Fig. 3: Mechanism for anisotropic growth of Au nanocrystals on heterostuctural MoS₂ nanosheets.

a TEM, HRTEM, and the corresponding selected area electron diffraction pattern for Au/MoS₂ cracked nanocrystals (CNCs) which are synthesized in the absence of cysteine. b–d TEM and HRTEM images indicating time-resolved morphologies of Au/MoS₂ CNCs (b), DNCs-1 (c), and DNCs-2 (d), respectively. e, f TEM, HAADF, and EDX element map for Au/MoS₂ nanostructures obtained after reacting for 20 s in the presence of 1.2 μM L-Cys. g Illustration showing homogeneous nucleation of Au nanostructures in solution and heterogeneous nucleation based on competitive deposition and diffusion of gold atoms on exfoliated MoS₂ nanosheets. h TEM and HRTEM images of crack-free Au nanocrystals synthesized by homogeneous nucleation in the reaction solution rather than at MoS₂ edges. i Anisotropic growth by deposition of Au atoms at edges of the multilayer MoS₂ nanosheets, resulting in cracked structures. j Schematic of R-S pairs showing morphological development and comparison of the atomic arrangements of the {321}^R and {321}^S gold surfaces for region indicated by the dotted box. k TEM images and schematics of DNCs-1 synthesized in the presence of L-Cys and D-Cys, respectively.