Surface‐enhanced Raman scattering (SERS) of aromatic amino acids and their glycyl dipeptides in silver sol

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Abstract
The surface‐enhanced Raman (SER) spectra of aromatic amino acids (L‐phenylalanine, L‐tyrosine and tryptophan) and their glycyl dipeptides (glycyl‐L‐phenylalanine, glycyl‐L‐tyrosine and glycyl‐L‐tryptophan) adsorbed on Ag colloidal particles have been obtained. The surface‐enhanced and ordinary Raman spectra show satisfactory correlations. The most prominent features in the SER spectra of all compounds are the strongly enhanced peaks at about 930 and 1390 cm−1 due to the CCOO− stretching and COO− symmetric stretching vibrational modes, respectively. This is interpreted as suggesting that the above compounds are adsorbed on the Ag surface through the carboxylate group. In the SER spectrum of glycyl‐L‐phenylalanine, the amide I and II bands are observed at about 1670 and 1520 cm−1, respectively.