Chiral Seeded Growth of Gold Nanorods Into Fourfold Twisted Nanoparticles with Plasmonic Optical Activity

• Published in: Advanced materials (Weinheim) 2023-01, Vol.35 (1), p.e2208299-n/a
• Main Authors: Ni, Bing, Mychinko, Mikhail, Gómez‐Graña, Sergio, Morales‐Vidal, Jordi, Obelleiro‐Liz, Manuel, Heyvaert, Wouter, Vila‐Liarte, David, Zhuo, Xiaolu, Albrecht, Wiebke, Zheng, Guangchao, González‐Rubio, Guillermo, Taboada, José M., Obelleiro, Fernando, López, Núria, Pérez‐Juste, Jorge, Pastoriza‐Santos, Isabel, Cölfen, Helmut, Bals, Sara, Liz‐Marzán, Luis M.
• Format: Article
• Language: English
• Subjects: Amino acids; Ascorbic acid; Au nanorods; chiral seeded growth; Crystal structure; Crystallography; Cysteine; Cysteine - chemistry; Density functional theory; Enantiomers; Gold; Gold - chemistry; Materials science; Morphology; Nanoparticles; Nanoparticles - chemistry; Nanorods; Nanotubes - chemistry; Optical activity; Optical Rotation; plasmonic optical activity; Plasmonics; Reducing agents; Ridges; twisted nanoparticles; Wulff construction
• ISSN: 0935-9648; 1521-4095
• DOI: 10.1002/adma.202208299

A robust and reproducible methodology to prepare stable inorganic nanoparticles with chiral morphology may hold the key to the practical utilization of these materials. An optimized chiral growth method to prepare fourfold twisted gold nanorods is described herein, where the amino acid cysteine is used as a dissymmetry inducer. Four tilted ridges are found to develop on the surface of single‐crystal nanorods upon repeated reduction of HAuCl4, in the presence of cysteine as the chiral inducer and ascorbic acid as a reducing agent. From detailed electron microscopy analysis of the crystallographic structures, it is proposed that the dissymmetry results from the development of chiral facets in the form of protrusions (tilted ridges) on the initial nanorods, eventually leading to a twisted shape. The role of cysteine is attributed to assisting enantioselective facet evolution, which is supported by density functional theory simulations of the surface energies, modified upon adsorption of the chiral molecule. The development of R‐type and S‐type chiral structures (small facets, terraces, or kinks) would thus be non‐equal, removing the mirror symmetry of the Au NR and in turn resulting in a markedly chiral morphology with high plasmonic optical activity. Fourfold twisted Au nanorods can be prepared via chiral seeded growth, using cysteine as a chiral inducer. A high dissymmetry factor is obtained and electromagnetic simulations show chiral plasmon modes with largely asymmetric near‐field enhancement. The mechanism involved in chiral growth is related with cysteine‐induced enantioselective development of chiral facets.