题　目：Zone-selective XPS and Raman spectroscopy of graphene nanoribbons

报告人：Dr. Chang Q Sun (孙长庆)

单　位：Nanyang Technological University, Singapore 639798，e-mail address: ecqsun@ntu.edu.sg

时　间：6月28日（周五）14:30-16:00

地　点：李薰楼249会议室

欢迎参加！

Zone-selective XPS and Raman spectroscopy of graphene nanoribbons

A combination of the bond order-length-strength (BOLS) correlation notation, zone-selective XPS (ZPS, US patent), Raman shift, and DFT/TB calculations revealed the following information:

1. C-C bonds in the monolayer skin (equivalent of GRN interior) of graphite are 20% shorter and 130% stronger than those in the bulk diamond but longer and weaker than those surrounding point defects (GNR edges, see right Figure).

2. The atomic cohesive energy (the product of bond energy and atomic coordination number) depression lowers the melting point of the single-layer GNR/CNT from the bulk value of 3800 K to 1600 K and the binding energy density enhancement raises the elastic modulus from the bulk value of 1.0 TPa to 2.6 TPa.

3. Dirac-Fermi polarons with non-zero spins create at the defect and the ZGNR edges due to isolation and polarization of the dangling s bond electrons by the locally and densely entrapped core and bond electrons. Quasi-p bond formation between the inhomogeneous distanced C atoms along the AGNR edges prevents the polaron, which ensures the AGNR to be semiconductor like.

4. Decoding the Raman shift caused by strain, the number-of-layer, compression, and heating results in the information of force constant, energy density, atomic cohesive energy, Debye temperature, effective atomic CN, etc.

孙长庆，辽宁建昌人, 新加坡南洋理工大学任职，湘潭大学（义务）和中国计量学院兼职（组建配位键计量与调控研究中心）。主要研究兴趣及经历包括固体表面氧、氮、碳化学吸附成键与能带重构(3B)、氢键非对称弛豫（水的反常物性）、低配位系统的键弛豫(BOLS)、非键电子局域极化(NEP)、混配位系统的量子钉扎与极化等理论探索；局域键平均(LBA)近似和BOLS-TB局域态数值算法；以及原子尺度选区光电子能谱提纯(ZPS)、扫描隧道谱、超低能电子衍射谱、和拉曼谱的解析方法和定量信息提取技术等。

1. Sun CQ, et al, Zone-selective photoelectronic measurements of the local bonding and electronic dynamics associated with the monolayer skin and point defects of graphite. RSC Adv., 2012; 2: 2377-83.

2. Yang XX, et al, Raman determination of the length, strength, compressibility, elasticity, Debye temperature and force constant of the C-C bond in graphene, Nanoscale 2012; 4: 502-10.

3. Zheng WT and Sun CQ, Underneath the fascinations of carbon nanotubes and graphene ribbons. Energy & Environment Science, 2011. 4: 627-55.

4. Zhang X, et al, Discriminative generation and hydrogen modulation of the Dirac-Fermi polarons at graphene edges and atomic vacancies, Carbon 2011; 49: 3615-21.

5. Zhang X., et al., Graphene nanoribbon band-gap expansion: Broken-bond-induced edge strain and quantum entrapment. Nanoscale, 2010. 2: 2160-3.

6. Sun CQ, et al., Coordination-Resolved C-C Bond Length and the C 1s Binding Energy of Carbon Allotropes and the Effective Atomic Coordination of the Few-Layer Graphene. J Chem Phys C, 2009. 113: 16464-7.

7. Sun CQ, et al, Dominance of Broken Bonds and Unpaired Nonbonding pi-Electrons in the Band Gap Expansion and Edge States Generation in Graphene Nanoribbons. J Chem Phys C, 2008. 112: 18927-34.

8. Sun CQ, et al., Dimension, strength, and chemical and thermal stability of a single C-C bond in carbon nanotubes. J. Phys. Chem. B, 2003. 107: 7544-6.