Study of photocatalytic activity of Al+ and In+ implanted rutile TiO2 crystals: methyl orange and methylene blue degradation

Rutile titanium dioxide crystals were implanted with Al+ and In+ ions with energy of 25 and 50 keV, respectively. The ion dose was 3 x 10(16) ions/cm(2) for both samples. Subsequently, samples were annealed at 500 degrees C resulting in doping of the material by substitution of titanium ions. Besides, ion implantation induced formation of localized defects in the TiO2 crystals, which resulted in formation of additional energy levels within the forbidden band gap. The surface chemical, structural, and optical properties of the samples were characterized by Secondary Ion Mass Spectroscopy, X-ray Photoelectron Spectroscopy, Raman spectroscopy, and X-ray Diffraction. The redistribution of implanted ions was confirmed by SIMS, whereas XPS, XRD, and Raman spectroscopy suggested the incorporation of implanted atoms as dopants in TiO2 and proved the decrease of the band-gap energy in the rutile TiO2 crystal. The photocatalytic activity of samples was tested for degradation of methyl orange (MO) and methylene blue (MB). The obtained results showed that In+ implanted TiO2 has a higher photocatalytic activity. This sample achieved decomposition of 60% of MO and 30% of MB after 360 min. The latter result could be a consequence of the lower band-gap energy of the materials due to a shift of the valence band maximum as measured by X-ray Photoelectron Spectroscopy.