Seeded Growth Synthesis of Uniform Gold Nanoparticles with Controlled Diameters up to 220 nm

A method for seeded growth of particles with uniform, smooth spherical shape, and narrow size distributions is presented. By using formaldehyde (HCHO) as a reductant and without any stabilizer in an aqueous solution, gold nanoparticles with sizes up to 220 nm were prepared at room temperature. The gold nanoparticles (diameter in the range of 1–3 nm) for the first seeds are synthesized by the reduction of tetrachloroauric acid trihydrate (HAuCl 4 ) with tetrakis (hydroxymethyl) phosphonium chloride THPC (P(CH 2 OH) 4 Cl). These seeds are dispersed in the gold plating solution at pH 9.0 in the presence of HCHO. Through multi-step seeding growth, their sizes are precisely controlled just by adjusting the ratio of gold precursor to seeds. The obtained gold nanospheres are characterized by using transmission electron microscopy, a Zetasizer Nano, and UV–VIS absorption spectroscopy. This approach has excellent reproducibility and can significantly improve the monodispersity of nanospheres. Graphic abstract