*2.2. Characterization of Nanoparticles*

The surface and elemental analysis of the SnO2 nanomaterials, Ag nanomaterials, and SnO2-Ag composite nanomaterials were carried out using JEOL SEM 5310 scanning electron microscope and Oxford EDX System, respectively. The pour-plate technique was then utilized to confirm the antimicrobial properties of the nanomaterials. In the said technique, *E*. *coli* bacterial solutions of 10<sup>í</sup><sup>4</sup> dilution factor were prepared through serial dilution from 0.5 Macfarland based standard solution. 2 mm of the said solutions were then poured into 6 opened quartz tubes. One quartz tube contained Ag nanomaterials, one quartz tube contained SnO2 nanomaterials, while the other four tubes contained SnO2-Ag nanomaterials of varying ratio of 1:4, 2:3, 3:2, and 4:1. Two additional quartz tubes were used, one containing Ag powder and another containing SnO2 powder, in order to compare the effect on the bacterial activity of the bulk powders and nanomaterials. The quartz tubes containing the bacterial solutions were then shaken. One hundred microliters of the bacterial solution from each quartz tube was poured in separate sterile petri dishes. A 9 mL sterile and cold nutrient agar medium was then poured into each petri dish containing the bacterial solutions. The contents were thoroughly mixed and allowed to solidify. The dishes were then incubated at 35 °C for 24 h before comparing the colonies grown on each petri dish.
