Self-Organization of Anatase TiO2 Nanoparticles to Regular Shape Clusters

Self-organization of titanium dioxide (TiO2) nanoparticles to regular shape clusters (regular triangle, hexagon, pyramid, and rhomb) has been observed. The accumulation of TiO2 nanoparticles to clusters occurs during transformation of TiO2 nanotubes to nanoparticles, which is achieved by annealing of electrochemically grown TiO2 nanotubes in fluorine ambient. Size of clusters varied in range 0.5-30 mu m, which is determined by the time elapsed from the start of the nanotube-nanoparticle transformation. Systematic studies of cluster size and density have been done on preparation conditions that revealed, in particular, that accumulation of nanoparticles to clusters occurs when nanoparticle size is less than 100 nm. The origin of this interesting phenomenon is discussed.