Photoluminescence enhancement by controllable aggregation and polymerization of octanuclear gold clusters

Halide-Directed Ligand Engineering Enables Expedient, Controlled and Divergent Syntheses of Diphosphine-Protected Au Nanoclusters

Despite substantial progress in ligand engineering, the efforts in the field of Au nanoclusters have been concentrated almost exclusively on organic ligands. Halides, the most typical auxiliary inorganic ligands widely present in Au clusters, remain virtually unexplored, particularly regarding their effects on cluster construction. Herein, diphosphine Ph2P(CH2)nPPh2 (Ln, n = 1-6) is chosen as the co-protecting organic ligands and a comparative analysis on the influential roles of halide ions (Cl-, Br-, I-) in guiding Au cluster synthesis is conducted. A simple yet efficient halide-directed synthetic approach has been developed and a series of Au nanoclusters, including the known [Au18(L1)6Br4]2+, [Au13(L2)5Cl2]3+ and [Au8(L3)4Cl2]2+ that however crystallized in new polymorphic forms, as well as the new reduction-active [Au18(L1)6Cl4]2+, luminescence-enhanced [Au14(L3)5Br4]2+ and core-isomeric [Au11(Ln)4X2]+ (n = 4-6; X = Cl, Br, I), are obtained in a more expedient and controllable manner. This work clearly demonstrates the non-negligible roles of halide ions in directing cluster synthesis, and provides an easier access to diverse diphosphine-protected Au nanoclusters. This approach, promising in gram-scale synthesis, is expected to further extend the ligand scope and holds promise for advancing the diversified syntheses of a broader range of ligand-protected metal nanoclusters.

NIR-Emitting Gold Nanoclusters Encapsulated in PS-b-PEG Polymer Micelles

Gold nanoclusters (AuNCs) are an emerging type of luminescent probe, featuring good biocompatibility, high photostability, and large Stoke shifts. Their lack of colloidal stability is, however, a drawback for many applications. Here, we report the stabilization of AuNCs emitting in the NIR by a thiol-terminated polystyrene chain (Mn = 5000 g mol-1). The optical properties of this nanocomposite remain invariant for 2 years in THF. To use the PS5k-AuNCs in an aqueous environment, these were encapsulated into polymer micelles using a polystyrene-b-poly(ethylene glycol) copolymer. The resulting hierarchical constructs, with diameters of ca. 125 to 215 nm, have promising properties for applications as luminescent probes such as contrast agents for biomedical imaging.

Rapid preparation of water-soluble Ag@Au nanoclusters with bright deep-red emission

Deep-red (λ_em ∼ 710 nm) thiolated Ag@Au nanoclusters with a quantum yield of ∼18% were rapidly (∼12 min) prepared in aqueous solutions. The effects of pH and silver ions were demonstrated. The surface modification further resulted in nanoclusters with a quantum yield of ∼38%, the highest value ever reported for water-soluble red Au nanoclusters. This will highly facilitate their applications in sensing, bioimaging, etc.

Controllable synthesis and electrocatalytic applications of atomically precise gold nanoclusters

Nanoclusters are composed of metal atoms and ligands with sizes up to 2-3 nm. Due to their stability and unique structure, gold nanoclusters with precise atomic numbers have been widely studied. Until now, atomically precise gold nanoclusters have been synthesised by various methods. Common ones include the Brust-Schiffrin method and the size-focusing method. With more detailed research on gold nanoclusters, more novel methods have been adopted to synthesise atomically precise gold nanoclusters, such as anti-galvanic reduction, ligand-exchange reactions from metal nanoclusters, the seed growth method, and so on. Besides, the nanoclusters also have many unique properties in electrochemical catalyses, such as the ORR, OER, etc., which are helpful for the development of the energy and environment. In this review, the synthesis methods and electrochemical applications of atomically accurate gold nanoclusters in recent years are introduced.