Monitoring the Synthesis of Au Nanoparticles Using SEC

In this paper, it is demonstrated that size-exclusion chromatography (SEC) with SDS (10 mM) as the mobile phase can be used to rapidly determine the sizes of Au nanoparticles (NPs). It was found that standard particles at sizes ranging from 12.1 to 79.1 nm eluted in a linear manner with respect to the elution time. The reproducibility of the separation over the entire range of the calibration curve was high; the relative standard deviations of the elution times were less than 0.3%. Next, the separation conditions to characterize the sizes of Au NPs prepared through seed-assisted synthesis were employed. Using this approach, it was found that the rate of addition of the reducing agent influenced the sizes of the final products; for example, rapid addition of the reducing agent resulted in polydisperse Au NP products. SEC analysis revealed that the presence of NaOH in the synthesis medium decreased the sizes of the Au NPs dramatically. When using SEC to analyze Au NPs produced through seed-assisted synthesis, a good correlation existed between the sizes obtained using SEC and those provided by transmission electron microscopy (TEM). Based on these findings, SEC appears to be an efficient and accurate tool for characterizing the sizes of NPs fabricated through seed-assisted synthesis.