Surface-enhanced Raman scattering (SERS) of phthalic acid and 4-methyl phthalic acid on silver colloids as a function of pH

The adsorption of phthalic acid (PA) and 4-methyl phthalic acid (4MPA) on a silver sol surface is studied with surface-enhanced Raman spectroscopy as a function of pH. It is shown that at every pH value studied the (4M)PA molecules are adsorbed on the surface as dicarboxylate. The spectra indicate that the molecules bond through the COO−COO− groups by the simultaneous involvement of a π and σ-type coordination. This results in a tilted orientation with respect to the surface normal.