Cryogenic Synthesis of Homochiral Gold Nanoparticles in the Absence of Chiral Ligands and Their Performance in Enantiomer Recognition.

Currently, the chiral ligand-directed growth strategy has been predominantly employed for preparing chiral gold nanoparticles (AuNPs). In this work, we report the unexpected discovery of homochiral AuNP formation under cryogenic conditions (0 °C) without chiral ligand induction. Systematic investigations revealed significant temperature-dependent evolution of nanoparticle morphology and chiroptical properties across a broad thermal range (-10 to 75 °C). Notably, AuNPs synthesized at 0 °C exhibited a 4.2-fold enhancement in the extinction dissymmetry factor (-factor) compared to those prepared at 60 °C. We propose a temperature-modulated crystallization mechanism governing chiral symmetry breaking during nanoparticle growth. The 0 °C-synthesized chiral AuNPs demonstrated exceptional enantioselective recognition capabilities, particularly as colorimetric probes for glutamine (Gln) enantiomer discrimination. This work developed a chiral ligand-free synthesis method for chiral AuNPs. Our findings establish temperature engineering as a crucial parameter for controlling nanoscale chirality and open new avenues for designing chiral plasmonic materials.