Controlling Electron Trap Depth To Enhance Optical Properties of Persistent Luminescence Nanoparticles for In Vivo Imaging

Abstract

Focusing on the use of nanophosphors for in vivo imaging and diagnosis applications, we used thermally stimulated luminescence (TSL) measurements to study the influence of trivalent lanthanide Ln³⁺ (Ln = Dy, Pr, Ce, Nd) electron traps on the optical properties of Mn²⁺-doped diopside-based persistent luminescence nanoparticles. This work reveals that Pr³⁺ is the most suitable Ln³⁺ electron trap in the diopside lattice, providing optimal trap depth for room temperature afterglow and resulting in the most intense luminescence decay curve after X-ray irradiation. This luminescence dependency toward the electron trap is maintained through additional doping with Eu²⁺, allowing UV-light excitation, critical for bioimaging applications in living animals. We finally identify a novel composition (CaMgSi₂O₆:Eu²⁺,Mn²⁺,Pr³⁺) for in vivo imaging, displaying a strong near-infrared afterglow centered on 685 nm, and present evidence that intravenous injection of such persistent luminescence nanoparticles in mice allows not only improved but highly sensitive detection through living tissues.