Adsorption of 2,2′-biquinoline and 8-hydroxyquinoline on gold and silver nanoparticle surfaces

The adsorption behaviors of 2,2′-biquinoline (BiQu) and 8-hydroxyquinoline (8HQu) on gold and silver nanoparticle surfaces have been investigated by means of surface-enhanced Raman scattering (SERS) with the detailed vibrational assignment. The aromatic ring of BiQu and 8HQu appeared to assume a perpendicular or a tilted structure with respect to the gold and silver surface from the presence of the ν(CH) band at 3050-3060 cm−1. By determining the relative enhancement factor of each vibrational band, we attempted to explain the orientation and enhancement mechanism on Au and Ag surfaces in a more quantitative way. Raman analysis indicated that the SERS enhancement mechanism could be different for BiQu and 8HQu as indicated from a different UV-vis absorbance spectral change in aggregation of gold nanoparticles upon injection of the adsorbates.