*2.3.5 UV-visible spectrophotometry*

UV-visible spectra of all the samples were recorded using UV-Vis double beam spectrophotometer (Hitachi U-2000) in the range 200–800 nm. The course of

reduction of noble metal ions on TiO2 particles and extent of decolourisation were studied using this technique. Further, the band gap energies (Eg) of the synthesised catalysts were calculated according to the equation

$$\mathbf{E\_{g} = h \ c/h} \tag{2}$$

where h, Planck's constant; c, velocity of light (m/s); λ, wavelength (nm).
