Organothiol-directed synthesis and growth mechanism of Ag octahedra with tunable optical properties in aqueous solution

Abstract

Shape-selective synthesis of Ag nanocrystals in the aqueous system remains a challenge, and insight into the mechanism of crystal growth is lacking. Here, we synthesized Ag octahedra (Ag Oh) with sharp corners and edges by the seed-mediated method in an aqueous solution at low temperatures (35 °C) and wide ranges of edge lengths (52–187 nm). l-cysteine directs the kinetic transformation of Ag cubes into octahedral nanocrystals of different sizes by selective deposition on the {100} plane. The thermodynamic product of the organothiol-directed synthesis was discovered to be truncated tetrahedra. The regrowth of octahedral nanocrystals in the absence of surfactant leads to corner deposition of Ag with the formation of concave Oh. Au@Ag tip-blobbed and concave Oh with tunable optical properties were synthesized using octahedral nanocrystals as a sacrificial template. Furthermore, by measuring the refractive index sensitivity and figure of merit (FOM) of Ag Oh, we have demonstrated its potential as a promising candidate for plasmonic sensors. The proposed concept of organothiol-directed deposition can be used to synthesize various nanocrystals with tunable properties as promising candidates for progress in optics, catalysis, and biomedicine applications.