Ligand-Mediated Nanocluster Formation with Classical and Autocatalytic Growth

Abstract

We present a systematic study of ligand-mediated nanocluster (NC) formation using a kinetic model, which provides atomic insight into sub-nanometer cluster (S-NC) and NC formation. Our model describes the role of ligand-mediated nucleation and growth in obtaining monodisperse NCs. Nucleation includes metal ion reduction, reversible ligand association to the metal ion/atom, and formation of dimer nuclei. Growth can occur through autocatalytic surface growth and ligand-associated monomer addition to the cluster, depending on the rate of metal ion to neutral metal atom conversion. Furthermore, we studied the effect of the initial concentration of metal ions on NC formation using fast and slow reducing agents in the presence of slowly and rapidly binding ligands. The model shows that fast nucleation, slow growth, and a high molar ratio of rapidly binding ligand to metal ions promote the formation of S-NCs and NCs. Our results can guide experiments in the synthesis of ultrasmall clusters.