Understanding seed-mediated growth of gold nanoclusters at molecular level

Abstract

The continuous development of total synthesis chemistry has allowed many organic and biomolecules to be produced with known synthetic history–that is, a complete set of step reactions in their synthetic routes. Here, we extend such molecular-level precise reaction routes to nanochemistry, particularly to a seed-mediated synthesis of inorganic nanoparticles. By systematically investigating the time−dependent abundance of 35 intermediate species in total, we map out relevant step reactions in a model size growth reaction from molecularly pure Au25 to Au44 nanoparticles. The size growth of Au nanoparticles involves two different size−evolution processes (monotonic LaMer growth and volcano-shaped aggregative growth), which are driven by a sequential 2-electron boosting of the valence electron count of Au nanoparticles. Such fundamental findings not only provide guiding principles to produce other sizes of Au nanoparticles (e.g., Au38), but also represent molecular-level insights on long-standing puzzles in nanochemistry, including LaMer growth, aggregative growth, and digestive ripening.

Miscible‐Solvent‐Assisted Two‐Phase Synthesis of Monolayer‐Ligand‐Protected Metal Nanoclusters with Various Sizes

“…While various wet‐chemical protocols have been developed to control the size, composition and shape of nanocrystals in polar and nonpolar solvents, relatively little advance has been made toward tailoring NCs . Despite two decades of research efforts, the synthesis of metal NCs with different size and composition remains a major challenge due to the lack of deep understanding on the synthetic mechanism of metal NCs …”

Nanoscale Lacing by Electrons

“…This computational identification provided both structural and electronic information on Au 4 to function as the building block for further growth and size‐focusing to produce the final NCs. Furthermore, in a latest study of the size growth from Au 25 NCs to Au 44 NPs, monotonic LaMer growth and volcano‐shaped aggregative growth processes were proposed, in which the individual growth processes are driven by a sequential two‐electron boosting of the valence electron. On the basis of the theoretical findings, an aggregative growth mechanism is believed to be operative for the nucleation and aggregative growth of the templated Au(I)‐thiolate strings induced by electrons from the STEM source.…”

Engineering Functional Metal Materials at the Atomic Level

“…The cluster size of metal NCs could be tailored by a variety of conversion reactions based on atomically precise parent metal NCs, including ligand exchange induced size conversion (LEISC, Approach I in Figure ) and redox induced size conversion (Approach IV in Figure ) . In a typical LEISC reaction (Approach I in Figure ), parent metal NCs are allowed to react with foreign thiolate ligands, which usually possess vastly different structure (e.g., steric hindrance in particular) from the thiolate ligands on NC surface.…”

“…In parallel to LEISC, the size conversion of metal NCs could also be driven by redox reactions (Approach IV, Figure ). For example, in a recent contribution, we developed a seeded‐growth method for synthesis of molecularly pure [Au 44 (SR) 26 ] 2− . As shown in Figure a, atomically precise [Au 25 (SR) 18 ] − was used as cluster seed, whose further growth was fueled by CO reduction of external Au(I)–SR complexes.…”