Perovskite light-emitting diodes (PeLEDs) with an external quantum efficiency exceeding 20% have been achieved in both green and red wavelengths
; however, the performance of blue-emitting PeLEDs ...lags behind
. Ultrasmall CsPbBr
quantum dots are promising candidates with which to realize efficient and stable blue PeLEDs, although it has proven challenging to synthesize a monodispersed population of ultrasmall CsPbBr
quantum dots, and difficult to retain their solution-phase properties when casting into solid films
. Here we report the direct synthesis-on-substrate of films of suitably coupled, monodispersed, ultrasmall perovskite QDs. We develop ligand structures that enable control over the quantum dots' size, monodispersity and coupling during film-based synthesis. A head group (the side with higher electrostatic potential) on the ligand provides steric hindrance that suppresses the formation of layered perovskites. The tail (the side with lower electrostatic potential) is modified using halide substitution to increase the surface binding affinity, constraining resulting grains to sizes within the quantum confinement regime. The approach achieves high monodispersity (full-width at half-maximum = 23 nm with emission centred at 478 nm) united with strong coupling. We report as a result blue PeLEDs with an external quantum efficiency of 18% at 480 nm and 10% at 465 nm, to our knowledge the highest reported among perovskite blue LEDs by a factor of 1.5 and 2, respectively
.
Rapid Auger recombination represents an important challenge faced by quasi-2D perovskites, which induces resulting perovskite light-emitting diodes' (PeLEDs) efficiency roll-off. In principle, Auger ...recombination rate is proportional to materials' exciton binding energy (E
). Thus, Auger recombination can be suppressed by reducing the corresponding materials' E
. Here, a polar molecule, p-fluorophenethylammonium, is employed to generate quasi-2D perovskites with reduced E
. Recombination kinetics reveal the Auger recombination rate does decrease to one-order-of magnitude lower compared to its PEA
analogues. After effective passivation, nonradiative recombination is greatly suppressed, which enables resulting films to exhibit outstanding photoluminescence quantum yields in a broad range of excitation density. We herein demonstrate the very efficient PeLEDs with a peak external quantum efficiency of 20.36%. More importantly, devices exhibit a record luminance of 82,480 cd m
due to the suppressed efficiency roll-off, which represent one of the brightest visible PeLEDs yet.
Abstract
Resonant dielectric metasurfaces have been demonstrated to hold a great promise for manipulation of light-wave dispersion at the nanoscale due to their resonant photonic environment and high ...refractive index. However, the efficiency of devices based on dielectric nanostructures is usually limited by the quality (
Q
) factor of their resonant modes. The physics of the bound sates in the continuum (BICs) provide an elegant solution for control over the
Q
factor of resonant modes. Here, by engineering the substrate of Si-based metasurfaces, we demonstrate two eigenmodes that exhibit an intrinsic magnetic dipole (MD)character and have an infinite radiation lifetime. We reveal that they are characterized by in-plane and out-of-plane MD modes and respectively correspond to two groups of BICs, that is, Fabry–Pérot BICs and symmetry-protected BICs. Using temporal coupled-mode theory and numerical simulations, we show that these BIC modes can transform into high-
Q
quasi-BIC resonances with near-unity absorption under normal incidence through tuning structural parameters. Our work provides a promising route to use BIC-inspired metasurfaces for designing ultra-narrowband absorbers which can be used as absorption filters, photodetectors, and sensors.
Antibiotic resistance genes, as newly emerging contaminants, have become a serious challenge to public health through the food chain. The gut of humans and animals is an important reservoir for the ...development and dissemination of antibiotic resistance genes because of the great abundance and diversity of intestinal microbiota. In the present study, we evaluated the influence of goat milk on the diversity and abundance of antibiotic resistance genes and gut microbial communities, especially pathogenic bacteria. Male mice were used, 12 for each of the 2 groups: a control group that received sterile distilled water and a treated group that received goat milk, and gut microbiota and antibiotic resistance genes were compared in these groups using metagenomic analysis. The results revealed that ingestion of goat milk decreased the diversity and abundance of antibiotic resistance genes in the mice gut. The relative abundance of fluoroquinolone, peptide, macrolide, and β-lactam resistance genes in the total microbial genes significantly decreased after the intervention. Goat milk intake also significantly reduced the abundance of pathogenic bacteria, such as Clostridium bolteae, Clostridium symbiosum, Helicobacter cinaedi, and Helicobacter bilis. Therefore, goat milk intake might decrease the transfer potential of antibiotic resistance gene to pathogenic bacteria in the gut. In addition, bacteria with multiple resistance mechanisms accounted for approximately 4.5% of total microbial communities in the control group, whereas it was not detectable in the goat milk group, indicating the total inhibition by goat milk intake. This study highlights the influence of goat milk on antibiotic resistome and microbial communities in the gut, and provides a new insight into the function of goat milk for further study.
A photoresponsive organogel surface (POS), which integrates characteristics of the photothermal property of Fe3O4 nanoparticles and the low hysteresis feature of lubricant‐infused organogels, is ...shown. A photothermally induced dynamic temperature gradient can be formed rapidly at the location of near‐infrared‐light irradiation (NIR) on POS with suitable Fe3O4 nanoparticles content. Thus, various droplets (e.g., water, glycerol, ethylene glycol, propylene glycol, and ethanol) can be transported effectively and nimbly (e.g., along desired trajectories with controllable velocity and direction, even run uphill and deliver solid particles). This work reveals a synergistic effect between the asymmetrical droplet deformation and the inside Marangoni flows, which forms a unique driving force for droplet transport with high efficiency. This finding offers insight into the design of novel responsive interface materials for droplet transportation, which would be significant for laboratory‐on‐a‐chip contexts, mass transportation, and microengines.
A synergistic effect between asymmetrical droplet deformation and the inside Marangoni flows forms a unique driving force for droplet transport with high efficiency on photothermal organogel surfaces.
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•Proton transfer for the probe EP1 is energy unfavorable in the S0 and S1 states.•The adduct EP1-CN has a spontaneous proton transfer process in the S0 state.•The large charge ...transfer extent is responsible for EP1-CN’s spectral red-shift.•A new detection mechanism is proposed that different from the experiment.
Excited state intramolecular proton transfer (ESIPT) process of a fluorescent probe (EP1) and its fluorescent detection mechanism for cyanide anion (CN−) have been investigated theoretically. Optimized structures indicate that the hydrogen bond (O1H2···O3) in EP1 is strengthened upon photo-excitation and the O1H2 proton in EP1-CN formed after adding CN− transfers spontaneously to O3. Potential energy curves confirm that proton transfer in EP1 is impossible because energies of the S0 and S1 states increase with the O1H2 bond length. While proton transfer in EP1-CN is unobstructed because energies of the S0 state decrease with the O1H2 bond length. Compared to EP1, the absorption and fluorescence spectra of EP1-CN are both red-shifted (87 and 41nm) due to the large charge transfer extent. Orbital-weighted dual descriptor isosurface and condensed local nucleophilicity indices confirm that the carbon atom on the aldehyde group is the nucleophilic site of CN−. Transition state searching demonstrates that the occurrence of nucleophilic addition reaction between EP1 and CN− should overcome a reaction barrier of 14.29kcal/mol and then get EP1-CN, which has 6.61kcal/mol lower energy than reactants. Thus, EP1 detecting CN− is through the fluorescence variation induced by the large charge transfer extent rather than by hampering ESIPT.
Near-infrared II fluorescence imaging holds great promise for
imaging and imaging-guided surgery with deep penetration and high spatiotemporal resolution. However, most NIR-II aromatic luminophores ...suffer from the notorious aggregation-caused quenching (ACQ) effect in the aqueous solution, which largely hinders their biomedical application
. In this study, the first NIR-II organic aggregation-induced emission (AIE) fluorophore (
), encapsulated as nanoparticles (
dots) for
biomedical imaging, was designed and synthesized. The NIR-II AIE
dots showed high temporal resolution, high photostability, outstanding water-solubility and biocompatibility
and
. The
dots were further used for long-term breast tumor imaging and visualizing tumor-feeding blood vessels, long-term hind limb vasculature and incomplete hind limb ischemia. More importantly, as a proof-of-concept, this is the first time that non-invasive and real-time NIR-II imaging of the gastrointestinal tract in health and disease has been performed, making the AIE dots a promising tool for gastrointestinal (GI) tract research, such as understanding the healthy status of GI peristalsis, diagnosing and evaluating intestinal motility dysfunction, and assessing drug effects on intestinal obstruction.
Since the emergence of inorganic–organic hybrid perovskites a few years ago, there have been many promising achievements in the field of green and red perovskite light‐emitting diodes (PeLEDs). ...Nevertheless, the performance of blue‐light PeLEDs faces challenges. In this work, the unique synergy obtained by introducing two different ligands to successfully form quasi‐2D perovskite films, which can exhibit stable blue‐light emission, is utilized. The fabricated PeLEDs have a maximum external quantum efficiency of 2.62% and a half lifetime (T50) of 8.8 min. Meanwhile, the electroluminescence spectrum with its peak located at 485 nm, demonstrates improved stability by applying different voltage bias. The finding in this work offers a new way to achieve steady blue PeLEDs with high performance.
Utilizing synergistic effects with two different ligands, a stable blue perovskite emitter is successfully fabricated. The corresponding blue perovskite light‐emitting diode shows excellent device performance with a peak external quantum efficiency of 2.62% and a T50 lifetime of 8.8 min, demonstrating remarkable color stability under operation.
This study aimed to achieve the simultaneous measurement of a mass concentration of a glucose solution and temperature. We proposed an asymmetric dual-taper sensor approach, based on a cascade ...structure of three-core fiber, which can effectively overcome cross-sensitivity. With this approach, our experiment successfully fabricated a sensor with a distance of 3 mm between the double tapers: One taper was fabricated at the three-core fiber (TCF) near the TCF-multimode fiber junction and the other taper was fabricated at the TCF–MMF junction. Afterwards, the length of the sensor increased by only 1.31 mm, which indicated that the sensor was not easy to break. The interference contrasts of the two interference resonance dips exceeded 16 dB. Considering the feasibility of double-parameter sensing and the improvement of sensitivity, an asymmetric double-taper was designed. The temperature responses to the proposed sensor were tested in the range from 25 °C to 75 °C, and responses of the mass concentration of glucose solution were tested in the range from 1% to 15%. Experimental results showed that the two interference peaks of an asymmetric dual-taper robust structure had different sensitivities to changes in the mass concentration of the glucose solution and to temperature. Moreover, these two parameters can be simultaneously demodulated by use of matrix method.
Near-infrared fluorescence imaging in the 1500-1700 nm sub-window (NIR-IIb) has shown a deeper penetration depth, higher resolution and zero auto-fluorescence for biomedical imaging. Till now, very ...few small molecule NIR-IIb fluorophores have been reported due to the extremely rare organic NIR-IIb skeleton and a notorious aggregation-caused quenching (ACQ) effect in aqueous solution. In this study, highly twisted NIR-II small molecule fluorophores such as
HL3
(45.5° at the S
0
state) with the emission wavelength extending into the NIR-IIb region were designed and synthesized using an aggregation-induced emission (AIE) strategy.
HL3
dots showed a remarkable increase in fluorescence intensity with a QY of 11.7% in the NIR-II window (>1000 nm) and 0.05% in the NIR-IIb region (>1550 nm) in water. High-resolution
in vivo
imaging of the whole body, cerebral vasculature, and lymphatic drainage beyond 1550 nm was achieved using NIR-II AIE
HL3
dots for the first time. These attractive results may promote the development of small-molecule NIR-IIb fluorophores with the maximum emission wavelength beyond 1500 nm with a deeper penetration depth and higher resolution.
Novel NIR-II organic fluorophores were designed and synthesized using an AIE and highly twisted donor-acceptor distortion strategy for bio-imaging beyond 1550 nm.
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