Acta Phys. -Chim. Sin. ›› 2014, Vol. 30 ›› Issue (12): 2342-2348.doi: 10.3866/PKU.WHXB201410172

• PHOTOCHEMISTRY AND RADIATION CHEMISTRY • Previous Articles     Next Articles

Nonlinear Optical Responses of Thiol Chains in Different Confined States

LU Xiao-Lin1,2, ZHOU Jie2, LI Bo-Lin1   

  1. 1. State Key Laboratory of Bioelectronics, School of Biological Science & Medical Engineering, Southeast University, Nanjing 210096, P. R. China;
    2. Key Laboratory of Advanced Textile Materials and Manufacturing Technology of Education Ministry, Department of Chemistry, Zhejiang Sci-Tech University, Hangzhou 310018, P. R. China
  • Received:2014-09-23 Revised:2014-10-17 Published:2014-11-27
  • Contact: LU Xiao-Lin E-mail:lxl@seu.edu.cn
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (51173169, 21004054), Scientific Research Foundation for the Returned Overseas Chinese Scholars, Ministry of Education of China, Zhejiang Province Human Resources and Social Security Bureau, China, and Priority Academic Program Development of Jiangsu Higher Education Institutions, China (PAPD 1107037001).

Abstract:

The molecular vibrational signals of n-dodecanethiol (DDT) were detected in different confined states using sum frequency generation (SFG) vibrational spectroscopy. Samples with three different confined states were used, including a self-assembled monolayer (SAM) of DDTmolecules on a gold (Au) substrate, DDT surface-functionalized Au nanoparticles on a silica substrate, and surface-functionalized Au nanoparticles dispersed in a toluene solution. The vibrational spectra of the DDT molecules were successfully captured for all three samples, and the spectral differences provided evidence of the different confined structures. On the Au substrate, the DDT molecules orderly packed together; on the silica substrate, the DDT molecules attached to the Au nanoparticle surfaces were somehow flexible; and at the air-toluene interface, the DDT molecules attached to the Au nanoparticle surfaces were highly disordered. The spectral analysis indicated that the molecular vibrational signals generated from the Au nanoparticle surfaces were enhanced because of the localized enhanced fields near the Au nanoparticle surfaces, with the enhancement factors of 102-103 over the SAM of DDT molecules on the Au substrate, depending on the selected polarization combination.

Key words: Sum frequency generation vibrational spectroscopy, Au nanoparticle, n-Dodecanethiol, Self-assembled monolayer, Air-liquid interface

MSC2000: 

  • O647