Strategy for Patterning Titania Dendrites by Gas-Solution Interaction at Droplet Surfaces

Interaction of the solution droplet surface with gaseous components of the environment can lead to the formation of highly ordered patterns, such as dendrites. Here, we show that these structures can be spontaneously created during the open-air interaction of aqueous solution drop of titanium(III) salt with gaseous NH₃ at the contact boundary thereof. The conditions have been identified under which radially ordered dendritic patterns can form on the surface of the TiCl₃ solution droplet. The formation of these self-organized dendrite patterns can be attributed to the surface instability manifesting in Marangoni thermal flows in a droplet occurring during open-air fabrication. The composition of as-synthesized structures corresponds to coprecipitated crystalline NH₄Cl and amorphous TiO₂nH₂O. After thermal treatment at 450 °C, TiO₂ with the anatase crystal lattice is formed; meanwhile, the ordered dendrite patterns are preserved.