Mechanochemical Synthesis of Carbon Nanothread Single Crystals

Abstract

Synthesis of well-ordered reduced dimensional carbon solids with extended bonding remains a challenge. For example, few single-crystal organic monomers react under topochemical control to produce single-crystal extended solids. We report a mechanochemical synthesis in which slow compression at room temperature under uniaxial stress can convert polycrystalline or single-crystal benzene monomer into single-crystalline packings of carbon nanothreads, a one-dimensional sp carbon nanomaterial. The long-range order over hundreds of microns of these crystals allows them to readily exfoliate into fibers. The mechanochemical reaction produces macroscopic single crystals despite large dimensional changes caused by the formation of multiple strong, covalent C-C bonds to each monomer and a lack of reactant single-crystal order. Therefore, it appears not to follow a topochemical pathway, but rather one guided by uniaxial stress, to which the nanothreads consistently align. Slow-compression room-temperature synthesis may allow diverse molecular monomers to form single-crystalline packings of polymers, threads, and higher dimensional carbon networks.

Local Structure and Bonding of Carbon Nanothreads Probed by High-Resolution Transmission Electron Microscopy

“…A simulated electron diffraction pattern and molecular model of hexagonally-packed stiff-chiral-3 with packing disregistry viewed along constraints at higher pressures. Alternatively, we note that residual benzene -frozen under compression -melts under decompression, 5 and this phase change could produce inhomogeneous stresses on the lattice due to the associated volume or pressure changes.…”

“…X-ray diffraction of samples recovered to ambient pressure probes longer length scales between 300 μm (laboratory source) and 5 μm (synchrotron); they show broadened arcs of similar widths: 8-12 degrees. 5 However, in-situ xray diffraction measurements at high pressure, collected as nanothreads form from benzene, reveal much narrower arc widths of a degree or less. 5 At these high pressures, volumetric packing efficiency is highly favored and may "squeeze out" gentle bends associated with on-thread structural defects.…”

“…2 A thread-level view of this packing is of much interest because nanothreads assemble into a high-symmetry pseudohexagonal lattice from an initial lower-symmetry monoclinic benzene molecular crystal while shrinking by as much as 40 to 50% in length as threads form. 5 Individual nanothreads must extend parallel to [0001] through a substantial fraction of the 80-100 nm sample thickness (estimated by EELS) to produce the distinct points of contrast observed in the HREM image (Figure 4d). These columnar points are compelling evidence beyond diffraction that nanothreads have a one-dimensional structure with a large aspect ratio.…”

High density mechanical energy storage with carbon nanothread bundle

“…The carbon nanothread is also reported to possess a tailorable thermal conductivity 30,31 . Particularly, researchers have already reported the synthesis of single-crystalline packing of nanothreads (across hundreds of microns) 32 . This opens up a facile way to exfoliate nanothread bundles.…”

From Molecules to Carbon Materials—High Pressure Induced Polymerization and Bonding Mechanisms of Unsaturated Compounds

“…Recently, Thomas C. Fitzgibbons et al obtained a crystalline one-dimensional sp 3 carbon nanomaterial when compressing benzene molecules at a relatively slow rate [103]. Further research shows the uniaxial stress is the key factor in helping the polycrystalline or single-crystalline benzene monomer to transform into single-crystalline packings of carbon nanothreads [104]. The theoretical groups tried to investigate the reaction mechanism.…”