Directing Sequential\nSelf-Organization with Self-Assembled\nNanocrystals

Sequential self-organization can be used to design the\nhierarchy\nand complexity of materials beyond what is possible with single-step\nsynthesis. However, such sequential approaches introduce additional\nchallenges in maintaining control over the process. To guide the position\nand orientation of newly nucleated material, we propose the use of\nself-assembled nanocrystals (SANCs). We test the potential of SANCs\nin BaCO<sub>3</sub>|SiO<sub>2</sub> nanocomposites, also termed silica\nbiomorphs, to direct the formation of nascent microscopic crystals.\nWe find that SANCs can direct the location and crystallographic orientation\nof microcrystals at the nucleation stage, while the material, polymorph,\nand growth behavior of the crystal can be tuned largely independently.\nUsing ion exchange reactions, we show that structures can be unified\ninto a single material of interest in subsequent steps. This level\nof control over material position, orientation, and chemical composition\nallows for the retrosynthetic design of complex hierarchical structures.