Hybrid Amino Acid-TiO2 Materials with Tuneable Crystalline Structure and Morphology for Photocatalytic Applications

Abstract

A method to produce hybrid organotitanias, both as thin films and suspensions, showing excellent photocatalyic activity in the degradation of organic dyes in aqueous solutions under visible light irradiation is disclosed. This method is based on the in situ incorporation of an amino acid, l-tyrosine, during the synthesis of the titanias owing to its coordination and co-condensation with the titania precursor under acidic conditions. This methodology allows the fine-tuning of their crystalline structure, size, and shape by simply varying the pH of the synthesis gel, leading to anatase nanoparticles of ≈5 nm and surface areas of ≈200 m2 g−1 at pH = 2.2, while highly crystalline rutile nanorods are formed at pH = 0. The incorporation of l-tyrosine to both anatase nanoparticles and rutile nanorods enables these materials to absorb light in the visible range due to both the decrease in their band gap, as compared to the reference materials, and the presence of additional absorption edges at wavelengths higher than 400 nm. Consequently, the photocatalytic activity of both hybrid anatase nanoparticles and rutile nanorods exhibits a 120% enhanced photocatalytic efficiency, as compared to that of l-Tyr-free titanias and the commercial P25, which confirms their potential application in water remediation.