Phosphine-Protected Atomically Precise Silver–Gold Alloy Nanoclusters and Their Luminescent Superstructures

Abstract

Superstructures made by assemblies of metal nanoclusters (NCs) have gained interest due to their atomic precision and exciting photophysical properties. Although there are some reports of cluster-assembled materials of NCs protected with thiols, the preparation of stable thiol-free analogs is largely unexplored due to the poor stability of such structures. Herein, we report the synthesis of phosphine-protected alloy NCs of silver with varying gold doping and superstructures of such systems. We show that alloying of phosphine-protected silver clusters with gold results in comparatively more stable clusters than weakly ligated hydride-and phosphine-coprotected silver clusters. Two new Ag− Au alloy cluster series, [Ag 11−x Au x (DPPB) 5 Cl 5 O 2 ] 2+ , where x = 1− 10 (Ag 11−x Au x in short), and [Ag 15−x Au x (DPPP) 6 Cl 5 ] 2+ , where x = 1−6 (Ag 15−x Au x in short), have been synthesized using two different phosphines, 1,4-bis(diphenylphosphino)butane (DPPB) and 1,3-bis(diphenylphosphino)propane (DPPP), respectively. These alloy clusters possess aggregation-induced emission (AIE) property, which was unexplored till now for phosphine-protected silver clusters. A visibly nonluminescent methanol solution of these clusters showed strong red luminescence in the presence of water due to the formation of cluster-assembled spherical hollow superstructures without any template. A solvophobic effect along with π•••π and C−H•••π interactions in the ligand shell make the alloy NCs assemble compactly within the hollow spheres. The assembly makes them highly emitting due to the restriction of intramolecular motion. The emissive states of the alloy clusters show a many-fold increase in lifetime in the presence of water. Femtosecond transient absorption studies revealed the lifetime of the excited-state charge carriers in their monomeric and aggregated states. Apart from enriching the limited family of phosphine-protected silver alloy NCs, this work also provides a new strategy to build a controlled assembly of NCs with tailored luminescence. These materials could be new phosphors for applications in composites, sensors, thin films, and photonic materials.

Structure and Electrocatalytic Performance of Cocrystallized Ternary Molybdenum Oxosulfide Clusters for Efficient Water Splitting

“…Theoretical mass calculations revealed that the crystal consisted of these clusters and a certain number of water and methanol molecules that were derived from the solvent system. Similar solvent-associated peaks were also observed in other metal nanoclusters. − The broad isotopic distribution in the mass spectrum can be attributed to two factors: (1) molybdenum (Mo) has seven naturally stable isotopes, resulting in a wide isotopic distribution along with the contributions of naturally abundant isotopes from various atoms i.e., Na, O, S, C, P, and H present in the nanoclusters, and (2) the small mass differences (Δ m ≈ 9–11) between individual nanoclusters in their trianionic state. Additionally, these nanoclusters ionize by getting attached to one or two solvent molecules (H 2 O = 18 and MeOH = 32), which further contributes to the broad distribution of a specific charge state observed.…”

Atomic Precise Gold Nanoclusters: Toward the Customize Synthesis, Precision Medicine

“…[ 10 ] The synergistic effect between metals induced by heterometallic doping can greatly improve the physicochemical properties of materials, which is an important strategy to change the properties of materials. [ 39 ] Au clusters exhibit strong quantum size effects, with molecular‐like electron transitions leading to the formation of discrete electron levels and multiple absorption bands. Adding or replacing an Au atom will cause large electronic and structural perturbations, which further significantly affect its performance.…”

“…The ligands of Au clusters can be divided into two categories, hydrophilic and hydrophobic ligands, including thiols, phosphines, alkynes, N‐heterocyclic carbene, and biomolecules. [ 39a,60 ] In the past half century, over 100 Au clusters protected by various ligands have been reported. [ 61 ] Researchers usually adopt two methods for ligand regulation: one is to directly select commercial ligands, for example, ligands with electron‐withdrawing groups can enhance the chemical reactivity of Au clusters, while ligands containing cationic groups such as cyclopentadienyl groups can improve the stability of Au clusters.…”

PtAg18 superatoms costabilized by phosphines and halides: synthesis, structure, and catalysis

“…[51][52][53][54] Though most reports of phosphine ligand-protected metal nanoclusters have focused on gold nanoclusters, studies on Ag nanoclusters remains sluggish. 41,[55][56][57][58][59][60] On the other hand, silver nanoclusters have recently attracted great research interest due to their benefits of good photostability, easy surface modification, and efficient catalytic activity. 6,19,24,26,[31][32][33]50,52,[61][62][63][64][65] In the continuous studies on silver nanoclusters, doping other metals into the silver framework has proved to be one of the most efficient strategies to improve stability and modulate the properties of silver nanoclusters.…”

“…51–54 Though most reports of phosphine ligand-protected metal nanoclusters have focused on gold nanoclusters, studies on Ag nanoclusters remains sluggish. 41,55–60…”