Recently, we have successfully incorporated gold nanoclusters into silica matrix by a sol-gel technique, where the synthesis of gold clusters was conducted in presence of PVP. In this paper, we report linear and nonlinear optical properties of the polymer-blocked gold clusters in silica matrix. The Au/SiO2 glass were characterized by transverse electron microscopy (TEM), x-ray diffraction (XRD), and Mie-Drude analysis of linear absorption spectra. The hydrophilic polymer, exhibiting the strong metal-polymer interaction which stemmed from the lone pair from the nitrogen with the metal particles, prohibited the flocculation and growth of gold clusters in gel-glass transition. The degenerate four-wave mixing experiment was performed to obtain the nonlinear susceptibility (chi) (3), which was evaluated to be 1.7 X 10-9 esu, in consistent with a theoretical value expected from hot electron contribution.
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