Microfluidic Synthesis of Discrete Chiral Gold Nanorods with Tunable Morphologies and Enantioselective Recognition

We present a continuous and efficient strategy for synthesizing discrete chiral gold nanorods (dc-Au NRs) with tunable morphologies and stable chiroptical responses by using a microfluidic platform. Gold nanorods (Au NRs), synthesized via a seed-mediated growth method, served as the core. l- or d-cysteine (Cys) and gold shells were sequentially deposited onto the Au NRs, with Cys molecules embedded in the core-shell gap. This configuration enabled pronounced plasmonic circular dichroism (PCD) responses in the visible- to near-infrared region, attributed to the coupling between Cys and the intense electromagnetic field at the localized "hot spots". By precisely tuning the flow rates of Au NRs and Cys within the micromixer, dc-Au NRs with diverse morphologies were obtained, exhibiting PCD responses with a g-factor as high as ∼0.009. Furthermore, dc-Au NRs synthesized with either l- or d-Cys demonstrated the effective enantioselective recognition of tryptophan enantiomers.