A simple approach towards citrate-stabilized Ag nanoparticles with widely tunable sizes

Hydroquinone (HQ) can quickly reduce Au or Ag precursors only in the presence of preformed metallic seeds at room temperature without stabilizing effects and therefore is appealing for controllable synthesis of citrate-stabilized spherical Ag or Au nanoparticles (NPs). In this work, we examined the conventional room-temperature growth of citrate-stabilized Ag NPs through hydroquinone reduction in the presence of NaBH 4 -reduced Ag seeds. By control experiments and electron microscopy analysis, we reveal that this growth process is essentially under kinetic control, unlike those of Au NPs. As a result, the final Ag NPs contain a mass of kinetically favored plate-like nanostructures. Further evaluation experiments found that the selective reducibility of HQ remains at elevated temperatures. Inspired by this, we developed a thermal seeding approach for uniform citrate-stabilized Ag NPs with tunable diameters over the range 15–150 nm by simply altering the amount of Ag seeds, without previously necessary multi-cycle growth or multi-parameter adjustment.