Polarity-Mediated Antisolvent Control Enables Efficient Lanthanide-Based near-Infrared Perovskite LEDs.

Alloying lanthanide ions (Yb3+) into perovskite quantum dots (Yb3+:CsPb(Cl1-xBrx)3) is an effective method to achieve efficient near-infrared (NIR) luminescence (>950 nm). Increasing the Yb3+ alloying ratio in the perovskite matrix enhances the luminescence intensity of Yb3+ emission at 990 nm. However, high Yb3+ alloying (>15%) results in vacancy-induced inferior material stability. In this work, we developed a polarity-mediated antisolvent manipulation strategy to resolve the incompatibility between a high Yb3+ alloying ratio and inferior stability of Yb3+:CsPb(Cl1-xBrx)3. Precise control of solution polarity enables increased uniformity of the perovskite matrix with fewer trap densities. Employing this strategy, we obtain Yb3+:CsPb(Cl1-xBrx)3 with the highest Yb3+ alloying ratio of 30.2% and a 2-fold higher electroluminescence intensity at 990 nm. We lever the engineered Yb3+:CsPb(Cl1-xBrx)3 to fabricate NIR-LEDs, achieving a peak external quantum efficiency (EQE) of 8.5% at 990 nm: this represents the highest among perovskite NIR-LEDs with an emission wavelength above 950 nm.

Dual-emission Tb-based coordination polymer as a ratiometric fluorescence probe for the detection of phosphate.

A simple, sensitive dual-emission probe was developed for the detection of phosphate (Pi). The probe Tb-BTB/DPA was synthesized by mixing dual-ligand, 1,3,5-tri(4-carboxyphenyl) benzene (H3BTB) and dipicolinic acid (DPA), with metal ions Tb3+ in ethanol-water solution at 40℃ for 2 h. Tb-BTB/DPA exhibits two emission peaks, the emission at 362 nm is attributed to H3BTB, an energy transfer between Tb3+ nodes, and DPA further enhances the fluorescence of Tb3+ at 544 nm. Pi competes with ligand H3BTB to coordinate Tb3+, resulting in partial collapse of the Tb-BTB/DPA structure and interrupting the electron transfer between H3BTB and Tb3+. Therefore, the emission at 362 nm is enhanced, while the emission at 544 nm is unchanged, and a ratiometric fluorescence method is developed to detect Pi. Tb-BTB/DPA exhibits good linearity within the Pi concentration range (0.1-50 µmol/L), and the detection limit was 25.8 nmol/L. This study provides a new way to prepare probes with dual emission sensing properties.

Shell Engineering on Thermal Sensitivity of Lifetime-Based NIR Nanothermometers for Accurate Temperature Measurement in Murine Internal Liver Organ.

Lifetime-based NIR luminescent nanothermometry is ideally suited for temperature detection in living cells and in vivo, but the thermal sensitivity (Sr) modulation remains elusive. Herein, a thorough investigation is performed to unveil the shell effect on lifetime-based Sr by finely controlling the shell thickness of lanthanide-doped core-shell-shell nanoparticles. Owing to the space-dependent energy transfer and back energy transfer between Nd3+ and Yb3+ as well as the energy migration to surface quenchers, both active and inert shells can regulate the thermal-dependent nonradiative decays and NIR luminescence lifetime of Yb3+, which in turn modulates the Sr from 0.56% to 1.54% °C-1. After poly(acrylic acid) modification of the optimal architecture, the tiny nanoprobes possess robust stability to fluctuations in the microenvironment, which enables accurate temperature mapping of inflammation in the internal liver organ of living mouse. This work will provide new insights for optimizing Sr and guidance for precise temperature measurements in vivo.

Novel Aspects about "Lifetime" in Upconversion Luminescence.

Recent progress on the temporal response (TR) of lanthanide-doped upconversion luminescence (UCL) has enriched the means of UCL regulation, promoted advanced designs for customized applications such as biological diagnosis, high-capacity optical coding, and dynamic optical anti-counterfeiting, and pushed us to reacquaint the dynamic responses of sensitizer/activator ions in UCL systems. In particular, the lifetime of UCL should be revisited after discovery of novel experimental phenomena and luminescence mechanisms, i. e., it should be understood as the collective TR (in the decay edge) of all the involved ions rather than the reciprocal of the radiative rate of an individual ion. In this Concept, we retraced the latest understanding of the dynamics in UCL with special attention to the relationship between excitation and emission, means of TR regulation, and discussed existing challenges. It is expected to provide some fundamental insights to deepened understanding, further regulation, and frontier applications of TR features of UCL.

Time-resolved Fluorescence DNA-based Sensors for Reducing Background Fluorescence of Environment.

The fluorescence assay is one of the popular methods that is applied for detection of different targets. However, this method may show low sensitivity and high background in biological samples due to the natural fluorescence of different compounds in complicated samples. In addition, it inevitably affects the detection results accuracy. A fundamental solution to this problem is the use of the time-resolved fluorescence technique (TRF). The main component of this technique is the use of long fluorescence lifetime reagents. In this review, various time-resolved fluorescent reagents such as complexes of lanthanide ions, lanthanide-doped inorganic nanoparticles; Mn-doped ZnS quantum dots (QDs) and pyrene excimer are introduced. Moreover, TRF sensors, especially TRF aptasensors (DNA-based sensors) are discussed. This review will give new ideas for researchers to develop novel high-sensitive TRF sensors that can remove or decrease background fluorescence and use them for the detection of various targets in complicated samples without treatment.

Hydrothermal deposition synthesis of dual-mode luminescent material GdVO4 :Eu3+ /carbon dots with optimal luminescence and its application in anti-counterfeiting.

To obtain optimal luminescence, 0.12 g of GdVO4 :3%Eu3+ nanocrystals (NCs) and different volumes of nitrogen-doped carbon dots (N-CDs) crude solution were used as precursors, and the composite synthesized using the hydrothermal deposition method showed optimal luminescence when 11 ml (2.45 mmol) crude solution was used. In addition, similar composites with the same molar ratio as GVE/cCDs(11) were also prepared with the hydrothermal and physical mixing processes. Based on the test results of XRD, XPS, and PL spectra, for the composite GVE/cCDs(11), the highest (lowest) peak intensity of the C-C/C=C (C=O/C=N) bond, which was 1.18 (0.75) times that of GVE/cCDs-m, indicated most N-CDs deposition and led to their highest emission intensity under 365 nm excitation, although nitrogen atoms in the composite were shed slightly during the deposition process. Finally, as can be seen from the patterns designed for security applications that the optimally luminescent composite is one of the most promising candidates in the anti-counterfeiting field.

Development of an Active Optical Lens for Arc Flashing Detection.

This paper contains the design of active optical lenses used for the detection of arc flashing emissions. The phenomenon of an arc flashing emission and its characteristics were contemplated. Methods of preventing these emissions in electric power systems were discussed as well. The article also includes a comparison of commercially available detectors. An analysis of the material properties of fluorescent optical fiber UV-VIS-detecting sensors constitutes a major part of the paper. The main purpose of the work was to make an active lens using photoluminescent materials, which can convert ultraviolet radiation into visible light. As part of the work, active lenses with materials such as Poly(methyl 2-methylpropenoate) (PMMA) and phosphate glass doped with lanthanides, such as terbium (Tb3+) and europium (Eu3+) ions, were analyzed. These lenses were used to make optical sensors, which were supported by commercially available sensors in their construction.

A Series of Novel 3D Coordination Polymers Based on the Quinoline-2,4-dicarboxylate Building Block and Lanthanide(III) Ions-Temperature Dependence Investigations.

A series of novel 3D coordination polymers [Ln2(Qdca)3(H2O)x]·yH2O (x = 3 or 4, y = 0-4) assembled from selected lanthanide ions (Ln(III) = Nd, Eu, Tb, and Er) and a non-explored quinoline-2,4-dicarboxylate building block (Qdca2- = C11H5NO42-) were prepared under hydrothermal conditions at temperatures of 100, 120, and 150 °C. Generally, an increase in synthesis temperature resulted in structural transformations and the formation of more hydrated compounds. The metal complexes were characterized by elemental analysis, single-crystal and powder X-ray diffraction methods, thermal analysis (TG-DSC), ATR/FTIR, UV/Vis, and luminescence spectroscopy. The structural variety of three-dimensional coordination polymers can be ascribed to the temperature effect, which enforces the diversity of quinoline-2,4-dicarboxylate ligand denticity and conformation. The Qdca2- ligand only behaves as a bridging or bridging-chelating building block binding two to five metal centers with seven different coordination modes arising mainly from different carboxylate group coordination types. The presence of water molecules in the structures of complexes is crucial for their stability. The removal of both coordinated and non-coordinated water molecules leads to the disintegration and combustion of metal-organic frameworks to the appropriate lanthanide oxides. The luminescence features of complexes, quantum yield, and luminescent lifetimes were measured and analyzed. Only the Eu complexes show emission in the VIS region, whereas Nd and Er complexes emit in the NIR range. The luminescence properties of complexes were correlated with the crystal structures of the investigated complexes.

Luminescent Papers with Asymmetric Complexes of Eu(III) and Tb(III) in Polymeric Matrices and Suggested Combinations for Color Tuning.

Complexes of lanthanide ions, such as Eu(III) (red light emission) and Tb(III) (green light emission), with proper ligands can be highly luminescent and color-tunable, also attaining yellow and orange emission under UV radiation. The ligands employed in this work were poly(sodium acrylate), working as polymeric matrix, and 1,10-phenanthroline, taking advantage of its antenna effect. Possibilities of color display were further enhanced by incorporating a cationic polyfluorene with blue emission. This strategy allowed for obtaining cyan and magenta, besides the aforementioned colors. Uncoated cellulose paper was impregnated with the resulting luminescent inks, observing a strong hypsochromic shift in excitation wavelength upon drying. Hence, while a cheap UV-A lamp sufficed to reveal the polyfluorene's blue emission, shorter wavelengths were necessary to visualize the emission due to lanthanide ions as well. The capacity to reveal, with UV-C radiation, a full-color image that remains invisible under natural light is undoubtedly useful for anti-counterfeiting applications. Furthermore, both lanthanide ion complexes and polyfluorenes were shown to have their luminescence quenched by Cu(II) ions and nitroarenes, respectively.

Wide-coverage and Efficient NIR Emission from Single-component Nanophosphors through Shaping Multiple Metal-halide Packages.

Wide-coverage near infrared (NIR) phosphor-converted LEDs possess promising potential for practical applications, but little is developed towards the efficient and wide-coverage NIR phosphors. Here, we report the single-component lanthanide (Ln3+ ) ions doped Cs2 M(In0.95 Sb0.05 )Cl6 (M=alkali metal) nanocrystals (NCs), exhibiting emission from 850 to 1650 nm with high photoluminescence quantum yield of 20.3 %, which is accomplished by shaping the multiple metal halide octahedra of double perovskite via the simple alkali metal substitution. From Judd-Ofelt theoretical calculation and spectroscopic investigations, the shaping of metal halide octahedra in Cs2 M(In1-x Sbx )Cl6 NCs can break the forbidden of f-f transition of Ln3+ , thus increasing their radiative transition rates and simultaneously boosting the energy transfer efficiency from host to Ln3+ . Finally, the wide-coverage NIR LEDs based on Sm3+ , Nd3+ , Er3+ -tridoped Cs2 K0.5 Rb0.5 (In0.95 Sb0.05 )Cl6 NCs are fabricated and employed in the multiplex gas sensing and night-vision application.

Solution Structure of a Lanthanide-binding DNA Aptamer Determined Using High Quality pseudocontact shift restraints.

In this contribution we report the high-resolution NMR structure of a recently identified lanthanide-binding aptamer (LnA). We demonstrate that the rigid lanthanide binding by LnA allows for the measurement of anisotropic paramagnetic NMR restraints which to date remain largely inaccessible for nucleic acids. One type of such restraints - pseudocontact shifts (PCS) induced by four different paramagnetic lanthanides - was extensively used throughout the current structure determination study and the measured PCS turned out to be exceptionally well reproduced by the final aptamer structure. This finding opens the perspective for a broader application of paramagnetic effects in NMR studies of nucleic acids through the transplantation of the binding site found in LnA into other DNA/RNA systems.

Spectroscopic study of the 4fn-15dtransitions of LaPO4doped with Pr3+ or co-doped with Pr3+ and Gd3+ in the vacuum ultra violet region.

The energy off-dtransitions depends on the crystalline field in which the lanthanide ion is inserted. Depending on the experimental setup, these transitions could occur at high energy, so several studies regarding theoretical data have been conducted. Here, we present the experimental determination of the energy of interconfigurational 4fn â†’ 4fn-15d (f-d)transitions from Pr3+ions to the lanthanum orthophosphate LaPO4matrix; we have also determined the bandgap value for this host. The experiments were carried out at the Synchrotron setup of the Brazilian LNLS laboratory. Specifically, we synthesized LaPO4:Pr3+and LaPO4:Pr3+/Gd3+by the hydrothermal method under different pH conditions or by spray pyrolysis. The particles resulting from hydrothermal synthesis had different morphologies and the influence of pH value was showed: the reaction medium was controlled along the process, which changed the surface potential. On the basis of Raman spectroscopy and x-ray diffraction analyses, we found that the crystalline phase was monoclinic monazite for all the samples. We studied the 4f5dlevel and bandgap transitions at high energy by absorption analysis in the VUV range. The experimental results were 7.5 eV (LaPO4bandgap) and 5 eV (4fn→ 4fn-15dtransition of the Pr3+ion), which were close to the theoretical values reported in the literature for this ion and this matrix.

One-pot synthesis of copper nanocluster/Tb-MOF composites for the ratiometric fluorescence detection of Cu2.

The increasing degradation of ecosystems due to heavy metal residues has led to environment and food contamination, prompting the development of convenient platforms for monitoring heavy metals. Here, a new dual-emission fluorescent sensor CuNCs@Tb@UiO-66-(COOH)2 for the detection of copper ions (Cu2+ ) has been synthesized using one-pot encapsulation of Tb(III) and glutathione-stabilized copper nanoclusters (CuNCs) into metal-organic frameworks (MOFs) UiO-66-(COOH)2 . In this ratiometric sensor, the fluorescence intensity of Tb3+ decreased significantly upon the addition of Cu2+ , whereas that of CuNCs showed good stability, together with an apparent colour change. Therefore, ratiometric fluorescence detection of Cu2+ can be accomplished by measuring the ratio of the fluorescence intensity at the 450 nm (F450 ) wavelength of CuNCs to the 548 nm (F548 ) emission of Tb3+ in the fluorescence spectra of the CuNCs@Tb@UiO-66-(COOH)2 suspension. Moreover, the obtained fluorescent probe showed good results in the detection of actual samples. This work can provide the basis of method for the exploration of ratiometric fluorescence and visual sensors of trace pollutants analysis in complicated samples.

Ratiometric Fluorescent Sensor Based on Tb(III) Functionalized Metal-Organic Framework for Formic Acid.

Formic acid is a common chemical raw material, the effective detection of which is of importance to food safety and environmental quality. In this work, the lanthanide functionalized dual-emission metal-organic framework (TH25) was prepared as a ratiometric fluorescent sensor for formic acid. This ratiometric sensor has a good detection performance with high selectivity, sensitivity, and reproducibility. Together with a low limit of detection of 2.1 ppm, these characters promise the ability to sense at low levels as well as a practical detection ability. This work provides ideas for the design and synthesis of effective chemical sensors for organic acids.

Enhancing Dye-Triplet-Sensitized Upconversion Emission Through the Heavy-Atom Effect in CsLu2 F7 :Yb/Er Nanoprobes.

Lanthanide (Ln3+ )-doped upconversion (UC) nanoprobes, which have drawn extensive attention for various bioapplications, usually suffer from small absorption cross-sections and weak luminescence intensity of Ln3+ ions. Herein, we report the controlled synthesis of a new class of Ln3+ -doped UC nanoprobes based on CsLu2 F7 :Yb/Er nanocrystals (NCs), which can effectively increase the intersystem crossing (ISC) efficiency from singlet excited state to triplet excited state of IR808 up to 99.3 % through the heavy atom effect. By virtue of the efficient triplet sensitization of IR808, the optimal UC luminescence (UCL) intensity of IR808-modified CsLu2 F7 :Yb/Er NCs is enhanced by 1309 times upon excitation at 808 nm. Benefiting from the intense dye-triplet-sensitized UCL, the nanoprobes are demonstrated for sensitive assay of extracellular and intracellular hypochlorite with an 808-nm/980-nm dual excited ratiometric strategy.

Boosting Near-Infrared Luminescence of Lanthanide in Cs2 AgBiCl6 Double Perovskites via Breakdown of the Local Site Symmetry.

Currently, lanthanide (Ln3+ )-doped near-infrared (NIR)-emitting double perovskites (DPs) suffer from low photoluminescence quantum yield (PLQY). Herein, we develop a new class of NIR-emitting DPs based on Ln3+ -doped Cs2 (Na/Ag)BiCl6 . Benefiting from the Na+ -induced breakdown of local site symmetry in the Cs2 AgBiCl6 DPs, effective NIR emissions of Ln3+ are realized through Bi3+ sensitization. Specifically, 7.3-fold and 362.9-fold enhanced NIR emissions of Yb3+ and Er3+ are achieved in Cs2 Ag0.2 Na0.8 BiCl6 DPs relative to those in Na-free Cs2 AgBiCl6 counterparts, respectively. The optimal absolute NIR PLQYs for Yb3+ and Er3+ in Cs2 Ag0.2 Na0.8 BiCl6 DPs are determined to be 19.0 % and 4.3 %, respectively. Raman spectroscopy and first-principles density functional theory calculations verify the sublattice distortion in Cs2 (Na/Ag)BiCl6 DPs via Na+ doping. These findings provide fundamental insights into the design of efficient NIR-emitting Ln3+ -doped DPs for versatile optoelectronic applications.

Incorporating of Lanthanides Ions into Perovskite Film for Efficient and Stable Perovskite Solar Cells.

Since Yan's work, incorporation of some lanthanide elements, such as Eu and Nd, into MAPbI3 layer has been proven to be a powerful strategy on improving the permanence of the perovskite solar cells (PSCs). However, a comprehensive configuration has not been given for different lanthanide elements doping while the mechanism has not been clarified. Herein, the incorporation of various lanthanides ions (Ln3+ = Ce3+ , Eu3+ , Nd3+ , Sm3+ , or Yb3+ ) into perovskite films to largely enhance the performance of PSCs is presented. Arising from the enlarged grain size and crystallinity of perovskite film upon Ln3+ ions doping, the efficiency and stability of PSCs are significantly improved. Extraordinarily, PSCs with Ce3+ doping achieve the best performance, with a champion power conversion efficiency (PCE) of 21.67% in contrast to 18.50% for pristine PSCs, and outstanding long-term and UV irradiation stability. Such high performance of PSCs after Ce3+ doping originates from special Ce3+ /Ce4+ redox pair and the unique 4f-5d absorption in the UV region. Finally, the flexible PSCs with low-temperature preparation are explored. Considering the richer deposition of cerium element in the earth and lower price, the findings may provide new opportunities for developing low-cost, highly efficient, air/UV stable, and flexible PSCs.

Lanthanide-Doped Core@Multishell Nanoarchitectures: Multimodal Excitable Upconverting/Downshifting Luminescence and High-Level Anti-Counterfeiting.

The development of luminescent materials with concurrent multimodal emissions is a great challenge to improve security and data storage density. Lanthanide-doped nanocrystals are particularly appropriate for such applications for their abundant intermediate energy states and distinguishable spectroscopic profiles. However, traditional lanthanide luminescent nanoparticles have a limited capacity for information storage or complexity to shield against counterfeiting. Herein, it is demonstrated that the combination of upconverting and downshifting emissions in a particulate designed lanthanide-doped core@multishell nanoarchitecture allows the generation of multicolor dual-modal luminescence over a wide spectral range for complex information storage. Precise control of lanthanide dopants distribution in the core and distinct shells enables simultaneous excitation of 980/808 nm focusing/defocusing laser and 254 nm light and produces complex upconverting emissions from Er, Tm, Eu, and Tb via multiphoton energy transfer processes and downshifting emissions from Eu and Tb via efficient energy transfer from Ce to Eu/Tb in Gd-assisted lattices. It is experimentally proven that multiple visualized anti-counterfeit and information encryption with facile decryption and authentication using screen-printing inks containing the present core@multishell nanocrystals are practically applicable by selecting different excitation modes.

pH dependence of water anomaly temperature investigated by Eu(III) cryptate luminescence.

Although water has been extensively studied, not all of its unique properties have been fully understood. There is still controversy about the temperature at which hydrogen bonds are broken or weakened, producing the anomalous temperature dependence of many water properties. Different temperatures between 23 and 48 °C have been reported, but no study has scrutinized the reasons for this discrepancy. We suggest the determining role of pH in the alteration of the water anomaly temperature. We employed a luminescent europium trisbipyridine cryptate, which is highly sensitive to changes in the arrangement of water molecules and whose luminescence intensity and lifetime are not significantly influenced by variations over a broad pH range. Our results revealed an increase of the crossover temperature from circa 35 °C at pH 3.5 to circa 45 °C at pH 7 to 9, which explains the discrepancies of previous studies. The pH dependence of water anomaly temperature is an important property for a better understanding of water and water-based systems and applications.

New Horizons in Chemical Functionalization of Endohedral Metallofullerenes.

This overview explains some new aspects of chemical functionalization of endohedral metallofullerenes (EMFs) that have been unveiled in recent years. After differences in chemical reactivity between EMFs and the corresponding empty fullerenes are discussed, cage-opening reactions of EMFs are examined. Then, the selective bisfunctionalization of EMFs is explained. Finally, single-bonding derivatization of EMFs is addressed. The diversity and applicability of the chemical functionalization of endohedral metallofullerenes are presented to readers worldwide.