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Integrating multimode optical properties into a single material simultaneously is promising for improving the security level of fluorescent anticounterfeiting. However, there has been a lack of affirmative principles and unambiguous mechanisms that guide the design of such material. Herein, we achieve color-tunable photoluminescence, long-lived persistent emission, thermally stimulated luminescence, and reversible photochromism in a Tb3+-activated Mg4Ga8Ge2O20 phosphor by employing the F-like color center as an energy reservoir. It is experimentally revealed that the role of oxygen vacancies in the lattice of Mg4Ga8Ge2O20 is assumed as the main trap for the photogenerated electronic carriers, which is the origin of metastable F-like color centers. The formed color centers with the estimated depths of 0.48-0.95 eV could suppress the recombination of electron-hole pairs, thus giving rise to good photochromism and persistent emission properties, while under various modes of stimulation such as thermal attack or photo radiation, a quick recombination of electron holes happens, accounting for the bright thermally stimulated luminescence and the accompanied color bleaching. Finally, we fabricate a flexible phosphor/polymer composite by encapsulating the developed phosphor into a polydimethylsiloxane matrix, and conceptual demonstration of the composite for the high-security fluorescent anticounterfeiting technology, by virtue of multimode optical phenomena as authentication signals.
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Copper-based halide perovskites have shown great potential in lighting and photodetection due to their excellent photoelectric properties, good stability and lead-free nature. However, as an important piece of copper-based perovskites, the synthesis and application of RbCu2I3have never been reported. Here, we demonstrate the synthesis of high-quality RbCu2I3microwires (MWs) by a fast-cooling hot saturated solution method. The prepared MWs exhibit an orthorhombic structure with a smooth surface. Optical measurements show the RbCu2I3MWs have a sharp ultraviolet absorption edge with 3.63 eV optical band gap and ultra-large stokes shift (300 nm) in photoluminescence. The subsequent photodetector based on a single RbCu2I3MW shows excellent ultraviolet detection performance. Under the 340 nm illumination, the device shows a specific detectivity of 5.0 × 109Jones and a responsivity of 380 mA·W-1. The synthesis method and physical properties of RbCu2I3could be a guide to the future optoelectronic application of the new material.
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Orange Eu2+ -doped phosphors are essential for light-emitting diodes for cornering lights to prevent fatal road accidents at night, but such phosphors require features of high thermal, chemical stability and facile synthesis. This study reports a series of yellow-orange-red emitting SrAl2 Si3 ON6 :Eu2+ oxynitride phosphors, derived from the SrAlSi4 N7 nitride iso-structure by replacing Si4+ -N3- with Al3+ -O2- . The introduction of a certain amount of oxygen enabled the facile synthesis under atmospheric pressure using the air-stable raw materials SrCO3 , Eu2 O3 , AlN and Si3 N4 . SrAl2 Si3 ON6 has a smaller band gap and lower structure rigidity than SrAlSi4 N7 (5.19â eV vs 5.50â eV, Debye temperature 719â K vs 760â K), but exhibits higher thermal stability with 100 % of room temperature intensity remaining at 150 °C compared to 85 % for SrAlSi4 N7 . Electron paramagnetic resonance, thermoluminescence and density functional theory revealed that the oxygen vacancy electron traps compensated the thermal loss. Additionally, no decrease in emission intensity was found after either being heated at 500 °C for 2â hours or being immersed in water for 20â days, implying both of the thermal and chemical stability of SrAl2 Si3 ON6 :Eu2+ phosphors. The strategy of oxynitride-introduction from nitride promotes the development of low-cost thermally and chemically stable luminescent materials.
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The minimization of thermal quenching, which leads to luminescence loss at high temperatures, is one of the most important issues for near-infrared phosphors. In the present work, we investigated the properties of near-infrared Ca(Sc,Mg)(Al, Si)O6 : Cr3+ phosphors with a pyroxene-type structure under blue light excitation. The CaScAlSiO6 : Cr3+ end member of Ca(Sc,Mg)(Al,Si)O6 : Cr3+ phosphor led to broadband emission at a full-width half maximum of 215â nm, whereas the CaMgSi2 O6 : Cr3+ end member exhibited high thermal stability at 150 °C, with an intensity of 88.4 % of that at room temperature. The structural analysis and density functional theory calculations revealed the absence of soft conformations and local space confinement contributed to the high structural rigidity and weakened the thermal quenching effect.
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Interfacial engineering and heterostructures designing are two efficient routes to improve photoelectric characteristics of a photodetector. Herein, a Ti3 C2 MXene/Si heterojunction photodetector with ultrahigh specific detectivity (2.03 × 1013 Jones) and remarkable responsivity (402 mA W-1 ) at zero external bias without decline as with increasing the light power is reported. This is achieved by chemically regrown interfacial SiOx layer and the control of Ti3 C2 MXene thickness to suppress the dark noise current and improve the photoresponse. The photodetector demonstrates a high light on/off ratio of over 106 , an outstanding peak external quantum efficiency (EQE) of 60.3%, while it maintains an ultralow dark current at 0 V bias. Moreover, the device holds high performance with EQE of over 55% even after encapsulated with silicone, trying to resolve the air stability issue of Ti3 C2 MXene. Such a photodetector with high detectivity, high responsivity, and self-powered capability is particularly applicable to detect weak light signal, which presents high potential for imaging, communication and sensing applications.
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Currently, the study of Mn4+-doped oxide red phosphor is a hot research topic to solve the lack of red component in phosphor-converted white-light-emitting diodes (pc-WLEDs). In this Article, we designed Gd3+/Nb5+ cation substitution by Bi3+/Mn4+ in Ba2GdNbO6 with double-perovskite structure based on the radius and coordination of the cations through high-temperature solid-state reaction. The phase purity and microstructure of double-perovskite Ba2GdNbO6:Bi3+,Mn4+ phosphors were characterized by X-ray diffraction and scanning electron microscopy examination. The crystal structures were also determined by the Rietveld refinement, and the photoluminescence (PL) properties were systematically studied. Bi3+ and Mn4+ ions can be effectively doped in the Ba2GdNbO6 matrix with an optical band gap of 3.94 eV. Upon 315 nm UV excitation, the Ba2GdNbO6:Bi3+,Mn4+ phosphor shows two emission bands at 464 nm from Bi3+ and 689 nm from Mn4+, respectively. By the design of Bi3+ â Mn4+ energy transfer, systematic luminescence tuning from blue to red could be achieved because of spectral overlap between the emission spectrum of Bi3+ and the excitation spectrum of Mn4+. The corresponding mechanism of the Bi3+ â Mn4+ energy-transfer process was investigated in detail by the fluorescence decays and PL spectra. The red emission intensity of Mn4+ has been greatly improved by Bi3+ â Mn4+ energy transfer. Moreover, the phonon vibration and zero phonon line of Mn4+ were studied through temperature-dependent PL. Finally, a WLED was fabricated using a 460 nm blue chip with a yellow YAG:Ce3+ phosphor and a red Ba2GdNbO6:0.01Bi3+,0.01Mn4+ phosphor, which has a low correlated color temperature (3550 K) and a high color rendering index (89.6). The above results imply that the improved red emission phosphors have a potential application in warm pc-WLED lighting.
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Optical assembly as a multiple optical trapping technique enables patterned arrangements of matter ranging from atoms to microparticles for diverse applications in biophysics, quantum physics, surface chemistry, and cell biology. Optical potential energy landscapes based on evanescent fields are conventionally employed for optical assembly of subwavelength particles, but are typically limited to predefined patterns and lacking in tunability. Here we present a microfiber photonic crystal cavity applicable for tunable optical assembly of subwavelength particles along a flexible path. This is enabled by excellent mechanical flexibility of the microfiber cavity as well as its broadband photonic crystal reflectors. By virtue of the broadband reflectors, the lattice constant of the assembled particles is precisely tunable via altering the wavelength of input light. Three-dimensional optical assembly is also realized by making use of the high-order transverse mode of the microfiber cavity. Moreover, the optical assembly process is detectable by simply monitoring the reflection/transmission spectrum of the microfiber cavity. The design of the microfiber cavity heralds a new way for tunable optical assembly of subwavelength particles, potentially applicable for development of tunable photonic crystals, metamaterials, and sensors.
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Nowadays, photodynamic therapy (PDT) is under the research spotlight as an appealing modality for various malignant tumors. Compared with conventional PDT treatment activated by ultraviolet or visible light, near infrared (NIR) light-triggered PDT possessing deeper penetration to lesion area and lower photodamage to normal tissue holds great potential for in vivo deep-seated tumor. In this review, recent research progress related to the exploration of NIR light responsive PDT nanosystems is summarized. To address current obstacles of PDT treatment and facilitate the effective utilization, several innovative strategies are developed and introduced into PDT nanosystems, including the conjugation with targeted moieties, O2 self-sufficient PDT, dual photosensitizers (PSs)-loaded PDT nanoplatform, and PDT-involved synergistic therapy. Finally, the potential challenges as well as the prospective for further development are also discussed.
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Raios Infravermelhos , Fotoquimioterapia , Antineoplásicos/farmacologia , Humanos , Nanopartículas/química , Fármacos Fotossensibilizantes/farmacologiaRESUMO
We fabricated a high-performance film heater based on a silver nanowire and polymethyl methacrylate (Ag NW-PMMA) composite film, which was synthesized with the assistance of mechanical lamination and an in situ transfer method. The films exhibit excellent conductivity, high figure of merit, and strong adhesion of percolation network to substrate. By controlling NW density, we prepared the films with a transmittance of 44.9-85.0% at 550 nm and a sheet resistance of 0.13-1.40 Ω sq-1. A stable temperature ranging from 130 °C-40 °C was generated at 3.0 V within 10-30 s, indicating that the resulting film heaters show a rapid thermal response, low driving voltage and stable temperature recoverability. Furthermore, we demonstrated the applications of the film heater in defrosting and a physical therapeutic instrument. A fast defrosting on the composite film with a transmittance of 88% was observed by applying a 9 V driving voltage for 20 s. Meanwhile, we developed a physical therapeutic instrument with two modes of thermotherapy and electronic-pulse massage by using the composite films as two electrodes, greatly decreasing the weight and power consumption compared to a traditional instrument. Therefore, Ag NW-PMMA film can be a promising candidate for diversified heating applications.
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A significant challenge in epistasis detection is the huge amount of data, which leads to combinatorial explosion. This study focuses on a two-stage approach for detecting epistasis only among single nucleotide polymorphisms (SNPs) that show some marginal effect. We present this two-stage approach based on the fusion of two criteria (TwoFC) to detect epistatic interactions. We fuse the G (2) test and absolute probability difference function as a scoring function to measure the strength of association between SNPs and disease status. The fused scoring function is an excellent measure of the strength of such an association. The two-stage strategy greatly reduces the computation load on epistasis detection. We use both simulated data sets and a real disease data set to evaluate our method. The results of an experiment on the simulated data sets show that TwoFC exhibits high power and sample efficiency. The results of an experiment on the real disease data set show that our method performs well even with large-scale data sets.
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Epistasia Genética , Genoma Humano , Estudos de Casos e Controles , Biologia Computacional , Simulação por Computador , Bases de Dados Genéticas , Humanos , Degeneração Macular/genética , Polimorfismo de Nucleotídeo ÚnicoRESUMO
The challenge of developing phosphors with tailored near-infrared (NIR) emission ranges to meet the diverse demands of various applications is a paramount concern in the contemporary realm of NIR phosphor research. A strong dependence of NIR emission on Cr3+ concentration has been demonstrated in Sc2-xSi2O7:xCr3+, which exhibits an NIR emission band at 840 nm for low Cr3+ doping concentrations (x = 0.001-0.01) and an anomalous NIR emission band at 1300 nm for high Cr3+ doping concentrations (x = 0.01-0.10). Careful investigation of the crystal structure, excitation and emission spectra, and luminescence decay curves indicates that the two NIR emissions can be attributed to the isolated Cr3+ ions and the Cr3+-Cr3+ pairs, respectively. The strong interaction of exchange-coupled Cr3+-Cr3+ pairs is supported by temperature-dependent emission spectra, luminescence decay curves and electron paramagnetic resonance (EPR) measurements. This work provides a new insight into the study of Cr3+-Cr3+ pairs for broadband NIR emission.
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The discovery of phosphors with highly efficient broadband near-infrared emission is urgent for constructing NIR sources for various applications. Herein, we synthesized a series of near-infrared emitting garnet-type (A3B2C3O12) Lu2-xCaAl3.99Cr0.01SiO12:xGd/La and Lu2CaAl3.99-yCr0.01SiO12:ySc/Ga phosphors and systematically investigated the effect of A/B-site substitution on the crystal structure and luminescence properties. Structural and optical analyses revealed that the A/B-site substitution weakened the crystal field strength, further enhancing the broadband emission of the allowed 4T2 â 4A2transition and diminishing the narrow-peak emission of the forbidden 2E â 4A2 transition. As expected, NIR phosphors, exemplified by Lu1.7CaAl3.99Cr0.01SiO12:0.3Gd and Lu2CaAl3.49Cr0.01SiO12:0.5Sc, showed outstanding thermal stabilities at 423 K (150 °C) registering values of 103.02% and 94.91%, with high quantum efficiencies of 80.48% and 85.01%, respectively. In addition, pc-LEDs with broadband NIR output and good optoelectronic properties have been realized, demonstrating the great potential of broadband NIR pc-LEDs for applications. This work not only provides a series of high-efficiency phosphors for NIR pc-LED applications, but also provides a systematic idea and an efficient method to improve the luminescence performance of garnet-type phosphors.
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The design and fabrication of bifunctional catalysts with high electrocatalytic activity and stability are critical for developing highly reversible Li-O2 batteries (LOBs). Herein, the N, P co-doped MXene (NP-MXene) is prepared by one-step annealing method and evaluated as bifunctional catalyst for LOBs. The results suggest that the P doping plays a crucial role in increasing interlayer distance of MXene, thereby effectively providing more active sites, fast mass transfer, and ample space for the deposition/decomposition of Li2O2. Moreover, the N doping can significantly elevate the d-band center of Ti, thereby remarkably improving the adsorption of reaction intermediates and accelerating the deposition/decomposition of Li2O2 films. Consequently, the MXene-based LOBs deliver an ultrahigh specific capacity of 13,995 mAh/g at 500 mA g-1, a discharge/charge voltage gap of 0.89 V, and a cycle life up to 523 cycles with a limited capacity of 1000 mAh/g at 500 mA g-1. Impressively, the as-fabricated flexible LOBs with NP-MXene cathode display excellent cycling stability and ability to continuously power LEDs even after bending. Our findings pave the road of heteroatom doped MXenes as next-generation electrodes for high-performance energy storage and conversion systems.
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A low water-solubility but hydrophilic coating of CaF2 is demonstrated to be effective in mitigating the susceptibility of nickel-rich cathodes to moisture and even water. The ability of the cathode to resist water erosion is not inherently linked to either hydrophobicity or hydrophilicity, but lies in robust chemical bonding within the protective layer exhibiting low water solubility.
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An in situ gel separator based on an electrospun three-layer nanofibrous membrane (PSE11-Gel) is developed for high-performance lithium-organic batteries (LOBs). The highly efficient shuttle effect inhibition of organic cathode molecules or lithiated intermediates has been demonstrated for PSE11-Gel to realize high-capacity stable LOBs.
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In this paper, nano-polycrystalline WO3 thin films with the thickness in the range of 100-200 nm have been uniformly prepared on the designed regions of ITO (indium tin oxide) glass substrates by thermal evaporation deposition. Their crystal structures, surface morphologies and uniformities are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM), respectively. The solid-state electrochromic display (ECD) devices based on these nano-polycrystalline WO3 thin films have been also fabricated and have demonstrated to have better performance than normal thin films, including shorter response time, higher contrast, and furthermore, higher stability to keep the colored state without power consumption. These results demonstrate nano-polycrystalline WO3 thin films can be applied to improve the performance of ECD devices, especially suitable to static display.
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The luminescence efficiency and thermal stability are enduring topics in the realm of phosphors. It is acknowledged that the structural transformation from disorder to order results in increased lattice rigidity, consequently inducing heightened efficiency and enhanced thermal stability. In this case study of the structural evolution of Ca3Ga2Ge4O14:Cr3+, NaCa2GaGe5O14:Cr3+ and Na2CaGe6O14:Cr3+ near-infrared (NIR) phosphors, a significant paradox is revealed: the incongruent relationship between the fluctuating degrees of disorder and the simultaneous improvements in efficiency and thermal stability. By drawing on insights gained from structural analysis, optical investigations, and theoretical calculations, a notable revelation surfaces: the primary factor affecting rigidity and optical performance is not the disordering of the entire lattice, but rather the disordering of the framework itself. The findings elucidate the principle of framework-order engineering for crafting high-performance NIR phosphors.
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Considerable efforts have been devoted to the development of visible light-emitting phosphors for anti-counterfeiting application, but the design of multifunctional near-infrared materials with suitable luminescent properties was lacking. Based on the crystal field theory, a near ultraviolet excitable and near-infrared emitting Ca2Sn2(1-x)Al2(1-x)O9:2xCr3+,2xSi4+ phosphor was designed. On the one hand, the Ca2Sn2(1-x)Al2(1-x)O9:2xCr3+,2xSi4+ phosphor showed great potential for applications including anti-counterfeiting and secret signals under a 405 nm near UV laser. The integrated intensity at 150 °C was 75.9%, implying high thermal stability when irradiated with a high power light source. On the other hand, an unexpected red emission component originating from the Cr3+-Cr3+ dimer was observed and was confirmed by fast luminescence decay and electron spin resonance signals. The different thermal stabilities of Cr3+ near-infrared and Cr3+-Cr3+ red emissions opened up a new opportunity for luminescence ratiometric thermometers.
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A perylene diimide containing side-chain amines (PDIN) was studied as an organic cathode for application in lithium batteries, showing a high capacity of 174 mA h g-1. The chemical structures, experimental results, and calculation analyses verify that PDIN performed a 4-electron redox reaction jointly involving its CîO and side-chain amine groups. This study promotes the development of organic cathodes with multi-electron redox reactions.
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Mixed-valence europium-activated phosphors are receiving attention in many fields, such as lighting, anti-counterfeiting, optical recording, encryption, and temperature sensing. However, it remains difficult to construct mixed-valence europium-activated compounds due to the reductive and oxidative synthesis conditions required to obtain Eu2+ and Eu3+ ions, respectively. Herein, mixed-valence Eu2+/Eu3+ was realized in the CaBPO5 built by rigidly connected BO4 and PO4 tetrahedrons by partial Eu3+ â Eu2+ self-reduction in the air atmosphere. Commendably, the CaBPO5:Eu2+/Eu3+ phosphor exhibits excellent ratiometric temperature sensing performance with the maximum absolute and relative sensitivity being as high as 0.184 K-1 and 3.444% K-1 with good signal discriminability, due to the high and low, respectively, temperature-dependence of Eu2+ and Eu3+ emissions. The rapid dropping intensity of Eu2+ in CaBPO5 with increasing temperature was due to the small energy gap (â¼0.48 eV) between the Eu2+-5d state and the conduction band. Our work not only provides a novel thermometer candidate but also enlightens researchers to a method of effectively designing new mixed-valence metal-ion activated luminescent thermometers via selective tetrahedrally coordinated rigid crystal structure.