| 1. |
- Cui, Wen, et al.
(författare)
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Reversible pressure-induced polymerization of Fe(C5H5)(2) doped C-70
- 2013
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Ingår i: Carbon. - : Pergamon-Elsevier Science. - 0008-6223 .- 1873-3891. ; 62, s. 447-454
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Tidskriftsartikel (refereegranskat)abstract
- High pressure Raman, IR and X-ray diffraction (XRD) studies have been carried out on C-70(Fe(C5H5)(2))(2) (hereafter, "C-70(Fc)(2)") sheets. Theoretical calculation is further used to analyze the Electron Localization Function (ELF) and charge transfer in the crystal and thus to understand the transformation of C-70(Fc)(2) under pressure. Our results show that even at room temperature dimeric phase and one dimensional (1D) polymer phase of C-70 molecules can be formed at about 3 and 8 GPa, respectively. The polymerization is found to be reversible Upon decompression and the reversibility is related to the pressure-tuned charge transfer, as well as the overridden steric repulsion of counter ions. According to the layered structure of the intercalated ferrocene molecules formed in the crystal, we suggest that ferrocene acts as not only a spacer to restrict the polymerization of C-70 molecules within a layer, but also as charge reservoir to tune the polymerization process. This supplies a possible way for us to design the polymerization of fullerenes at suitable conditions.
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| 2. |
- Yin, Xiu, et al.
(författare)
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Doping of charge-transfer molecules in cocrystals for the design of materials with novel piezo-activated luminescence
- 2023
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Ingår i: Chemical Science. - : Royal Society of Chemistry. - 2041-6520 .- 2041-6539. ; 14:6, s. 1479-1484
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Tidskriftsartikel (refereegranskat)abstract
- A novel piezo-activated luminescent material with wide range modulation of the luminescence wavelength and a giant intensity enhancement upon compression was prepared using a strategy of molecular doping. The doping of THT molecules into TCNB-perylene cocrystals results in the formation of a weak but pressure-enhanced emission center in the material at ambient pressure. Upon compression, the emissive band from the undoped component TCNB-perylene undergoes a normal red shift and emission quenching, while the weak emission center shows an anomalous blue shift from 615 nm to 574 nm and a giant luminescence enhancement up to 16 GPa. Further theoretical calculations show that doping by THT could modify intermolecular interactions, promote molecular deformation, and importantly, inject electrons into the host TCNB-perylene upon compression, which contributes to the novel piezochromic luminescence behavior. Based on this finding, we further propose a universal approach to design and regulate the piezo-activated luminescence of materials by using other similar dopants.
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| 3. |
- Zhang, Ying, et al.
(författare)
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Capture of novel sp3 hybridized Z-BN by compressing boron nitride nanotubes with small diameter
- 2022
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Ingår i: Diamond and related materials. - : Elsevier. - 0925-9635 .- 1879-0062. ; 130
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Tidskriftsartikel (refereegranskat)abstract
- Experimental synthesis of new sp3 hybridized carbon/boron nitride structures remains challenging despite that numerous sp3 structures have been proposed in theory. Here, we showed that compressed multi-walled boron nitride nanotubes (MWBNNTs) and boron nitride peapods (C60@BNNTs) with small diameters could transform into a new sp3 hybridized boron nitride allotrope (Z-BN). This strategy is considered from the topological transition point of view in boron nitride nanotubes upon compression. Due to the increased curvature in compressed small-diameter MWBNNTs, the uncommon 4- and 8-membered rings in Z-BN could be more favorably formed. And the irreversible tube collapse is proved to be a critical factor for the capture of the formed Z-BN, because of the competition between the resilience of tube before collapse and the stress limitation for the lattice stabilization of Z-BN upon decompression. In this case, Z-BN starts to form above 19.0 GPa, which is fully reversible below 45 GPa and finally becomes quenchable at 93.5 GPa. This collapse-induced capture of the high-pressure phase could also be extended to other tubular materials for quenching novel sp3 structures.
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| 4. |
- Cui, Jinxing, et al.
(författare)
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Structural Deformation of Sm@C88under High Pressure
- 2015
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 5
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the structural transformation of Sm@C88 under pressure up to 18 GPa by infraredspectroscopy combined with theoretical simulations. The infrared-active vibrational modes of Sm@C88 at ambient conditions have been assigned for the first time. Pressure-induced blue and red shiftsof the corresponding vibrational modes indicate an anisotropic deformation of the carbon cage uponcompression. We propose that the carbon cage changes from ellipsoidal to approximately sphericalaround 7 GPa. A smaller deformation of the carbon bonds in the area close to the Sm atom in thecage suggests that the trapped Sm atom plays a role in minimizing the compression of the adjacentbonds. Pressure induced a significant reduction of the band gap of the crystal. The HOMO-LUMOgap of the Sm@C88 molecule decreases remarkably at 7 GPa as the carbon cage is deformed. Also,compression enhances intermolecular interactions and causes a widening of the energy bands. Botheffects decrease the band gap of the sample. The carbon cage deforms significantly above 7 GPa,from spherical to a peanut-like shape and collapses at 18 GPa.
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| 5. |
- Cui, Wen, et al.
(författare)
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Synthesis of alkali-metal-doped C60 nanotubes
- 2011
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Ingår i: Diamond and Related Materials. - : Elsevier BV. ; , s. 93-96
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Konferensbidrag (refereegranskat)abstract
- C60 nanotubes have been synthesized by a solution–solution method. After degassing in a dynamic vacuum, the C60 nanotubes were doped with alkali metals by means of vapor evaporation method. Different temperatures have been studied to evaporate the alkali metals for the doping experiments. Raman spectrum was further employed to analyze the doping concentration of the obtained samples. It was found that all three alkali metals (Li, Na and K) used can be efficiently doped into the C60 nanotubes, forming AxC60 nanotubes. The doping concentration of Li, Na changed from low to high level, depending on the experiment temperatures, while K doping always gave saturated doping. The melt points, the ionic sizes and vapor pressures of alkali metals were thought to affect the final doping results.
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| 6. |
- Du, Mingrun, et al.
(författare)
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High pressure infrared spectroscopy study on C60*CS2 solvates
- 2017
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Ingår i: Chemical Physics Letters. - : Elsevier. - 0009-2614 .- 1873-4448. ; 669, s. 49-53
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Tidskriftsartikel (refereegranskat)abstract
- High pressure IR study has been carried out on C-60*CS2 solvates up to 34.8 GPa. It is found that the intercalated CS2 molecules significantly affect the transformations of C-60 molecules under pressure. As a probe, the intercalated CS2 molecules can well detect the orientational ordering transition and deformation of C-60 molecules under pressure. The chemical stability of CS2 molecules under pressure is also dramatically enhanced due to the spacial shielding effet from C-60 molecules around in the solvated crystal. These results provide new insight into the effect of interactions between intercalants and fullerenes on the transformations in fullerene solvates under pressure.
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| 7. |
- Du, Mingrun, et al.
(författare)
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New ordered structure of amorphous carbon clusters induced by fullerene-cubane reactions
- 2018
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Ingår i: Advanced Materials. - : Wiley-VCH Verlagsgesellschaft. - 0935-9648 .- 1521-4095. ; 30
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Tidskriftsartikel (refereegranskat)abstract
- As a new category of solids, crystalline materials constructed with amorphous building blocks expand the structure categorization of solids, for which designing such new structures and understanding the corresponding formation mechanisms are fundamentally important. Unlike previous reports, new amorphous carbon clusters constructed ordered carbon phases are found here by compressing C8H8/C60 cocrystals, in which the highly energetic cubane (C8H8) exhibits unusual roles as to the structure formation and transformations under pressure. The significant role of C8H8 is to stabilize the boundary interactions of the highly compressed or collapsed C60 clusters which preserves their long‐range ordered arrangement up to 45 GPa. With increasing time at high pressure, the gradual random bonding between C8H8 and carbon clusters, due to “energy release” of highly compressed cubane, leads to the loss of the ability of C8H8 to stabilize the carbon cluster arrangement. Thus a transition from short‐range disorder to long‐range disorder (amorphization) occurs in the formed material. The spontaneous bonding reconstruction most likely results in a 3D network in the material, which can create ring cracks on diamond anvils.
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| 8. |
- Jiang, Linhai, et al.
(författare)
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Controlled Synthesis of CeO2/Graphene Nanocomposites with Highly Enhanced Optical and Catalytic Properties
- 2012
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 116:21, s. 11741-11745
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, CeO2 nanocubes with the (200)-terminated surface/graphene sheet composites have been prepared successfully by a simple hydrothermal method. It is found that the CeO2 nanocubes with high crystallinity and specific exposed surface are well dispersed on well-exfoliated graphene surface. The (200)-terminated surface/graphene sheet composites modified electrode showed much higher sensitivity and excellent selectivity in its catalytic performance compared to a CeO2 nanoparticle-modified electrode. The photoluminescence intensity of the CeO2 anchored on graphene is about 30 times higher than that of pristine CeO2 crystals in air. The higher oxygen vacancy concentration in CeO2 is supposed to be an important cause for the higher photoluminescence and better electrochemical catalytic performance observed in the (200)-terminated surface/graphene sheet composites. Such ingenious design of supported well-dispersed catalysts in nanostructured ceria catalysts, synthesized in one step with an exposed high-activity surface, is important for technical applications and theoretical investigations.
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| 9. |
- Yang, Xigui, et al.
(författare)
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Novel Superhard sp3 Carbon Allotrope from Cold-Compressed C70 Peapods
- 2017
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Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 118:24
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Tidskriftsartikel (refereegranskat)abstract
- Design and synthesis of new carbon allotropes have always been important topics in condensed matter physics and materials science. Here we report a new carbon allotrope, formed from cold-compressed C70 peapods, which most likely can be identified with a fully sp3-bonded monoclinic structure, here named V carbon, predicted from our simulation. The simulated x-ray diffraction pattern, near K-edge spectroscopy, and phonon spectrum agree well with our experimental data. Theoretical calculations reveal that V carbon has a Vickers hardness of 90 GPa and a bulk modulus ∼400 GPa, which well explains the "ring crack" left on the diamond anvils by the transformed phase in our experiments. The V carbon is thermodynamically stable over a wide pressure range up to 100 GPa, suggesting that once V carbon forms, it is stable and can be recovered to ambient conditions. A transition pathway from peapod to V carbon has also been suggested. These findings suggest a new strategy for creating new sp3-hybridized carbon structures by using fullerene@nanotubes carbon precursor containing odd-numbered rings in the structures.
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| 10. |
- Yang, Xigui, et al.
(författare)
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Polarized Raman study of aligned multiwalled carbon nanotubes arrays under high pressure
- 2015
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 119:49, s. 27759-27767
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Tidskriftsartikel (refereegranskat)abstract
- Tuning the intertube interaction and the topological structure of carbon nanotubes by the application of pressure may obviously affect their properties such as optical and electronic properties. However, characterizing such changes is still challenging. Here, we performed polarized Raman scattering studies on aligned multiwalled carbon nanotube arrays (MWNTAs). Unlike researchers from the previous literature, we found that the MWNTAs exhibit a polarization dependence similar to that of isolated single walled carbon nanotubes at ambient conditions. Upon compression, the polarization dependence weakens gradually with increasing pressure up to ∼20 GPa, which has been discussed in terms of pressure-induced enhancement of intertube interactions. At around 20 GPa, the depolarization effect vanishes, which can be explained by the formation of interlinked sp3 bonding in the MWNTAs. Our results show that polarized Raman spectroscopy is an efficient method to explore not only intertube interaction but also structural transition changes in MWNTs, which overcome the difficulty that MWNTs have no obvious fingerprints like those of single-walled carbon nanotubes in the study of structural transformations.
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