*2*.*1*. *Preparation of Nanoparticles*

The raw materials used were Sigma Aldrich (St. Louis, MO, USA) Ag powder with 99.99% purity and <45 ȝm grain size and Merck SnO2 powder of 99% purity with <5 ȝm grain size. The horizontal vapor phase crystal growth technique (HVPG) was used in the fabrication of SnO2 nanomaterials, Ag nanomaterials, and SnO2-Ag composite nanomaterials. In the said technique, 35 mg of SnO2, Ag, and mixtures of SnO2 with Ag powders at 1:4, 2:3, 3:2, and 4:1 mass ratio were placed into an ultrasonically clean closed-end quartz tubes with inner diameter of 8.5 mm, outer diameter of 11 mm, and length of 220 mm. The tube was evacuated using the Thermionics High Vacuum System with a vacuum pressure of 10<sup>í</sup><sup>6</sup> Torr which was sealed on the other end using by an Oxy-LPG gas mixture blow torch. The sealed quartz tubes were then placed in a Thermolyne horizontal tube furnace and were baked at a temperature of 800 °C with growth time of 6 h and ramp time of 80 min.
