Investigation of amino acids as templates for the sol–gel synthesis of mesoporous nano TiO₂ for photocatalysis

TiO₂ nanoparticulates of well-defined size were synthesized using amino acid templates employing sol–gel method. Eight different amino acids were studied. The samples were characterized by various methods such as X-ray diffraction, Fourier transform infrared spectroscopy, ultraviolet–visible diffuse reflectance spectroscopy, Brunauer–Emmett–Teller surface area measurement, and transmission electron microscopy. Of the amino acids used, catalyst employing aspartic acid was found to have minimum particle size of 10.4 nm and maximum surface area of 95.3 m²/g. The catalytic activity of the prepared TiO₂ samples was compared with Degussa-P25 catalyst for direct sunlight photodegradation of methylene blue and calmagite dyes. Catalyst prepared form branched amino acids, proline, valine, and aspartic acids, were found to give better results. Based on infrared spectroscopy studies, it is proposed that amino acids act as a surfactant by hydrogen bonding between the hydrogen of the ammonium ion and the surface hydroxyl group of the colloid. Graphical abstract: .