Anisotropic Evolution of Nanoclusters from Ag₄₀ to Ag₄₅: Halogen- and Defect-Induced Epitaxial Growth in Nanoclusters

Halogens have widely served as handles for regulating the growth of nanoparticles and the control of their physicochemical properties. However, their regulatory mechanism is poorly understood. Nanoclusters are the early morphology of nanoparticles and play an important role in revealing the formation and growth of nanoparticles due to their precise structures. Here, we report that halogens induce the anisotropic growth of Ag₄₀(C₆H₅COO)₁₃(SR)₁₉(CH₃CN) (Ag-II, where SR = 4-tert-butylbenzylmercaptan) into Ag₄₅(C₆H₅COO)₁₃(SR)₂₂Cl₂ (Ag), where Ag-II is converted from Ag₄₀(CH₃COO)₁₀(SR)₂₂ (Ag-I). Experiments and theoretical simulations showed that halogen ions adsorb at both ends of the cluster, forming defect sites. The -SR-Ag- complexes fill the defects and complete the anisotropic transition from Ag-II to Ag. Circular dichroism spectra show that the chirality of Ag decreases 15-fold compared with that of Ag-II. This work provides important insights into the effects of halogens on the growth mechanism and property regulation for nanomaterials at the atomic level and the benefits of further applications of halogen-induced nanomaterials.