Programmable Stepwise Heteroepitaxial Growth of Colloidal Crystals With Different Phases

Heteroepitaxial growth is a powerful strategy for constructing hierarchical systems by integrating materials with different structures across the angstrom to nanometer length scale. However, lattice mismatches between different phases often impact the resulting crystal stability. This is especially true for colloidal crystal systems. Here, colloidal crystal engineering with DNA is used to assemble multi-phase colloidal crystals, with extreme tolerance for lattice strain. Most notably, the structural flexibility of DNA can accommodate lattice mismatch up to 18%, allowing one to grow, for the first time, face-centered cubic (fcc) lattices with (111) facets on body-centered cubic (bcc) crystals with (110) facets (a 13% bcc-fcc phase misfit for the particles studied; 2%-4% in an atomic system). By adjusting particle size, more or less strain can be induced, allowing one to determine the upper limit for bcc-fcc phase misfit (34%). Finite-difference time-domain (FDTD) optical simulations reveal that these multi-phase heteroepitaxial structures can function as waveguides, making them attractive targets for those interested in optics. The lattice mismatches accommodated through DNA bonding exceed those typical in atomic heteroepitaxy (a few percent without a buffer layer), highlighting the versatility of this technique for designing and preparing hierarchical materials with tailored structure-function relationships.