Spontaneous growth of one-dimensional nanostructures from films in ambient atmosphere at room temperature: ZnO and TiO2

One-dimensional oxide-based nanostructures have been intensively studied because of their excellent optoelectronic properties. Due to the drawbacks of vapor-phase or aqueous solution growth, including complex processes, high synthesis temperatures, expensive precursors, and also preceding patterned seeding or subsequent patterning processes, there is an urgent need to grow patterned nanostructures by a simple and direct process at low temperatures. In the present study, stress-induced growth of one-dimensional single-crystalline ZnO and TiO2 nanostructures directly from ZnO and TiO2 films, respectively, in an ambient atmosphere at room temperature were developed by indentation or scratching without the use of any reaction precursors. Under large applied stresses, oxide bonds were broken, assisted by hydrolysis in the presence of moisture, and subsequently were reconstructed (defined as a bond breaking-hydrolysis-reconstruction mechanism) leading to the spontaneous growth of one-dimensional nanocrystals. The direct growth at controlled locations provides an opportunity for the simple preparation of patterned nanostructures of oxide-based materials.