Morphologic evolution of Au nanocrystals grown in ionic liquid by plasma reduction

Shape controlled Au nanocrystal growth in ionic liquid has been studied by glow discharge plasma reduction. In an 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF(4)]) solution with poly(vinyl pyrrolidone) (PVP) as surfactant, Au nanocrystals grow from faceted NPs to peanut-like particle aggregates, and eventually worm-like nanorods and nanowires as the growth time increases. This process is further found to be dependent on the concentration of employed surfactant. Based on systematic microscopic analysis and control experiments, a polymer-assisted oriented attachment mechanism is proposed to explain the observed morphologic evolution. Our work may have great implications for the employment of ionic liquids for shape controlled synthesis of nanocrystals.