Papers by Author: Pradeepan Periyat

Abstract: This review focuses on the recent developments of high temperature stable anatase TiO₂ photocatalyst. Eventhough TiO₂ exists in different forms anatase, rutile and brookite, anatase phase stabilization is often the key to obtain the highest photocatalytic performance for TiO₂, particularly for the use as an antibacterial and self-cleaning coatings in high temperature processed ceramics. Different methods available for the anatase stabilization in literature are critically reviewed and emphasis is placed on relatively recent developments. Currently available methods of anatase stabilizations are classified in to four categories viz (i) doping with metal ions (ii) doping with non-metal ions (iii) co-doping with metal and non-metal ions and (iv) dopant free stabilization by oxygen richness. Further to this, the application of these high temperature stabilized anatase TiO₂ photocatalyst on various ceramics substrates such as tile, glass and sanitary wares as self-cleaning and antibacterial coatings are also been briefly discussed.

Abstract: TiO₂ and Sm³⁺ doped TiO₂ nanocrystalline has been successfully synthesized by a modified sol-gel method. As synthesized samples of TiO₂ and Sm³⁺ doped TiO₂ were calcined at 300, 500, 700 and 800^OC and characterized by various techniques such as XRD, UV/Vis Reflectance spectroscopy, FTIR, SEM-EDS and TEM. The crystallite size of Sm³⁺ doped TiO₂ at all calcination temperature is lower than that of TiO₂ due the doping Sm³⁺ ion and thereby induced more nanobehavior. FTIR spectroscopy confirmed the presence of Ti-O and Ti-O-Ti bond in TiO₂, in Sm³⁺ doped TiO₂ along with Ti-O and Ti-O-Ti, the presence Sm-O and Ti-O-Sm bonds are confirmed. Diffuse reflectance spectra showed that the Sm³⁺ doped TiO₂ have a significant shift to longer wavelengths and an extension of the absorption in the visible region compared to the TiO₂. SEM images confirmed that the particles are agglomerated and the particle size was decreased in the Sm³⁺ doped TiO₂ in comparison with the TiO₂. EDS analysis showed the presence of Sm³⁺ ion present in the lattice of TiO₂ in doped sample. Finally the photocatalytic activity of TiO₂ and Sm³⁺ doped TiO₂ at various calcinations temperatures was investigated by the degradation of methylene blue solution under UV light and visible light. Doping with the samarium ions significantly enhanced the overall photocatalytic activity for MB degradation under both UV and visible light irradiation. The results showed that the Sm³⁺ doped TiO₂ sample calcined at 700 ^OC shows the highest photocatalytic activity under UV light and visible light irradiation.

Abstract: Photocatalytically active TiO2 and silica doped TiO₂ (Si-TiO₂) synthesised using an aqueous sol-gel method and is characterised by particle size analysis, XRD, diffuse reflectance spectra and BET measurements. The photocatalytic analysis using methylene blue proved that the Si-TiO₂ possesses higher activity than pure TiO₂. This Si-TiO₂ having higher photo-catalytic activity was incorporated into white portland cement and this modified cement exhibited photo-catalytic activity as evaluated by using methylene blue degradation experiments. This novel work is considered to be useful for further development of self-cleaning cements. Moreover silica doped to TiO₂ improved surface area and thermal stability of anatase TiO₂ significantly. At 800 ^оC, 100 percentage anatase phase was obtained for Si-TiO₂ whereas pure TiO₂ showed 100 percentage rutile phase at the same temperature and surface aera of the Si-TiO₂ was 93 m²/g while pure TiO₂ showed only 2 m²/g.