Size- and Shape-Dependent Photoexcitation Electron Transfer in Metal Nanoclusters

There are some unresolved fundamental issues for metal nanoclusters; for instance, the close-packed structure trans-formation from face-centered cubic (fcc) to hexagonal close-packed (hcp) has not yet been reported, and photoexcitation electron transfer is not well understood. Herein, we realized for the first time the fcc-to-hcp structure transformation and revealed the size-and shape-dependent photoexcitation electron transfer for metal nanoclusters. Specifically, a thermally induced ligand exchange method was developed, and a rod-shaped hcp Au42(SCH2Ph)32 (HSCH2Ph: benzyl mercaptan) with the largest aspect ratio was synthesized from fcc Au28(SPh-tBu)20 (HSPh-tBu: p-tert-butylphenol) and structurally resolved, which shows a sharp absorption at 815 nm and dual emission that is well interpreted by time-dependent density functional theory (TD-DFT) calculations. The structure transformation pathway was proposed, and a novel, rod-shaped hcp Au58(SR)40 with larger aspect ratio was predicted. Interestingly, it is found that the kernel-based middle-to-both ends sp <- sp photoexcitation electron transfer can be extended to other rod-like (one-dimensional) gold nanoclusters, and the major photoexcitation turns to the kernel-based sp <- sp transition from the staple-to-kernel sp <- d transition when the spherical gold nanocluster size is increased to Au42 and the Au(6sp) composition increases with increasing size for structure-similar nanoclusters. These findings deepen our understanding of metal nanocluster photoexcitation electron transfer and provide guidance for future nanocluster property tuning aimed at practical applications.

Automated summary

There are unresolved fundamental issues regarding metal nanoclusters, including the transformation from face-centered cubic (fcc) to hexagonal close-packed (hcp) structures and photoexcitation electron transfer. This study successfully achieved the fcc-to-hcp structure transformation and revealed size and shape-dependent photoexcitation electron transfer for metal nanoclusters. A new thermally induced ligand exchange method was developed to synthesize a rod-shaped hcp Au42(SCH2Ph)32 nanocluster, which exhibited specific absorption and dual emission properties. The findings also suggest a possible structure transformation pathway and predict a novel rod-shaped hcp Au58(SR)40 nanocluster with a larger aspect ratio. Additionally, a kernel-based middle-to-both ends sp <- sp photoexcitation electron transfer mechanism was observed in rod-like gold nanoclusters, indicating the potential for tunable and practical applications.