Morphology, optical and catalytic properties of polyethyleneimine-stabilized Au nanoparticles

Abstract

Stable colloidal solutions of gold in water and ethanol were produced in the presence of small amounts of linear polyethyleneimine (PEI). In aqueous solutions a lowering of PEI concentration from 0.05wt% to 0.0063wt% results in an increase of the average size of Au particles from 3–7nm to 30−40nm. In ethanol 5–10nm Au particles were produced in the presence of 0.0063–0.05wt% PEI. At 0.05wt% PEI the Au particles retain individual character but a lowering of PEI content to 0.0063wt% causes particle aggregation into 80–140nm globules. The Au–PEI nanoparticles exhibit catalytic activity in reduction of methylviologen bication to cation-radical by sulfide-ions as well as a co-catalyst of photocatalytic water reduction by ethanol with the participation of mesoporous TiO2. In both cases individual 4−8-nm Au–PEI particles show a much higher catalytic activity than 80−140-nm globules of aggregated Au–PEI NPs synthesized at a lower PEI content.