Controlled synthesis of multi-branched gold nanodendrites by dynamic microfluidic flow system

The synthesis of gold nanostructures with unique architectures has attracted a great deal of attention because of their architecture-dependent sensing, optical, and electrical properties. Gold nanodendrites with a tailored morphology have unique properties due to their enhanced surface areas caused by nanoscale branches. Although gold nanodendrites have been synthesized by many different methods, controllable and high-yield synthesis of gold nanodendrites remains a challenge. Here, for the first time, we show that multi-branched gold nanodendrite synthesis can be controlled using a dynamic microfluidic flow system with high yield and fluid dynamics that control the branching structure of the nanodentrites. The study shows that the architecture of the gold nanodendrites mainly depends on synthesis conditions such as flow dynamics, HAuCl₄ concentration, and reaction time. Dendrites grew faster when the flow rate reached 3 µL min⁻¹. We further show that by using microfluidic-assisted synthesis, simple and rapid gold nanodendrite length tuning (0.7 cm) is possible with a threefold branching and textured structure. It is shown that the growth of gold nanodendrites is significantly enhanced (1.7 times faster) under flow conditions in the microfluidic channel. This bottom-up method reduces undesirable effects related to the poor control of static growth and increased reproducibility. Such highly controllable and inexpensive microfluidic flow systems could potentially be used to fabricate high-yield gold nanodendrites for bioelectronics and sensing applications.