One-Phase Synthesis of Surface Modified Gold Nanoparticles and Generation of SERS Substrate by Seed Growth Method
Chemistry and Biochemistry
In this study, we report a novel and facile single-phase synthesis of stable AuNP-CTAB(NA) conjugates with good dispersibility, bearing a bilayer of cationic surfactant, cetyltrimethylammonium bromide (CTAB) supported by N-nonylamine (NA) as a cosurfactant. We investigated AuNP-CTAB(NA) conjugates by 1H NMR spectroscopy, UV–vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), and transmission electron microscopy (TEM). These studies suggest the presence of a CTAB bilayer on the nanoparticles surface forming an admicelle and NA embedded in the hydrophobic core of that bilayer. AuNP-CTAB(NA) conjugates remain dispersed in water even in the presence of high concentrations of salt and over a wide range of solution pHs. These conjugates further grow bigger when treated with additional AuCl4–, CTAB, and NA in the presence of the mild reducing agent, hydroquinone (HQ). The larger AuNP-CTAB(NA)-1 conjugates serve as SERS (surface-enhanced Raman Scattering) substrate of Raman active dye even at nanomolar concentrations.