期刊
JOURNAL OF RAMAN SPECTROSCOPY
卷 48, 期 4, 页码 538-548出版社
WILEY
DOI: 10.1002/jrs.5073
关键词
surface plasmon resonance; surface-enhanced Raman spectroscopy; photocatalysis; reaction mechanism; density functional theory
类别
资金
- Fundamental Research Funds for the Central Universities [SWU114076, XDJK2015C100]
- Open Funds of State Key Laboratory of Physical Chemistry of Solid Surfaces [201416]
- National Natural Science Foundation of China [21373712, 21321062, 21533006]
- National Key Basic Research Program of China [2015CB932303]
The synthesis of aromatic azo compounds from anilines and nitrobenzene usually requires environmentally unfriendly transition metal catalysts. Here, we propose that azobenzene oligomers are formed in surface-enhanced Raman experiments assisted by surface plasmon resonance. The photocatalytic polymerization of p-dinitrobenzene (DNB) and p-phenylenediamine (PDA) to the corresponding azo-like oligomers on silver surfaces is studied by the surface-enhanced Raman spectroscopy and density functional theory. First, the normal Raman and surface Raman spectra of DNB and PDA are simulated and measured. The simulated normal Raman spectra are in good agreement with their solid-state Raman spectra. However, the simulated surface Raman spectra of DNB-Ag-10 and PDA-Ag-10 complexes are significantly different from the experimental surface-enhanced Raman spectra. We propose that DNBs has a reductive coupling and PDAs undergo an oxidative coupling reaction during SERS experiments. Secondly, the Raman spectra of the possible NN coupling oligomers of DNB and PDA are simulated. They are compared with the SERS spectra of DNB and PDA adsorbed on silver surfaces. Especially, the Raman spectra of p,p-dinitroazobenzene and p,p-diaminoazobenzene are in good agreement with the SERS spectra of DNB and PDA adsorbed on silver surface. Finally, two reaction mechanisms are proposed to explain the surface photocatalysis of DNB and PDA. In the solution, the nitro group of DNB can be reduced by the excited hot electrons. DNBs are then converted to p,p-dinitroazobenzene through multiple proton and electron transfers. In the air and in the presence of O-2, O-2 is firstly activated through surface plasmon resonance. PDAs are then converted to p,p-diaminoazobenzene by the generated active oxygen species. Copyright (c) 2016 John Wiley & Sons, Ltd.
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