Abstract:
Controlling nucleation and growth is crucial in biological and artificial mineralization and self-assembly processes. The nucleation barrier is determined by the chemistry of the interfaces at which crystallization occurs and local supersaturation. Although chemically tailored substrates and lattice mismatches are routinely used to modify energy landscape at the substrate/nucleus interface and thereby steer heterogeneous nucleation, strategies to combine this with control over local supersaturations have remained virtually unexplored. Here we demonstrate simultaneous control over both parameters to direct the positioning and growth direction of mineralizing compounds on preselected polymorphic substrates. We exploit the polymorphic nature of calcium carbonate (CaCO3) to locally manipulate the carbonate concentration and lattice mismatch between the nucleus and substrate, such that barium carbonate (BaCO3) and strontium carbonate (SrCO3) nucleate only on specific CaCO3 polymorphs. Based on this approach we position different materials and shapes on predetermined CaCO3 polymorphs in sequential steps, and guide the growth direction using locally created supersaturations. These results shed light on nature’s remarkable mineralization capabilities and outline fabrication strategies for advanced materials, such as ceramics, photonic structures, and semiconductors.
Notes:
Dr. Liesbeth Janssen and Prof. Pieter Rein ter Wolde are kindly acknowledged for help with the manuscript. This research was supported by the NSF Designing Materials to Revolutionize and Engineer our Future under Award 15-33985 and the Harvard Materials Research Science and Engineering Centers under Award DMR 14-20570. W.L.N. thanks the Netherlands Organization for Scientific Research (NWO) for financial support from a VENI grant. L.L. thanks the Department of Mechanical Engineering at Virginia Polytechnic Institute and State University for support. Electron microscopy and FIB milling was performed at the Center for Nanoscale Systems at Harvard University, supported by the NSF under Award ECS-0335765, and at the Amsterdam nanoCenter, which was financially supported by NWO.
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