| 1. |
- Yang, Zhenxing, et al.
(författare)
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Anomalous phonon softening of G-band in compressed graphitic carbon nitride due to strong electrostatic repulsion
- 2021
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Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 118:2
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Tidskriftsartikel (refereegranskat)abstract
- Graphitic carbon nitride (C2N and C3N) with various p electron distributions on layers have been studied under pressure through acombined theoretical and experimental approach and a comparison with graphite. It is found that as these materials transform into lowcompressibility phases in the pressure range from 15 to 45 GPa, strong electrostatic repulsion between p electrons and in-plane sp2 electronsmay distort and soften the sp2 bonds, leading to anomalous pressure evolutions of the intralayer phonon vibrations, such as a plateau-likebehavior of E2g mode (G-band) in C2N and C3N. This also causes a slow increase in the resistivity/resistance of C2N and C3N as pressureincreases, and the gradual interlayer bonding leads to an abrupt increase in resistance of the materials but with different pressure responsesdue to their different p electron distributions. Moreover, the intensity enhancement of the G band in both CN materials may be related totheir electronic structure changes. The results deepen our understanding of the effects of p electron distribution on the structural transitionof graphitic materials and may explain some unexplained in previous studies.
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| 2. |
- Zhai, Chunguang, et al.
(författare)
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Molecular insertion regulates the donor-acceptor interactions in cocrystals for the design of piezochromic luminescent materials
- 2021
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Ingår i: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Developing a universal strategy to design piezochromic luminescent materials with desirable properties remains challenging. Here, we report that insertion of a non-emissive molecule into a donor (perylene) and acceptor (1,2,4,5-tetracyanobezene) binary cocrystal can realize fine manipulation of intermolecular interactions between perylene and 1,2,4,5-tetracyanobezene (TCNB) for desirable piezochromic luminescent properties. A continuous pressure-induced emission enhancement up to 3 GPa and a blue shift from 655 to 619 nm have been observed in perylene-TCNB cocrystals upon THF insertion, in contrast to the red-shifted and quenched emission observed when compressing perylene-TCNB cocrystals and other cocrystals reported earlier. By combining experiment with theory, it is further revealed that the inserted non-emissive THF forms blue-shifting hydrogen bonds with neighboring TCNB molecules and promote a conformation change of perylene molecules upon compression, causing the blue-shifted and enhanced emission. This strategy remains valid when inserting other molecules as non-emissive component into perylene-TCNB cocrystals for abnormal piezochromic luminescent behaviors.
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