Chemical Research in Chinese Universities ›› 2022, Vol. 38 ›› Issue (2): 579-587.doi: 10.1007/s40242-021-1090-x

• Articles • Previous Articles     Next Articles

Theoretical Studies on the Electronic Structure of Nano-graphenes for Applications in Nonlinear Optics

CHEN Kaichun1, ZHENG Xuelian1, YANG Cuicui1, TIAN Wei Quan1, LI Weiqibr2,3, YANG Ling4   

  1. 1. Chongqing Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering, Chongqing University, Huxi Campus, Chongqing 401331, P. R. China;
    2. School of Physics, Harbin Institute of Technology, Harbin 150001, P. R. China;
    3. Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, P. R. China;
    4. MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage, Institute of Theoretical and Simulational Chemistry, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China
  • Received:2021-03-07 Revised:2021-04-06 Online:2022-04-01 Published:2021-04-07
  • Contact: TIAN Wei Quan, LI Weiqi, YANG Ling E-mail:tianwq@cqu.edu.cn;tccliweiqi@hit.edu.cn;yangling@hit.edu.cn
  • Supported by:
    This work was supported by the National Natural Science Foundation of China (Nos.21673025, 11974091, 21203042, 11574062), the Open Projects of Key Laboratory of Polyoxometalate Science of Ministry of Education(NENU) of China and the State Key Laboratory of Supramolecular Structure and Materials(JLU) of China(No.SKLSSM2021020).

Abstract: In this work, azulene is introduced into nano-graphene with coronene center to enhance the second-order nonlinear optical (NLO) properties. The sum-over-states(SOS) model based calculations demonstrate that dipolar contributions are larger than octupolar contributions to the static first hyperpolarizability(〈β0〉) in most nano-graphenes except those with high symmetry(e.g., a C2v nano-graphene has octupolar contributions ΦJ=3 up to 59.0% of the 〈β0〉). Nano-graphenes containing two parallel orientating azulenes (i.e., Out-P and Out-Ps) have large dipole moments, while their ground state is triplet. Introducing B/N/BN atoms into the positions with a high spin density transfers the ground state of Out-P and Out-Ps to closed-shell singlet, and the Out-Ps-2N has a large 〈β0〉 of 1621.67×10−30 esu. Further addition of an electron donor(NH2) at the pentagon end enhances the 〈β0〉 to 1906.22×10−30 esu. The two-dimensional second-order NLO spectra predicted by using the SOS model find strong sum frequency generations and difference frequency generations, especially in the near-infrared and visible regions. The strategies to stabilize the electronic structure and improve the NLO properties of azulene-defect carbon nanomaterials are proposed, and those strategies to engineer nano-graphenes to be semiconducting while maintaining the π-framework are exten-dable to other similar systems.

Key words: Nonlinear optics, Azulene-defect nano-graphene, Two-dimensional second-order nonlinear optical spectrum, Sum frequency generation, Difference frequency generation

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