## 2 Materials and Methods  
The Al\({}_{2}\)O\({}_{3}\)/glass-ceramic composite coating was deposited onto brass substrates by the sol-gel process. Before deposition of the glass ceramic, an alumina interlayer (Al\({}_{2}\)O\({}_{3}\)) was deposited over the brass substrate using the standard air plasma spray technique to ensure the junction of the glass-ceramic layer. The brass substrates were cleaned by ultra-sound and alcohol without any special surface treatment. To achieve uniform porosity networks, we used a fused and crushed alumina powder (Metco 105&105 SF).  
For the preparation of the ZrO\({}_{2}\)-SiO\({}_{2}\) glass ceramic, silica was synthesized via acid hydrolysis of traethylorthosilicate (TEOS, Merck 98% purity), ethanol (Sigma-Aldrich, 99.5% purity), de-ionized water (Amresco) and nitric acid as the catalyzer. The mixture was pre-hydrolyzed for 1 h at 70 \({}^{\circ}\)C, and it was maintained under these conditions for another 3 h to induce gelation. The molar ratio of TEOS:HNO\({}_{3}\):EtOH:H\({}_{2}\)O was 0.1:0.00005:15.5:2.8. Pure zirconia was obtained from hydrolysis of two different precursors, Zr(C\({}_{3}\)H\({}_{7}\)O)\({}_{4}\) (Sigma-Aldrich) and ZrClO\({}_{2}\) -8H\({}_{2}\)O (Merck). The mixture was kept at 50 \({}^{\circ}\)C for 1 h under constant agitation. This suspension was then added to the TEOS solution, resulting in a Zr:Si molar ratio of 90:10, and maintained at 70 \({}^{\circ}\)C for 1 h. The preparation was deposited onto Al\({}_{2}\)O\({}_{3}\)/ brass substrates (1 in diameter) by the spin-coating technique (Laurell technologies vs-650 series). We established the rotation speed at 500 rpm and the rotation time at 50 s.  
The Al\({}_{2}\)O\({}_{3}\)/ZrO\({}_{2}\)-SiO\({}_{2}\) composite coating deposited on the brass substrate was then thermally treated at 850 \({}^{\circ}\)C for 60 min. Three samples were stabilized by a post-treatment using a CO\({}_{2}\) laser. This laser (Boye Laser HSLC-1206) of 10.6 \(\upmu\)m wavelength with a beam diameter of 6 mm was used for laser modification of the surface. The power density of the CO\({}_{2}\) laser beam was 0.69 (SSZ01), 1.04 (SSZ02) and 1.38 W/cm\({}^{2}\) (SSZ03). The samples were positioned at around 50 cm from the laser output and exposed for 1 min. In Figure 1, we present the computer-aided design (CAD) for the laser annealing path (1 in\({}^{2}\)).  
The photoluminescence signal was obtained by exciting the sample with the 488 nm line of an Argon laser. A 1 m focal distance spectrometer, with an 1800 g/mm grating and a thermoelectrically cooled CCD camera, was used to analyze the spectral response. The range for photoluminescence (PL) signal detection was between 550 and 900 nm.  
The crystalline structure of the sample was investigated by X-ray diffraction (XRD). The diffractometer used was a Bruker D8 Advance with a vertical goniometer; the emission used was 1.5 angstrom radiation emitted by a Cu anode (\(K_{\alpha}\) line) using 35 mA for the filament current and 30 kV for electron acceleration. The detector was a NaI crystal coupled to a photomultiplier tube. A graphite monochromator was located before the detector to eliminate the Cu-\(K_{\beta}\) line. The divergence and antiscattering slits used were 0.6 mm each and 0.1 mm for the detector slit. The microstructure of the samples was studied using a scanning electron microscope (SEM, Phenom PROX, Cali, Colombia).