## 2 Experimental Details  
The Porous Silicon (pSi) samples were prepared by anodic etching of epitaxial, \(<\)100\(>\), \(n\)-type mono crystalline-silicon with an electrical resistivity between 2 \(\Omega\)-cm and 0.025 \(\Omega\)-cm. A solution mixture of hydrofluoric acid (44%), hydrogen peroxide (44%) and methanol (99.9%) with a volume ratio of 4:3:3 was used with a constant current of 40 mA. The pSi samples were obtained using a standard configuration of lateral anodizing in which samples were introduced at a rate of 4 mm/h into the solution [28]. Then, Si-NCs were obtained either scratching or milling the porous silicon layer. Scratching produces Si-NCs with an intense red emission, and milling produces blue PL emission [29]. The Si-NCs were then dispersed into isopropanol [(CH\({}_{3}\))\({}_{2}\)CHOH)] to obtain colloidal solutions. The colloidal solutions were used to produce the coated or embedded test structures. Coated samples were fabricated by spraying the colloidal Si-NC solution onto Si substrates heated to 90 \({}^{\circ}\)C producing a layer of Si-NCs (~70 nm-thick). Then, these Si-NCs films were coated with a pure SOG solution (synthesized from a 99.99% Sigma Aldrich Tetraethyl orthosilicate, St. Louis, MO, USA). The SOG solution was spun at 3000 rpm for 50 s. The coated samples are schematized in Figure 1a.  
The embedded films were obtained by mixing the colloidal solution with the SOG solution with a volume ratio of 3:1 (Si-NCs:SOG). Then, the SOG with embedded Si-NC solution was spun onto the silicon substrates at 3000 rpm for 50 s. These films are schematized in Figure 1b.  
Both coated and embedded films were heated at 150 \({}^{\circ}\)C to solidify the SOG and some of them were thermally annealed at 1100 \({}^{\circ}\)C in N\({}_{2}\) atmosphere for 3 h. The thicknesses of all films were measured with a Gaertner L117 null ellipsometer (Gaertner Scientific Corporation, Skokie, IL, USA) using a He-Ne incident laser of 632.8 nm wavelength and 2 mW of power. The coated and embedded films resulted with a thickness of \(\sim\)190 nm and \(\sim\)260 nm, respectively. The micro-structural properties of both coated and embedded films were studied by transmission electron microscopy (TEM; Tecnai F30, FEI Company, Hillsboro, OR, USA). Grazing incidence X-ray diffraction data were obtained with an X Pert PRO MRD diffractometer from PANalytical (Almelo, The Netherlands). The measurements were carried out with a Cu K\({}_{\alpha}\) (\(\lambda\) = 1.5418 A) radiation as source. The grazing angle of the incident beam was fixed at 0.5\({}^{\circ}\) and the data acquisition angle was varied between 15\({}^{\circ}\) and 60\({}^{\circ}\) with a resolution of 0.05\({}^{\circ}\), and with an acquisition time per angular step of 800 s. A computer controlled spectrometer Bruker Fourier transform infrared (FTIR) model V22 (Bruker Optics Inc., Billerica, MA, USA) was used to obtain the FTIR spectra of the films. The absorption spectra were acquired from 400 cm\({}^{-1}\) to 4000 cm\({}^{-1}\). The photoluminescence measurements were carried out at room temperature for all samples using a computer controlled spectrofluorometer model Flouromax-3 (Horiba, Kyoto, Japan). The samples were excited with a 300 nm wavelength and the emission spectra were recorded in the range of 370 nm to 1000 nm. A 300 nm band pass filter was used in the excitation monochromatic source and a 370 nm high pass filter was used for the PL detector.