Boosting the Energy Migration Upconversion through Inter-Shell Energy Transfer in Tb ³⁺ -Doped Sandwich Structured Nanocrystals

Abstract

It remains challenging to fabricate Tb 3+ -doped lanthanide nanocrystals (NCs) for acquiring strong energy migration upconversion (EMU) emissions of Tb 3+ , while simultaneouly suppressing the Tm 3+ ultraviolet upconversion emissions that cause the issue of background biofluorescence in bioapplications based on Tb 3+doped EMU NCs. Herein, we report a novel sandwich structure core@shell@shell scheme for the design of EMU NCs, e.g. NaLuF 4 :Yb/Gd@NaGdF 4 :Tm@NaLuF 4 :Tb NCs, wherein Yb 3+ , Tm 3+ , and Tb 3+ are separately incorporated into the inner core, middle shell, and outer shell, respectively. We have found that, in the sandwich structure NCs, the effective inter-shell energy transfer from Gd 3+ in the middle shell to Tb 3+ in the outer shell accelerates the Yb 3+ -Tm 3+ five-photon upconversion and subsequent Tm 3+ to Gd 3+ energy transfer processes, which can eventually lead to the nearly completely inhibited Tm 3+ ultraviolet upconversion emissions concomitant with the strong EMU emissions of Tb 3+ . Our findings might stimulate new concepts for manipulating upconversion emissions of lanthanide NCs.

Lanthanide Upconversion Nanoplatforms for Advanced Bacteria‐Targeted Detection and Therapy

“…Improving the luminescence efficiency of UCNPs can effectively enhance the antibacterial treatment effect, increase the sensitivity of bacterial detection, and obtain clear UCL images with higher signal-to-noise ratios. Presently, several strategies including internal hydroxyl manipulating, [72] surface passivation, [73] ligand coordination, [74] dye sensitization, [75] localized surface plasmon resonance, [76] and inter-shell energy transfer [77] have been proposed to significantly boost the UC intensity. We are confident that the ongoing and future studies could bridge the gap between the current limits of UCL and the demand in clinical settings.…”

Lanthanide-Doped Inorganic Nanoprobes for Luminescent Assays of Biomarkers

“…It should be noted that these core-only NPs usually suffer from low PL intensity due to the nonradiative processes associated with surface quenching. One representative approach for surface passivation to improve optical properties is constructing core-shell architectures . For instance, we synthesized core-only CaF 2 :Ln 3+ NPs, which were then coated with multishells via seed-mediated epitaxial layer-by-layer (LBL) growth (Figure a) .…”

“…One representative approach for surface passivation to improve optical properties is constructing core-shell architectures. 24 For instance, we synthesized core-only CaF 2 :Ln 3+ NPs, which were then coated with multishells via seed-mediated epitaxial layer-by-layer (LBL) growth (Figure 1a). 12 The as-synthesized CaF 2 :Ln 3+ @ CaF 2 NPs exhibited ultrasmall sizes ranging from about 4 to 10 nm.…”

Selectively Manipulating Interactions between Lanthanide Sublattices in Nanostructure toward Orthogonal Upconversion

“…A multilayer core–shell nanostructure (MLCS) has been shown to be a powerful design for both fundamental research and application of UCNPs . By taking advantage of the MLCS designs, energy migration and luminescence dynamics can be easily probed. − It is also able to realize the orthogonal excitation–emission colors conveniently by using suitable dopants and chemical compositions in an MLCS nanostructure. ,− More importantly, such designs allow for the spatial control of dopants on the nanosized scale, providing a versatile nanoplatform toward diversities of frontier applications. − Thus, it would be highly desirable to construct the dual-lanthanide sublattices and finely manipulate their interfacial interactions in a single nanoparticle through rational nanostructure design and selection of lanthanide dopants with suitable doping contents.…”