Study on Surface-Enhanced Raman Scattering of Phenylalanine Using Different Aggregating Agents for Borohydride-Reduced Silver Colloid

In this paper, Surface-enhanced Raman scattering (SERS) spectra of phenylalanine were studied for borohydride-reduced silver colloid using different aggregating agents, and the effects on SERS of aggregation on this colloid environments were analysed. The choice of aggregating agent greatly influences the aggregation of colloid and the surface-enhanced Raman spectroscopy of the analyte. Sodium chloride, sodium sulfate, sodium nitrate, potassium chloride and calcium chloride were used as aggregating agents. The results show that the surface-enhanced Raman spectroscopy of phenylalanine varies observably when different kinds and concentration of aggregating agents are used. Sodium chloride gave the most intense bands among the three kinds of sodium salts for phenylalanine with the borohydride-reduced silver colloid. It can be concluded that chloride ions are mainly responsible for the aggregation of nanoparticles in this silver colloid. Potassium chloride and calcium chloride were used as aggregating agents to contrast the effect of different cations in colloid silver. It was found that a new peak emerged and the intensity of SERS spectrum decreased when calcium chloride were used as aggregating agent. The results indicate that not only the anions but also the cations influence the SERS of analyte. Through the study of SERS spectra for phenylalanine with different kinds of aggregating agents, the application of SERS technique in the field of biochemistry may be expanded.