High-Yield Production of Uniform Gold Nanoparticles with Sizes from 31 to 577 nm via One-Pot Seeded Growth and Size-Dependent SERS Property

In this work, uniform, quasi-spherical gold nanoparticles (Au NPs) with sizes of 31-577 nm are prepared via one-pot seeded growth with the aid of tris-base (TB). Distinct from the seeded growth methods available in literature, the present method can be simply implemented by subsequently adding the aqueous dispersion of the 17 nm Au-NP seeds and the aqueous solution of HAuCl4 into the boiling aqueous TB solution. It is found that at the optimal pH range, the sizes of the final Au NPs and their concentrations are simply controlled by either the particle number of the Au seed dispersion or the concentration of the HAuCl4 solution, while the latter enables us to produce large Au NPs at very high concentration. Moreover, as-prepared Au NPs of various sizes are coated on glass substrates to test their surface-enhanced Raman scattering (SERS) activities by using 4-aminothiophenol (4-ATP) molecules as probes, which exhibit "volcano type" dependence on the Au NP sizes at fixed excitation wavelength. Furthermore, the Au NPs with sizes of ≈97 and 408 nm exhibit the largest SERS enhancement at the excitation wavelength of 633 and 785 nm, respectively