Controllable Synthesis of Silver Nanoparticle Aggregates for Surface-Enhanced Raman Scattering Studies

Aggregation of citrate-reduced silver nanoparticles (Ag nps) induced by cetyltrimethylammonium bromide (CTAB) was studied by UV–vis absorption spectra, SEM, and zeta potential measurement. Subsequently, Rhodamin 6G (R6G) and 4-aminothiophenol (4-ATP) were used for testing the SERS activity on these aggregates with very low concentrations, and it was found that the enhancement ability was dependent on the concentration of CTAB. Maximum enhancement was achieved when 0.05 mM CTAB was added, and the enhancement factor (EF) was estimated to be as large as 7.9 × 10 6 (a 1 ) for 4-ATP. The observation is attributed to classical electromagnetic (EM) response of the strongly interacting Ag nps to the optical fields when surface plasmon resonances are induced. Therefore, these nanoparticles aggregates can be “tuned” to yield maximum SERS enhancement as different concentrations of CTAB are added.