## 4 Discussion
This impurity is a minor component in the silver oxynitrate control and observed at increasing relative quantities as silica ratios rise from 0.1:1 to 0.5:1, SiO2:Ag, as shown by relative peak area in Figure S1. Increasing the relative concentration of silica during the co-deposition reaction was also shown to be an effective method for crystalline size control of silver oxynitrate. Utilizing the FWHM for the four strongest reflections in the diffraction pattern for silver oxynitrate, observed at 31.2, 36.3, 52.3, 62,2 \({}^{\circ}\)2\(\Theta\), respectively (222), (400), (220) and (622) reflections, the relative size of the silver oxynitrate crystals were calculated as per the Debye-Scherrer equation [41; 42]. Based upon the average crystal size determination from these primary reflections, the crystal size of silver oxynitrate decreases from \(1032\pm 152\) A to \(500\pm 75\) A as the relative ratio of SiO2:Ag increases from 0.0:1 to 0.5:1. This same trend in silver oxynitrate crystalline size reduction upon increasing silica ratio may be observed the SEM and TEM images collected for the co-deposition products as shown in Figures 2 and 3. As silica is known to confer enhanced stability of active ingredients, the stability of silver oxynitrate and Ag\({}_{7}\)NO\({}_{11}\):SiO\({}_{2}\) were compared over the course of four months under ambient and 40 \({}^{\circ}\)C storage. The thermal degradation pathways for silver oxynitrate are well known [21; 23; 30]. The first two decomposition processes for silver oxynitrate, Equations (4) and (5) are exothermic with associated enthalpies of \(\Delta\)H = \(-244\) KJ/mol and \(-75.8\) KJ/mol and initiation temperatures of 80-85 \({}^{\circ}\)C and 115-120 \({}^{\circ}\)C respectively [21]. In contrast, the subsequent degradation processes, Equations (6) and (7), are endothermic with associated enthalpies of \(\Delta\)H = 659 KJ/mol and 338 KJ/mol and initiation temperatures of 350 \({}^{\circ}\)C and 425-435 \({}^{\circ}\)C respectively [21]. It is also known that the rate of decomposition of silver oxynitrate is accelerated in the presence of heat and water [30; 41]. Under ambient conditions, silver oxynitrate is observed to proceed through the first decomposition process as shown in Figure 4A. The rate of this degradation process is retarded in Ag\({}_{7}\)NO\({}_{11}\):SiO\({}_{2}\) as shown in Figure 4B. At elevated temperatures, a more rapid degradation of silver oxynitrate will result in increased thermal energy due to the exothermic nature of the first two degradation processes. In combination with the elevated storage temperature, initiation of subsequent endothermic degradation processes as shown in Equations (6) and (7) are observed to occur for silver oxynitrate as seen in Figure 5A. These advanced degradation processes are not observed in Ag\({}_{7}\)NO\({}_{11}\):SiO\({}_{2}\). At elevated temperatures only the first degradation process, Equation (4), is observed for Ag\({}_{7}\)NO\({}_{11}\):SiO\({}_{2}\) as seen in Figure 5B. Silica is a thermal insulator with a very low thermal conductivity; beneficial in aerospace and construction applications [43; 44; 45]. As an aerogel, [PERSON] et al. demonstrated silica granulates may afford a heat transfer coefficient of less than 0.4 W/(m\({}^{2}\) K) [44]. Silica is also well known as a desiccant, capable of sequestering water from organic solvents to less than 100 ppm and significant reductions in water content in solid-state powder samples [46; 47]. The results presented here suggest that the presence of an interspersed silica framework with thermally insulating and desiccating properties may obstruct heat transfer and restrict the step-wise degradation of silver oxynitrate. These properties enhance the long term and thermal stability of silver oxynitrate within the silica framework. Silver oxynitrate has been previously shown to rapidly and effectively eliminate bacterial organisms in both free and biofilm states [16; 17; 18].