Single crystals are usually faceted solids with homogeneous chemical compositions. Biogenic and synthetic calcite single crystals, however, have been found to incorporate macromolecules, spurring investigations of how large molecules are distributed within the crystals without substantially disrupting the crystalline lattice. Here, electron tomography reveals how random, three-dimensional networks of agarose nanofibers are incorporated into single crystals of synthetic calcite by allowing both high- and low-energy fiber/crystal interface facets to satisfy network curvatures. These results suggest that physical entrapment of polymer aggregates is a viable mechanism by which macromolecules can become incorporated inside inorganic single crystals. As such, this work has implications for understanding the structure and formation of biominerals as well as toward the development of new high–surface area, single-crystal composite materials.

Synthetic single crystals are usually homogeneous solids. Biogenic single crystals, however, can incorporate biomacromolecules and become inhomogeneous solids so that their properties are also extrinsically regulated by the incorporated materials. The discrepancy between the properties of synthetic and biogenic single crystals leads to the idea to modify the internal structure of synthetic crystals to achieve nonintrinsic properties by incorporation of foreign material. Intrinsically colorless and diamagnetic calcite single crystals are turned into colored and paramagnetic solids, through incorporation of Au and Fe3O4 nanoparticles without significantly disrupting the crystalline lattice of calcite. The crystals incorporate the nanoparticles and gel fibers when grown in agarose gel media containing the nanoparticles, whereas the solution-grown crystals do not. As such, our work extends the long-history gel method for crystallization into a platform to functionalize single-crystalline materials.

Organic single-crystalline p-n junctions are grown from mixed solutions. First, C60 crystals (n-type) form and, subsequently, C8-BTBT crystals (p-type) nucleate heterogeneously on the C60 crystals. Both crystals continue to grow simultaneously into single-crystalline p-n junctions that exhibit ambipolar charge transport characteristics. This work provides a platform to study organic single-crystalline p-n junctions.

Well-aligned C60 and TIPS-pentacene single-crystals grow on a common substrate by a droplet-pinned crystallization method. Complementary inverters based on the two aligned crystals show gain values as high as 155. This work demonstrates a simple solution-processing approach to investigate high-performance complementary circuits based on organic single-crystals.

Field-effect transistors based on single crystals of organic semiconductors have the highest reported charge carrier mobility among organic materials, demonstrating great potential of organic semiconductors for electronic applications. However, single-crystal devices are difficult to fabricate. One of the biggest challenges is to prepare dense arrays of single crystals over large-area substrates with controlled alignment. Here, we describe a solution processing method to grow large arrays of aligned C60 single crystals. Our well-aligned C60 single-crystal needles and ribbons show electron mobility as high as 11 cm2V–1s–1 (average mobility: 5.2 ± 2.1 cm2V–1s–1 from needles; 3.0 ± 0.87 cm2V–1s–1 from ribbons). This observed mobility is ∼8-fold higher than the maximum reported mobility for solution-grown n-channel organic materials (1.5 cm2V–1s–1) and is ∼2-fold higher than the highest mobility of any n-channel organic material (∼6 cm2V–1s–1). Furthermore, our deposition method is scalable to a 100 mm wafer substrate, with around 50% of the wafer surface covered by aligned crystals. Hence, our method facilitates the fabrication of large amounts of high-quality semiconductor crystals for fundamental studies, and with substantial improvement on the surface coverage of crystals, this method might be suitable for large-area applications based on single crystals of organic semiconductors.