nature (Au/TiO2 > Au/ZrO2 > Au/CeO2 if we consider the number of cytokines whose concentration was reduced by the NPs), and on the inflammatory mediator considered. The effect of Au/TiO2 NPs was not related to Au NPs size (at least in the case of Au/TiO2 NPs in the range of 3-8 nm). To the best of our knowledge, this is the first demonstration of an anti-inflammatory effect of Au/MOx.

/pdf/anti-inflammatory-effect-of-gold-nanoparticles-supported-on-2k7a6qs759.pdf

Anti-inflammatory effect of gold nanoparticles supported on metal oxides.

Effects of Size and Contact Structure of Supported Noble Metal Catalysts in Low-Temperature CO Oxidation

A gold cluster catalyst is capable of promoting/controlling a chemical reaction with high catalytic activity and selectivity. The gold cluster catalyst has a carrier supporting clusters, each of which is an aggregate of a plurality of gold atoms, which can be obtained by providing the carrier supporting a plurality of gold cluster compounds and then processing the gold cluster compounds on the carrier, in which each of the gold cluster compounds is stabilized by an organic ligand and including a predetermined number of gold atoms. In the gold cluster catalyst, each of the clusters may have a particle diameter of 10 nm or less and be formed substantially only of gold atoms.

Gold cluster catalyst and method for producing same

Supported gold nanoparticles (Au NPs) exhibit unique catalytic properties for the oxidation of organic compounds. The catalytic activities and the selectivities of the supported Au catalysts largely depend on the kind of support and the particle size of Au. For oxidation of alcohols to aldehydes and ketones, the reducibility of metal oxide (MOx) supports plays a prominent role, while the basicity of the supports or the size of Au particles are more important factors for non-reducible MOx, non-oxides, and other supports. The size effect is more pronounced for dehydrogenation than aerobic oxidation because dehydrogenation takes place mainly on the low-coordinated edge and corner Au atoms. Oxidation of alkenes to epoxides using O2 as a sole oxidant has been achieved by supported Au clusters having a diameter of 2 nm or less. For oxidation of cyclohexane using O2 as a sole oxidant, the presence of Bronsted acid sites contributes to the production of K/A oil. The size of Au particles also largely affects the reaction rate and product selectivity; sub-nanometer Au clusters exhibited significantly higher catalytic activity and K/A oil selectivity than Au NPs.

Masatake Haruta

Papers

Low-temperature Combustion Catalysts Mainly for CO Oxidation

Anti-inflammatory effect of gold nanoparticles supported on metal oxides.

Effects of Size and Contact Structure of Supported Noble Metal Catalysts in Low-Temperature CO Oxidation

Gold cluster catalyst and method for producing same

Gold Nanoparticles for Oxidation Reactions: Critical Role of Supports and Au Particle Size