Stability tests of gold nanoparticles are crucial to understand their behavior in various environments and applications. We conducted a stability test by exposing the SiGNPs (both uncoated and coated with copoly azide 4%) and GNPs (both uncoated and coated with copoly azide positive 4%) to a solution of HCl 0.1 M or NaOH 0.1 M. Solutions properties were analyzed acquiring absorbance spectra between 400 and 1000 nm.