Reversible Size Control of Silver Nanoclusters via Ligand-Exchange

Abstract

The properties of atomically monodisperse noble metal nanoclusters (NCs) are intricately intertwined with their precise molecular formula. The vast majority of size-specific NC syntheses start from the reduction of the metal salt and thiol ligand mixture. Only in gold was it recently shown that ligand-exchange could induce the growth of NCs from one atomically precise species to another; a process of yet unknown reversibility. Here, we present a process for the ligand-exchange-induced growth of atomically precise silver NCs, in a biphasic liquid-liquid system, which is particularly of interest because of its complete reversibility and ability to occur at room temperature. We explore this phenomenon in-depth using Ag 35 (SG) 18

[Ag25(SR)18]−: The “Golden” Silver Nanoparticle

“…The Ag 25 was also found to exhibit luminescence in the near-infrared region ∼850 nm. Typically, silver clusters are brown to red 11,[26][27][28] and usually are associated with that color, but the color resemblance between Ag 25 cluster and that of large plasmonic Ag nanoparticles may have delayed its discovery. To naked eyes, the purified Ag 25 cluster solution appeared yellow (Figure 1, inset) similar to Au 25 prepared ( Figure S2) using the same thiol.…”

Switching a Nanocluster Core from Hollow to Nonhollow

“…The Ag 44 (SPhF) 30 NCs were synthesized as per the literature 11 and also, see Supporting Information (SI) for details. About 5 mg of Ag 44 (SPhF) 30 NCs in 5 mL of DCM was stirred with 5 µL (2.3 times excess, in mmol, compared to the total ligand amount in the starting material) of a desired thiol HSPhMe 2 , HSPhF 2 , or HSPhCl 2 .…”

“…Organic-soluble NCs were dissolved in a DCM+acetonitrile mixture and electrosprayed. The Ag 44 (SPhCOOH) 30 was dissolved in DMF after protonation with citric acid. The typical instrument parameters used were: mass range 100-10,000Da; flow rate: 600 µL/h; capillary voltage 3.5-4.0 kV; source temperature 80-120 0 C; dry gas 0.2-0.4 L/min, and nebulizer gas 0.3-0.5 bar.…”

“…The typical routes for metal NC synthesis are: i) direct reduction of metal precursors in the presence of desired ligands, [22][23][24][25][26][27][28] ii) postsynthetic ligand-exchange (LE), [29][30][31][32][33][34][35] and iii) metal-exchange 15,[36][37][38][39][40][41] . Among these methods, LE has recently been widely adopted for preparing novel gold NCs [42][43][44] .…”

“…In this work, we designed a single phase LE reaction to understand the step-by-step conversion of Ag 44 (SR) 30 NCs to Ag 25 (SR) 18 NCs, and vice versa, where studying the interconversion of these NCs was challenging in a biphasic LE. The single phase LE of Ag 44 18 solution (2 mg/mL DCM) was added to 5 mL of alkaline aqueous HSPhCOOH (10 mg/mL) and stirred.…”