Multielementary Alloy Chiral Nanoparticles with Strong Optical Activities

Structural chirality has been imposed onto nano-alloys to introduce diverse new properties. Chiral nanoparticles (CNPs) with the atomic scale chirality are composed of metastable chiral lattices having low thermal stability, so multielementary (>2 elements) CNPs are very challenging to produce using traditional high-energy fabrication methods. Herein, layer-by-layer glancing angle deposition (LbL-GLAD) at a low substrate temperature of ≈−40 °C, consisting of GLAD of the host CNPs and the subsequent GLAD of guests, is devised to extend the alloy compositional space to the ternary (e.g., Ag:Al:Cu and Ag:Al:Au) and quaternary (e.g., Ag:Al:Cu:Au and Al:In:Sn:Ti). The low-temperature GLAD-induced alloying facilitates the formation of the metastable multi-layer chiral twisting of achiral facets, chiral defects due to the diffusion of the guests, and chiral electronic bands, leading to a significant amplification of chiroplasmonic optical activities in 20–30 folds. The LbL-GLAD can be generally adapted to fabricate multielementary alloy CNPs composed of a wide range of elements, with a prospective application of asymmetric catalysts to synthesize an enantiomer with designable chirality, one of the most important topics in modern chemistry and biochemistry to solve the problems of health and environmental pollution.