Tunable optical properties of icosahedral, dodecahedral, and tetrahedral clusters

Using time-dependent density-functional theory, we show that the first singlet excitations of a series of icosahedral, dodecahedral, and tetrahedral clusters are optically forbidden and that their optical absorption gaps and spectral properties are size, shape, and composition dependent and can be tuned broadly in the ultraviolet-visible region. Taking icosahedral clusters Al@Al-12 and Al@Pb-12 as examples, we demonstrate that the optical gaps of icosahedral clusters can be tailored from the ultraviolet to near infrared by properly doping them with (transition) metals, hydrogen, group VIIB atoms, and organic functional groups. Our study suggests icosahedral, dodecahedral, and tetrahedral clusters are suitable for tunable optical applications.