Optical properties of metal clusters

Atomically protected metal nanoclusters have prominent quantum confinement, generating optical properties in these clusters. Exploring these optical properties of nanoclusters has gained the wide attention of scientists for a long time. Optical spectroscopy is one of the major tools for the characterization of metal nanoclusters. These properties are highly dependent on the size of the clusters, and the distinct optical absorption features evolve to surface plasmon resonance with an increase in size. Understanding the excitation dynamics is essential to reveal the transition of metal clusters from molecular to the metallic regime. The photoluminescence and nonlinear optical properties of metal clusters make them potential candidates for various practical applications like sensing, photoenergy storage, etc. This chapter will briefly overview the above aspects of optical properties in metal clusters and their future directions.