Continuous microfluidic synthesis and functionalization of gold nanorods

A microfluidic platform with multiple reactant additions has been used for the continuous, unseeded synthesis of gold nanorods. This system allows separate control of the seed forming and nanorod growing stages, increasing reproducibility and reducing undesired effects related to a poor control of the seed aging stage. Also, on-stream surface functionalization with poly(ethylene glycol)-methyl ether thiol (SH-PEG) has been performed, allowing a 100-fold reduction in the consumption of this reactant compared to the amounts used in a conventional batch reactor. The system also facilitates tuning the concentration of halide anions (Cl− and Br−) that are used to modify the aspect ratio of the resulting rods.