Energy Migration Up-conversion of Tb3+ in Yb3+ and Nd3+ Codoped Active-Core/Active-Shell Colloidal Nanoparticles

摘要

The intentional design of chemical architecture of lanthanide doped luminescent nanoparticles through the proper selection of dopants in core-shell and core-shell-shell structures enables optimization of their optical properties. Such an approach allows one to achieve energy transfer up-conversion (ETU) and energy migration mediated up-conversion (EMU) and green emission from Tb3+ ions with the Yb3+ and Nd3+ sensitizers at 980 and 808 nm photo excitation, respectively. The [Nd3+ -> Yb3+] -> [Yb3+ -> Tb3+] EMU phenomenon was significantly enhanced by spatial displacement of the sensitizing Nd3+ ions from the activator Tb3+ ions by intentionally introducing an intermediate Yb3+ sensitizer layer forming a [Nd3+ -> Yb3+] -> [Yb3+] -> [Yb3+ -> Tb3+] system. Otherwise Tb3+ emission was considerably quenched by Nd3+ ions even though they were spitted between the core and shell, respectively. Moreover, (Tb3+,Yb3+) -> (Tb4+,Yb2+) valence change has been discovered to limit the Tb3+ up-conversion emission. The studies explain how the chemical architecture of the smartly designed active-core @ active-shell luminescent nanoparticles may improve their spectral properties.