Facile Synthesis and Spectral Properties of Aged Gold Colloids

The present paper described the spectra properties of aged gold colloids, which were synthesized by only adding NaOH to the chloroauric acid and hexadecyl trimethyl ammonium bromide (CTAB) mixture solution. The formation mechanism for the gold nanoparticles (AuNPs) was discussed based on the Fourier transform infrared spectroscopy (FTIR) analysis. The gold colloids with different amounts of NaOH were aged for three months and then characterized by UV-Vis spectrometer and transmission electron microscopy (TEM). Moreover, surface-enhanced Raman scattering (SERS) spectra of methylene blue (MB) on the three months aged gold colloids were obtained. UV-Vis spectrometer showed the broadening of plasmon absorption peak of three months aged gold colloids. And an explanation for the broadening changes was provided in the as-prepared samples. TEM images demonstrate that the diameter and shape change of the AuNPs depend on addition difference NaOH at the stage of the synthesis, and the NaOH also affect the aging process. The corresponding SERS spectra on the aged three months gold colloid display the size/shape-dependent properties. Therefore, we expect that the aged colloidal gold will be developed and applied in biochemical analysis field.