*2.2. Nanocomposite Preparation and Coating*

The commercial grade resins, Lapox® L-12 [liquid epoxy resin based on bisphenol-A, (4,4'-Isopropylidenediphenol, oligomeric reaction products with 1-chloro-2,3-epoxypropane)] and reactive diluent, Lapox® XR-19 (Diglycidyl ether of polypropylene glycol) were procured from Atul Ltd., Ahmedabad, India. Diethylenetriamine (DETA) as a curative agent from Sigma-Aldrich was employed. The low molecular weight epoxy Lapox® XR-19, was added as diluents to lower the viscosity of the base resin and improve the initial physical dispersion of TiO2 in the epoxy. The nanocomposites were prepared as follows: (i) the resin mixture was prepared (resin + diluant); (ii) the resin solution was diluted with ethanol to further decrease the viscosity of the resin mixture at 1:5 ratio; (iii) different amount of TiO2 or Ag-TiO2 was mixed into the diluted resin mixture. Then, the mixtures were sonicated under water bath for 30 min and degassed under vacuum. The resin-to-curative ratio in the material preparation at 10% of resin mixture weight was added. The mixtures were spin coated into the 50 mm × 12 mm (outer dia × height) size Borosil® S-Line petri plate on flat bottom dish and allowed to dry at room temperature for 24 h. The coatings were postcured at 100 °C for 2 h. Six different material samples were coated—neat epoxy resin, undoped TiO2/epoxy composite with 1 wt% loading and Ag-TiO2/epoxy composite with 0.5, 1.0, 1.5 and 2.0 wt% loading Figure 1. The epoxy/Ag-TiO2 composite turned pale brown indicating the formation of silver nanoparticles due to photoreduction. The coated substrates were sterilized by autoclaving at 121 °C, for 15 min before the start of experiments.

**Figure 1.** Assay petri dishes spin coated with neat epoxy, epoxy/TiO2 and epoxy/Ag-TiO2 composites.
