Highly efficient near-infrared solid solution phosphors with excellent thermal stability and tunable spectra for pc-LED light sources toward NIR spectroscopy applications.

Near-infrared (NIR) luminescent materials have attracted wide research interest due to their unique photophysical properties for designing NIR light-emitting diodes (NIR LEDs). Here, a series of Cr3+-activated NIR-emitting solid solution phosphors, Gd1-xLux(Al1-xScx)3(BO3)4:0.01Cr3+ (GLASB:Cr3+) (x = 0 to 0.5), are successfully synthesized via a cosubstitution approach. The GLASB:Cr3+ phosphors reveal extraordinary optical performance with a desirable high IQE of 93.6%, considerable broadened FWHM (from 128 nm to 196 nm) and redshift of 119 nm (747 → 866 nm) as the amount of [Lu3+-Sc3+] ion doping increases. Moreover, their photoluminescent thermal stability is substantially improved, maintaining 105.7% of the initial integral intensity up to 150 °C, namely zero-thermal-quenching. The NIR pc-LED fabricated using the GLASB:Cr3+ phosphor generates an NIR output power of 46 mW and an electro-optical efficiency of 37% at a 120 mA input current. Finally, the characteristic NIR emission of this phosphor can not only be utilized in the fields of night-vision technology and biometric identification, but also exhibits a perfect match with the absorption of the bacteriochlorophyll (BChl) and light-harvesting protein (LHP) of photosynthetic bacteria (PSB), presenting a high application prospect for improving PSB photosynthesis.

High-Quality Cs3Cu2I5@PMMA Scintillator Films Assisted by Multiprocessing for X-ray Imaging.

In recent years, novel metal halide scintillators have shown great application potential due to their tunable emission wavelength, high X-ray absorption, and high luminescence efficiency. However, poor stability and complex device packaging remain key issues for metal halide scintillators, making it difficult to achieve high-resolution and flexible X-ray imaging applications. To address the above issues, a multiprocessing strategy was introduced to prepare Cs3Cu2I5@PMMA scintillator films for long-term stable application, mainly undergo different annealing treatments to make Cs3Cu2I5 crystals to accurately nucleate and then grow in-situ in the PMMA matrix. Then, a series of characterization results illustrate that the prepared Cs3Cu2I5@PMMA scintillator films have high crystallinity, uniform size, excellent flexibility, high stable photoluminescence (PL) and radioluminescence (RL) performance, and high-resolution X-ray imaging capability. Most importantly, Cs3Cu2I5@PMMA scintillator films can not only provide clear and accurate imaging recognition of objects with different complex structures but also maintain stable X-ray imaging quality within 60 days and can achieve flexible X-ray imaging. Therefore, we have provided an effective strategy for producing high-quality scintillator films to meet the multidimensional needs of a new generation of scintillators.

A super water-resistant MXene sponge flexible sensor for bifunctional sensing of physical and chemical stimuli.

Flexible wearable sensors with multifunctional features have attracted great interest in various applications such as disease diagnosis, environmental detection and healthcare monitoring. However, it is still a challenge to achieve a multifunctional sensor with super water resistance without compromising the overall performance of the sensing material. Here, we developed a 3D bifunctional flexible sensor based on an MXene melamine sponge (MS) through a simple and effective ultrasonic mixing process and a further vacuum annealing process. The sensor is able to show excellent response to different stimuli, including pressure and humidity. The thermal annealing treatment allows MXene to adhere more firmly to the internal skeleton of the sponge, which does not easily fall off and improves the water resistance, thus achieving wearability and high sensitivity over a wide area. The T-MXene@MS sensor has a sensitivity of 9.97 kPa-1 in the 5-15 kPa range, a fast response time (180 ms), and good stability at 4000 cycles, enabling accurate monitoring of human movement. The sensor has a rich porous structure while maintaining its inherent flexibility, which allows for long term testing of human respiration as well as the ability to respond quickly to dynamic changes in humidity, demonstrating excellent long-term stability for 40 days of humidity detection.

Highly Stable Orange-Red Long-Persistent Luminescent CsCdCl3 :Mn2+ Perovskite Crystal.

Halide perovskite has been widely studied as a new generation of photoelectronic materials. However, their thermal and humidity-induced emission quenching have greatly limited their utility and reliability. Here, we report a hexagonal Mn2+ -doped CsCdCl3 perovskite crystal that possesses stable photoluminescence (PL) at both high temperature and humidity. The room temperature long-persistent luminescence (LPL) of the single crystals lasts up to 1480 s and can be adjusted by changing the concentration of Mn2+ ion doping. The characteristic emission of d-d transition of Mn2+ is realized, and the photoluminescence quantum yield (PLQY) is up to 91.4 %, it can maintain more than 90 % of the initial PL spectral integral area at 150 °C (423 K). High humid stability PL can be achieved more than 75 % of the initial PL intensity after 55 days of immersion in water. These excellent properties show the application prospect of the LPL material in lighting indication and anti-counterfeiting.

Post-doping induced morphology evolution boosts Mn2+ luminescence in the Cs2NaBiCl6:Mn2+ phosphor.

As we know, defects caused in the synthetic process of metal halide perovskite are the most difficult to overcome, and greatly limit their photoelectric performances. Herein, a post-doped strategy was utilized to achieve an interesting morphology evolution from a standard octahedron to a snowflake-like sheet during the Mn2+-doped Cs2NaBiCl6 process, which realizes the obvious photoluminescence quantum efficiency (PLQY) enhancement of the Cs2NaBiCl6:Mn2+ phosphor. This surprising evolution is ascribed to the morphology collapse and reconstruction induced by Mn2+ exchange. The obtained phosphor exhibits enhanced 31.56% PLQY, which is two-fold higher than that synthesized by the traditional co-precipitation method, with broad emission spectrum and good PL color stability at 150 °C. Combined with the Cs2SnCl6 : 1mol%Bi3+ phosphor to fabricate the phosphor-converted light-emitting diode, bright white light emission with Ra = 88, CCT = 4320 K, CIE (0.36, 0.33) and a good application potential in high-resolution PL imaging agents was obtained. This work provides a possible effective strategy to improve the PL performance for impurity-doped lead-free metal halide perovskite.

A Wearable Respiration Sensor for Real-Time Monitoring of Chronic Kidney Disease.

Human respiration is accompanied with abundant physiological and pathological information, such as the change in ammonia (NH3) content, which is related to chronic kidney disease (CKD); hence, monitoring the breathing behavior helps in health assessment and illness prediction. In this work, a wearable respiration sensor based on CeO2@polyaniline (CeO2@PANI) nanocomposites that underwent a hydrogen plasma treatment is developed. The results unambiguously show that the response of the corresponding nanocomposites is significantly enhanced from 165 to 670% to 100 ppm NH3 compared to the counterpart that did not undergo hydrogen plasma treatment and even reaches 24% to 50 ppb NH3, suggesting its fascinating capability of detecting the trace level of NH3 in human breathing. The superior response for NH3 is ascribed to the stable oxygen vacancies produced by the hydrogen plasma treatment. Furthermore, the clinical tests for patients with uremia suggest that the as-designed sensor has potential applications in clinical monitoring for CKD. Herein, this work offers a new strategy to obtain respiration sensors with high performance and provides a feasible approach for health evaluation and disease monitoring of patients with CKD.

The Response of Plants and Mycorrhizal Fungi to Nutritionally-Heterogeneous Environments Are Regulated by Nutrient Types and Plant Functional Groups.

Nutrient type and plant functional group are both important in influencing proliferation of roots or hyphae and their benefit to plant growth in nutritionally heterogeneous environments. However, the studies quantifying relative importance of roots vs. hyphae affecting the plant response to nutrient heterogeneity are lacking. Here, we used meta-analysis based on 879 observations from 66 published studies to evaluate response patterns of seven variables related to growth and morphological traits of plants and mycorrhizal fungi in nutritionally heterogeneous environments. We found that phosphorus [P] and organic fertilizer [OF] supply significantly increased shoot (+18.1 and +25.9%, respectively) and root biomass (+31.1 and +23.0%, respectively) and root foraging precision (+11.8 and +20.4%, respectively). However, there was no significant difference among functional groups of herbs (grasses, forbs, and legumes), between herbs and woody species, and between arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) tree species in the shoot, root and mycorrhizal fungi responses to nutrient heterogeneity, except for root biomass and root foraging precision among grasses, forbs, and legumes, and mycorrhizal hyphal foraging precision between AM and ECM tree species. Root diameter was uncorrelated with neither root foraging precision nor mycorrhizal hyphal foraging precision, regardless of mycorrhizal type or nutrient type. These results suggest that plant growth and foraging strategies are mainly influenced by nutrient type, among other factors including plant functional type and mycorrhizal type.

Novel Cyan-Green-Emitting Bi3+-Doped BaScO2F, R+ (R = Na, K, Rb) Perovskite Used for Achieving Full-Visible-Spectrum LED Lighting.

Cyan-emitting phosphors are important for near-ultraviolet (NUV) light-emitting diodes (LEDs) to gain high-quality white lighting. In the present work, a Bi3+-doped BaScO2F, R+ (R = Na, K, Rb) perovskite, which emits 506 nm cyan-green light under 360 or 415 nm excitation, is obtained via a high-temperature solid-state method for the first time. The obtained perovskite shows improved photoluminescence and thermal stability due to the charge compensation of Na+, K+, and Rb+ co-doping. Its spectral broadening is attributed to two centers Bi (1) and Bi (2), which are caused by the zone-boundary octahedral tilting due to the substitution of Bi3+ for the larger Ba2+. Employing the blend phosphors of Ba0.998ScO2F:0.001Bi3+,0.001K+ and the commercial BAM:Eu2+, YAG:Ce3+, and CaAlSiN3:Eu2+, a full-spectrum white LED device with Ra = 96 and CCT = 4434 K was fabricated with a 360 nm NUV chip. Interestingly, a novel strategy is proposed: the cyan-green Ba0.998ScO2F:0.001Bi3+,0.001K+ and orange Sr3SiO5:Eu2+ phosphors were packaged with a 415 nm NUV chip to produce the white LED with Ra = 85 and CCT = 4811 K.

Broadband, Enhanced, and Antithermally Quenched Near-Infrared Phosphors via a Cosubstitution Approach.

Wearable biosensing and food safety inspection devices with high thermal stability, high brightness, and broad near-infrared (NIR) phosphor-converted light-emitting diodes (pc-LEDs) could accelerate the next-generation NIR light applications. In this work, NIR La3-xGdxGa5GeO14:Cr3+ (x = 0 to 1.5) phosphors were successfully fabricated by a high-temperature solid-state method. Here, by doping Gd3+ ions into the La3+ sites in the La3Ga5GeO14 matrix, a 7.9-fold increase in the photoluminescence (PL) intensity of the Cr3+ ions, as well as a remarkably broadened full width at half-maximum (FWHM) of the corresponding PL spectra, is achieved. The enhancements in the PL, PLE intensity, and FWHM are attributed to the suppression of the nonradiative transition process of Cr3+ when Gd3+ ions are doped into the host, which can be demonstrated by the decay curves. Moreover, the La1.5Gd1.5Ga5GeO14:Cr3+ phosphor displays an abnormally negative thermal phenomenon that the integral PL intensity reaches 131% of the initial intensity when the ambient temperature increases to 160 °C. Finally, the broadband NIR pc-LED was fabricated based on the as-explored La1.5Gd1.5Ga5GeO14:Cr3+ phosphors combined with a 460 nm chip, and the potential applications for the broadband NIR pc-LEDs were discussed in detail.

Enhancing Structural Rigidity via a Strategy Involving Protons for Creating Water-Resistant Mn4+-Doped Fluoride Phosphors.

The poor water resistance property of a commercial Mn4+-activated narrow-band red-emitting fluoride phosphor restricts its promising applications in high-performance white LEDs and wide-gamut displays. Herein, we develop a structural rigidity-enhancing strategy using a novel KHF2:Mn4+ precursor as a Mn source to construct a proton-containing water-resistant phosphor K2(H)TiF6:Mn4+ (KHTFM). The parasitic [HMnF6]- complexes in the interstitial site from the fall off the KHF2:Mn4+ are also transferred to the K2TiF6 host by ion exchange to form KHTFM with rigid bonding networks, improving the water resistance and thermostability of the sample. The KHTFM sample retains at least 92% of the original emission value after 180 min of water immersion, while the non-water-resistant K2TiF6:Mn4+(KTFM) phosphor maintains only 23%. Therefore, these findings not only illustrate the effect of protons on fluoride but also provide a novel insight into commercial water-resistant fluoride phosphors.

Ultraviolet C lasing at 263 nm from Ba2LaF7:Yb3+,Tm3+ upconversion nanocrystal microcavities.

It is a daunting challenge to realize ultraviolet C (UVC) lasing (i.e., has a wavelength range from 200 to 275 nm) from upconversion nanocrystals due to their low upconversion efficiency. Here, we fabricate Ba2LaF7:Yb3+(90mol%), Tm3+(5mol%) upconversion nanocrystals from amorphous borosilicate glass to support emission at ∼263nm under 980 nm ns laser excitation. The excitation threshold can be further reduced from ∼130 to ∼26.5mJ/cm2 by using a cylindrical microcavity. We also found that the growth of defect-free Ba2LaF7 nanocrystals with a high concentration of codoping Yb3+ and Tm3+ ions inside high optical damage threshold borosilicate glass is the key to achieving room-temperature UVC upconversion lasing under high-intensity excitation.

Interface Design of SnO2@PANI Nanotube With Enhanced Sensing Performance for Ammonia Detection at Room Temperature.

Gas sensors with excellent stability and a high response at room temperature has drawn a great deal of attention and demand for them is huge. Surface designs provide inspiration toward making more useful sensor devices. The facile electrospinning process and Ar plasma treatment are used to fabricate rich and stable oxygen vacancies that contain a core-shell structured SnO2 polyaniline (PANI) nanotube. It shows that the induced surface oxygen vacancies would accelerate the PANI shell to generate more protons, which can enhance its sensor responsibility through reacting with the target Ammonia (NH3) gas. It was also found that the obtained oxygen vacancies can be well-protected by the coated PANI shell, which enhance and stabilize the gas response. It shows that the room temperature for the gas response of NH3 can reach up to 35.3 at 100 ppm. Finally, its good stability is demonstrated by the response-recovery performances carried out over 3 months and multiple cycles. This work indicates that this well-designed PANI-coated plasma-treated SnO2 is a potential way to design ammonia gas sensors.

Phase Transformation of a K2GeF6 Polymorph for Phosphors Driven by a Simple Precipitation-Dissolution Equilibrium and Ion Exchange.

Tuning crystal phase transformations is very important for obtaining polymorphs for phosphors with the ideal optical properties and stability. Mn4+-doped K2GeF6 (KGF) is a typical polymorphic phosphor, but the thermodynamic and kinetic mechanism of its phase transformation is still unclear. Herein, the phase transformation of polymorphs varying from P63mc KGF and trigonal KGF to P63mc Si4+-doped KGF is realized by introducing the synergistic action of an HF solution and Si4+ ions. The full structural refinements of KGF polymorphs at room temperature and the electronic band structure calculations were performed. The results show that the Si4+-doped hexagonal KGF polymorph with good photoluminescence properties is the most stable phase according to the calculated total energy landscape and relative formation energy. The morphologic changes were monitored in situ to clearly understand the rapid phase transformation mechanism, which proves that the phase transformation is driven by a simple precipitation-dissolution equilibrium and ionic exchange.

Novel Strategy for Designing Photochromic Ceramic: Reversible Upconversion Luminescence Modification and Optical Information Storage Application in the PbWO4:Yb3+, Er3+ Photochromic Ceramic.

Inorganic photochromic material is an available medium to obtain optical information storage. The photochromic property of the inorganic material is mainly from the defects of the host. However, the formation of defects in the host is uncontrollable, in particular, the revisable formation and removement of defects are difficult. Thus, there are few inorganic materials with the revisable photochromism upon the entire light stimulation. Therefore, it is an urgent need to find a suitable approach to design inorganic photochromic materials. Here, the photochromic PbWO4:Yb3+, Er3+ ceramic was designed with the help of valence state change of W6+ → W5+ and Pb2+ → Pb4+. Upon the 532 nm laser stimulation, the photochromism of the PbWO4:Yb3+, Er3+ ceramic was obtained based on the Pb2+ + hν (532 nm) → Pb4+ + 2e- and W6+ + e- + hν (532 nm) → W5+ reaction, resulting in the optical information writing. Under the stimulation of an 808 nm laser, the written optical information was erased based on the W5+ + hν (808 nm) → W6+ + e- and Pb4+ + 2e- + hν (808 nm) → Pb2+ reaction. In addition, the photochromism-induced upconversion emission modification was obtained in the PbWO4:Yb3+, Er3+ ceramic, realizing the effective and nondestructive reading out of optical information. The cyclic experiment demonstrated a good reproducibility of both photochromism and upconversion emission modification, exhibiting the potential application of the PbWO4:Yb3+, Er3+ ceramic as the optical data storage medium.

Interfacial engineering of Mo2C-Mo3C2 heteronanowires for high performance hydrogen evolution reactions.

Non-precious metal-based electrocatalysts with high activity and stability for efficient hydrogen evolution reactions are of critical importance for low-cost and large-scale water splitting. In this work, Mo2C-Mo3C2 heteronanowires with significantly enhanced catalytic performance are constructed from an MoAn precursor via an accurate phase transition process. The structure disordering and surface carbon shell of Mo2C-Mo3C2 heteronanowires can be precisely regulated, resulting in an enlarged surface area and a defect-rich catalytic surface. Density functional theory calculations are used to identify the effect of the defective sites and carbon shell on the free energy for hydrogen adsorption in hydrogen evolution. Meanwhile, the synergistic effect between different phases and the introduced lattice defects of Mo2C-Mo3C2 are considered to enhance the HER catalytic performance. The designed catalyst exhibits optimal electrocatalytic activity in both acidic and alkaline media: low overpotentials of 134 and 116 mV at 10 mA cm-2, a small Tafel slope of 64 mV dec-1, and a long-term stability for 5000 cycles. This work will provide new insights into the design of high-efficiency HER catalysts via interfacial engineering at the nanoscale for commercial water splitting.

Detection of Cell Viability via Fluorescence Labeling of Silicate Phosphor with a Low-Temperature Superlong Persistent Luminescence.

Cell viability detection is usually accompanied by large errors and toxicity. For the accuracy and safety of detection, it is urgent to develop a practical approach to realize the real-time monitoring of cell viability. Here, a low-temperature persistent phosphor was employed to facilitate the detection of cell viability. Stable low-temperature persistent luminescence originating from Ba4Si6O16:Eu2+, Pr3+ (BSEP) was developed, which could be quantified to describe the viability of baby Syrian hamster kidney (BHK-21) cells. The defect state structure guarantees the excellent persistent luminescence at 193 K of more than 200 h of the as-prepared BSEP phosphor, which ensures the long-term biological application. The structural thermal stability and water tolerance of BSEP suggest the feasibility of the practical application. Our results provide the underlying insights of the low-temperature persistent phosphors for real-time biological detection.

Preparation and Characterization of Mo Doped in BiVO4 with Enhanced Photocatalytic Properties.

Molybdenum (Mo) doped BiVO4 was fabricated via a simple electrospun method. Morphology, structure, chemical states and optical properties of the obtained catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (DRS), N2 adsorption-desorption isotherms (BET) and photoluminescence spectrum (PL), respectively. The photocatalytic properties indicate that doping Mo into BiVO4 can enhance the photocatalytic activity and dark adsorption ability. The photocatalytic test suggests that the 1% Mo-BiVO4 shows the best photocatalytic activity, which is about three times higher than pure BiVO4. Meanwhile, 3% Mo-BiVO4 shows stronger dark adsorption than pure BiVO4 and 1% Mo-BiVO4. The enhancement in photocatalytic property should be ascribed to that BiVO4 with small amount of Mo doping could efficiently separate the photogenerated carries and improve the electronic conductivity. The high concentration doping would lead the crystal structure transformation from monoclinic to tetragonal phase, as well as the formation of MoO3 nanoparticles on the BiVO4 surface, which could also act as recombination centers to decrease the photocatalytic activity.

Diverse belowground resource strategies underlie plant species coexistence and spatial distribution in three grasslands along a precipitation gradient.

Functional traits and their variation mediate plant species coexistence and spatial distribution. Yet, how patterns of variation in belowground traits influence resource acquisition across species and plant communities remains obscure. To characterize diverse belowground strategies in relation to species coexistence and abundance, we assessed four key belowground traits - root diameter, root branching intensity, first-order root length and mycorrhizal colonization - in 27 coexisting species from three grassland communities along a precipitation gradient. Species with thinner roots had higher root branching intensity, but shorter first-order root length and consistently low mycorrhizal colonization, whereas species with thicker roots enhanced their capacity for resource acquisition by producing longer first-order roots and maintaining high mycorrhizal colonization. Plant species observed across multiple sites consistently decreased root branching and/or mycorrhizal colonization, but increased lateral root length with decreasing precipitation. Additionally, the degree of intraspecific trait variation was positively correlated with species abundance across the gradient, indicating that high intraspecific trait variation belowground may facilitate greater fitness and chances of survival across multiple habitats. These results suggest that a small set of critical belowground traits can effectively define diverse resource acquisition strategies in different environments and may forecast species survival and range shifts under climate change.

Stable and Controllable Synthesis of Silver Nanowires for Transparent Conducting Film.

Silver nanowires without particles are synthesized by a solvothermal method at temperature 150 °C. Silver nanowires are prepared via a reducing agent of glycerol and a capping agent of polyvinylpyrrolidone (M w ≈ 1,300,000). Both of them can improve the purity of the as-prepared silver nanowires. With controllable shapes and sizes, silver nanowires are grown continuously up to 10-20 µm in length with 40-50 nm in diameter. To improve the yield of silver nanowires, the different concentrations of AgNO3 synthesis silver nanowires are discussed. The characterizations of the synthesized silver nanowires are analyzed by UV-visible absorption spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscope (AFM), and silver nanowires are pumped on the cellulose membrane and heated stress on the PET. Then, the cellulose membrane is dissolved by the steam of acetone to prepare flexible transparent conducting thin film, which is detected 89.9 of transmittance and 58 Ω/□. Additionally, there is a close loop connected by the thin film, a blue LED, a pair of batteries, and a number of wires, to determinate directly the film if conductive or not.

Synthesis of Fe and N Co-doped Bi2Ti2O7 Nanofiber with Enhanced Photocatalytic Activity Under Visible Light Irradiation.

A series of N-Fe-Bi2Ti2O7 nanofibers were successfully synthesized. The structure, morphology, visible light photocatalytic properties, and the degradation mechanism of N-Fe-Bi2Ti2O7 were investigated. A new phase of Bi4Ti3O7 and smaller band gap could be observed after doing Fe and N into Bi2Ti2O7. It can degrade 66 % MO and 87 % MB in 120 min under visible light irradiation, which is much more than that of pure Bi2Ti2O7. The results indicate that such unique structure could enhance the charge transfer between the nanostructure interfaces and therefore improve its photocatalytic activities.