Mechanism Study Of Ionic Liquid Controlled Nanomaterial Morphology:a Density Functional Theory Study

Ionic liquids as functional solvents have been attracted great attention to prepare inorganic nanomaterials. Recently, ILs have become a kind of fascinating reaction medium component for the synthesis of inorganic materials, because they offer the potential for morphology control that is not possible from other synthetic methods. ILs can form highly ordered structures on the growing crystal facets through their wealth non-covalent interactions, and this modification of surface chemistry and energetics of primary nanocrystals are both important factors for affecting the shape of nanocrystals. On the basis of DFT calculations and experiment, we proposed a new concept, geometric matching principle, in which is meaningful for prediction of the adsorption selectivity of ILs on crystal facets and clarification of the mechanism for shape-controlled chemistry. We think this geometric matching principle opens a new perspective for creating new nanosructures and is a significant step toward the ultimate goal of controlling synthesis of inorganic nanomaterials. The main content is as follows:(1) We obtain a profound understanding of ionic liquids affect the morphologies of TiO2nanocrystals. DFT calculations have been performed to study [Emim]Br adsorption of the TiO2surfaces, and the equilibrium crystal shape of TiO2has been predicted using the Wulff construction. The gap of surface energy is shown an obvious increase after [Emim]Br adsorption, especially, between (101) and (001) for anatase, and also between (110) and (001) for rutile. This gap variation results in increasing the (100) facet exposure of anatase, and an increase in the aspect ratio of rutile nanocrystals, which is verified by our experiments.(2) We proposed a new concept, geometric matching principle, in which the adsorption site of substrate should not only meet the space requirement for interionic stacking of imidazole cations, but also maximize the interaction of the adsorbed imidazole cations within ILs. In this case, the interaction between adsorbed ILs and substrate is thus maximized. This geometric matching principle is a significant step toward the ultimate goal of controlling synthesis of inorganic nanomaterials. (3) Morphology-controllable ZnO nanorings with high crystallinity were synthesized by a simple hydrothermal approach, using ionic liquid as a stabilizing agent or template. The growth mechanism of these ring-like ZnO nanocrystals was explored based on first-principles calculations and a series of controlled experiments where the concentration of [C3mim]Br was tuned. The photoluminescence spectra reveal that the as-prepared ZnO nanorings exhibit blue emission.