Optimizing the Key Variables to Generate Host Sensitized Lanthanide Doped Semiconductor Nanoparticle Luminophores

Abstract

Trivalent lanthanide (Ln3+) doped semiconductor nanoparticles (NPs) provide an avenue for developing unique luminophores, which combine the properties of Ln3+ and NPs. Realizing their promise requires a thorough understanding of their underlying photophysical processes. This article summarizes experimental findings and uses them to sketch a framework for understanding the important NP core and surface properties that affect Ln3+ luminescence. A charge trapping mediated Ln3+ emission sensitization mechanism is shown to operate in both the synthetically doped and postsynthetically modified NPs, and it is strongly affected by the energy offsets between the lanthanide and NP electronic states. While both the host (semiconductor NP) and guest (Ln3+) properties must be considered in designing and controlling the photophysical outcome, the predictable trends in Ln3+ energetics make it possible to predict trends and behaviors semiempirically. The role of spectral overlap mediated energy transfer mechanisms are shown to contribute negligibly to the sensitization. Proof of principle experiments to uncover the roles of surface localized dopants and surface capping ligands in governing the dopant emission, and the realization of emission from distinct Ln3+ in a codoped assembly, are discussed.