Chromatographic isolation of "missing" Au55 clusters protected by alkanethiolates

Area of Science:

• Nanomaterials Science
• Inorganic Chemistry
• Surface Chemistry

Background:

• Gold clusters are crucial in catalysis and electronics.
• The synthesis of specific gold cluster sizes, like Au55, has been challenging.
• Alkanethiolate ligands are commonly used to stabilize metal nanoparticles.

Purpose of the Study:

• To report the first synthesis of alkanethiolate-protected gold 55 (Au55) clusters.
• To characterize the structure and properties of the synthesized Au55 clusters.
• To compare the new Au55 clusters with existing gold cluster structures.

Main Methods:

• Reaction of alkanethiol (CxSH) with polymer-stabilized gold clusters.
• Incubation in neat alkanethiol.
• Fractionation using recycling gel permeation chromatography.
• Identification via laser-desorption ionization mass spectrometry.
• Characterization using IR spectroscopy and hydrodynamic diameter measurements.

Main Results:

• Successful synthesis and isolation of Au approximately 38:SCx and Au approximately 55:SCx clusters.
• Au55:SCx clusters displayed structured optical spectra, indicating molecular-like behavior.
• Thiolate monolayers on Au55 clusters exhibited liquid-like characteristics.
• Monolayer thickness was estimated from hydrodynamic diameter.

Conclusions:

• The study presents the first synthesis of alkanethiolate-protected Au55 clusters.
• These Au55 clusters possess unique optical properties and molecular-like characteristics.
• The liquid-like nature of the thiolate monolayer was confirmed, offering insights into cluster surface dynamics.