Size Gold Clusters. The Au55 Case

Large-Size Gold Clusters. The Au55 Case 

The fuzzy frontier between the molecular and the nanometric level can be elucidated from an electronic point of view. Molecules and small clusters can be described as systems in which the metal atoms form well-defined bonding and antibonding orbitals. Large clusters or small nanoparticles (quantum dots) with dimensions of a few nanometers are intermediate between the size of molecules and bulk material, presenting discrete energy levels with a small band gap owing to quantum-mechanical rules. Finally, larger particles tend to lose this trend and display a typical band structure similar to that of the bulk material. 

Multilayer systems of [Au55(PPh3)i2Cl6] double layers and Si02 films can also be synthesized and characterized. For this purpose, a combination of techniques is 

In this section, we will emphasize how the different chemical approaches allow control over the size, shape and assembly of Au NPs. The first subsection describes the most common synthetic approaches for the synthesis of gold nanoparticles, based on historically known methods from Faraday and Turkevitch. The surface chemistry of Au NPs, Au nano-bio hybrids synthesis and certain properties and applications of gold nanoparticles will be briefly summarized. 

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