ABSTRACT Near‐infrared cyanine dyes are widely employed for sensitizing lanthanide upconversion luminescence (UCL), but generally suffer from aggregation‐caused quenching (ACQ) and photobleaching. Herein, we report a ligand engineering strategy utilizing pyridine‐2‐carboxylic acid (2PA) to competitively modify with cyanine dyes (e.g., IR808) on the lanthanide‐doped nanoparticles (e.g., Cs2NaYbF6:Er, Nd). Specifically, 2PA suppresses ACQ of dye via physical isolation, passivates surface defects to reduce lanthanide dopants quenching, and actively quenches singlet oxygen to enhance the photostability of the sensitized system. This synergy ultimately enhances the dye‐sensitized lanthanide UCL by over one order of magnitude and shows superior photostability under continuous stimulation. Remarkably, this strategy shows universality across multiple dye‐sensitized systems and demonstrates UCL enhancement and photostability improvement at the single‐particle level upon high‐power excitation. This work overcomes the fundamental bottlenecks in dye‐sensitized lanthanide systems, offering a facile strategy for designing high‐performance UCL nanoplatforms for versatile applications.

Reactive oxygen species (ROS) are pivotal in maintaining redox homeostasis and regulating physiological functions. However, the intrinsically short lifetime and high reactivity of ROS present substantial challenges for their sensing. Lanthanide-doped inorganic nanoparticles (LnNPs) offer promising solutions due to their tunable photoluminescence and superior photostability. This review begins with the structural optimization and surface modification of LnNPs. The design strategies for ROS-responsive LnNPs are systematically summarized, focusing on valence conversion, Förster resonance energy transfer and absorption competition-induced emission modulation. Next, representative applications of LnNPs in the detection and imaging of major ROS are highlighted, evaluating their performance from temporal, spatial, and multimodal perspectives. Finally, we address current technical limitations and proposed future research directions, emphasizing the importance of interdisciplinary collaboration in this active research field.

808 nm excited energy migration upconversion (EMU) nanocrystals (NCs) exhibit great superiority over their 980 nm excited counterparts in alleviating the overheating effect of excitation laser in biodetection and imaging applications based on EMU NCs. However, it remains challenging to fabricate 808 nm excited EMU NCs to acquire the strong EMU emissions of Tb3+ or Eu3+ while simultaneously suppressing the ultraviolet (UV) upconversion emissions of Tm3+ and Gd3+ that cause the issue of autofluorescence interference. Herein, we report a novel sandwich structured core-triple shell NaLuF4:Nd,Yb@NaLuF4:Yb@NaGdF4:Tm@NaLuF4:Tb (or Eu) NC, wherein the efficiency of five-photon upconversion energy migration (i.e., Tm3+ → Gd3+ → Tb3+ (or Eu3+)) can approach 100% upon 808 nm excitation with power density above a threshold of ∼150 W cm-2, thus resulting in the nearly complete inhibition of UV upconversion emissions of Tm3+ and Gd3+ concomitant with the strong EMU emissions of Tb3+ or Eu3+. Our findings may open new opportunities for further bioapplications of EMU NCs.

Current optical manometers that rely on ultraviolet (UV) excitation suffer from low pressure sensitivity, high cost of UV lasers, and severe photoluminescence interference caused by spectral overlap between the excitation/emission light and background fluorescence. To address these issues, we herein explored a kind of novel optical manometry based on Cs2NaBiCl6:Yb3+/Mn2+ double perovskite, exhibiting pressure-sensitive broadband upconversion emission that originated from Yb3+-Mn2+ dimers. By virtue of near-infrared (NIR) energy transfer from Yb3+ to Yb3+-Mn2+ dimers, a linear upconversion pressure sensitivity as high as 15.03 nm/GPa was achieved upon 980-nm excitation, which is over forty times higher than that of commercial manometer Ruby (0.36 nm/GPa) and traditional lanthanide (Ln3+)-doped upconversion luminescence (UCL) phosphors (∼0.20 nm/GPa). Through in situ pressure-dependent structural analysis, it was demonstrated that such exceptional pressure-sensing performance stems from the soft lattice of Cs2NaBiCl6, which has a significantly low bulk modulus of 23.69 GPa. In addition, the pressure-dependent Raman spectra further verified the stability and repeatability of Cs2NaBiCl6:Yb3+/Mn2+ at extreme conditions. This work develops an ultrasensitive pressure-responsive upconversion luminescent material, establishing a reliable visual optical strategy for high-precision pressure monitoring in versatile scenarios.

Lanthanide nanocrystals hold exceptional promise for electroluminescence applications due to their unique optical properties. However, their intrinsic insulating character and localized 4f orbitals severely restrict carrier injection, thereby hindering direct electrical excitation. In a recent study published in Nature, Tan and colleagues circumvented this fundamental bottleneck via molecular engineering of the nanocrystal surface. They developed a series of functionalized ligands (e.g., carbazole-phosphine oxide) to establish an electroactive interface, facilitating efficient transfer of electro-generated triplet excitons to lanthanide ions. Notably, a wide-ranging multicolor electroluminescence from lanthanide nanocrystals was achieved for the first time, exhibiting high power efficiency and external quantum efficiency. These findings provide new opportunities for electrically driven luminescence in lanthanide nanocrystals or other insulating systems.

Manganese (Mn)-based halide perovskites have attracted tremendous attention due to their low-cost and environment-friendly characteristics. Nevertheless, their applications are hindered by limited photoluminescence (PL) efficiency and insufficient stability. Dimensional engineering offers a viable pathway to modulate their photophysical properties and enhance their robustness. Herein, we design 2D@3D perovskites based on the dimensional reduction of CsMnCl3 & centerdot;2H2O 3D perovskites via alternating cation interactions (ACIs) by employing chitosan as a polymeric spacer cation. ACI effectively stabilized the 2D@3D perovskite and passivated surface defects through enriched H-bonding. As such, the PL intensity can be boosted by 50 times with a PL quantum yield (PLQY) of 18.1%. Intriguingly, 2D@3D perovskites experienced valence transition (VT: Mn2+ -> Mn4+) at high temperatures, resulting in NH4CsMnCl6 perovskite. Density functional theory calculations indicated that an interfacial orbital hybridization-driven reaction mechanism triggered VT, which was initiated by the synergistic effect of octahedral distortion and ACI within 2D@3D perovskite. Notably, the proposed VT perovskites exhibited narrowband emission of Mn4+ with remarkable air-, photo-, and thermally stability, achieving a PLQY up to 80.7%. This approach paves the way for exploring organic-inorganic interactions in designing highly luminescent Mn-based perovskites.

ABSTRACT Carbon dots (CDs) featuring bright photoluminescence (PL) have emerged as a focal point of research due to their extraordinary attributes, including low toxicity, inexpensive synthesis, eco‐friendliness, and outstanding biocompatibility. To date, various methodologies for synthesizing CDs have been recorded; however, the origin of their luminescence is still a debatable point, which hinders the achievement of the desired optical properties. Likewise, there persists a need for thorough analysis that encompasses experimentally guided structural design and mechanistic understanding of CDs’ PL, involving fluorescence (FL) and afterglow luminescence. This review aims to provide a comprehensive account of spectral elaborations from the deep ultraviolet (DUV) to the near‐infrared (NIR) region, inherent to distinct exciton transition pathways. Furthermore, by carefully integrating pieces of the mechanistic puzzle owing to underlying emission centers, we systematically explore the impact of structural engineering on FL modulation, which material scientists could set foot on in the future. Subsequently, we delve into recent findings to elucidate the transition from FL to afterglow luminescence in CDs with the aid of involved substrates to harvest triplet excitons. Ultimately, we discuss practical challenges and emerging opportunities for scalable synthesis and spatially governed optical properties.

Near-infrared (NIR) photodetectors (PDs) based on Er 3+ -doped upconversion luminescence (UCL) have significant potential for application in 1532-nm optical communications. However, Er 3+ -activated NIR PDs exhibit low responsivity due to their weak absorption of 1532-nm photons. Herein, we developed Cs 2 NaErF 6 double perovskite nanocrystals (NCs) with a large cell structure to alleviate concentration quenching of Er 3+ ions, facilitating efficient self-sensitized UCL of Er 3+ under 1532 nm excitation. Furthermore, the UCL can be enhanced by ~ 22000 times through Tm 3+ doping and CaF 2 shell coating. Notably, NIR PDs were fabricated based on Cs 2 NaErF 6 :Tm 3+ @CaF 2 NCs, exhibiting an outstanding responsivity of 4.97 A/W under 1532 nm illumination, which is among the highest values reported for lanthanide-doped upconversion PDs. Furthermore, the fabricated PDs displayed good signal reception capabilities in NIR optical communication applications in water. This work provides new insight for designing highly efficient 1532-nm excited UCL NCs, which may accelerate the development of high-sensitivity and low-cost NIR PDs.

This Editorial highlights a recent study published in Nature Photonics, in which a versatile Lanbow spectral palette was proposed based on excitation-encoded and single-NIR-II emission for multispectral imaging.

Lanthanide coordination polymers (LnCPs) have garnered considerable attention in the biomedical field due to their distinctive optical properties, including strong ligand-sensitized photoluminescence and long luminescence lifetimes. However, their practical applications, especially in luminescent immunoassays (LIA), are constrained by challenges in nanoscale regulation and luminescence stability in aqueous media. Herein, a unique class of nanosized LnCPs (Ln = Eu/Tb) was fabricated by using biphenyl-3,4',5-tricarboxylic acid (H3BPT) as the organic ligand. Focusing on Eu-BPT CPs as the main representative, we conducted an in-depth investigation into their controllable synthesis, structural and spectroscopic properties, and aqueous stability. Finally, bioconjugated EuBPT nanoprobes were successfully applied to the time-resolved LIA for the cancer biomarker prostate-specific antigen, achieving an ultralow detection limit of 105 fg mL-1. These results highlighted the promising potential of Ln-BPT CP-based nanoplatforms for ultrasensitive biodetection applications.

Optical probes hold great promise for temperature sensing owing to their attractive properties including rapid response,high spatial resolution,and remote non-invasive detection.However,the exploration of thermometric probes is hindered by their low relative sensitivity(Sr)or poor structural stability in water.Herein,we propose the first example of organic-inorganic metal halides based on TPP3Cu2Br2(TPP=triphenylphosphine)that simultaneously present excellent water resistance and sensitive temperature-dependent photoluminescence lifetime in water.Benefiting from the soft lattice induced by the organic molecule of TPP,giant thermal expansion and great lattice distortion were achieved with increasing temperature.As such,the self-trapped exciton luminescence lifetime of TPP3Cu2Br2 can be shortened to 1.9％of the initial value from 280 to 380 K,resulting in the highest Sr of 12.82％K-1 among the undoped metal halides based luminescent thermometers.Significantly,TPP3Cu2Br2 displayed extraordinary water stability with emission intensity remaining nearly unchanged after immersing in water for 15 days.Moreover,high-precision luminescence lifetime based thermal sensing in water environment was successfully conducted,which proved to be inert to the detection depth in water with a small read-out error.This work offers new routes in the exploration of novel metal halides for highly sensitive thermometric probes toward versatile application scenarios.

Lanthanide-ion-activated nanoparticles stimulated by 808 or 980 nm lasers present promising applications in biological imaging. This contribution reveals their physicochemical properties and explores their potential as near-infrared-II (NIR-II) fluorescent agents for bioimaging. Specifically, the NIR-IIb window (1500-1700 nm) has the advantages of low scattering and less autofluorescence from the tissues, which makes this region suitable for imaging with greater clarity. Lanthanides offer diverse emission possibilities due to their rich energy levels, which make them highly effective nanoprobes. This study focuses on gadolinium oxide (Gd2O3) as the host material due to its facile fabrication and low toxicity. The Gd2O3 system is doped with Yb3+ and Er3+ ions and achieves a high quantum efficiency of 22.8% in the NIR-IIx and NIR-IIb windows. Moreover, the superior penetrability of the NIR-IIb window is unveiled by the penetration depth testing and in vivo imaging studies. Additionally, Gd3+ ions exhibit magnetic properties, which support their application in magnetic resonance imaging (MRI). This work reveals the high brightness and high energy transfer efficiency of the Yb3+-Er3+ system and explores the feasibility of Gd2O3 nanoparticles in MRI. Therefore, we believe that this work provides a superior and biocompatible candidate for understanding the dynamics of MRI/NIR-II imaging of the nanophosphor for clinical applications.

The ultrasensitive detection of prostate-specific antigen (PSA) remains challenging for therapeutic evaluation and management of prostate cancer, particularly in monitoring post-prostatectomy recurrence. Current immunoassays, however, lack the sensitivity and robustness necessary for detecting trace-level PSA in clinical samples. To address this limitation, we develop a triplet energy transfer (TET)-sensitized downshifting luminescence immunosorbent assay (TET-DLISA) platform by utilizing size-optimized NaGdF4:Yb3+/Er3+ downshifting nanoparticles (DSNPs) functionalized with a carboxylated near-infrared dye (Cypate) as signal reporters, for background-free NIR-II detection. Under 808-nm excitation, efficient TET from Cypate to Yb3+ amplifies the NIR-II emission of Er3+ by 284 times in 5.8-nm DSNPs, achieving a highly enhanced intersystem crossing efficiency (82.8%) while minimizing interfacial energy loss. By introducing DSNP@Cypate as an NIR-II signal reporter, the proposed TET-DLISA enables ultrasensitive PSA quantification via alkaline phosphatase (ALP)-catalyzed phosphate displacement of Cypate, yielding an outstanding signal-to-background ratio (SBR) of 273 and a detection limit of 98 fg mL-1, which is three orders of magnitude more sensitive than the corresponding ALP-based ELISA. Clinical validation with patient sera confirms a strong correlation with the results from commercial kits, demonstrating the platform's clinical utility for post-surgical monitoring. This TET-DLISA platform provides a transformative paradigm for ultrasensitive biomarker detection, addressing unmet needs in precision diagnostics.

Zero-dimensional(OD)organic-inorganic metal halide perovskite is one of the hot research topics in the field of optoelectronic materials.Their structure generally consists of discrete metal halide octahedra entirely isolated by surrounding organic cations,forming indepen-dent luminescent centers[1,2].Such a configuration results in high exciton binding energy and exceptional luminescence efficiency,due to strong quantum confinement[3,4].Note that the component design of diverse organic and inorganic components markedly affects their structure and luminescent properties,which grants them broad application potential in various optoelectronic devices like light-emitting diodes(LEDs)and remote thermography[5,6].As such,a comprehensive investigation into OD metal halide per-ovskites is essential for elucidating the functions of organic cations and metal ions in organic-inorganic metal halide perovskites.However,current synthesis methods for OD organic-inorganic metal halide perovskites lack universality,hindering precise component manipulation.This limitation poses a significant challenge in optimizing material properties for diverse applications.

Near-infrared (NIR) dyes can overcome the weak absorption of lanthanide nanoparticles (NPs) by antenna sensitization, offering new avenues to develop efficient and versatile lanthanide nanomaterials. However, current research on dye-sensitized lanthanide NPs for photothermal conversion is still preliminary, and the involved excited-state dynamics and interfacial interactions remain elusive. Herein, steady-state/transient absorption spectroscopy and theoretical calculation are used to investigate the coordination and aggregation states of cypate dyes on NaNdF4 NPs, revealing the influence of interfacial interactions on resonant energy transfer. Synergetic heat-generation mechanism of lanthanide cross-relaxation and dye intermolecular collisions is further proposed. The photothermal conversion efficiency of cypate-NaNdF4 nanocomposites reaches 50.4%, outperforming those of typical photothermal materials with high NIR absorption. Moreover, the intersystem crossing of cypate can be inhibited due to the depopulation of the S1 exciton via ET, thereby improving anti-photobleaching ability. These dye-sensitized NaNdF4 nanocomposites exhibit superior photothermal effect, stability and NIR-II luminescence, showing great potential in theranostic applications.

>The controlled self-assembly of colloidal nanocrystals(NCs)is a fundamental research challenge in nanoscale materials science, aimed at constructing artificially engineered superlattices capable of rivaling or even exceeding the structural complexity in natural crystalline materials [1,2]. Significantly, such precisely engineered superlattice architecture may exhibit intriguing optical, electronic, and catalytic functionalities stemming from both the individual NCs and the long-range ordered superlattice matrix [3,4].

Self-trapped excitons (STEs) have garnered significant attention due to their broadband emission and large Stokes shift. However, achieving multiband, particularly near-infrared (NIR) STE emissions remains a challenge, restricting their optoelectronic applications. Herein, we realize efficient dual-band STE emissions encompassing blue and NIR regions based on Cs2NaScCl6 double perovskites (DPs) via minor Li+-doping structural engineering. The dual-band emissions in the blue and NIR regions originated from the STE states associated with [ScCl6]3- and [NaCl6]5- octahedra, respectively. Li+ doping markedly enhanced the photoluminescence (PL) quantum yields of dual-band STE emissions from 3.2% and 2.7% to 98.2% and 45.4%, respectively. Steady-state/transient PL spectroscopies and density functional theory calculations revealed that Li+ doping intensified sublattice distortion and enhanced charge carrier localization within Cs2NaScCl6 DPs, thus boosting the dual-band STE emissions. These findings gain deep insights into STE manipulation in DPs through local structural engineering, thus stimulating the exploitation of DPs toward versatile applications.

Lanthanide‐doped photo‐stimulated luminescence (PSL) phosphors, as one of the most prominent electron‐trapping materials, have emerged as a highly attractive class of luminescent materials in recent decades. These phosphors exhibit unique optical properties resulting from their ability to store charge carriers and subsequently release energy upon photo‐stimulation. Such distinctive features of energy storage and controllable release have driven significant interest in lanthanide‐doped PSL phosphors, owing to their vast potential in diverse applications such as optical data storage, security encoding, and bioimaging. Recent advancements in synthesis methodologies and characterization tools have significantly deepened the understanding of the photophysical and photochemical behaviors of PSL phosphors, thus expanding their application scope. Consequently, there is an urgent need to update the knowledge in this rapidly evolving field. This review aims to highlight the latest achievements in the luminescence mechanisms, trap manipulation strategies, and emerging applications of lanthanide‐doped PSL phosphors. Furthermore, we discuss the main challenges and propose future research directions for this dynamic domain.