The growth of TiO2 nano-particles has been studied with reactive molecular dynamics (ReaxFF) by researchers from Penn State. While in vacuum the particles aggregate in the orientation of approach, in aqueous phase the nanocrystals have time to reorient before attaching and thus grow single or twinned crystals. This oriented attachment mechanism is dominant on the surfaces that most strongly dissociate water, indicative of the underlying role of the solvent mediating crystal growth.
In aqueous phase nanoparticles can connect and disconnect, rotating to find the optimum alignment. The two particles on the left need 25ps to align along the anatase (112) direction.
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M. Raju, A. C. T. van Duin, and K. A. Fichthorn, Mechanisms of Oriented Attachment of TiO2 Nanocrystals in Vacuum and Humid Environments: Reactive Molecular Dynamics, Nano Lett. 14, 1836-1842 (2014).Key conceptsmaterials science nanoscience ReaxFF