Atomic-Level Doping of Metal Clusters

Abstract

Conspectus Atomically precise noble metal (mainly silver and gold) nanoclusters are an emerging category of promising functional materials for future applications in energy, sensing, catalysis, and nanoelectronics. These nanoclusters are protected by ligands such as thiols, phosphines, and hydride and have sizes between those of atoms and plasmonic nanoparticles. In metallurgy, the properties of a pure metal are modified by the addition of other metals, which often offers augmented characteristics, making them more utilizable for real-life applications. In this Account, we discuss how the incorporation of various metal atoms into existing protected nanoclusters tunes their structure and properties. The process of incorporating metals into an existing cluster is known as doping; the product is known as a doped cluster, and the incorporated metal atom is called a dopant/foreign atom. We first present a brief historical overview of protected clusters and the need for doping and explain (with examples) the difference between an “alloy” and a “doped” cluster, which are two frequently confused terms. We then discuss several commonly observed challenges in the synthesis of doped clusters: (i) doping produces a mixture of compositions that prevents the growth of single crystals; (ii) doping with foreign atoms sometimes changes the overall composition and structure of the parent cluster; and (iii) doping beyond a certain number of foreign atoms decomposes the doped cluster. After delineating the challenges, we review a few potential synthetic methods for doped clusters: (i) the co-reduction method, (ii) the galvanic exchange method, (iii) ligand-induced conversion of bimetallic clusters to doped clusters, and (iv) intercluster reactions. As a foreign atom is able to occupy different positions within the structure of the parent cluster, we examine the structural relationship between the parent clusters and their different foreign-atom-doped clusters. We then show how doping enhances the stability, luminescence, and catalytic properties of clusters. The enhancement factor highly depends on the number and nature of the foreign atoms, which can also alter the charge state of the parent cluster. Atomic-level doping of foreign atoms in the parent cluster is confirmed by high-resolution electrospray ionization and matrix-assisted laser desorption ionization mass spectrometry techniques and single-crystal X-ray diffraction methods. The photophysical properties of the doped clusters are investigated using both time-dependent and steady-state luminescence and optical absorption spectroscopies. After presenting an overview of atomic-level doping in metal clusters and demonstrating its importance for enriching the chemistry and photophysics of clusters and extending their applications, we conclude this Account with a brief perspective on the field’s future.

Gold nanoclusters as electrocatalysts: size, ligands, heteroatom doping, and charge dependences

“…S14 †), the negative ion was oxidized 18 ] 0 (a) before and (b) after the HER experiment with twenty scans. The peaks indicated by asterisk (*) and hash (#) symbols are assigned to Au 23 (PET) 16 and Au 25 (PET) 18 18 ] 0 is a metal cluster showing high potential for use as an HER catalyst.…”

“…Therefore, in recent years, there has been intensive research on controlling these energies by using alloy catalysts. 1 Thiolate (SR)-protected gold clusters (Au n (SR) m ) [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] are sizecontrollable at the atomic level and have high stability in both solution and solid states. Au in these clusters can be partially substituted with silver (Ag), copper (Cu), platinum (Pt), palladium (Pd), cadmium (Cd), and mercury (Hg).…”

Understanding and designing one-dimensional assemblies of ligand-protected metal nanoclusters

“…In recent years, it has become possible to synthesize metal clusters composed of elements such as gold (Au), silver (Ag), platinum (Pt), palladium (Pd) and alloy clusters containing mixtures of these metal elements with atomic accuracy using thiolates (SR), [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] selenolates, 20,21 alkynyl, 22 phosphines, 23,24 and carbon monoxide 25,26 as ligands. These metal clusters have also been extensively studied for applications in chemical sensors, 27 photosensitization, 28 catalyst, [29][30][31] and solar cells.…”

Elucidating ligand effects in thiolate-protected metal clusters using Au24Pt(TBBT)18 as a model cluster

“…Thiolates (SRs), [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] selenolates, 20,21 alkynylates groups, 22 phosphines, 23,24 and carbon monoxide 25,26 can be used as ligands, and then metal clusters can be synthesized with atomic precision. Among them, thiolate-protected gold clusters (Au n (SR) m ) have a high stability in the solution and solid state, and exhibit multiple physical/chemical properties and functions that are suitable for application including photoluminescence, redox behavior, and catalysis.…”