Precise Tuning of Surface Quenching for Luminescence Enhancement in Core–Shell Lanthanide-Doped Nanocrystals

Abstract

Lanthanide-doped nanocrystals are of particular interest for the research community not only due to their ability to shape light by downshifting, quantum cutting, and upconversion but also because novel optical properties can be found by the precise engineering of core-shell nanocrystals. Because of the large surface area-to-volume ratio of nanocrystals, the luminescence is typically suppressed by surface quenching. Here, we demonstrate a mechanism that exploits surface quenching processes to improve the luminescence of our core-shell lanthanide-doped nanocrystals. By carefully tuning the shell thickness of inert β-NaLuF around β-NaYF nanocrystals doped with Yb and Er, we unravel the relationship between quantum yield and shell thickness, and quantify surface quenching rates for the relevant Er and Yb energy levels. This enhanced understanding of the system's dynamics allowed us to design nanocrystals with a surface quenching-assisted mechanism for bright NIR to NIR downshifting with a distinctive efficiency peak for an optimized shell thickness.

Precisely Tailoring Upconversion Dynamics via Energy Migration in Core–Shell Nanostructures

“…Note that without the long‐distance energy migration, such a large time span modulation of the rise is hardly achieved in traditional Yb 3+ /Er 3+ co‐doping systems 7e, 9. Importantly, such a tuning effect is well predicted by our simulation model (Figure 3 c, dotted traces).…”

Interfacial Defects Dictated In Situ Fabrication of Yolk–Shell Upconversion Nanoparticles by Electron‐Beam Irradiation

“…To verify the above conversion mechanism, NaLuF 4 :Gd/Yb/Er@NaYF 4 :Nd/Yb@NaLuF 4 NPs as control were synthesized under the otherwise same conditions as that of NaLuF 4 :Gd/Yb/Er@NaLuF 4 :Nd/Yb@NaLuF 4 NPs except for varied middle‐shell host components, and exposed to e‐beam irradiation as well ( Figure a and its inset). It is well known that NaYF 4 is isostructural and has analogous lattice energy and chemical properties to NaLuF 4 , except for the much smaller Z and M for Y than for Lu. According to the atom displacement model (Figure d), the σ K for Y is much smaller than that for Lu.…”

Vanadium‐Sensitized Photon Upconversion of Lanthanide Ions (Er, Tm, Ho, Eu, Nd) in Yb3Al5O12 for In Vivo Imaging

“…Generally, upconversion intensity of lanthanide ions was greatly affected by a series of parameters such as crystallography phase, doping level, particle size . Since the crystallography phase and doping level keep constant for all the samples with and without vanadium codoping (Figure ; Figure S2, Supporting Information), we could exclude their effects on upconversion intensity in the present work.…”