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.

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.

Interest in catalysis by metal nanoparticles (NPs) is increasing dramatically, as reflected by the large number of publications in the last five years. This field, "semi-heterogeneous catalysis", is at the frontier between homogeneous and heterogeneous catalysis, and progress has been made in the efficiency and selectivity of reactions and recovery and recyclability of the catalytic materials. Usually NP catalysts are prepared from a metal salt, a reducing agent, and a stabilizer and are supported on an oxide, charcoal, or a zeolite. Besides the polymers and oxides that used to be employed as standard, innovative stabilizers, media, and supports have appeared, such as dendrimers, specific ligands, ionic liquids, surfactants, membranes, carbon nanotubes, and a variety of oxides. Ligand-free procedures have provided remarkable results with extremely low metal loading. The Review presents the recent developments and the use of NP catalysis in organic synthesis, for example, in hydrogenation and C--C coupling reactions, and the heterogeneous oxidation of CO on gold NPs.

Nanoparticles as Recyclable Catalysts: The Frontier between Homogeneous and Heterogeneous Catalysis

The development of novel materials is a fundamental focal point of chemical research; and this interest is mandated by advancements in all areas of industry and technology. A good example of the synergism between scientific discovery and technological development is the electronics industry, where discoveries of new semiconducting materials resulted in the evolution from vacuum tubes to diodes and transistors, and eventually to miniature chips. The progression of this technology led to the development * To whom correspondence should be addressed. B.L.C.: (504) 2801385 (phone); (504) 280-3185 (fax); bcushing@uno.edu (e-mail). C.J.O.: (504)280-6846(phone);(504)280-3185(fax);coconnor@uno.edu (e-mail). 3893 Chem. Rev. 2004, 104, 3893−3946

http://depa.fquim.unam.mx/amyd//archivero/FidelmarLechugaSanabria_4940.pdf

Recent advances in the liquid-phase syntheses of inorganic nanoparticles.

3.7. Palladium Nanoparticles as Catalysts 888 3.8. Other Transition-Metal Complexes 888 3.9. Transition-Metal-Free Reactions 889 4. Applications 889 4.1. Alkynylation of Arenes 889 4.2. Alkynylation of Heterocycles 891 4.3. Synthesis of Enynes and Enediynes 894 4.4. Synthesis of Ynones 896 4.5. Synthesis of Carbocyclic Systems 897 4.6. Synthesis of Heterocyclic Systems 898 4.7. Synthesis of Natural Products 903 4.8. Synthesis of Electronic and Electrooptical Molecules 906

https://www.chem.ccu.edu.tw/~joyce/referance/ericyang/Chem.%20Rev/Chem.%20Rev.%202007,%20107,%20874-922.pdf

The Sonogashira Reaction: A Booming Methodology in Synthetic Organic Chemistry†

Reduced transition metal colloids: a novel family of reusable catalysts

Reduced Transition Metal Colloids: A Novel Family of Reusable Catalysts?

Microheterogeneous catalytic systems using aqueous suspensions of rhodium particles are proved to be efficient for alkene hydrogenation in biphasic liquid-liquid medium provided that the method of stabilization and the interfacial phenomena are properly chosen and controlled. Aqueous supensions stabilized by specially designed trianionic molecules or by hydrophilic polymer (PVA) have been studied. A series of trisulfonated molecules 1 with modulated solution behaviors (surfactant or hydrotrope) depending on the nature of the substituents has been used to stabilize aqueous suspensions of oxidized (polar) or reduced (non polar) rhodium particles. Stabilization of polar particles occurs whatever the substituents when stabilization of metallic apolar particles requires surfactants bearing a significant lipophilic part. In the former case, highly stable suspensions of rhodium nanoparticles with controlled size are obtained in micellar solutions. Both oxidized and reduced rhodium suspensions efficiently catalyzed octene hydrogenation in liquid-liquid medium and it is established that high activity and possible recovery and recycling of the catalyst can be achieved by the control of interfacial parameter e.g. the interfacial tension. In the same way, common polymer-protected colloidal suspensions of Rh(0) particles are proved to efficiently catalyze hydrogenation in two liquid phases systems provided that optimized amounts of surfactants are added to reduce the interfacial tension without emulsification. From these results a relationship between interfacial tension and catalytic activity in biphasic system is proposed.

Biphasic liquid-liquid hydrogenation catalysis by aqueous colloidal suspensions of rhodium: The choice of the protective-colloid agent and the role of interfacial phenomena

New highly water-soluble surfactants stabilize colloidal rhodium(0) suspensions useful in biphasic catalysis

Highly water-soluble trisulfonated compounds 2:R-C(p-C 6 H 4 SO 3 Na) 3 bearing polar, non-polar or lipophilic R substituents have been used to stabilize a catalytically active colloidal suspension of polyhydroxylated rhodim particles allowing the hydrogenation of liquid alkenes in biphasic medium. Experiment carried out on a series of hydrotropic or surface active molecules 2 demonstrate that the stabilization occurs via adsorption of the polyanionic head group on the polar colloid surface affording electrostatic or electrosteric repulsions which prevent aggregation

Henri Patin

Papers

Reduced transition metal colloids: a novel family of reusable catalysts

Reduced Transition Metal Colloids: A Novel Family of Reusable Catalysts?

Biphasic liquid-liquid hydrogenation catalysis by aqueous colloidal suspensions of rhodium: The choice of the protective-colloid agent and the role of interfacial phenomena

New highly water-soluble surfactants stabilize colloidal rhodium(0) suspensions useful in biphasic catalysis

Colloidal rhodium suspensions stabilized by various hydrotropic or surface active triphenylmethyl trisulfonates and their use in biphasic catalysis