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Acta Chimica Sinica >

2013 , Vol. 71 >Issue 07: 1059 - 1063

DOI: https://doi.org/10.6023/A13020197

Article

SERS Investigation of the Interfacial Structure at Fe Electrode in Ionic Liquids

  • Mei Jinhua ,
  • Xu Minmin ,
  • Yuan Yaxian ,
  • Yang Fengzhu ,
  • Gu Ren'ao ,
  • Yao Jianlin
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  • College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123

Received date: 2013-02-19

  Online published: 2013-05-02

Supported by

Project supported by the National Natural Science Foundation of China (Nos. 21073128, 21033007, 21173155) and the Natural Science Foundation of Jiangsu Province (No. BK2012187).

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Abstract

The surface enhanced factor, potential zero charge (pzc), surface adsorption and structures of electrostatic double layer were electrochemically investigated at ionic liquids/Fe electrode interfaces through high sensitive surface enhanced Raman spectroscopy (SERS) combined with probe molecules of various lengths. In order to improve the intensity of Raman signals from adsorbed species and decrease the influences from the bulk ionic liquids, Au@SiO2 nanoparticles were spread over the Fe electrode, that is, shell-isolated nanoparticles-enhanced Raman spectroscopy (SHINERS) was employed. Based on the SHINERS technology, the adsorption behaviors of 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm]BF4) on a Au@SiO2 modified Fe electrode were investigated. It was found that the adsorption behaviors depended on the applied potentials. When the potentials were positive than-1.3 V[vs. a Pt quasireference electrode (PQRE)],[BMIm]BF4 was adsorbed with the imidazolium ring nearly perpendicular to the surface. While it kept tilted or even parallel as the potentials negative to-1.3 V. At a extremely negative potential (-2.3 V), the imidazolium cation was reduced to carbene. In addition, SCN- and 4-cyanopyridine (4-CNPy) with different molecular lengths were employed as probes. Electrochemical Stark effects of C≡N stretching band was measured to monitor the double structures at ionic liquids/Fe electrode interfaces. It was resulted that SCN- and 4-CNPy were adsorbed through N atom and N atom of pyridine ring, respectively. The results revealed that the C≡N stretching band of SCN- was shifted to low frequency with the negative moved potentials. The electrochemical Stark coefficient was about 17 cm-1/V. However, the C≡N stretching band of 4-CNPy nearly kept constant, that is, Stark coefficient was 0 cm-1/V. It was suggested that there were big differences comparing with aqueous systems. The surface electric field was mainly distributed in the compact layer of ionic liquids/Fe electrode interface. Moreover, through the calculation based on the SERS of SCN-, the surface enhancement factor of rough Fe electrode in[BMIm]BF4 was about 1.5×102.

Key words： surface enhanced Raman spectroscopy (SERS); interface; ionic liquids; Fe electrode; adsorption

Cite this article

Mei Jinhua , Xu Minmin , Yuan Yaxian , Yang Fengzhu , Gu Ren'ao , Yao Jianlin . SERS Investigation of the Interfacial Structure at Fe Electrode in Ionic Liquids[J]. Acta Chimica Sinica, 2013 , 71(07) : 1059 -1063 . DOI: 10.6023/A13020197

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