Impact of Ligands on Structural and Optical Properties of Ag29 Nanoclusters

A ligand exchange strategy has been employed to understand the role of ligands on the structural and optical properties of atomically precise 29 atom silver nanoclusters (NCs). By ligand optimization, similar to 44-fold quantum yield (QY) enhancement of Ag-29(BDT)(12-x)(DHLA)(x) NCs (x = 1-6) was achieved, where BDT and DHLA refer to 1,3-benzene-dithiol and dihydrolipoic acid, respectively. High-resolution mass spectrometry was used to monitor ligand exchange, and structures of the different NCs were obtained through density functional theory (DFT). The DFT results from Ag-29(BDT)(11)(DHLA) NCs were further experimentally verified through collisional cross-section (CCS) analysis using ion mobility mass spectrometry (IM MS). An excellent match in predicted CCS values and optical properties with the respective experimental data led to a likely structure of Ag-29(DHLA)(12) NCs consisting of an icosahedral core with an Ag16S24 shell. Combining the experimental observation with DFT structural analysis of a series of atomically precise NCs, Ag29-yAuy(BDT)(12-x)(DHLA)(x) (where y, x = 0,0; 0,1; 0,12 and 1,12; respectively), it was found that while the metal core is responsible for the origin of photoluminescence (PL), ligands play vital roles in determining their resultant PLQY.

Automated summary

By employing a ligand exchange strategy, the ligands' role in determining the structural and optical properties of atomically precise silver nanoclusters with 29 atoms was investigated. Through ligand optimization, a significant enhancement in quantum yield was achieved, with the ligands playing a crucial role in determining the photoluminescence properties. The metal core was found to be responsible for the origin of photoluminescence, while the ligands played a vital role in determining the resulting photoluminescence quantum yield.