The silver-doped titanium dioxide (Ag−TiO 2 ) photocatalysts with varied silver content ranging from 0.75 at % to 3.5 at % were synthesized by a single-step sol−gel method. The role of silver content on the properties of photocatalyst has been studied. The doping of 0.75 at % silver in TiO 2 produced thermally stable TiO 2 anatase phase with smallest particle size, uniform particles size and morphology, high surface area and low-energy excitation characteristics. The Ag−TiO 2 sample with 0.75 at % silver possesses predominantly finely dispersed silver species (Ag 2 O and AgO) on the surface. The proportion of surface agglomerated silver metal (Ag 0 ) increases as the silver content in the Ag−TiO 2 sample increases. The silver oxide species were observed to be responsible for better physicochemical and catalytic properties. The TiO 2 with 0.75 at % silver was found to be an efficient photocatalyst showing enhanced photocatalytic activity for aqueous medium photocatalytic degradation of phthalic acid in the presence of UV radiation and air.

Titanium dioxide (Titania; TiO2) is one of the most widely used metal oxide semiconductor in the field of photocatalysis for removal of pollutants. It has been noted that titanium dioxide is a research friendly material as its physico-chemical and catalytic properties can be easily altered as per specific application. Since many years, researchers have tried to modify the properties of titanium dioxide by means of doping with metals and non-metals to improve its performance for photocatalytic degradation (PCD) applications. The doping of various metal ions like Ag, Ni, Co, Au, Cu, V, Ru, Fe, La, Pt, Cr, Ce, etc. in titanium dioxide have been found to be influencing the band gap, surface area, particle size, thermal property, etc. and therefore the photocatalytic activity in PCD. Moreover, photocatalytic activity of doped titanium dioxide has been observed in visible light range (i.e., at wavelength >400 nm). In this review, different synthesis route for doping of metal ions in titanium dioxide have been emphasised. The effect of metal dopant on the structural, textural and photocatalytic properties of titanium dioxide has been reviewed.

An Ag–TiO 2 photocatalyst with 3.5 atom % silver content, synthesized by a single step sol–gel method, possessed silver nanoparticles (AgNPs; 1–5 nm) on the TiO 2 surface, but owing to the nonplasmonic nature of AgNPs and the wide band gap of TiO 2 , this material exhibited poor activity in a photocatalytic degradation reaction. However, this least active Ag–TiO 2 catalyst showed a sudden increase in activity during a photocatalytic amine self-coupling reaction showing the highest activity, which was interpreted as amine (reactant) adsorption-driven activity enhancement. We found that amine adsorption occurred over AgNPs converting into plasmonic AgNPs as well as on the TiO 2 surface reducing the band gap and therefore facilitated the visible light excitation and the electron-transfer process efficiently, resulting into overall enhancement in the photocatalytic activity. Thus, a very efficient, stable, and visible light active photocatalyst (amine-adsorbed Ag–TiO 2 ) was developed by simply adsorbing an amine in the least active Ag–TiO 2 photocatalyst.