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Lanthanide-doped upconversion nanoparticles are promising for applications ranging from biosensing, bioimaging to solid-state lasing. However, their brightness remains limited by the concentration quenching effect of lanthanide activator ions, which greatly restricts their utility. Here, we develop a heterogeneous core–shell–shell nanostructure based on hexagonal NaYF 4 , in which Tm 3+ activator and Yb 3+ sensitizer are separated into the core and inner shell, while the outmost shell is used to suppress surface quenching effects. We show that this design can alleviate the activator concentration quenching effect, resulting in optimal Tm 3+ concentration increasing from 1% to 8% at sub-100 W/cm 2 irradiance, compared with the canonical core-only NaYF 4 :Yb 3+ /Tm 3+ . Moreover, under high excitation irradiance (20 MW/cm 2 ), the optimal Tm 3+ concentration could be further increased to 50%. Mechanistic investigations reveal that the spatial separation of sensitizer and activator effectively suppresses the back energy transfer from Tm 3+ to Yb 3+ , driving the increase of optimal activator concentration. These findings enhance our understanding of lanthanide concentration quenching effect, unleashing opportunities for developing bright upconverting materials. The brightness of lanthanide-doped upconversion nanoparticles is limited by concentration quenching. Here the authors separate activator and sensitizer lanthanides in a core-shell-shell system, which optimizes energy transfer and concentration quenching.

Tuning the emissive chromaticity of parallel photon avalanches in Ho 3+ -doped nanoparticles with dual reservoir levels enables multicolor super-resolution imaging under 965 nm single wavelength continuous-wave excitation.

Beam splitters are widely used in various optical systems, but traditional beam splitters are bulky and heavy, which are not conducive to the integrated utilization of optical devices. Metamaterials have attracted extensive attention as a kind of miniature artificial materials, and there have been many works on the design of metasurface beam splitters. Using metasurfaces, multiple functions of traditional beam splitters can be achieved. Meanwhile, metasurface beam splitters have the advantages of small size, easy integration, flexible design of beam-splitting performance, and tunable functions. This review surveys the current work on metasurface beam splitters and provides a classification and introduction to metasurface beam splitters. Metasurface beam splitters are expected to play a huge role in interferometers, multiplexing, multi-beam communications, and more.

Lanthanide-doped upconversion nanoparticles are promising for applications ranging from biosensing, bioimaging to solid-state lasing. However, their brightness remains limited by the concentration quenching effect of lanthanide activator ions, which greatly restricts their utility. Here, we develop a heterogeneous core–shell–shell nanostructure based on hexagonal NaYF 4 , in which Tm 3+ activator and Yb 3+ sensitizer are separated into the core and inner shell, while the outmost shell is used to suppress surface quenching effects. We show that this design can alleviate the activator concentration quenching effect, resulting in optimal Tm 3+ concentration increasing from 1% to 8% at sub-100 W/cm 2 irradiance, compared with the canonical core-only NaYF 4 :Yb 3+ /Tm 3+ . Moreover, under high excitation irradiance (20 MW/cm 2 ), the optimal Tm 3+ concentration could be further increased to 50%. Mechanistic investigations reveal that the spatial separation of sensitizer and activator effectively suppresses the back energy transfer from Tm 3+ to Yb 3+ , driving the increase of optimal activator concentration. These findings enhance our understanding of lanthanide concentration quenching effect, unleashing opportunities for developing bright upconverting materials.

Optical upconversion from lanthanide-doped nanoparticles is promising for a variety of applications ranging from bioimaging, optogenetics, nanothermometry, super-resolution nanoscopy and volumetric displays to solar cells. Despite remarkable progress made in enhancing upconversion to fuel these applications, achieving luminescence of upconversion nanoparticles (UCNPs) that is comparable to or higher than the bulk counterparts has been challenging due to nanoscale-induced quenching effects. Here we demonstrate a size-dependent lanthanide energy transfer effect in a conceptual design of hexagonal sodium yttrium fluoride (NaYF 4 ) core–shell–shell NaYF 4 @NaYF 4 :Yb/Tm@NaYF 4 UCNPs with depleted surface quenching. We show that precise control over the domain size (or the thickness of the middle shell doped with ytterbium (Yb) and thulium (Tm) from 1.2 to 13 nm) increases the lanthanide energy transfer efficiency (from 30.2 to 50.4%) and amplifies the upconversion quantum yield to a high value of 13.0 ± 1.3% in sub-50 nm UCNPs (excitation: 980 nm, 100 W cm −2 ), which is around fourfold higher than the micrometre-scale hexagonal NaYF 4 :Yb/Tm bulk counterparts. Spectroscopic studies and theoretical microscopic modelling reveal that long-range lanthanide energy transfer (>9.5 nm) takes place and underlies the observed size-dependent phenomena. Demonstration of size-dependent lanthanide energy transfer and upconversion quantum yields at the nanoscale transforms our long-existing conceptual understanding of lanthanide energy transfer (size independence), thereby having important implications for applications of lanthanide nanophotonics and biophotonics. Researchers demonstrate a size-dependent lanthanide energy transfer effect in upconversion nanoparticles with depleted surface quenching, resulting in upconversion quantum yields of 13.0 ± 1.3%.

Lanthanide-doped nanocrystals have been actively pursued as anti-Stokes emitters in various contexts, including bioimaging, photovoltaics, catalysis, displays, anticounterfeiting, sensing and lasers. The success of these applications crucially relies on their high brightness under low excitation. To enhance their upconversion luminescence, researchers have improved the internal material properties of nanocrystals (their composition, doping, and crystal and surface structures) and, in parallel, engineered external optical responses using plasmonic couplings. However, despite impressive progress, upconversion brightness still falls short of what is required for applications, and a systematic understanding of plasmon-enhanced upconversion remains elusive. Here we report an important conceptual advance in understanding and demonstrate unprecedentedly bright upconversion of single nanocrystals via coupling to a single plasmonic nanocavity mode. We present in situ-controlled single-nanocrystal-level studies with unified internal and external treatment, and unambiguously experimentally demonstrate the phenomenon of plasmonic enhancement saturation. We show that the saturation is doping-dependent, and we report a 2.3 × 105-fold enhancement of upconversion luminescence. More importantly, we outline a new strategy to devise ultrabright upconversion nanomaterials and demonstrate that single sub-30-nm nanocrystals can provide up to 560 detected photons per second at an ultralow excitation intensity of 0.45 W cm−2. These findings help to establish the link between the optical physics and material science in lanthanide-doped nanocrystals and facilitate the engineering of optimal upconversion nanomaterials for various applications.Bright upconversion of single nanocrystals is enabled by coupling to a single plasmonic nanocavity mode. An upconversion luminescence enhancement of ~105 was achieved. Single sub-30-nm nanocrystals provided 560 detected photons per second at an excitation intensity of just 0.45 W cm−2.

Tuning the emissive chromaticity of parallel photon avalanches in Ho -doped nanoparticles with dual reservoir levels enables multicolor super-resolution imaging under 965 nm single wavelength continuous-wave excitation.

Lanthanide-doped upconversion nanoparticles are promising for applications ranging from biosensing, bioimaging to solid-state lasing. However, their brightness remains limited by the concentration quenching effect of lanthanide activator ions, which greatly restricts their utility. Here, we develop a heterogeneous core-shell-shell nanostructure based on hexagonal NaYF , in which Tm activator and Yb sensitizer are separated into the core and inner shell, while the outmost shell is used to suppress surface quenching effects. We show that this design can alleviate the activator concentration quenching effect, resulting in optimal Tm concentration increasing from 1% to 8% at sub-100 W/cm irradiance, compared with the canonical core-only NaYF :Yb /Tm . Moreover, under high excitation irradiance (20 MW/cm ), the optimal Tm concentration could be further increased to 50%. Mechanistic investigations reveal that the spatial separation of sensitizer and activator effectively suppresses the back energy transfer from Tm to Yb , driving the increase of optimal activator concentration. These findings enhance our understanding of lanthanide concentration quenching effect, unleashing opportunities for developing bright upconverting materials.

Herein, we disclose a highly efficient cobalt-catalyzed cross-electrophile alkynylation of a broad range of unactivated chlorosilanes with alkynyl sulfides as a stable and practical alkynyl electrophiles. Strategically, employing easily synthesized alkynyl sulfides as alkynyl precursors allows access to various alkynylsilanes in good to excellent yields. Notably, this method avoids the utilization of strong bases, noble metal catalysts, high temperature and forcing reaction conditions, thus presenting apparent advantages, such as broad substrate scope (72 examples, up to 97% yield), high Csp-S chemo-selectivity and excellent functional group compatibility (Ar-X, X = Cl, Br, I, OTf, OTs). Moreover, the utilities of this method are also illustrated by downstream transformations and late-stage modification of structurally complex natural products and pharmaceuticals. Mechanistic studies elucidated that the cobalt catalyst initially reacted with alkynyl sulfides, and the activation of chlorosilanes occurred via an S N 2 process instead of a radical pathway. Transition-metal catalyzed cross-electrophile coupling (XEC) is a powerful tool for the construction of molecules but XEC between carbon electrophile and chlorosilanes to access organosilicon compounds remains underdeveloped. Here the authors disclose a highly efficient cobalt-catalyzed cross-electrophile alkynylation of a broad range of unactivated chlorosilanes with alkynyl sulfides as a stable and practical alkynyl electrophiles.

Ride-hailing global positioning system (GPS) mobile probe data provide flexible urban traffic observations, but their sparse and uneven coverage makes model evaluation difficult because observed targets, valid predictions, and historical input support do not always coincide. This study audits ultra-short-term road-segment speed forecasting under sparse mobile sensing using a mask-consistent support-chain framework. A three-day GPS dataset is aggregated into 5 min speed observations over 1970 road segments and used as a controlled sparse-sensing case study rather than a general-purpose long-term forecasting benchmark. The evaluation protocol distinguishes the full test grid, the set of directly observed target speeds, model-valid prediction support, strict complete-history support, and common-support subsets for coverage-limited baselines. The directly observed target set is used as the primary relaxed support because it retains all verifiable ground-truth targets, while strict and common-support subsets are reported as sensitivity checks. Under this support-conditioned evaluation, the adaptive graph convolutional recurrent network (AGCRN) is associated with lower mean absolute error (MAE) among full-coverage models, the historical mean (HIST_MEAN) baseline is associated with lower root mean squared error (RMSE), and congestion recall remains below 0.24 for all full-coverage deep models. These complementary results indicate conditional and metric-dependent strengths rather than universal model superiority. Because the dataset covers only three consecutive days, weekday/weekend variation, incident-specific fluctuations, seasonal effects, and spatial transferability cannot be fully examined and are treated as limitations. Overall, the findings show that evaluation support should be reported as a first-order experimental factor alongside model accuracy under sparse mobile probe sensing.