*2.5. X-Ray Di*ff*ractometry*

The crystalline structures of silver oxynitrate and Ag7NO11:SiO2 were determined by X-ray diffractometry (XRD). In brief, approximately 0.5 g of either the silver oxynitrate or Ag7NO11:SiO2 powder was spread evenly into the depression in the powder XRD sample holder and placed into the X-ray diffractometer and measured from 10 to 90 ◦2Θ recorded over 30 min. From crystal lattice structure diffraction patterns, the crystalline solid-state composition of the samples was determined. The silver oxynitrate and other solid-state compounds were identified using XRD spectra deferring the Crystallography Open Database (COD) [21,23,29]. The relative compositions of the primary silver oxynitrate species and by-product or degradation products were approximated using the percent relative peak height of silver oxynitrate (36.3 ◦2Θ, COD Card 2310073) versus the additional solid-state compounds identified: AgO (32.4 ◦2Θ, COD Card 1509488), Ag2O (32.8 ◦2Θ, COD Card 4318188), Ag (38.0 ◦2Θ, COD Card 1100136), AgNO3 (29.7 ◦2Θ, COD Card 1509468), and Ag2SO4 (28.1 ◦2Θ, COD Card 1509700). Over a four-month time course, the relative solid crystalline composition of each of the samples was observed. In this manner, the stability of the higher oxidation state silver compounds was evaluated under both ambient or room temperature and at elevated temperature, 40 ◦C, in a temperature regulated incubator.
