Enhancing light extraction efficiency of the inclined-sidewall-shaped DUV micro-LED array by hybridizing a nanopatterned sapphire substrate and an air-cavity reflector.

In this work, we hybridize an air cavity reflector and a nanopatterned sapphire substrate (NPSS) for making an inclined-sidewall-shaped deep ultraviolet micro light-emitting diode (DUV micro-LED) array to enhance the light extraction efficiency (LEE). A cost-effective hybrid photolithography process involving positive and negative photoresist (PR) is explored to fabricate air-cavity reflectors. The experimental results demonstrate a 9.88% increase in the optical power for the DUV micro-LED array with a bottom air-cavity reflector when compared with the conventional DUV micro-LED array with only a sidewall metal reflector. The bottom air-cavity reflector significantly contributes to the reduction of the light absorption and provides more escape paths for light, which in turn increases the LEE. Our investigations also report that such a designed air-cavity reflector exhibits a more pronounced impact on small-size micro-LED arrays, because more photons can propagate into escape cones by experiencing fewer scattering events from the air-cavity structure. Furthermore, the NPSS can enlarge the escape cone and serve as scattering centers to eliminate the waveguiding effect, which further enables the improved LEE for the DUV micro-LED array with an air-cavity reflector.

On the origin of the enhanced light extraction efficiency of DUV LED by using inclined sidewalls.

It is known that light extraction efficiency (LEE) for AlGaN-based deep ultraviolet (DUV) light-emitting diodes (LEDs) can be enhanced by using an inclined sidewall of mesa. However, the reported optimal inclined angles are different. In this work, to explore the origin for enhancing the LEE of DUV LED by using inclined sidewalls, we investigate the effect of an inclined sidewall angle on the LEE for AlGaN-based DUV LEDs with different mesa diameters by using ray tracing. It is found that when compared to large-size DUV LEDs with inclined sidewall, the LEE of small-size DUV LEDs with inclined sidewall is enhanced from both the bottom and side surfaces due to the reduced scattering length and material absorption. Additionally, the optimal inclined sidewall angle is recommended within the range of 25°-65°, and the optimal angle for DUV LEDs decreases as the chip size increases. It can be attributed to the fact that there are two scattering mechanisms for the inclined sidewall. For smaller chip sizes, most of the light is directly scattered into escape cones by the inclined sidewall, resulting in a larger optimal angle. For larger chip sizes, the light firstly experiences total internal reflections by the out-light plane and then is scattered into escape cones by the inclined sidewalls, leading to a smaller optimal angle.

DDX5 inhibits inflammation by modulating m6A levels of TLR2/4 transcripts during bacterial infection.

DExD/H-box helicases are crucial regulators of RNA metabolism and antiviral innate immune responses; however, their role in bacteria-induced inflammation remains unclear. Here, we report that DDX5 interacts with METTL3 and METTL14 to form an m6A writing complex, which adds N6-methyladenosine to transcripts of toll-like receptor (TLR) 2 and TLR4, promoting their decay via YTHDF2-mediated RNA degradation, resulting in reduced expression of TLR2/4. Upon bacterial infection, DDX5 is recruited to Hrd1 at the endoplasmic reticulum in an MyD88-dependent manner and is degraded by the ubiquitin-proteasome pathway. This process disrupts the DDX5 m6A writing complex and halts m6A modification as well as degradation of TLR2/4 mRNAs, thereby promoting the expression of TLR2 and TLR4 and downstream NF-κB activation. The role of DDX5 in regulating inflammation is also validated in vivo, as DDX5- and METTL3-KO mice exhibit enhanced expression of inflammatory cytokines. Our findings show that DDX5 acts as a molecular switch to regulate inflammation during bacterial infection and shed light on mechanisms of quiescent inflammation during homeostasis.

Fabricating and investigating a beveled mesa with a specific inclination angle to improve electrical and optical performances for GaN-based micro-light-emitting diodes.

In this Letter, beveled mesas for 30 × 30 µm2 GaN-based micro-light-emitting diodes (µLEDs) with different inclination angles are designed, fabricated, and measured. We find that µLED with a mesa inclination angle of 28° has the lowest internal quantum efficiency (IQE) and the highest injection current density at which the peak IQE is obtained. This is due to the increased quantum confined Stark effect (QCSE) at the mesa edge. The increased QCSE results from the strong electric field coupling effect. Instead of radiative recombination, more nonradiative recombination and leakage current will be generated in the sidewall regions. Besides, the smallest angle (28°) also produces the lowest light extraction efficiency (LEE), which arises from the optical loss caused by the sidewall reflection at the beveled surface sides. Therefore, the inclination angle for the beveled mesa has to be increased to 52° and 61° by using Ni and SiO2 as hard masks, respectively. Experimental and numerical results show that the external quantum efficiency (EQE) and the optical power can be enhanced for the fabricated devices. Meanwhile, the reduced surface recombination rate also decreases the leakage current.

Paeonol repurposing for cancer therapy: From mechanism to clinical translation.

Paeonol (PAE) is a natural phenolic monomer isolated from the root bark of Paeonia suffruticosa that has been widely used in the clinical treatment of some inflammatory-related diseases and cardiovascular diseases. Much preclinical evidence has demonstrated that PAE not only exhibits a broad spectrum of anticancer effects by inhibiting cell proliferation, invasion and migration and inducing cell apoptosis and cycle arrest through multiple molecular pathways, but also shows excellent performance in improving cancer drug sensitivity, reversing chemoresistance and reducing the toxic side effects of anticancer drugs. However, studies indicate that PAE has the characteristics of poor stability, low bioavailability and short half-life, which makes the effective dose of PAE in many cancers usually high and greatly limits its clinical translation. Fortunately, nanomaterials and derivatives are being developed to ameliorate PAE's shortcomings. This review aims to systematically cover the anticancer advances of PAE in pharmacology, pharmacokinetics, nano delivery systems and derivatives, to provide researchers with the latest and comprehensive information, and to point out the limitations of current studies and areas that need to be strengthened in future studies. We believe this work will be beneficial for further exploration and repurposing of this natural compound as a new clinical anticancer drug.

Lattice-matched AlInN/GaN bottom DBR impact on GaN-based vertical-cavity-surface-emitting laser diodes: systematical investigations.

In this paper, by using advanced numerical models, we investigate the impact of the AlN/GaN distributed Bragg reflector (DBR) and AlInN/GaN DBR on stimulated radiative recombination for GaN-based vertical-cavity-surface-emitting lasers (VCSELs). According to our results, when compared with the VCSEL with AlN/GaN DBR, we find that the VCSEL with AlInN/GaN DBR decreases the polarization-induced electric field in the active region, and this helps to increase the electron-hole radiative recombination. However, we also find that the AlInN/GaN DBR has a reduced reflectivity when compared with the AlN/GaN DBR with the same number of pairs. Furthermore, this paper suggests that more pairs of AlInN/GaN DBR will be set, which helps to even further increase the laser power. Hence, the 3 dB frequency can be increased for the proposed device. In spite of the increased laser power, the smaller thermal conductivity for AlInN than AlN results in the earlier thermal droop in the laser power for the proposed VCSEL.

Optimizing metal/n-AlGaN contact by recessed AlGaN heterostructure with a polarization effect.

With increasing Al mole fraction, n-contact has become an important issue limiting the development of Al-rich AlGaN-based devices. In this work, we have proposed an alternative strategy to optimize the metal/n-AlGaN contact by introducing a heterostructure with a polarization effect and by etching a recess structure through the heterostructure beneath the n-contact metal. Experimentally, we inserted an n-Al0.6Ga0.4N layer into an Al0.5Ga0.5N p-n diode on the n-Al0.5Ga0.5N layer to form a heterostructure, where a high interface electron concentration of 6 × 1018 cm-3 was achieved with the aid of a polarization effect. As a result, a quasi-vertical Al0.5Ga0.5N p-n diode with a ∼1 V reduced forward voltage was demonstrated. Numerical calculations verified that the increased electron concentration beneath the n-metal induced by the polarization effect and recess structure was the main reason for the reduced forward voltage. This strategy could simultaneously decrease the Schottky barrier height as well as provide a better carrier transport channel, enhancing both the thermionic emission and tunneling processes. This investigation provides an alternative approach to obtain a good n-contact, especially for Al-rich AlGaN-based devices, such as diodes and LEDs.

Recent Advances on GaN-Based Micro-LEDs.

GaN-based micro-size light-emitting diodes (µLEDs) have a variety of attractive and distinctive advantages for display, visible-light communication (VLC), and other novel applications. The smaller size of LEDs affords them the benefits of enhanced current expansion, fewer self-heating effects, and higher current density bearing capacity. Low external quantum efficiency (EQE) resulting from non-radiative recombination and quantum confined stark effect (QCSE) is a serious barrier for application of µLEDs. In this work, the reasons for the poor EQE of µLEDs are reviewed, as are the optimization techniques for improving the EQE of µLEDs.

Suppressing optical crosstalk for GaN/InGaN based flip-chip micro light-emitting diodes by using an air-cavity patterned sapphire substrate as a light filter.

In this work, by using three-dimensional finite-difference time-domain (3D FDTD) method, the effect of conventional nano-patterned sapphire substrate (NPSS) on the optical crosstalk and the light extraction efficiency (LEE) for InGaN/GaN-based flip-chip micro light-emitting diodes (µ-LEDs) are systematically studied. We find that the conventional NPSS is not suitable for µ-LEDs. It is because the inclined mesa sidewall for µ-LEDs possesses a good scattering effect for µ-LEDs, but the introduced conventional NPSS causes part of the light be off escape cone between sapphire and air and become the guided light. To suppress the guided light and improve the optical crosstalk, a thick air layer between the n-GaN layer and the sapphire substrate can be used as a light filter to prevent the guided light from propagating into the sapphire. However, in reality, it is challenging to make the aforementioned air layer from point of fabrication view. Therefore, we propose the air-cavity patterned sapphire substrate (AC-PSS) as the light filter. Our results show that the crosstalk ratio can be decreased to the value even lower than 10%. The LEE can also be enhanced simultaneously due to combination effects of the filtering effect of the AC-PSS and the scattering effect of the inclined mesa sidewall.

Influence of affinity tags and tobacco PR1a signal peptide on detection, purification and bioactivity analyses of the small oomycete apoplastic effectors.

OBJECTIVE: To examine the influence of widely used protein affinity tags and the tobacco PR1a signal peptide (SP) on detection, purification and bioactivity analyses of the small oomycete apoplastic effector SCR96 in planta. RESULTS: Through agroinfiltration, the phytotoxic effector SCR96 of Phytophthora cactorum was expressed in Nicotiana benthamiana leaf apoplast as a fusion protein carrying single affinity tag (His, HA or FLAG) at either C- or N-terminus. Leaf necrosis caused by different affinity-tagged SCR96 varied among tags and replicates. All of tagged proteins can be detected by antibodies against SCR96. All of SCR96 fusions except N-terminally fused 6His-tagged protein were detected using tag antibodies, indicating that 6His tag may be degraded when fused at N-terminus. Interestingly, C-terminal His- and FLAG-tagged SCR96 maintained the biological activity after purification. In the substitution assay of SCR96 SP, we observed that PR1a SP can lead chimeric SCR96 expression in N. benthamiana, but the replacement totally disrupted its bioactivity. CONCLUSION: C-terminal His or FLAG tag, along with its original SP, is efficient enough to enable detection and purification of functional SCR96 from N. benthamiana leaf apoplast, which would facilitate plant-pathogen interaction studies.

On the impact of the beveled mesa for GaN-based micro-light emitting diodes: electrical and optical properties.

In this report, the impact of different mesa designs on the optical and electrical characteristics for GaN-based micro-light emitting diodes (µLEDs) has been systematically and numerically investigated by using TCAD simulation tools. Our results show that an enhanced light extraction efficiency can be obtained by using beveled mesas. The inclined mesa angles can more effectively reflect the photons to the substrate, and this helps to extract the photons to free air for flip-chip µLEDs. However, it is found that the current injection is influenced by inclination angles for the investigated µLEDs, such that the beveled mesas make stronger charge-coupling effect and increase the electric field magnitude in the multiple quantum wells at the mesa edge, so that the carriers cannot be effective consumed by radiative recombination. As a result, this gives rise to stronger defect-induced nonradiative recombination at mesa surfaces. Therefore, there are tradeoffs between the LEEs and IQEs when changing the beveled angle, to maximize external quantum efficiency for GaN-based µLEDs, the beveled mesa angle shall be carefully designed and optimized.

Improving the performance for flip-chip AlGaN-based deep ultraviolet light-emitting diodes using surface textured Ga-face n-AlGaN.

Low light extraction efficiency (LEE), high forward voltage and severe self-heating effect greatly affect the performance for AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs). In this work, surface-textured Ga-face n-AlGaN is fabricated low-costly using self-assembled SiO2 nanosphere as hard mask. The experimental results manifest that when compared with conventional DUV LEDs, the optical power, the forward voltage and the thermal characteristics for the DUV LEDs with surface-textured Ga-face n-AlGaN are improved obviously. It is because the surface-textured Ga-face n-AlGaN between mesa and the n-electrode can be used as the scattering center for trapped light, and this leads to the enhanced LEE. Furthermore, thanks to the surface-textured n-AlGaN under the n-electrode, the n-type ohmic contact area can be increased effectively. Therefore, the n-type ohmic contact resistance can be reduced and the better heat dissipation can be attained for the proposed flip-chip DUV LED.

[Relationship between community composition and water infiltration of biological soil crusts in the hilly Loess Plateau, China]. / é»„åœŸä¸˜é™µåŒºç”Ÿç‰©ç»“çš®ç¾¤è½ç»„æˆä¸Žæ°´åˆ†å ¥æ¸—çš„å ³ç³».

Biological soil crusts (biocrusts) are the mixed community composed of different ratios of cyanobacteria, mosses, and lichens at the slope scale in the Hilly Loess Plateau region. Biocrusts significantly affect water infiltration in this area. The relationship between infiltration rate and community structure of mixed biocrusts is unknown, which would hinder the assessment of soil permeability of biocrusts at the slope scale. We measured the stable infiltration rate of cyanobacteria, moss, and mixed biocrusts with different proportions of cyanobacteria and moss including moss coverage of <15%, 15%-30%, 30%-45%, 45%-60% and >60%, respectively. The principal component analysis and path analysis were used to understand the influencing factors of stable infiltration rate of mixed biocrusts, and to clarify the relationship between the stable infiltration rate and the community structure of mixed biocrusts. The results showed that the saturated hydraulic conductivity of cyanobacteria and moss crusts was 0.66 mm·min-1 and 2.40 mm·min-1, respectively. The stable infiltration rates of mixed biocrusts with moss coverage <15% to >60% were 0.80-2.30 mm·min-1. The stable infiltration rate of mixed biocrusts at the slope scale depended on moss coverage and its improvement on soil pore structure, with the correlation coefficients being 0.636 (P=0.011) and 0.835 (P=0.000) respectively. Herein, the saturated hydraulic conductivity and coverage of cyanobacteria and moss confirmed the weighted prediction of water infiltration volume (y) i.e., a significant correlation (r=0.945) with the measured water infiltration volume (x) of mixed biocrusts. The linear fitting of measured and predicted water infiltration volume of mixed biocrusts was y=0.85x (R2=0.98, P<0.05). This study clarified the relationship between water infiltration of mixed biocrust community composition and individual biocrust composition, which provided a scientific basis for accurately evaluating the hydrological process of biocrusts in this area.

[Effects of simulated grazing disturbance on soil water infiltration of biocrust slope in the hilly Loess Pla-teau, China]. / æ¨¡æ‹Ÿæ”¾ç‰§å¹²æ‰°å¯¹é»„åœŸä¸˜é™µåŒºç”Ÿç‰©ç»“çš®å¡é¢åœŸå£¤æ°´åˆ†å ¥æ¸—çš„å½±å“.

Water is the key factor for vegetation restoration in the Loess Plateau region. Biological soil crust (biocrust), a widely distributed soil surface cover, significantly affects soil infiltration. Disturbance would affect soil water infiltration of biocrust. The effects of different intensities of disturbance on soil water infiltration of biocrust are still unclear. By simulating the trampling disturbance of sheep, we examined the effects of disturbance intensity (10%, 20%, 30%, and 40%) estimated by the coverage of broken biocrust on the surface cover of biocrust slope in the Hegou catchment of Wuqi County, Shaanxi Province. Soil water infiltration under different intensities were measured by the linear source infiltration method. The influence mechanisms of disturbance on soil water infiltration of biocrust slope were investigated with a structural equation model and correlation analysis. Results showed that compared to that without disturbance, the coverage of cyanobacterial crust was increased by 33.6% at 10% of disturbance intensity, no difference at 20% of disturbance intensity, and decreased by 36.1% and 75.0% at 30% and 40% of disturbance intensities, respectively. Litter coverage was increased by 34.3% under 40% of disturbance intensity, while that of other treatments were not changed. Surface roughness was decreased by 22.3%, 11.1%, and 5.6% at 10%, 20%, and 30% of disturbance intensities, respectively, but increased by 8.2% at the 40% of disturbance intensity. The initial infiltration rate at 40% of disturbance intensity was 77.1% higher than that without disturbance, while other treatments had no significant difference at the initial infiltration rate. Furthermore, distur-bance did not affect the stable and average infiltration rate. Our results confirmed that disturbance mainly promoted the initial infiltration by reducing the coverage of cyanobacterial crust, increasing the coverage of litter, and changing soil roughness. This study would provide scientific basis for the management of biocrust of rehabilitated lands in the Loess Plateau region.

Local dielectric tunnel junction to manage the current distribution for AlGaN-based deep-ultraviolet light-emitting diodes with a thin p-GaN layer.

In this report, a p+-GaN/SiO2/Ni tunnel junction with a local SiO2 insulation layer is designed to manage the current distribution for commercially structured AlGaN-based deep-ultraviolet light-emitting diodes (DUV LEDs) with a thin p-GaN layer. The experimental and calculated results prove that, besides the increased hole injection at the p+-GaN/SiO2/Ni tunnel junction, the local SiO2 layer produces an in-plane unbalanced energy band in the p-GaN layer for the proposed DUV LEDs, thus modulating the carrier transport paths and increasing the spread of holes. Enhanced optical power is obtained when compared to conventional DUV LEDs. In addition, the influence of the position of the SiO2 insulation layer on the current distribution is also investigated in this work. Placing the SiO2 insulation layer in the middle position of the p+-GaN layer is most helpful for increasing the hole injection efficiency for commercially structured DUV LEDs.

Corybungines A-K: Isoquinoline alkaloids from Corydalis bungeana with dopamine D2 receptor activity.

Eleven undescribed isoquinoline alkaloids corybungines A-K including a protoberberine-type alkaloid, an isoquinoline alkaloid with a unique 6-norprotoberberine skeleton, one 13,14-seco-protoberberine-type alkaloid, two 1a,14-seco-protoberberine-type alkaloids with a 4-(hydroxymethyl)phenoxy moiety and six aporphine alkaloids, together with seven known alkaloids, have been isolated from the whole herb extract of Corydalis bungeana Turcz. Their structures and absolute configurations were elucidated based on an analysis of spectroscopic data and electronic circular dichroism (ECD) spectra. (R)-stephanine displayed high antagonistic activity against the dopamine D2 receptor with an IC50 value of 0.85 ± 0.09 µM in CHO-D2 cells. Additionally, corybungines D, F, H, (R)-roemerine, (R)-vireakine and (R)-tuduranine showed moderate D2 antagonism (IC50 5.20-26.07 µM). The preliminary structure-activity relationships (SARs) of aporphine alkaloids were discussed.

Structurally diverse isoquinoline and amide alkaloids with dopamine D2 receptor antagonism from Corydalis bungeana.

Four new isoquinoline alkaloids including a benzophenanthridine alkaloid (1), a morphine derivative (2), a narceine-type alkaloid (3) and a simple isoquinoline alkaloid (4), a new amide alkaloid (5) and a new phthalic acid derivative (6), together with eleven known alkaloids (7-17) were obtained from the whole herbs extract of Corydalis bungeana Turcz. Their structures and absolute configurations were elucidated by extensive spectroscopic data analysis including HRESIMS, NMR and electronic circular dichroism (ECD) and ECD calculation. Compounds 1-17 were evaluated for dopamine D2 receptor activity in CHO-D2 cells. Among them, 16 showed the highest antagonistic activity on the D2 receptor with an IC50 value of 2.04 ± 0.01 µM. Compounds 14 and 15 exhibited moderate antagonism with IC50 values of 13.66 ± 2.28 and 31.72 ± 2.52 µM, respectively.

Hybrid metal/Ga2O3/GaN ultraviolet detector for obtaining low dark current and high responsivity.

In this work, we have proposed and fabricated a metal/Ga2O3/GaN hybrid structure metal-semiconductor-metal ultraviolet photodetector with low dark current and high responsivity. The Schottky contact of Ni/Ga2O3 makes the Ga2O3 layer fully depleted. The strong electric field in the Ga2O3 depletion region can push the photo-induced electrons from the Ga2O3 layer into the GaN layer for more efficient carrier transport. Therefore, the hybrid structure simultaneously utilizes the advantage of the absorption to solar-blind ultraviolet light by the Ga2O3 layer and the high electron mobility of the GaN layer. Thus, the dark current and the photocurrent for the proposed device can be greatly improved. As a result, an extremely high photo-to-dark-current ratio of 1.46 × 106 can be achieved. Furthermore, quick rise and fall times of 0.213 s and 0.027 s at the applied bias of 6 V are also obtained, respectively.

Enhanced performance of an AlGaN-based deep ultraviolet light-emitting diode using a p+-GaN/SiO2/ITO tunnel junction.

In this work, a 280-nm-wavelength deep-ultraviolet light-emitting diode (DUV LED) with a p+-GaN/SiO2/ITO tunnel junction is fabricated and investigated. Due to the decreased tunnel region width and enhanced electric field intensity in the 1-nm-thick SiO2 layer, the interband tunneling efficiency and the corresponding hole injection efficiency are promoted. Therefore, the external quantum efficiency (EQE) for the proposed device is increased when compared with a traditional DUV LED. In addition, an improved current spreading effect is observed for our proposed device. As a result, improved wall-plug efficiency (WPE) is obtained owing to the increased optical power and decreased forward operating voltage. Meanwhile, the enhanced electric field intensity in the SiO2 layer reduces the voltage drop in the p-n junction region for the proposed device, and thus the leakage current is reduced.

Perovskite energy funnels for efficient white emission.

Doping Mn2+ into CsPbCl3 nanocrystals (NCs) yields strong orange emission, while the related emission in Mn2+ doped CsPbBr3 NCs is impaired seriously. This is mainly ascribed to back energy transfer from the Mn2+ dopant to the host. Doping Mn2+ into perovskites with multiple-quantum-well (MQW) structures may address this issue, where the energy funnels ensure a rapid energy transfer process, and thus resulting in a high photoluminescence quantum yield (PLQY). Here, we have developed an Ag+ assisted Mn2+ doping method in which Mn2+ can be easily doped into Br-based MQW perovskites. In this MQW perovskites, both nanoplatelets (NPLs) and NCs were formed simultaneously, where efficient energy transfer occurred from the NPLs with a higher energy bandgap to the NCs with a smaller energy bandgap, and then to the Mn2+ dopants. White lighting solution with a PLQY up to 98% has been acquired by altering the experimental parameters, such as reaction time and the Pb-to-Mn feed ratio. The successful doping of Mn2+ into CsPbBr3 host has great significance and shows promising application for next-generation white lighting.