Nanosized noble metal gold

Nanosized noble metal gold nanoparticles (AuNPs 10 nm)-doped dielectric composite titania films [323] with large third-order nonlinear susceptibility were reported to be applied to optical information processing devices, such as optical switch or all optical logical gates. The third-order nonlinear refractive index and nonlinear absorption coefficient of the films were on the order of 10 cm and 10 cm with nonlinear susceptibility = 6.88 x 10 ° esu. 

As is well known, gold is the most chemically inert metal, and as such the most noble metal. However, when it is present as particles of nanosize (<5 nm), it becomes reactive. This may be due to the increasing fraction of low coordination surface sites as particle size decreases, on which, for instance, CO molecules can adsorb, and H2 can dissociate. This may be due also to changes in the electronic properties exemplified, for instance, by the contraction of the Au—Au bond when the gold particles are smaller than 2 nm [1-3]. 

Noble metal quantum clusters. Chemistry of gold-sulphur interface on monolayer protected clusters (MFCs) has long attracted research interest. These materials have a nanosized metal core containing hundreds or thousands of atoms with monolayers of surfactants/ligands on its surface. The metal core made of dense packing of metal atoms forming nanocrystals with specific lattice planes on its surface. 

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