Controlled morphology evolution of branched Au nanostructures and their shape-dependent catalytic and photo-thermal properties

Morphology evolution of branched Au nanostructures (AuNSs) from Au nanoflowers to Au nanostars and finally to Au nanosnowflakes was obtained using catechol as both reducing and structure-inducing agent. These branched AuNSs were characterized by TEM and UV–vis spectroscopy and the results reveal that the increasing of number of nuclei and accelerating of growth rate after the increase of catechol concentration play an important role in the morphology evolution of branched AuNSs. The morphology of the AuNSs strongly affects their surface plasmon resonance (SPR) properties, which in turn influences their applications. The catalytic study towards p-nitrophenol suggests that the branched AuNSs with sharp tips (Au nanosnowflakes) possess the highest catalytic capacity while these with blunt tips (Au nanoflowers) have the lowest catalytic capacity. Moreover, the photothermal therapy (PTT) properties of these branched AuNSs are also shape-dependent with the highly branched Au nanosnowflakes hold the highest photothermal conversion efficiency.