Buckminsterfullerene: A Strong, Covalently Bonded, Reinforcing Filler and Reversible Cross-Linker in the Form of Clusters in a Polymer

A Buckminsterfullerene/polyisoprene (C₆₀/PI) composite was synthesized at high-temperature, high-pressure (HP&HT) conditions. The composite has significantly improved tensile strength and Young’s modulus, by up to 49% and 88% per wt % C₆₀, respectively, which is much higher than for corresponding composites with carbon nanotube (CNT) fillers. The reinforcing action of C₆₀ fillers is different from that of CNTs as C₆₀ becomes covalently bonded to PI chains, and C₆₀ clusters in PI form C₆₀–C₆₀ covalent bonds. The latter are reversible and break by heating at 1 bar, which suggests improved recyclability of the material and indicates that carbon nanostructures can be used as strong reversible cross-linkers (“vulcanizers”) in elastomers

Direct Conversion of Graphene Aerogel into Low-Density Diamond Aerogel Composed of Ultrasmall Nanocrystals

Diamond aerogel, a special kind of carbon aerogel made by sp³ carbon atoms, has been attracting intensive research interest due to its potential applications since it is first synthesized by the conversion of amorphous carbon. Despite of many expectations in diamond aerogel, the study on its synthesis is still not adequate compared with other carbon aerogel. Here we report the synthesis of diamond aerogel by laser heating graphene aerogel (GA) under high pressure in a diamond anvil cell. The results suggest that the density and microstructure of GA, as well as the heating duration obviously affect the diamond aerogel growth. When heating GA with lower laser power, we also observe a transparent carbon phase in experiment, which transforms into graphite and amorphous carbon upon decompression. These results present new insights into our understanding on the transformation from ultralow density carbon to sp³ carbon under high pressure and high temperature. It is possible to tune the microstructures of diamond aerogel by controlling the synthesis of GA precursors

Isolation of Three Isomers of Sm@C₈₄ and X-ray Crystallographic Characterization of Sm@<i>D</i>_3<i>d</i>(19)-C₈₄ and Sm@<i>C</i>₂(13)-C₈₄

Three isomers with the composition Sm@C₈₄ were isolated from carbon soot obtained by electric arc vaporization of carbon rods doped with Sm₂O₃. These isomers were labeled Sm@C₈₄(I), Sm@C₈₄(II), and Sm@C₈₄(III) in order of their elution times during chromatography on a Buckyprep column with toluene as the eluent. Analysis of the structures by single-crystal X-ray diffraction on cocrystals formed with Ni^II(octaethylporphyrin) reveals the identities of two of the isomers: Sm@C₈₄(I) is Sm@<i>C</i>₂(13)-C₈₄, and Sm@C₈₄(III) is Sm@ <i>D</i>_3<i>d</i>(19)-C₈₄. Sm@C₈₄(II) can be identified as Sm@<i>C</i>₂(11)-C₈₄ on the basis of the similarity of its UV/vis/NIR spectrum with that of Yb@<i>C</i>₂(11)-C₈₄, whose carbon cage has been characterized by ¹³C NMR spectroscopy. Comparison of the three Sm@C₈₄ isomers identified in this project with two prior reports of the preparation and isolation of isomers of Sm@C₈₄ indicate that five different Sm@C₈₄ isomers have been found and that the source of samarium used for the generation of fullerene soot is important in determining which of these isomers form

Isolation of Three Isomers of Sm@C₈₄ and X-ray Crystallographic Characterization of Sm@<i>D</i>_3<i>d</i>(19)-C₈₄ and Sm@<i>C</i>₂(13)-C₈₄

Three isomers with the composition Sm@C₈₄ were isolated from carbon soot obtained by electric arc vaporization of carbon rods doped with Sm₂O₃. These isomers were labeled Sm@C₈₄(I), Sm@C₈₄(II), and Sm@C₈₄(III) in order of their elution times during chromatography on a Buckyprep column with toluene as the eluent. Analysis of the structures by single-crystal X-ray diffraction on cocrystals formed with Ni^II(octaethylporphyrin) reveals the identities of two of the isomers: Sm@C₈₄(I) is Sm@<i>C</i>₂(13)-C₈₄, and Sm@C₈₄(III) is Sm@ <i>D</i>_3<i>d</i>(19)-C₈₄. Sm@C₈₄(II) can be identified as Sm@<i>C</i>₂(11)-C₈₄ on the basis of the similarity of its UV/vis/NIR spectrum with that of Yb@<i>C</i>₂(11)-C₈₄, whose carbon cage has been characterized by ¹³C NMR spectroscopy. Comparison of the three Sm@C₈₄ isomers identified in this project with two prior reports of the preparation and isolation of isomers of Sm@C₈₄ indicate that five different Sm@C₈₄ isomers have been found and that the source of samarium used for the generation of fullerene soot is important in determining which of these isomers form

Isolation of Three Isomers of Sm@C₈₄ and X-ray Crystallographic Characterization of Sm@<i>D</i>_3<i>d</i>(19)-C₈₄ and Sm@<i>C</i>₂(13)-C₈₄

Three isomers with the composition Sm@C₈₄ were isolated from carbon soot obtained by electric arc vaporization of carbon rods doped with Sm₂O₃. These isomers were labeled Sm@C₈₄(I), Sm@C₈₄(II), and Sm@C₈₄(III) in order of their elution times during chromatography on a Buckyprep column with toluene as the eluent. Analysis of the structures by single-crystal X-ray diffraction on cocrystals formed with Ni^II(octaethylporphyrin) reveals the identities of two of the isomers: Sm@C₈₄(I) is Sm@<i>C</i>₂(13)-C₈₄, and Sm@C₈₄(III) is Sm@ <i>D</i>_3<i>d</i>(19)-C₈₄. Sm@C₈₄(II) can be identified as Sm@<i>C</i>₂(11)-C₈₄ on the basis of the similarity of its UV/vis/NIR spectrum with that of Yb@<i>C</i>₂(11)-C₈₄, whose carbon cage has been characterized by ¹³C NMR spectroscopy. Comparison of the three Sm@C₈₄ isomers identified in this project with two prior reports of the preparation and isolation of isomers of Sm@C₈₄ indicate that five different Sm@C₈₄ isomers have been found and that the source of samarium used for the generation of fullerene soot is important in determining which of these isomers form

Increasing Interlayer Coupling Prevented the Deformation in Compressed Multilayer WSe₂

High-pressure investigations on transition-metal dichalcogenides (TMD) have been considered as an efficient way to investigate their unique crystalline and electronic properties. Here we studied the vibrational behaviors of pressurized multilayer WSe₂ with two (2TL) to six layers (6TL) by Raman spectroscopy. The intralayer and interlayer vibrations of WSe₂ all show a monotonous blue shift without any discontinuity. Due to the strong interlayer coupling interactions, no structural transition occurs, but nondegeneration splitting of shear mode vibrations coming from pressure-induced in-plane deformation is observed. As the interlayer coupling increases in thicker WSe₂, the in-plane deformation is suppressed and takes place at higher pressure. The monotonous increase of force constants and elastic constants suggested a stable structure of WSe₂ within our studied pressure range

Pressure-Driven Topological Transformations of Iodine Confined in One-Dimensional Channels

The behavior of molecules and molecular chains confined in 1D nanochannels imposed by external interactions is a problem of fundamental interest. Here, we report structural manipulation of iodine confined inside zeolite (AFI) nanochannels by the application of high pressure. Structural transformations of the confined iodine under pressure have been unambiguously identified by polarized Raman spectroscopy combined with theoretical simulation. The length of the iodine chains and the orientation and intermolecular interaction of the confined iodine have been tuned at the molecular level by applied pressure. Almost all the confined iodine can be tuned into an axially oriented state upon compression, favoring the formation of long chains. The long iodine chains can be preserved to ambient pressure when released from intermediate pressures

Pressure-Dependent Structural and Band Gap Tuning of Semiconductor Copper(I) Thiocyanate (CuSCN)

Copper­(I) thiocyanate (CuSCN) is a p-type semiconductor with exceptional properties for optoelectronic devices such as solar cells, thin-film transistors , organic light-emitting diodes, etc. Understanding the structure–optical property relationships in CuSCN is critical for its optoelectronic applications. Herein, high-pressure techniques combined with theoretical calculations are used to thoroughly investigate the structural and optical changes of CuSCN upon compression. Under high pressure, CuSCN exhibits a progressive decrease of the band gap with different rates, which is relevant to the β to α phase transition in CuSCN and the subsequent amorphization through polymerization. UV–vis spectra measurements reveal a reduction in band gap from 3.4 to 1.3 eV upon decompression to ambient conditions. Such transitions could be attributed to the pressure-induced rotation of CuNS3 tetrahedron and bond length shrinkage. The severe distortion of the polyhedral units prompts breakdown of the structure and thus the amorphization, which is quenchable to ambient conditions. Our study demonstrates that high pressure can be utilized to adjust the structure and optical characteristics of CuSCN compound, potentially extending the material’s uses in optoelectronic devices

Stacking faults enabled second harmonic generation in centrosymmetric van der Waals RhI3

Second harmonic generation (SHG) in van der Waals (vdWs) materials has garnered significant attention due to its potential for integrated nonlinear optical and optoelectronic applications. Stacking faults in vdWs materials, a typical kind of planar defect, can introduce a new degree of freedom to modulate the crystal symmetry and resultant SHG response, however, the physical origin and tunability of stacking-fault-governed SHG in vdWs materials remain unclear. Here, taking the intrinsically centrosymmetric vdWs RhI3 as an example, we theoretically reveal the origin of stacking-fault-governed SHG response, where the SHG response comes from the energetically favorable AC- Cstacking fault of which the electrical transitions along the high symmetry paths Gamma-M and Gamma-K in the Brillion zone play the dominant role at 810 nm. Such stacking-fault-governed SHG response is further confirmed via structural characterizations and SHG measurements. Furthermore, by applying hydrostatic pressure on RhI3, the correlation between structural evolution and SHG response is revealed with SHG enhancement up to 6.9 times, where the decreased electronic transition energies and huger momentum matrix elements due to the stronger interlayer interactions upon compression magnify the SHG susceptibility. This study develops a promising foundation based on strategically designed stacking faults for pioneering new avenues in nonlinear nano-optics

Pressure-Induced Emission Enhancement and Multicolor Emission for 1,2,3,4-Tetraphenyl-1,3-cyclopentadiene: Controlled Structure Evolution

Mechanoresponsive luminescent (MRL) materials have attracted considerable attention because of their potential applications in mechanical sensors, memory chips, and security inks; MRL materials possessing high efficiency and multicolor emission qualities are especially interesting. In this Letter, we found 1,2,3,4-tetraphenyl-1,3-cyclopentadiene (TPC) crystal exhibited both pressure-induced emission enhancement (PIEE) and multicolor behavior. In addition, infrared spectroscopy analysis indicated that the ring-opening reaction of the phenyl ring occurred when pressure was beyond 24.7 GPa. The reaction was promoted from 24.7 to 35.9 GPa, which resulted in the redder irreversible color change for the sample released from 35.9 GPa than from 24.7 GPa. The results regarding the mechanoresponsive behavior of TPC offered a deep insight into PIEE and multicolor properties from the structural point of view and inspired the idea of capturing different colors by hydrostatic pressure, which will facilitate the design of and search for high-performance MRL materials