Binding of Aromatic Isocyanides on Gold Nanoparticle Surfaces Investigated by Surface-Enhanced Raman Scattering

Author： Joo Sang-Woo Kim Wan-Joong Yun Wan Soo Hwang Sungu Choi Insung S.

Publisher： Society for Applied Spectroscopy

ISSN： 0003-7028

Source： Applied Spectroscopy, Vol.58, Iss.2, 2004-02, pp. : 218-223

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Abstract

The adsorption structure and binding of phenyl isocyanide (PNC), 2,6-dimethyl phenyl isocyanide (DMPNC), and benzyl isocyanide (BZI) on gold nanoparticle surfaces have been studied by means of surface-enhanced Raman scattering (SERS). PNC, DMPNC, and BZI have been found to adsorb on gold assuming a standing geometry with respect to the surfaces. The presence of the ν(CH) band in the SERS spectra denotes a vertical orientation of the phenyl ring of PNC, DMPNC, and BZI on Au. The lack of a substantial red shift and significant band broadening of the ring breathing modes implied that a direct ring π orbital interaction with metal substrates should be quite low. For PNC, the band ascribed to the C-NC stretching vibration was found to almost disappear after adsorption on Au. On the other hand, the C-NC band remained quite strong for DMPNC after adsorption. This result suggests a rather bent angle of C-N≡C: for the nitrogen atom of the NC binding group on the surfaces, whereas a linear angle of C-N≡C: should be more favorable on gold surfaces due to an intramolecular steric hindrance of its two methyl groups. SERS of BZI on gold nanopaticles also supports a bent angle of :C≡N-CH₂ for its nitrogen atom, suggesting a preference of sp³ (or sp²) hybridization for the nitrogen atom.