Nanosized Au clusters

While die scientific understanding of nanostructures is deficient their use in technology is at least two thousand years old. The Lycurgis ciqi, a Roman artifact pictured in the lower left of Figure 1, utilizes nanosized Au clusters to provide different colors depending on fixint or back lighting. The Roman artisans knew how to achieve the effect they didn t know its nanocluster basis. 

The well-defined large bimetallic Au—Ag cluster as [(Ph3P)i2AuigAg2oCli4] can achieve nearly two orders of magnitude of attenuation of high-intensity laser power and, consequently opens the door to a new class of optical materials based on nanosized metal clusters 3269... 

Ancient colored glasses contained nanoparticles of Au and Cu. How were these synthesized i.e., what metal salts were used, along with other experimental conditions required to yield nanosized metal clusters) ... 

Palladium metallic clusters have been prepared at room temperature by sonochemical reduction of Pd(OAc)2 and a surfactant, myristyltrimethylammonium bromide, in THE or MeOH [160[. It is noteworthy that nanosized amorphous Pd is obtained in THE, but in a crystalline form in MeOH. In this solvent, and in higher homologous alcohols, sonolysis of tetrachloropalladate(II) leads to Pd nanoclusters in which carbon atoms, formed by complete decomposition of the solvent, can diffuse. This results in an interstitial solid having the formula PdQ (0 < x < 0.15) [161]. Noble metal nanoparticles of Au, Pd, and Ag are obtained by sonicating aqueous solutions of the corresponding salts in the presence of a surfactant, which largely stabilise the naked col-... 

In recent years, W/O microemulsions have found numerous applications as microreactors for specific reactions (for comprehensive reviews, see Refs. 94 and 95). Thus, it has been shown that hydrophilic enzymes can be solubilized without loss of enzymatic activity and used to catalyze various chemical and photochemical reactions [96,97]. Other interesting applications involve the polymerization of solubilizates in microemulsions [98] and the preparation of micro-porous polymeric materials by polymerization of single-phase microemulsions [99]. Furthermore, microemulsions have been used as microreactors for the synthesis of nanosized particles for various applications [93,95] such as metal clusters (Pt, Pd, Rh, Au) for catalysis [100,101], semiconductor clusters [102-104] (ZnS, CdS, etc.), silver halides [105], calcium carbonates, and calcium fiuoride [106]. Recently it was shown [107,108] that it is possible to use W/O microemulsions for the control of polymorphism of water-soluble organic compounds. In most of these appUcations, one or more reactants are solubilized within a microemulsion and then a reaction is initiated. Depending on its molecular structure. 

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