Photodriven chiral nanoparticle assembly

Nanomaterials Circularly polarized (CP) light can drive the synthesis of chiral small molecules and polymers. Kim et al. now show that photoreduction of a solution of a gold(III) salt (HAuCl4) and citrate with green CP laser light (543 nanometers) produces chiral gold nanocolloids. Initially, gold nanoparticles (about 3 nanometers in diameter) form and then assemble into chiral clusters. Red solutions had circular dichroism (CD) peak at 550 nanometers (the gold plasmon resonance) that changed sign for assemblies made with left- or right-handed CP light. The CD spectra could be quantitatively modeled on the basis of the irregular shapes revealed by electron tomography of these nanocolloids. J. Am. Chem. Soc. 141 , 11739 (2019).