Rather, large spherical clusters are

formed by explosive diffusion of gold atoms. Figure 5 Local growth of Au-NP in xerogels doped with HAuCl 4 . (a) Optical absorption after fs irradiation. Photograph and TEM image buy Sotrastaurin obtained on a sample co-doped with sodium carbonate. (b) Optical absorption after CW irradiation. Photograph and TEM image obtained on a sample co-doped with sodium carbonate. (a and b) adapted from [29] and [30], respectively. Such a scheme is quite different from the one explaining the photoprecipitation of Au-NP in the same kind of samples under CW laser irradiation [30]. The CW irradiation conditions being more or less the same as previously described for Ag-NP and the Au-doped sample being the same as Napabucasin datasheet in the fs experiment, the result shown in Figure 5b is the local production of Au-NP at the surface of the sample, with a size distribution between 5 and 15 nm and a rather good space resolution of 20 μm. Although limited to the sample surface, this approach presents two main advantages over the IR fs experiment: firstly, CW lasers are obviously cheaper than a fs laser chain. Secondly, since one-photon absorption generates sufficient energy to extract electrons from

the matrix, no carbonate additive is required here. In any case, both growing processes can be qualified as efficient to produce Au-NPs in a porous silica gel. Semiconductor nanoparticles in a xerogel Semiconducting nanoparticles (SC-NP) are particularly suited to increase the linear refractive index of a glass, because their own refractive indices are among the highest [31]. For example, Bragg mirrors of high efficiency can be foreseen using a series of PbS-doped and nondoped regions in an optical fiber. Moreover, quantum confinement in SC-NP is the base for the well-known narrow and tunable light emission having a great potential in display and lighting technologies [32]. SC-NPs are also of particular interest

for their high nonlinear refractive indices [11] and absorption coefficients [33], which depend on why particle size too. Cadmium sulfide nanoparticles Xerogels of mean pore diameter of 5 nm were impregnated with a 0.56-M concentrated solution containing cadmium acetate and thiourea as precursors of CdS. After drying, they were irradiated under fs laser beam at 800 nm. Since neither the matrix nor the CdS precursors do absorb light linearly at this wavelength, the process involves essentially multiphoton absorption. The scanning setup enabled to cover a wide CdS-doped area in the bulk volume of the sample; with a mean power of 60 mW, a small part of the deposited energy (1,600 J/cm2) is absorbed and transformed into heat to break down precursor molecules and to form CdS-NP. This thermal process is however quite inefficient in the fs regime at low repetition rate [34]. Hence, a pale yellow color appeared when using the most concentrated doping solution and the highest laser power.