metaalclusters

Metaalclusters are aggregates consisting of a small number of metal atoms, typically ranging from a few to several hundred, that exhibit properties distinct from bulk metals. They can exist in the gas phase, on surfaces, or in solution, and are studied as an intermediate between molecules and bulk metal.

The geometry and properties of metal clusters depend on size and composition. Common structural motifs include icosahedral, cuboctahedral, and decahedral cores. For very small clusters, electronic states are discrete and spectra resemble those of molecules; as size increases, electronic levels broaden and plasmonic or metallic behavior emerges, approaching the characteristics of bulk metals. The concept of electronic shell structure and stability at certain sizes—often described by magic numbers—helps explain observed abundances and reactivity patterns in some cluster systems.

Synthesis and stabilization methods vary. Gas-phase production uses laser ablation or other vaporization techniques followed by cooling and aggregation, with mass separation or deposition for analysis. In solution, chemical synthesis with reducing agents and ligands can yield stabilized clusters. Clusters may be supported on substrates or capped with ligands to prevent agglomeration and enable handling, imaging, and use in applications.

Properties and applications depend on size, composition, and environment. Optical properties are tunable with size, making clusters useful in sensing and plasmonics. Catalytic activity often shows strong size and facet dependence. Magnetic moments can be significant for certain alloy or transition-metal clusters. Applications span heterogeneous catalysis, nanoelectronics, photonics, and materials science research, with ongoing work to understand and exploit size-dependent phenomena and stability. Characterization typically involves mass spectrometry, photoelectron spectroscopy, UV-Vis spectroscopy, electron microscopy, and scanning probe techniques.