Bioinspired synthesis of crystalline TiO2:: Effect of amino acids on nanoparticles structure and shape

Crystalline titanium dioxide particles were obtained through the thermohydrolysis at 60 degrees C of an aqueous TiCl4 precursor in the presence of various amino acids. These protein building blocks were employed to modify the phase distribution, size, and shape of the formed nanoparticles. The consequences of the presence of biological species during the different steps of the inorganic condensation were characterized by a variety of techniques, including X-ray diffraction, transmission electron microscopy, and thermogravimetric analysis coupled with differential scanning calorimetry. The amino acid side chain functions were shown to be of particular importance in regard to the modification of the TiO2 structure and morphology. More specifically, aspartic acid, glutamic acid, and serine allowed the formation of pure anatase nanoparticles. The pH of the reacting solution also proved to be a relevant parameter to control the particle size and shape. Explanations based on the actual knowledge on the titania/amino acids interface were proposed for every observed modification.