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.

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.

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.

Carbon black (CB) nanoparticles were encapsulated by poly(vinyl alcohol) (PVA) by a simple method of coacervation. Transmission electron microscopy (TEM) images clearly demonstrated that the successful encapsulation of PVA happened at the surfaces of CB nanoparticles. The particle-size distribution measurements indicated that the diameters of the obtained PVA-encapsulated CB (CB@PVA) nanoparticles were distributed within the nanoscale dimension. This strategy avoids the complicated polymerization process involved in the counterpart of polymer-coating approaches.

This paper describes the internal structure of calcite (CaCO3) crystals grown in an agarose hydrogel and demonstrates that the gel-grown calcite crystals, like biogenic calcite crystals, incorporate the organic matrix, resulting in internal structures with pores on the order of 100's of nanometers.

This paper describes the control of the nucleation and growth of calcite crystals by a matrix composed of an agarose hydrogel on top of a carboxylate-terminated self-assembled monolayer (SAM). The design of this matrix is based upon examples from biomineralization in which hydrogels are coupled with functionalized, organic surfaces to control, simultaneously, crystal morphology and orientation. In the synthetic system, calcite crystals nucleate from the (012) plane (the same plane that is observed in solution growth). The aspect ratio (length/width) of the crystals decreases from 2.1 ± 0.22 in solution to 1.2 ± 0.04 in a 3 w/v % agarose gel. One possible explanation for the change in morphology is the incorporation of gel fibers inside of the crystals during the growth process. Etching of the gel-grown crystals with deionized water reveals an interpenetrating network of gel fibers and crystalline material. This work begins to provide insight into why organisms use hydrogels to control the growth of crystals.

Calcite crystals grown in agarose hydrogels incorporate the gel network while retaining their single-crystal nature. The amount of gel network that is incorporated is determined by two competing factors: crystallization pressure promotes the exclusion of the gel network, while faster growth rates favor its incorporation.

Calcium tartrate tetrahydrate and α-glycine single crystals grown in agarose hydrogels incorporate agarose polymer networks, resulting in polymer/single-crystal composites.

Biogenic single-crystal composites, such as sea urchin spines and calcitic prisms from mollusk shells, contain organic macromolecules inside of inorganic single-crystal matrices. The nanoscale internal structure of these materials, however, is poorly understood, especially how the biomacromolecules are distributed within the crystals without significantly disrupting the crystalline lattice. Here, annular dark-field scanning transmission electron microscopy and electron tomography reveal, in three dimensions, how biomacromolecules are distributed within the calcitic prisms from Atrina rigida shells. Disk-like nanopatches, whose scattering intensity is consistent with organic inclusions, are observed to be anisotropically arranged within a continuous, single-crystalline calcite matrix. These nanopatches are preferentially aligned with the (000l) planes of calcite. Along the crystallographic c-axis, there are alternating organic-rich and -poor regions on a length scale of tens of nanometers, while, in the ab plane, the distribution of nanopatches is more random and uniform. The structural features elucidated in this work have relevance to understanding the structure–property relationships and formation mechanisms of biominerals, as well as to the development of bio-inspired strategies to extrinsically tune the properties of 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.