Abstract:The present article described the spectra properties of aged gold colloids, which were synthesized by only adding NaOH to chloroauric acid and Hexadecyl trimethyl ammonium bromide (CTAB) mixture solution. The formation mechanism for the fabrication of gold nanoparticles (AuNPs) was discussed based on the Fourier transform infrared spectroscopy (FTIR) analysis. The gold colloids with the different amount of NaOH were aged three months and characterized by UV-Vis spectrometer and transmission electron microscopy (TEM). Moreover, surface-enhanced Raman scattering (SERS) spectra of methylene blue (MB) on the aged three months gold colloids were obtained. UV-Vis spectrometer showed the broadening of plasmon absorption peak of aged three months gold colloids. And an explanation for the broadening changes was provided in the as-prepared samples. TEM images demonstrated that the diameter and shape change of the AuNPs depended on adding different of NaOH on the stage of the synthesis, and the NaOH was also affected the aging process. The corresponding SERS spectra on the aged three months gold colloid displayed the size/shape-dependent properties. The aged colloidal gold was expected to exploit and utilize in biochemical analysis field.