Selectively Manipulating Interactions between Lanthanide Sublattices in Nanostructure toward Orthogonal Upconversion

Smart control of ionic interactions is a key factor to manipulate the luminescence dynamics of lanthanides and tune their emission colors. However, it remains challenging to gain a deep insight into the physics involving the interactions between heavily doped lanthanide ions and in particular between the lanthanide sublattices for luminescent materials. Here we report a conceptual model to selectively manipulate the spatial interactions between erbium and ytterbium sublattices by designing a multilayer core–shell nanostructure. The interfacial cross-relaxation is found to be a leading process to quench the green emission of Er3+, and red-to-green color-switchable upconversion is realized by fine manipulation of the interfacial energy transfer on the nanoscale. Moreover, the temporal control of up-transition dynamics can also lead to an observation of green emission due to its fast rise time. Our results demonstrate a new strategy to achieve orthogonal upconversion, showing great promise in frontier photonic applications

Multichannel Control of PersL/Upconversion/Down-Shifting Luminescence in a Single Core–Shell Nanoparticle for Information Encryption

Persistent luminescence (PersL) has been attracting substantial attention in diverse frontier applications such as optical information security and in vivo bioimaging. However, most of the reported PersL emissions are based on the dopants instead of the host matrix, which also plays an important role. In addition, there are few works on the PersL-based multifunctional nanoplatform in nanosized materials. Here, we report a class of novel nanostructure designs with PersL, upconversion, and down-shifting luminescence to realize the fine-tuning of emission colors under different excitation modes including steady-state irradiation, time-gating, and PersL generation. Blue, orange, and green emissions were easily achieved in such a single nanoparticle under suitable excitation modes. Moreover, the physical origin of the PersL of the CaF2 matrix was discussed by simulating the energy band structure with CaxFy defects. Our results provide new opportunities for the design of a new class of multifunctional materials, showing great promise in the field of information encryption security and multilevel anticounterfeiting

Thermodynamics and Kinetics Accounting for Antithermal Quenching of Luminescence in Sc₂(MoO₄)₃: Yb/Er: Perspective beyond Negative Thermal Expansion

Defects are common in inorganic materials and not static upon annealing of the heat effect. Antithermal quenching of luminescence in phosphors may be ascribed to the migration of defects and/or ions, which has not been well-studied. Herein, we investigate the antithermal quenching mechanism of upconversion luminescence in Sc2(MoO4)3: 9%Yb1%Er with negative thermal expansion via a fresh perspective on thermodynamics and kinetics, concerning the thermally activated movement of defects and/or ions. Our results reveal a second-order phase transition taking place at ∼573 K induced by oxide-ion migration. The resulting variation of the thermodynamics and kinetics of the host lattice owing to the thermally induced oxide-ion movement contributes to a more suppressed nonradiative decay rate. The dynamic defects no longer act as quenching centers with regard to the time scale during which they stay nearby the Yb3+/Er3+ site in our proposed model. This research opens an avenue for understanding the antithermal quenching mechanism of luminescence via thermodynamics and kinetics