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  Zone-selective XPS and Raman spectroscopy of graphene nanoribbons  
Dr. Chang Q Sun:Nanyang Technological University
    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.
 
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