Novel 2D-ordered dome films of nano titania (2D-TiO₂) and nano Ag²⁺ doped titania (2D-Ag-TiO₂) were prepared by RF magnetron sputtering method. The existence of oxygen vacancies or Ti³⁺ ions in the 2D-ordered dome films extends the absorption of TiO₂ from UV region to visible region up to 530 nm. Doping of Ag²⁺ in the 2D-TiO₂ film considerably enhance the visible light absorption of the 2D-Ag-TiO₂ film. Remarkably, for the photodegradation of cationic crystal violet (CV) and anionic methyl orange (MO), the 2D-ordered dome films exhibit 100% photodegradation selectivity to cationic CV. The 2D-Ag-TiO₂ film shows excellent selective photocatalytic durability and photostability without detectable photoreduction of Ag²⁺ ions after long time illumination. Furthermore, the 2D-ordered dome films exhibit unique ratiometric photoelectrochemical sensing property with 100% selectivity to the cationic CV. Ag²⁺ doping in the 2D-TiO₂ film significantly improves the photocatalytic activity and photoelectrochemical sensitivity as it considerably enhances the charge transfer efficiency from excited dye to titania.