Lithium-sublattice nanoparticles have recently shown to be a promising nano-sized host candidate for photon upconversion of lanthanides. However, it remains a challenge for the controllable synthesis of high-quality lithium-sublattice core-shell nanostructures due to its tetragonal crystal structure in contrast to the commonly investigated hexagonal (or cubic) sodium-sublattice counterparts. Herein, we present a novel synthetic strategy of using the pre-synthesized optically-active (sensitive or emissive) seeds to guide the epitaxial growth of LiGdF 4 -based core-shell nanostructures. By further constructing the Gd 3+ -mediated interfacial energy transfer in such nanoparticles , both upconverting and down-shifting emissions from a set of lanthanide ions including Eu 3+ , Tb 3+ , Dy 3+ , Sm 3+ and Nd 3+ were realized. Such core-shell nanoparticles also show good spectral Stark-splitting feature owing to their lower local structural symmetry compared to other nano-sized hosts. Moreover, the tri-channel emission from a single nanoparticle was achieved by integrating upconverting and down-shifting emissions under the dual wavelength excitations (980/254 nm), exhibiting a great promise in the multiple anti-counterfeiting identification. These results open a door to the research on new kinds of efficient luminescent nanomaterials, and further help the design of multi-functional nanostructures towards emerging cutting-edge applications.
Yuansheng Shi,Fushan Geng,Yang Sun,Pengfeng Jiang,Wang Hay Kan,Wei Tong,Xueyi Lu,Guoyu Qian,Nan Zhang,Bin Wei,Bingwen Hu,Dapeng Cao,Xia Lu
The irrational utilization of an anionic electron often accompanies structural degradation with an irreversible cation migration process upon cycling in sodium-layered oxide cathodes. Moreover, the insufficient understanding of the anionic redox involved cation migration makes the design strategies of high energy density electrodes even less effective. Herein, a P3-Na0.67Li0.2Fe0.2Mn0.6O2 (P3-NLFM) cathode is proposed with the in-plane disordered Li distribution after an in-depth remolding of the Li ribbon-ordered P3-Na0.6Li0.2Mn0.8O2 (P3-NLM) layered oxide. The disordered Li sublattice in the transition metal slab of P3-NLFM leads to the dispersed |O2p orbitals, the lowered charge transfer gap, and the suppressed phase transition at high voltages. Then the enhanced Mn–O interaction and electronic stability are disclosed by the crystal orbital Hamilton population (COHP) analysis at high voltage in P3-NLFM. Furthermore, ab initio molecular dynamics (AIMD) simulation suggests the order/disorder of the transition metal layer is highly correlated with the stability of the Li sublattice. The cross-layer migration and loss of Li in P3-NLM are suppressed in P3-NLFM to enable the high reversibility upon cycling. As a result, the P3-NLFM delivers a high capacity of 163 mAh g–1 without oxygen release and an enhanced capacity retention of 81.9% (vs 42.9% in P3-NLM) after 200 cycles, which constitutes a promising approach for sustainable oxygen redox in rechargeable batteries.
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