Seeded Growth Synthesis of Uniform Gold Nanoparticles with Diameters of 15-300 nm

In this work, we present a simple seeded growth approach to obtain gold nanoparticles over a large range of sizes. The method produces particles with uniform spherical shape and narrow size distributions. Using ascorbic acid as a reductant and sodium citrate as stabilizer we utilize biocompatible and easy to exchange substances. The investigation of the growth process via TEM measurements revealed the formation of small gold clusters on the surface of the seeds, which subsequently grow and result in a blackberry-like intermediate shape of the gold nanoparticles. Applying heat caused an intraparticle ripening process, which finally lead to a smooth spherical particle shape. Furthermore, the optical properties of the resulting gold sols are discussed in the light of Mie theory and an influence of the polydispersity was found for large particles.