Energetics of Oriented Attachment of Mn-Doped SnO2 Nanoparticles

Growth of nanoparticles by oriented attachment (OA) can occur in electrolyte solutions, in vacuum, or even in air. The energy change in this event is determined by the difference between the excess interface energies of the free nanoparticles and the arrangement with attached grains. Therefore, low energy boundaries (highly coherent) are more likely to attach, and after attachment, atomic rearrangement will allow crystals to effectively grow by coalescing two or more grains. However, if the energy of the boundary formed by attachment is low but the activation energy for coalescence is high, it is possible for the system to enter a metastable state that disables nanocrystals' growth (enabling design of growth resistant nanocrystals). In this work, we test this hypothesis in manganese-doped SnO2 nanopartides in the absence of organic agents. We observe that manganese dramatically lowers the energies of (noncoherent) grain boundaries of SnO2, which enhances nanostability and slows grain growth due to the increased activation energy for OA.