Boosting chiroptical activity of homochiral gold nanoparticles: iodide ion-assisted synthesis via citrate-reduction...

The chiral ligand-directed and seed-mediated growth method is commonly used for synthesizing chiral gold nanoparticles (AuNPs). However, the method requires the use of chiral ligands and the seeds with a certain morphology, and is quite complex and time-consuming, impeding further advancements in application. In this work, we introduced iodide ion (I^-) into the traditional citrate-reduction method to obtain homochiral AuNPs. The obtained AuNPs exhibited the amplified plasmonic circular dichroism with dissymmetry factor (g-factor) reaching 1.23 × 10^-3, representing a 7.7-fold enhancement compared to I^--free counterpart. Mechanistic investigation revealed that chiral amplification originated from preferential adsorption of I^- on specific crystal plane, leading to the anisotropic growth of Au nanocrystals. Furthermore, the obtained chiral AuNPs were used as colorimetric probes for recognizing glutamine enantiomers. This method for synthesizing chiral AuNPs does not require any chiral ligands and Au seeds, and is rather simple and facile. This work opens new avenues for scalable fabrication of chiral plasmonic nanomaterials in enantioselective sensing and asymmetric catalysis applications.