Engineering low-symmetry colloidal crystals with optical anisotropies

Engineered low-symmetry colloidal crystals are emerging as promising performance-enhancing alternatives to natural materials for optical devices. However, current synthesis methods cannot precisely control structural features such as the orientation of the optical axes in these crystals. Here, DNA-modified nanorods and nanopentabipyramids were used as programmable atom equivalents to synthesize low-symmetry colloidal crystals. These crystals display three different lattice symmetries and crystal habits, aligning their optical axes in perpendicular, parallel, and oblique configurations relative to the crystal surface. The low lattice symmetries of the colloidal crystals define their optical anisotropies. Specifically, the rhombohedral colloidal crystals exhibit substantial polarization-dependent transmission and scattering characteristics. Optical measurements supported by simulations suggest that these colloidal crystals exhibit large optical anisotropy. This work expands the potential of programmable matter by developing a class of optically anisotropic materials engineered from DNA upon conjugation with relatively simple and readily available nanoparticle building blocks.