Size and morphology controlled synthesis of gold nanoparticles in green solvent: Effect of reducing agents

The effect of reducing agents on the synthesis of Au(0) metallic nanoparticles (Au NPs) prepared in green solvent medium of β-d-glucose–water dispersions has been reported first. The different equivalent amounts of NaBH4 and pH values adjusted by NaOH were tested for the reduction of Au salt (HAuCl4·3H2O (hydrogen tetrachloroaurate (III) trihydrate) to obtain Au NPs. The type and the amount of reducing agent and the pH of the solution affected the size and morphology of the NPs. Addition of 4 equivalents of NaBH4 produced homogeneously dispersed 5.3 nm (σ = 0.7) diameter particles. Excess addition of NaBH4 caused the NPs to settle down as the precipitate forming mesh or wire structure. When salt was reduced by the addition of NaOH (pH = 8.0) the particles were larger (14.2 nm) and less homogeneous (σ = 2.8). At pH = 12.2 the NPs settled at the bottom of the vial when preparation was left overnight. The wire and mesh like structures were obtained at higher pH = 12.2.