“…These methods include sol-gel, chemical vapor deposition, hydrothermal, electrophoretic deposition, flame-aerosol, sputtering deposition, and spray pyrolysis [27,84,92,[107][108][109][110][111]. Below, each method is summarized for the preparation of photocatalyst nanoparticles and thin films of TiO 2 while Table 1 summarizes the relative merits and demerits of each technique for comparative purposes.…”