Intraband transition and localized surface plasmon resonance of metal chalcogenide nanocrystals and their dependence on crystal structure

Understanding the localized surface plasmon resonance (LSPR) and the intraband transition of semiconductor nanocrystals (NCs) has attracted considerable attention since it can provide the opportunity to investigate the boundary between the metal and the semiconductor. It has been reported that optical properties in semiconductor NCs can vary from excitonic to plasmonic by tuning the free carrier density level. Although many researchers have developed doping methods that inject impurity dopants into NCs for varying the LSPR frequency, other factors have not been focused on yet. In this feature article, we highlight the optical change of heavily doped NCs arising from the transformation of the crystal phase. By examining various metal chalcogenide NCs, we emphasize the impact of synthesis conditions, composition ratio, heterogeneous elements, and surface ligands on the crystal phase, which simultaneously has a critical role in shifting the LSPR frequency. Moreover, the future directions suggest numerous promising research objects on metal chalcogenide materials related to LSPR properties for potential applications.