Hydrothermal synthesis of highly crystalline nanotubes/nanoplates of pure and silver-doped anatase-titania using acid-catalyst-modified sol-gel precursors

Highly crystalline nanotubes/nanoplates of pure and Ag-doped anatase-titania (TiO2) having high aspect-ratio have been synthesized, without the involvement of thermal treatment, via the hydrothermal method using the acetic-acid-modified sol-gel processed nanocrystalline pure and Ag-doped anatase-TiO2 as precursors. The samples have been characterized for analyzing their morphology, structure, specific surface-area, and surface-chemistry using the transmission electron microscope, selected-area electron diffraction (SAED), X-ray diffraction, Brunauer-Emmett-Teller specific surface-area measurement, and Fourier transform infrared techniques. It has been observed that the hydrothermal treatment of acid-catyalyst-modified pure and Ag-doped nanocrystalline anatase-TiO2 precursors and the subsequent washing of hydrothermal products result in the formation of nanotubes/nanoplates of pure and Ag-doped anatase-TiO2 instead of those of hydrogen titanate which is invariably obtained with the use of unmodified-precursors. It has been proposed that the formation of nanotubes/nanoplates of pure and Ag-doped anatase-TiO2 via the hydrothermal method without the involvement of thermal treatment, under the given processing conditions, is due to the operation of double ion-exchange mechanism which is in contrast to that of conventional single ion-exchange mechanism responsible for the formation of nanotubes of hydrogen titanate. The operation of as-proposed double ion-exchange mechanism has been strongly supported by the experimentally observed variation in the solution-pH involved during the washing treatment of hydrothermal product.