Phosphor‐converted light‐emitting diode (pc‐LED) has drawn much interest due to the efficient light in solid‐state lighting, backlight display, security, and electronic devices. Thermal quenching ...(TQ) induced by nonradiative relaxation is one of the vital challenges that limits the widespread use of phosphors. Much efforts are devoted to designing different approaches to solve the emission loss at increasing temperature. Here, the mechanism of TQ and recent advances of anti‐TQ‐phosphor‐involved 5d–4f, 4f–4f, 6p–6s, 3d–3d transitions are discussed. Several important design strategies for anti‐TQ phosphors are summarized as follows: 1) defect engineering; 2) energy transfer; 3) structural modulation; 4) enhancing crystallinity; 5) layer structural design; 6) negative/zero thermal expansion; 7) surface coating and glass technology. Additionally, some future challenges and opportunities in this field are proposed. This review promotes the discovery of novel anti‐TQ phosphor materials for LED applications.
Recent advances for anti‐thermal‐quenching (anti‐TQ) phosphor materials in light‐emitting diode (LED) applications are based on design strategies: defect engineering, energy transfer, structural modulations, enhancing crystallinity, layer structural design, negative/zero thermal expansion, and surface coating strategy. These strategies contribute to the development and discovery of new anti‐TQ luminescent materials for high performance phosphor‐converted‐LED devices.
We present results from the "Mint" resolution DC Justice League suite of Milky Way-like zoom-in cosmological simulations, which extend our study of nearby galaxies down into the ultrafaint dwarf ...(UFD) regime for the first time. The mass resolution of these simulations is the highest ever published for cosmological Milky Way zoom-in simulations run to z = 0, with initial star (dark matter) particle masses of 994 (17900) M , and a force resolution of 87 pc. We study the surrounding dwarfs and UFDs, and find that the simulations match the observed dynamical properties of galaxies with −3 > MV > −19, and reproduce the scatter seen in the size-luminosity plane for rh 200 pc. We predict the vast majority of nearby galaxies will be observable by the Vera Rubin Observatory's coadded Legacy Survey of Space and Time. We additionally show that faint dwarfs with velocity dispersions 5 km s−1 result from severe tidal stripping of the host halo. We investigate the quenching of UFDs in a hydrodynamical Milky Way context and find that the majority of UFDs are quenched prior to interactions with the Milky Way, though some of the quenched UFDs retain their gas until infall. Additionally, these simulations yield some unique dwarfs that are the first of their kind to be simulated, e.g., an H i-rich field UFD, a late-forming UFD that has structural properties similar to Crater 2, as well as a compact dwarf satellite that has no dark matter at z = 0.
We report measurements of the nuclear modification factor RCP for charged hadrons as well as identified π+(−), K+(−), and p(p¯) for Au+Au collision energies of sNN=7.7, 11.5, 14.5, 19.6, 27, 39, and ...62.4 GeV. We observe a clear high-pT net suppression in central collisions at 62.4 GeV for charged hadrons which evolves smoothly to a large net enhancement at lower energies. This trend is driven by the evolution of the pion spectra but is also very similar for the kaon spectra. While the magnitude of the proton RCP at high pT does depend on the collision energy, neither the proton nor the antiproton RCP at high pT exhibit net suppression at any energy. A study of how the binary collision-scaled high-pT yield evolves with centrality reveals a nonmonotonic shape that is consistent with the idea that jet quenching is increasing faster than the combined phenomena that lead to enhancement.
Fluorescent organic nanoparticles (NPs) with exceptional brightness hold significant promise for demanding fluorescence bioimaging applications. Although considerable efforts are invested in ...developing novel organic dyes with enhanced performance, augmenting the brightness of conventional fluorophores is still one of the biggest challenges to overcome. This study presents a supramolecular strategy for constructing ultrabright fluorescent nanoparticles in aqueous media (referred to as “Supra‐fluorophores”) derived from conventional fluorophores. To achieve this, this course has employed a cylindrical nanoparticle with a hydrophobic microdomain, assembled by a cyclic peptide‐diblock copolymer conjugate in water, as a supramolecular scaffold. The noncovalent dispersion of fluorophore moieties within the hydrophobic microdomain of the scaffold effectively mitigates the undesired aggregation‐caused quenching and fluorescence quenching by water, resulting in fluorescent NPs with high brightness. This strategy is applicable to a broad spectrum of fluorophore families, covering polyaromatic hydrocarbons, coumarins, boron‐dipyrromethenes, cyanines, xanthenes, and squaraines. The resulting fluorescent NPs demonstrate high fluorescence quantum yield (>30%) and brightness per volume (as high as 12 060 m−1 cm−1 nm−3). Moreover, high‐performance NPs with emission in the NIR region are constructed, showcasing up to 20‐fold increase in both brightness and photostability. This Supra‐fluorophore strategy offers a versatile and effective method for transforming existing fluorophores into ultrabright fluorescent NPs in aqueous environments, for applications such as bioimaging.
This work presents a supramolecular strategy for constructing ultrabright fluorescent supramolecular assemblies in aqueous media (referred to as “Supra‐fluorophores”) derived from conventional fluorophores. The noncovalent dispersion of fluorophore moieties within the hydrophobic microdomain of a cyclic peptide‐based supramolecular scaffold effectively mitigates the undesired aggregation‐caused quenching and fluorescence quenching by water, resulting in Supra‐fluorophores with high brightness.
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•Cold–hot composite dies were proposed to use in hot forming–quenching integrated process.•The effects of hot die temperature, quenching condition and precipitate distribution on ...strengthening were evaluated.•Lower die heating avoids rapid temperature decrease of heated sheet and results in good strength of parts.•Upper cold die ensures effective quenching and reduces thermal distortion of final part.
The novel technology combining hot forming and quenching together has been developed to improve formability and avoid thermal distortion for heat-treatable aluminum alloy forming. In this paper, cold–hot composite dies are proposed to use in hot forming–quenching integrated process. Heated lower dies are used to avoid rapid temperature decrease of heated sheet. Water-cooled upper dies are then used to accomplish quenching and reduce thermal distortion. The effects of temperature of lower dies, quenching condition and precipitate distribution on strengthening behavior in this process were investigated systematically. The strengths were measured by Vickers hardness and uniaxial tensile tests. It was found that the upper cold dies could ensure effective quenching. Lower dies could be heated to avoid rapid temperature decrease of heated sheet resulting in good strength of parts. The corresponding hardness, yield and tensile strengths were 140.7HV, 295.7 and 469.2MPa, respectively. For comparison, the process with both hot dies at temperatures ranging from 100 to 350°C was investigated. The temperature of both hot dies could only be improved to 250°C, otherwise the strength decreased. The strengthening phase was dispersed lath-shaped S phase with an average cross-section of approximately 50×100nm, which was observed with TEM and SEM methods.
Nd3+‐sensitized quenching‐shield sandwich‐structured upconversion nanoparticles are reported, which exhibit highly efficient upconversion photoluminescence under excitation by an 800 nm ...continuous‐wave laser. The transition‐layer structure is essential to bridge energy transfer from the sensitizer to the activator and simultaneously block energy back‐transfer from the activator to the sensitizer. These 800 nm‐excited upconversion nanoparticles are a key step toward the development of upconversion nanophosphors for biological applications.
The controllable incorporation of multiple immiscible elements into a single nanoparticle merits untold scientific and technological potential, yet remains a challenge using conventional synthetic ...techniques. We present a general route for alloying up to eight dissimilar elements into single-phase solid-solution nanoparticles, referred to as high-entropy-alloy nanoparticles (HEA-NPs), by thermally shocking precursor metal salt mixtures loaded onto carbon supports temperature ~2000 kelvin (K), 55-millisecond duration, rate of ~10
K per second. We synthesized a wide range of multicomponent nanoparticles with a desired chemistry (composition), size, and phase (solid solution, phase-separated) by controlling the carbothermal shock (CTS) parameters (substrate, temperature, shock duration, and heating/cooling rate). To prove utility, we synthesized quinary HEA-NPs as ammonia oxidation catalysts with ~100% conversion and >99% nitrogen oxide selectivity over prolonged operations.
Bioprobes Based on AIE Fluorogens Ding, Dan; Li, Kai; Liu, Bin ...
Accounts of chemical research,
11/2013, Letnik:
46, Številka:
11
Journal Article
Recenzirano
Fluorescent bioprobes are powerful tools for analytical sensing and optical imaging, which allow direct visualization of biological analytes at the molecular level and offer useful insights into ...complex biological structures and processes. The sensing and imaging sensitivity of a bioprobe is determined by the brightness and contrast of its fluorescence before and after analyte binding. Emission from a fluorophore is often quenched at high concentration or in aggregate state, which is notoriously known as concentration quenching or aggregation-caused quenching (ACQ). The ACQ effect limits the label-to-analyte ratio and forces researchers to use very dilute solutions of fluorophores. It compels many probes to operate in a fluorescence “turn-off” mode with a narrow scope of practical applications. The unique aggregation-induced emission (AIE) process offers a straightforward solution to the ACQ problem. Typical AIE fluorogens are characterized by their propeller-shaped rotorlike structures, which undergo low-frequency torsional motions as isolated molecules and emit very weakly in solutions. Their aggregates show strong fluorescence mainly due to the restriction of their intramolecular rotations in the aggregate state. This fascinating attribute of AIE fluorogens provides a new platform for the development of fluorescence light-up molecules and photostable nanoaggregates for specific analyte detection and imaging. In this Account, we review our recent AIE work to highlight the utility of AIE effect in the development of new fluorescent bioprobes, which allows the use of highly concentrated fluorogens for biosensing and imaging. The simple design and fluorescence turn-on feature of the molecular AIE bioprobes offer direct visualization of specific analytes and biological processes in aqueous media with higher sensitivity and better accuracy than traditional fluorescence turn-off probes. The AIE dot-based bioprobes with different formulations and surface functionalities show advanced features over quantum dots and small molecule dyes, such as large absorptivity, high luminosity, excellent biocompatibility, free of random blinking, and strong photobleaching resistance. These features enable cancer cell detection, long term cell tracing, and tumor imaging in a noninvasive and high contrast manner. Recent research has significantly expanded the scope of biological applications of AIE fluorogens and offers new strategies to fluorescent bioprobe design. We anticipate that future development on AIE bioprobes will combine one- or multiphoton fluorescence with other modalities (e.g., magnetic resonance imaging) or functionalities (e.g. therapy) to fully demonstrate their potential as a new generation of theranostic reagent. In parallel, the advances in molecular biology will provide more specific bioreceptors, which will enable the development of next generation AIE bioprobes with high selectivity and sensitivity for molecular sensing and imaging.
In the present study, we fundamentally explore the reasons underlying differences in mechanical properties in hot-rolled 0.2C-1.6Al-6.1Mn-Fe TRIP steels subjected to different heat treatments. ...Comparing with austenite reverted transformation annealing (ART) process, quenching and tempering (Q&T) process was effective in obtain excellent mechanical properties. Q&T (UTS: 902–1235MPa, TEL: 18–42%; ART (UTS: 885–945MPa, TEL: 13–28%). In the ART process, long time annealing led to excessive C and Mn enrichment in austenite, which rendered austenite too stable and deteriorated TRIP effect. Furthermore, long time annealing reduced dislocation density and led to low work-hardening rate. The Q&T process enabled appropriate enrichment of elements and hence desired stability for significant TRIP effect to be observed. Thus, the steel quenched from 625°C exhibited best combination of mechanical properties (UTS: 1038MPa, TEL: 42%, UTS×TEL: 43.6GPa%) because of significant contribution of TRIP effect and high dislocation density in austenite.
Multiresonance thermally activated delayed fluorescence (MR‐TADF) emitters manifest great potential for organic light‐emitting diodes (OLEDs) due to their high exciton‐utilization efficiency and ...narrowband emission. Nonetheless, their tendency toward self‐quenching caused by strong interchromophore interactions would induce doping sensitivity and deteriorate the device performances, and effective strategy to construct quenching‐resistant emitters without sacrifycing color purity is still to be developed. By segregating the planar MR‐TADF skeleton using two bulky carbazolyl units, herein a highly emissive molecule with enhanced quenching resistance is reported. The steric effect largely removes the formation of detrimental excimers/aggregates, and boosts the performance of the corresponding devices with a maximum external quantum efficiency (EQEmax) up to 40.0% and full width at half maximum (FWHM) of 25 nm, representative of the only example of single OLED that can concurrently achieve narrow bandwidth and high EL efficiency surpassing 40% to date. Even at doping ratio of 30 wt%, the EQEmax is retained to be 33.3% with nearly unchanged emission spectrum. This work provides a viable approach to realize doping‐insensitive MR‐TADF devices with extreme EL efficiency and color purity for high‐end OLED displays.
A molecular design tactic to achieve quenching‐resistant multiresonance thermally activated delayed fluorescence (MR‐TADF) emitters is proposed by fencing the MR‐skeleton with steric units. Excellent electroluminescence performances are recorded in corresponding organic light‐emitting diodes, with record‐breaking external quantum efficiencies up to 40.0% and full width at half maximum values of only 25 nm.
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