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- 2018
- electron-transparent membranes
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- Wroclaw University of Science and Technology
- Beijing Vacuum Electronics Research Institute
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- University of Surrey
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Enhancing Reverse Intersystem Crossing via Secondary Acceptors: towards Sky-Blue Fluorescent Diodes with Tenfold-Improved Exter-nal Quantum Efficiency
摘要： How to simply but effectively facilitate reverse intersystem crossing (RISC) transition is always the key issue for developing high-performance thermally activated delayed fluorescence (TADF) dyes. In this work, as a proof of concept, a feasible strategy named 'acceptor enhancement' is demonstrated with a series of ternary blue emitters (xCzmPOnTPTZ) using diphenylphosphine oxide (PO) as secondary acceptors. Compared with its PO-free binary analogue, such simple introduction of PO groups in pCzPO2TPTZ dramatically enhances its RISC rate constant (kRISC) by 10 times to the level of ~105 s-1, accompanied by RISC efficiency (ηRISC) of 92%, which further improves the triplet-to-singlet upconversion for effective triplet harvesting in its devices. As the result, on the basis of a trilayer device structure, pCzPO2TPTZ realized a state-of-the-art external quantum efficiency (EQE) beyond 20% with tenfold improvement.
关键词： Organic Light-Emitting Diode,Thermally Activated Delayed Fluorescence,Excited State Transition,Blue Emission,Reverse Intersystem Crossing,Phosphine Oxide Acceptor
更新于2025-09-23 15:23:52
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Narrow-Band Green-Emitting Sr <sub/>2</sub> MgAl <sub/>22</sub> O <sub/>36</sub> :Mn <sup>2+</sup> Phosphors with Superior Thermal Stability and Wide Color Gamut for Backlighting Display Applications
摘要： The narrow-band emitting phosphors have been extensively investigated in recent years, with the expectation that a wide color gamut of phosphor-converted backlighting device could be fabricated. Due to the weak electric–phonon interaction and low structural relaxation caused by the high rigid crystal structure and symmetric coordination environment, Sr2MgAl22O36:Mn2+ (SMAO:Mn2+) shows a narrow full-width at half-maximum of 26 nm, a high color purity of 81.5%, and a low thermal quenching (82% at 473 K of the initial intensity at 298 K). Using K2SiF6:Mn4+ as the red phosphor, SMAO:Mn2+ as the green one, and GaN-based chip as the blue component, the white light-emitting diode exhibits a National Television Standard Committee value of 127%. All the results demonstrate that the SMAO:Mn2+ phosphor has a promising application in the field of advanced wide-color-gamut backlight display, and the establishment of the relationships between the narrow-band emission and crystal structure can also be applied to design other novel narrow-band phosphors for backlighting technologies.
关键词： color gamut,inorganic phosphors,narrow-band emission,white light-emitting diodes,Sr2MgAl22O36:Mn2+,thermal stability,backlight displays
更新于2025-09-23 15:23:52
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A Photostable AIEgen for Specific and Real-time Monitoring of Lysosomal Processes
摘要： Lysosomes are recognized as advanced organelles involved in many cellular processes, and are also considered as crucial regulators of cell homeostasis. The current strategies for monitoring activities of lysosomes exhibit some limitations. Herein, we synthesized a novel fluorescent probe named 2M-DPAS with AIE characteristics, which was proved to have significant advantages of good biocompatibility, high selectivity, bright emission and excellent photostability. Based on those, 2M-DPAS can be used to continuously monitor the dynamic changes of lysosomes including autophagy and mitophagy, as well as to track the process of endocytosis of macromolecules in lysosomes, which are benefit to better know about the lysosomes-related diseases.
关键词： Aggregation-induced emission,Lysosomes,Autophagy,Monitoring,Phagocytosis of macromolecules
更新于2025-09-23 15:23:52
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Design and characterization of small detection modules based on scintillators and WLS bars with SiPM readout for a cosmic ray mini-array
摘要： This paper describes the design and characterization tests of detection modules for a low-cost, easily reconfigurable mini-array for cosmic rays. The basic layout of each individual module is based on a 400 cm2 scintillator tile, optically coupled to a Wavelength Shifter (WLS) bar and a Silicon Photomultiplier (SiPM) for light collection and readout. Low cost solutions, based on the Arduino MEGA board, have been adopted for electronics, triggering and data acquisition, in view of the operation of this facility. The first detection modules, equipped with 4×4 mm2 SiPMs were fully built and characterized. Additional tests were also carried out with photosensors having different sensitive area and technology.
关键词： Scintillators, scintillation and light emission processes (solid, gas and liquid scintillators),Particle detectors,Interaction of radiation with matter
更新于2025-09-23 15:23:52
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Alkali-metal-adsorbed g-GaN monolayer: ultralow work functions and optical properties
摘要： The electronic and optical properties of alkali-metal-adsorbed graphene-like gallium nitride (g-GaN) have been investigated using density functional theory. The results denote that alkali-metal-adsorbed g-GaN systems are stable compounds, with the most stable adsorption site being the center of the hexagonal ring. In addition, because of charge transfer from the alkali-metal atom to the host, the g-GaN layer shows clear n-type doping behavior. The adsorption of alkali metal atoms on g-GaN occurs via chemisorption. More importantly, the work function of g-GaN is substantially reduced following the adsorption of alkali-metal atoms. Specifically, the Cs-adsorbed g-GaN system shows an ultralow work function of 0.84 eV, which has great potential application in field-emission devices. In addition, the alkali-metal adsorption can lead to an increase in the static dielectric constant and extend the absorption spectrum of g-GaN.
关键词： Density functional theory,Optical properties,Field emission device,Adsorption,Work function,G-GaN
更新于2025-09-23 15:23:52
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The influence of nitrogen doping on the electronic structure of the valence and conduction band in TiO <sub/>2</sub>
摘要： X-ray emission spectroscopy (XES) and X-ray absorption spectroscopy (XAS) provide a unique opportunity to probe both the highest occupied and the lowest unoccupied states in matter with bulk sensitivity. In this work, a combination of valence-to-core XES and pre-edge XAS techniques are used to determine changes induced in the electronic structure of titanium dioxide doped with nitrogen atoms. Based on the experimental data it is shown that N-doping leads to incorporation of the p-states on the occupied electronic site. For the conduction band, a decrease in population of the lowest unoccupied d-localized orbitals with respect to the d-delocalized orbitals is observed. As confirmed by theoretical calculations, the N p-states in TiO2 structure are characterized by higher binding energy than the O p-states which gives a smaller value of the band-gap energy for the doped material.
关键词： TiO2 doping,X-ray absorption spectroscopy,electronic structure analysis,X-ray emission spectroscopy
更新于2025-09-23 15:23:52
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Positron emission tomography/computed tomography outperforms MRI in the diagnosis of local recurrence and residue of nasopharyngeal carcinoma: An update evidence from 44 studies
摘要： Studies on nasopharyngeal carcinoma (NPC) in five electronic databases were systematically searched online from the inception to June 5, 2018. Quality of the included studies was assessed using the updated Quality Assessment of Diagnostic Accuracy Studies 2. Data of sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, diagnostic odds ratio, and the 95% confidence intervals were pooled using a bivariate random‐effect model. Forty‐four studies with 61 groups of data and totally 3369 patients were included in the qualitative and quantitative synthesis analysis. The overall estimated sensitivity and specificity of positron emission tomography/computed tomography/magnetic resonance imaging (PET‐CT/MRI) for local recurrent/residual NPC were 0.90 and 0.85, respectively. The pooled area under the curve of (AUC) of PET‐CT/MRI in the summary receiver operator characteristic curve was 0.94. Subgroup analysis showed MRI vs PET‐CT had lower sensitivity (0.83 vs 0.92) and specificity (0.78 vs 0.89). The AUCs of MRI and PET‐CT were 0.87 and 0.96, respectively. No‐cross of 95% CI was found in MRI vs PET/CT (0.87‐0.90 vs 0.94‐0.98). Meta‐regression showed PET/CT vs MRI was a potential source of heterogeneity. PET/CT and MRI both showed quite high overall ability in diagnosing local recurrent/residual NPC, but the subgroup analysis indicated PET‐CT was superior over MRI in diagnosis of local recurrence and residue of NPC after radiotherapy. The examination methods affected the heterogeneity within studies.
关键词： specificity,positron emission tomography/computed tomography,sensitivity,magnetic resonance imaging,recurrence/residue,nasopharyngeal carcinoma
更新于2025-09-23 15:23:52
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Metamaterial-Based Radiative Cooling: Towards Energy-Free All-Day Cooling
摘要： In the light of the ever increasing dangers of global warming, the efforts to reduce energy consumption by radiative cooling techniques have been designed, but are inefficient under strong sunlight during the daytime. With the advent of metamaterials and their selective control over optical properties, radiative cooling under direct sunlight is now possible. The key principles of metamaterial-based radiative cooling are: almost perfect reflection in the visible and near-infrared spectrum (0.3–3 μm) and high thermal emission in the infrared atmospheric window region (8–13 μm). Based on these two basic principles, studies have been conducted using various materials and structures to find the most efficient radiative cooling system. In this review, we analyze the materials and structures being used for radiative cooling, and suggest the future perspectives as a substitute in the current cooling industry.
关键词： daytime radiative cooling,infrared atmospheric window,metamaterial,selective reflection,selective emission
更新于2025-09-23 15:23:52
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Estimation of winter time NOx emissions in Hefei, a typical inland city of China, using mobile MAX-DOAS observations
摘要： In this paper, we present a quantitative determination of the NOx emission in Hefei using mobile Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements. The measurements were carried out during winter time from December 2016 to February 2017. The measured NO2 vertical column densities (VCDs) show a strong spatial gradient with higher values within the city center, indicating the majority of NOx emission sources are located at the city center. A significant 'holiday effect' was found by comparing measurements taken during weekdays and weekend. The weekend reduction is more significant in the suburban (～28%) compared to the city center (～13%). Mobile measurements of NO2 vertical column densities (VCDs) were analyzed together with meteorological data to determine the NOx emission by applying the loop-integral method. Detailed error analysis of the NOx emission shows the variation of wind field and large measurement gap dominated the total error of NOx emission calculation. The result shows the NOx emission in Hefei during winter time varies in a wide range from 10 × 10^24 to 40 × 10^24 molec s^{-1} with an average of 18.44 × 10^24 molec s^{-1}. Our estimation is about 43% lower than the number reported in the previous emission inventory in 2012. The reduction of NOx emission reflects the successful implementation of emission control measures in recent years. Our result also shows about 73% of the total NOx in the city were transported from outside of the city during winter. The impacts of transported NOx are especially large when air masses originated from heavily polluted regions, i.e. North China Plain and Yangtze River Delta. The result presented provides a better understanding of the impacts of local emissions and transportation of pollutants on the local air quality of Hefei.
关键词： Mobile measurement,MAX-DOAS,Regional transport,NOx emission
更新于2025-09-23 15:23:52
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A multi-color and white-light emissive cucurbituril/terpyridine/lanthanide supramolecular nanofiber
摘要： Multi-color and white light luminescence materials based on supramolecular assemblies are attractive because of their potential applications in advanced light-emitting material. Herein, a cucurbit[8]uril-enhanced lanthanide luminescent supramolecular assembly was constructed in a facile but efficient way using terpyridine imidozalium cations, cucurbit[8]urils and rare earth ions such as Tb3+ and Eu3+. Significantly, the resultant fibrous supramolecular assembly, with an average width of 15 nm, could emit remarkable lanthanide luminescence, which was ten times higher than the corresponding terpyridine/Ln3+ without cucurbit[8]uril. And the solid state luminescence of supramolecular assembly could be smartly and easily turned among blue, green, red and white by adjusting the molar ratios between Tb3+ and Eu3+. The enhanced white-light emission by supramolecular strategy may provide a new approach for smart and tunable solid luminescent materials.
关键词： Cucurbit[8]uril,White-light emission,Supramolecular chemistry,Host-guest interaction,Lanthanide luminescence
更新于2025-09-23 15:23:52