Size-dependent carbon monoxide adsorption on neutral gold clusters.

Area of Science:

• Physical Chemistry
• Materials Science
• Surface Science

Background:

• Understanding the reactivity of metal clusters is crucial for catalysis and materials design.
• Gold clusters (Au(n)) exhibit unique properties influenced by size and electronic structure.
• Carbon monoxide (CO) adsorption is a fundamental probe of cluster surface chemistry.

Purpose of the Study:

• To investigate the reactivity of neutral gold clusters (Au(n), n = 9-68) with carbon monoxide (CO).
• To determine the influence of temperature (room temperature vs. liquid-nitrogen temperature) on cluster reactivity.
• To explore the size-dependent adsorption behavior of CO on gold clusters.

Main Methods:

• Production of neutral gold clusters using pulsed laser vaporization.
• Controlled reaction of clusters with CO in a low-pressure cell.
• Laser ionization and mass analysis using time-of-flight mass spectrometry to determine reaction probabilities.

Main Results:

• Reactivity of Au(n) clusters with CO shows strong temperature dependence.
• Cooling clusters to liquid-nitrogen temperature (LNT) increases reactivity by a factor of ~10 compared to room temperature (RT).
• Cold clusters adsorb multiple CO molecules (2-4), while RT clusters adsorb at most one; size dependence is consistent across temperatures.

Conclusions:

• Cluster temperature significantly impacts CO adsorption lifetime and reactivity.
• Electronic structure effects play a key role in the observed size-dependent reactivity of gold clusters.
• Tailoring cluster temperature offers a route to control reactivity for potential applications.