Figure 3.

(a) Fluorescence spectra of colloid obtained by fs laser ablation of Ag solid target in water for different centrifugation times. Excitation wavelength is ${\lambda }_{\mathrm{exc}}=$ 220  nm. A dominant band at 284 nm is readily seen. (b) Enlargement of the fluorescence curves for as-prepared and centrifuged samples for times smaller than 120 min, showing other fluorescence bands at 330 nm and 360 nm. The bands located at 284 nm and 360 nm correspond to different few atoms Ag NCs sizes. Inset shows spectra of the as-prepared and 20 min centrifugation samples as well as that for pure water for comparison.