**6. Structural composition of the SiO2-Ag composite films**

AFM technique was also used to analyze the structure of the SiO2-Ag composite films, the micrographs are shown in **Figure 9**. In different areas of the film it is observed that the spheres are arranged in a short-range hexagonal packing, a similar spatial distribution than the observed in the SiO2 films. Because of the absence of SiO2 and Ag NPs some voids are created. The single or agglomerates of Ag NPs are located in the interstices among SiO2 spheres. The fact that the Ag NPs do not surround the SiO2 spheres is because of the surface charge, of both Ag NPs and SiO2 spheres, is negative (52.5 mV and 44.1 mV, respectively).

**Figure 9.**

*AFM micrographs of the SiO2-Ag composite films at different amplifications. The right panel shows that Ag NPs are found in the interstices.*
