Single‐component materials with white‐light emission are ideal for lighting applications. However, it is very challenging to achieve white luminescence in single‐dopant activated solid phosphors. ...Herein, white NaLi3Si1−xO4:Eu2+ materials are designed via defect engineering and synthesized by reducing the Si content (0.15 ≤ x ≤ 0.25). Stochiometric NaLi3SiO4:Eu2+ exhibits a narrow‐band blue emission at 469 nm, ascribed to the 5d → 4f transition of Eu2+ at highly symmetric cuboid Na sites, while samples with Si content reduced by 15–25% display white emission with two peaks at 472 nm and 585 nm. The newly appeared broadband yellow peak arises from charge‐transfer transitions involving Eu2+ and nearby defects, as verified by an unusual bandwidth, a large Stokes shift, and a long decay time. A single‐component white light‐emitting diode device is fabricated by employing a white phosphor to demonstrate a color‐rendering index of 82.9. This result provides a new design strategy for single‐component white‐light materials with broad‐band defect‐induced charge‐transfer emission.
A single‐component white emitter is developed by introducing defect‐associated charge‐transfer emission in a NaLi3SiO4:Eu2+ phosphor via a facile composition modification strategy. An extra broadband yellow peak (585 nm) appears in addition to the narrow‐band blue emission (472 nm). A single‐component white light‐emitting diode with color‐rendering index of 82.9 is fabricated using the white phosphor.
The attenuation of low-frequency sound has been a challenging task because the intrinsic dissipation of materials is inherently weak in this regime. Here we present a thin-film acoustic metamaterial, ...comprising an elastic membrane decorated with asymmetric rigid platelets that aims to totally absorb low-frequency airborne sound at selective resonance frequencies ranging from 100-1,000 Hz. Our samples can reach almost unity absorption at frequencies where the relevant sound wavelength in air is three orders of magnitude larger than the membrane thickness. At resonances, the flapping motion of the rigid platelets leads naturally to large elastic curvature energy density at their perimeter regions. As the flapping motions couple only minimally to the radiation modes, the overall energy density in the membrane can be two-to-three orders of magnitude larger than the incident wave energy density at low frequencies, forming in essence an open cavity.
Near‐infrared (NIR) light‐emitting diodes (LEDs) light sources are desirable in photonic, optoelectronic, and biological applications. However, developing broadband red and NIR‐emitting phosphors ...with good thermal stability is always a challenge. Herein, the synthesis of Eu2+‐activated SrY2O4 red phosphor with high photoluminescence quantum efficiency and broad emission band ranging from 540 to 770 nm and peaking at 620 nm under 450 nm excitation is designed. Sr/Ba substitution in SrY2O4:Eu2+ has been further utilized to achieve tunable emission by modifying the local environment, which facilitates the giant red‐shifted emission from 620 to 773 nm while maintaining the outstanding thermal stability of SrY2O4:Eu2+. The NIR emission is attributed to the enhanced Stokes shift and crystal field strength originated from the local structural distortions of Y1/Eu1O6 and Y2/Eu2O6. The investigation in charge distribution around Y/Eu provides additional insight into increasing covalency to tune the emission toward the NIR region. As‐fabricated NIR phosphor‐converted LEDs demonstration shows its potential in night‐vision technologies. This study reveals the NIR luminescence mechanism of Eu2+ in oxide‐based hosts and provides a design principle for exploiting Eu2+‐doped NIR phosphors with good thermal stability.
A red phosphor SrY2O4:Eu2+ is developed and the NIR emission via Sr/Ba cation substitution is realized. The substitution enables photoluminescence tuning from 620 to 773 nm and maintains good thermal stability. This study reveals the NIR luminescence mechanism of Eu2+ in oxide‐based host and provides a design principle for exploiting Eu2+‐doped NIR phosphors with good thermal stability.
The electrochemical properties of transition metal oxides strongly depend on the coordination environment of metal atoms. Nevertheless, the relationship between the coordination environment of metal ...atoms and electrochemical performance of metal oxides is unclear, while the strategy of adjusting the coordination environment of metal atoms is rare. Herein, the engineering of the coordination environment of Mn atoms in manganese dioxides (MnO2) by using a triethanolamine (TEA) complex‐induced method is reported. The detailed experimental characterizations and density functional theory calculations show that the optimized Mn coordination environment with oxygen deficiency and more corner‐shared Mn–Mn shells results in apparent electron dislocation and forms an effective built‐in electrical field. As a result, the obtained MnO2‐TEA sample exhibits a high conductivity and an excellent ion diffusion capacity, with a remarkable specific capacitance of 417.5 F g−1 at 1 A g−1. At the power density of 450.0 W kg−1, the fabricated asymmetric supercapacitor delivers the maximal energy density (57.4 Wh kg−1). This work not only provides an effective strategy of adjusting the coordination environment of metal atoms in metal oxides, but also presents a deeper understanding of the electronic structure dependent electrochemical performance of electrode materials.
A simple triethanolamine complex method can significantly enhance the capacitive performance of MnO2 by adjusting the coordination environment of the Mn atoms, in which oxygen deficiency and more corner‐shared Mn–Mn shells (Mn–Mn2) are introduced to delocalize electrons and form a built‐in electrical field in MnO2, realizing a high conductivity and an excellent ion diffusion capacity.
Abstract
Physiological signal processing plays a key role in next-generation human-machine interfaces as physiological signals provide rich cognition- and health-related information. However, the ...explosion of physiological signal data presents challenges for traditional systems. Here, we propose a highly efficient neuromorphic physiological signal processing system based on VO
2
memristors. The volatile and positive/negative symmetric threshold switching characteristics of VO
2
memristors are leveraged to construct a sparse-spiking yet high-fidelity asynchronous spike encoder for physiological signals. Besides, the dynamical behavior of VO
2
memristors is utilized in compact Leaky Integrate and Fire (LIF) and Adaptive-LIF (ALIF) neurons, which are incorporated into a decision-making Long short-term memory Spiking Neural Network. The system demonstrates superior computing capabilities, needing only small-sized LSNNs to attain high accuracies of 95.83% and 99.79% in arrhythmia classification and epileptic seizure detection, respectively. This work highlights the potential of memristors in constructing efficient neuromorphic physiological signal processing systems and promoting next-generation human-machine interfaces.
Long noncoding RNAs (lncRNAs) play important roles in the development of vascular diseases. However, the effect of lncRNA NORAD on atherosclerosis remains unknown. This study aimed to investigate the ...effect NORAD on endothelial cell injury and atherosclerosis. Ox-LDL-treated human umbilical vein endothelial cells (HUVECs) and high-fat-diet (HFD)-fed ApoE
mice were used as
and
models. Results showed that NORAD-knockdown induced cell cycle arrest in G0/G1 phase, aggravated ox-LDL-induced cell viability reduction, cell apoptosis, and cell senescence along with the increased expression of Bax, P53, P21 and cleaved caspase-3 and the decreased expression of Bcl-2. The effect of NORAD on cell viability was further verified via NORAD-overexpression. NORAD- knockdown increased ox-LDL-induced reactive oxygen species, malondialdehyde, p-IKBα expression levels and NF-κB nuclear translocation. Proinflammatory molecules ICAM, VCAM, and IL-8 were also increased by NORAD- knockdown. Additionally, we identified the strong interaction of NORAD and IL-8 transcription repressor SFPQ in HUVECs. In ApoE
mice, NORAD-knockdown increased the lipid disorder and atherosclerotic lesions. The results have suggested that lncRNA NORAD attenuates endothelial cell senescence, endothelial cell apoptosis, and atherosclerosis via NF-κB and p53-p21 signaling pathways and IL-8, in which NORAD-mediated effect on IL-8 might through the direct interaction with SFPQ.
The detection of moisture in organic solvents is very important before their use in water-sensitive reactions. Herein, we report that coumarins D1 and D2 were able to generate the corresponding ...water-sensitive copper complexes D1-Cu and D2-Cu in common organic solvents, which can be used as efficient fluorescent turn-on sensors for water. Single-crystal diffraction analysis of the reaction product indicated that the sensing mechanism is based on the formation of a water-bridged 3D supramolecular hydrogen-bonding network. We demonstrated that a hydroxyl or amine group substituted at the 7-position of the coumarin framework played a key role in the water-sensing performance of D1-Cu and D2-Cu, by acting as a hydrogen bond acceptor in the supramolecular network. This provided a general strategy for designing such coumarin-based copper complexes for fluorescent water sensing. The water-sensing behavior of D1-Cu and D2-Cu were determined to be fast, pH tolerant, and sensitive. As low as 0.0525 wt % of water in methanol can be detected using D1-Cu as the sensor. Moreover, D1-Cu was successfully used for moisture sensing in real commercial products.
Cationization of cotton is considered to be an effective way to realize salt-free dyeing of reactive dyes. However, applying cotton modified with glycidyltrimethylammonium chloride (GTA) suffers from ...large consumption of the cationic reagent. One of the reasons is that high crystallinity of cotton fibers hinders the penetration of the reagents into the cellulose interior and limits the reaction between them. This paper designed to use alcohol-water-NaOH system to pretreat the fibers before cationization. With this method, crystallinity of the cotton fibers is decreased and more reactive -OH is exposed, resulting in much higher fiber-reagent reactivity and increased GTA utilization. Influence of alcohol type, alcohol-to-water ratio, and quantity of NaOH on fiber crystallinity and GTA dosage for cationization are all examined. It is found that for achieving 96.0% fixation of C.I. Reactive Black 5 in the absence of salt, GTA dosage can be reduced by half when the fibers are pretreated by alcohol-water-NaOH. Compared with ethanol,
-propanol and isopropanol,
-butyl alcohol incorporated system shows better performance in increasing fiber reactivity due to their weaker ability to dissolve ions. In this study, XRD and FT-IR are used to demonstrate changes in crystallinity of the fibers after pretreatment. The alteration in micromorphology and hydrophilicity of the pretreated fibers is observed by SEM and water contact angle test, respectively. Furthermore, the alcohol-water-NaOH system can be recycled to show very good repeatability. Notably, all dyed samples pretreated with the system present high color saturation and satisfactory color fastness, especially that the wet rub fastness reaches 4-5 grade, which is one grade higher than that obtained from the conventional dyeing with salt. The above findings prove that alcohol-water-NaOH pretreatment is effective in enhancing reactivity of the cotton fibers and penetrability of the agent, and it shows promising prospects in real application.
Chiral active particles (CAPs) are self-propelling particles that break time-reversal symmetry by orbiting or spinning, leading to intriguing behaviors. Here, we examined the dynamics of CAPs moving ...in 2D lattices of disk obstacles through active Brownian dynamics simulations and granular experiments with grass seeds. We find that the effective diffusivity of the CAPs is sensitive to the structure of the obstacle lattice, a feature absent in achiral active particles. We further studied the transport of CAPs in obstacle arrays under an external field and found a reentrant directional locking effect, which can be used to sort CAPs with different activities. Finally, we demonstrated that parallelogram lattices of obstacles without mirror symmetry can separate clockwise and counter-clockwise CAPs. The mechanisms of the above three novel phenomena are qualitatively explained. As such, our work provides a basis for designing chirality-based tools for single-cell diagnosis and separation, and active particle-based environmental sensors.
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