Ag 44 (EBT) 26 (TPP) 4 Nanoclusters With Tailored Molecular and Electronic Structure

Fluorescence or Phosphorescence? The Metallic Composition of the Nanocluster Kernel Does Matter

It remains challenging to manipulate the nature of photoluminescence as either fluorescence or phosphorescence for a correlated cluster series. In this work, two correlated nanoclusters, Au₅ Ag₁₁ (SR)₈ (DPPOE)₂ and Pt₁ Ag₁₆ (SR)₈ (DPPOE)₂ with comparable structure features, were synthesized and structurally determined. These two alloy nanoclusters displayed distinct photoluminescent nature-the Au₅ Ag₁₁ nanocluster is fluorescent, whereas the Pt₁ Ag₁₆ nanocluster is phosphorescent. The decay processes of the excited electrons in these two nanoclusters have been explicitly mapped out by both experimental and theoretical approaches, disclosing the mechanisms of their fluorescence and phosphorescence. Specifically, the metallic compositions of the nanocluster kernels mattered in determining their photoluminescent nature. The results herein provide an intriguing nanomodel that enables us to grasp the origin of photoluminescence at the atomic level, which further paves the way for fabricating novel nanoclusters or cluster-based nanomaterials with customized photophysical properties.

Assembling Silver Cluster-Based Organic Frameworks for Higher-Performance Hypergolic Properties

Increasing research efforts have been focused on developing next-generation propellants. In this work, we demonstrated that assembling zero-dimensional (0D) silver clusters with energetic ligands into 3D metal organic frameworks (MOFs) not only inherited the short ignition delay (ID) time of the alkynyl-silver cluster but also significantly increased the output energy. Among them, the open cationic framework of ZZU-363 incorporating counter NO₃ ^- ions achieved a considerably reduced energy barrier and eventually the shortest ID time (26 ms), together with the highest volumetric energy density (40.4 kJ cm^-3) and specific impulse (263.1 s), which is far superior to traditional hydrazine-based propellants. The underlying mechanisms are clearly revealed by theoretical calculations. This work opens a venue to significantly enhancing the hypergolic activity of metal clusters and MOFs.

[Cu36H10(PET)24(PPh3)6Cl2] Reveals Surface Vacancy Defects in Ligand-Stabilized Metal Nanoclusters

Precise identification and in-depth understanding of defects in nanomaterials can aid in rationally modulating defect-induced functionalities. However, few studies have explored vacancy defects in ligand-stabilized metal nanoclusters with well-defined structures, owing to the substantial challenge of synthesizing and isolating such defective metal nanoclusters. Herein, a novel defective copper hydride nanocluster, [Cu₃₆H₁₀(PET)₂₄(PPh₃)₆Cl₂] (Cu36; PET: phenylethanethiolate; PPh₃: triphenylphosphine), is successfully synthesized at the gram scale via a simple one-pot reduction method. Structural analysis reveals that Cu36 is a distorted half cubic nanocluster, evolved from the perfect Nichol's half cube. The two surface copper vacancies in Cu36 are found to be the principal imperfections, which result in some structural adjustments, including copper atom reconstruction near the vacancies as well as ligand modifications (e.g., substitution, migration, and exfoliation). Density functional theory calculations imply that the above-mentioned defects have a considerable influence on the electronic structure and properties. The modeling suggests that the formation of defective Cu36 rather than the perfect half cube is driven by the enlargement of the energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital of the nanocluster. The structural evolution induced by the surface copper atom vacancies provides atomically precise insights into the defect-induced readjustment of the local structure and introduces new avenues for understanding the chemistry of defects in nanomaterials.