Abstract

Metal atomic quantum clusters (AQCs), formed by a small number of metal (0) atoms (

≈

< 100-150 atoms), and with sizes below ≈ 1-2 nm, represent a novel state of matter located between classical bulk (or nanoparticles) and single atoms. Due to the strong quantum confinement, they present new and fascinating properties like luminescence, magnetism, circular dichroism, etc. One of the key properties of AQCs is the presence of a band gap at the Fermi level, so they can be considered to be a completely new type of atomic level semiconductors (SCs). Moreover, the value and position of the band gap (HOMO-LUMO gap) can be fine tuned just by changing the cluster size and the metal, opening unprecedented possibilities in the SC area.

In the last decade, a large number of chemical methods have been developed to synthesize AQCs, mainly based on the use of protecting ligands, being thiols the most used ones. However, for many applications, such as catalysis, clusters can be poisoned by the presence of such capping ligands. In the last years we have developed simple techniques, based on kinetic control, to synthesize small AQCs without any surfactant or capping agents. In this talk we will explain the background of such techniques and their application to prepare AQCs with sizes down to 2 or 3 atoms. We will then explain the reasons for the surprisinglylarge stability of clusters and discuss the main advantages of using such clusters in different fields, like catalysis, sensors and biomedical applications. Special emphasis will be given to the different chemistry, which seems to appear at this nanometric/sub-nanometric range of the matter.

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