Application of gold and silver colloidal nanoparticles for the surface-enhanced Raman spectrometric analysis of melamine and 4-aminobiphenyl

摘要

Colloidal nanoparticles of gold and silver were used in Surface-Enhanced Raman Scattering (SERS) analysis of melamine and 4-aminobiphenyl. Gold colloids allowed the SERS detection of melamine at levels below 0.1 ng/L using a previously unreported SERS peak at 275 cm~(-1) and yielded better detection limits compared to silver colloids. For 4-aminobiphenyl, the detection limits were found to be similar for both colloids at 0.05-0.1 mg/L. Analysis by transmission electron microscopy showed that the morphology of both Ag and Au nanoparticles were uniformly spherical with average diameters that were 69.3 ± 23.1 nm and 41.6 ± 19.1 ran, respectively. The SERS spectral intensities of both compounds were found to increase as the sample pH increased. The optimal signals were obtained at pH = 8.5 for 4-aminobiphenyl and pH = 11.5 for melamine. The enhancement factors for the determination of melamine are in range of 3.5 × 10~4-6.3 × 10~4 for the silver colloid and 5.2 × 10~7-2.1 × 10~9 for the gold colloid.