Abstract
The realization of upconversion at 808 nm excitation has shown great advantages in advancing the broad bioapplications of lanthanide-doped nanomaterials. In an 808 nm responsive system, Nd3+ and Yb3+ are both needed where Nd3+ acts as a sensitizer through absorbing the excitation irradiation. However, few studies have been dedicated to the role of Yb3+. Here, we report a systemic investigation on the role of Yb3+ by designing a set of core-shell-based nanostructures. We find that energy migration over the ytterbium sublattice plays a key role in facilitating the energy transportation, and moreover, we show that the interfacial energy transfer occurring at the core-shell interface also has a contribution to the upconversion. By optimizing the dopant concentration and surface anchoring the infrared indocyanine green dye, the 808 nm responsive upconversion is markedly enhanced. These results present an in-depth understanding of the fundamental interactions among lanthanides, and more importantly, they offer new possibilities to tune and control the upconversion of lanthanide-based luminescent materials.
Highlights
Substantial attention has been devoted to the lanthanide-doped nanoparticles due to their great infrared-to-visible photon upconversion performance (Auzel, 2004; Haase and Schafer, 2011; Zhou et al, 2015), which shows potential applications ranging from bioimaging (Zhu et al, 2017) to photodynamic therapy (Xu et al, 2017), 3D display (Deng et al, 2015), security (Lu et al, 2014), anti-counterfeiting (Li et al, 2016), and super-resolution nanoscopy (Liu et al, 2017)
Few studies have explored the role of Yb3+, which is necessary in the 808 nm pumped upconversion systems, and the mechanism of the luminescence physics occurring in the Nd/Yb coupled upconversion is still not clear
We demonstrated that energy migration over the Yb-sublattice plays a key role in facilitating the energy transportation from the Nd3+ sensitizer to the lanthanide emitter
Summary
Substantial attention has been devoted to the lanthanide-doped nanoparticles due to their great infrared-to-visible photon upconversion performance (Auzel, 2004; Haase and Schafer, 2011; Zhou et al, 2015), which shows potential applications ranging from bioimaging (Zhu et al, 2017) to photodynamic therapy (Xu et al, 2017), 3D display (Deng et al, 2015), security (Lu et al, 2014), anti-counterfeiting (Li et al, 2016), and super-resolution nanoscopy (Liu et al, 2017). We showed that the interfacial energy transfer from Yb3+ in the shell to the lanthanide emitter in the core across the core-shell interface contributes to the upconversion.
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