Low energy ion beam-induced joining of TiO₂ nanoparticles

Ion-irradiation of titanium oxide (TiO₂) nanoparticles is shown to result in the merging of the nanoparticles to form continuous chains of different shapes and dimensions, including one-dimensional nanostructures. Changes in the structure, morphology and surface chemistry of the nanoparticles were studied following irradiations with different ion-species and energies, and using scanning and transmission electron microscopies, X-ray diffraction, as well as various spectroscopic methods. High-resolution electron microscopic images confirm the merging of near-neighbor nanoparticles after irradiation, while X-ray diffraction reveals the formation of a new phase of titanium oxide resulting from ion-induced recrystallization. Analysis with X-ray photoelectron spectroscopy, Raman scattering, optical absorption, and infrared spectroscopy confirms the presence of oxygen vacancies and the formation of surface defects in the nanostructures. The resulting changes in surface chemistry and morphology are shown to affect the wettability and electrical conductivity of the material. The creation of defects and the evolution of the nanostructure, including the merging of nanoparticles and the formation of particle chain, are shown to be consistent with the predictions of Monte Carlo-based 3D TRI3DYN simulations, while the alteration of the wettability and electrical conductivity are explained using first principles-based calculations.