Light-Induced Conductance Potentiation and Depression in an All-Optically Controlled Memristor.

Optoelectronic memristors are new multifunctional devices with both electrically tunable and light-tunable synaptic plasticity, attracting great attention as key promising devices for optoelectronic neuromorphic computing systems. At present, the conductance modulation in most optoelectronic memristors is conducted in a hybrid photoelectric mode, suffering some problems such as heat generation and control complexity. Here, an optoelectronic memristor based on the p+-Si/n-ZnO heterojunction is proposed where the conductance can be reversibly modulated in an all-optically controlled mode. The electron detrapping/trapping mechanism at the p+-Si/n-ZnO interface barrier region is presented to explain the light-induced conductance potentiation/depression behavior. Furthermore, some synaptic functions, including excitatory postsynaptic current (EPSC), inhibitory postsynaptic current (IPSC), and paired-pulse facilitation (PPF), are successfully mimicked in the p+-Si/n-ZnO heterojunction memristor, instructing its application potential for optoelectronic neuromorphic computing.

Demonstration of 651†nm InGaN-based red light-emitting diode with an external quantum efficiency over 6% by InGaN/AlN strain release interlayer.

This work reports a high-performance InGaN-based red-emitting LED with a strain-release interlayer (SRI) consisting of an InGaN stress-release layer (SRL) and an AlN dislocation confinement layer (DCL) in unintentionally doped GaN (u-GaN). The SRL introduces a tensile strain which could decrease the in-plane compressive stress of the u-GaN layer, while the DCL could reduce the dislocation density and thus improve the crystal quality of the u-GaN layer. Consequently, a high-efficiency InGaN-based red-emitting LED with a peak wavelength of 651 nm and an external quantum efficiency of 6.04% is realized. In addition, the room-temperature photoluminescence (PL) mapping emission wavelength is uniform across a 4-inch wafer with a standard deviation of 3.3 nm. Therefore, the proposed SRI offers good potential for mass-producing high-performance and long-wavelength InGaN-based red-emitting LEDs.

Effect of boron nitride overlayers on Co@BNNSs/BN-Catalyzed aqueous phase selective hydrogenation of cinnamaldehyde.

The confinement effect known as efficient strategy to enhance the heterocatalytic activity and stability, but a clear view regarding the role of encapsulated overlayers is far from convincing at present, especially, the penetration of substrates with different size. Herein, the experimental evidence about the impacts of BN overlayers on hydrogenation is obtained over Co@BN/BN model catalysts with tuned thinness, in which BN overlayers encapsuled Co particles that dispersed on the defective BN supports, fabricating by the nitridizing of ball-milled BN microplates under NH3 atmosphere. The thinness and crystallinity of BN shells was simply tuned by controlling the pyrolyzed temperature (600-900 °C). The cinnamaldehyde (CAL) selective hydrogenation is taken as probe reaction due to (1) both larger CAL and small H2 molecule involved simultaneously, (2) the middle CC and terminal CO bonds all involved. Combined with structural analysis, the results demonstrate that small H2 molecule can penetrate into the metal-cover interface through the defect sites, then inner Co core dissociate it to atomic H, and the hydrogenation mainly resulting from the spillover of H atoms which occurred on the BN surface. As a result, the thickest BN shells (∼3.4 nm) with ordered-layer-lattice significantly hindered the adsorption and activation of CAL, also the longest H spillover distance led to the lowest activity of Co@BN/BN-900. Instead, Co@BN/BN-600 with merely 2 âˆ¼ 3 overlayers presented the most efficient and highly chemoselective hydrogenation activity. The ultrathin but turbostratic BN overlayers provide more migrating sites also shortened the H spillover distance effectively, and the more favorable CO hydrogenation was also achieved driven by the steric hindrance effect of thinner BN shells. These observations provide new insights towards understanding of confined effect on catalysis process through the accurate regulation of BN shells properties.

Concrescence of maxillary second molar and impacted third molar: A case report.

BACKGROUND: Morphological anomalies of teeth, including talon cusp, dens evaginatus, gemination, fusion, concrescence, root dilaceration, and taurodontism, always involve changes in the enamel, cementum and dentin. Diagnosing concrescent teeth through routine clinical examination alone is difficult, and most cases of concrescence are found accidentally during extraction. A definite preoperative diagnosis of concrescence would contribute to a better treatment plan and fewer undesirable complications. CASE SUMMARY: A 47-year-old woman who complained of left maxillary first molar loss for half a year presented to our department seeking treatment by dental implant restoration. Panoramic radiography and cone-beam computed tomography (CBCT) showed an unclear boundary between the distal root of the second molar and the mesial root of the third molar. The teeth were extracted under local anesthesia, and a definite diagnosis of concrescence was made by histopathological examination. CONCLUSION: CBCT is a useful tool for diagnosing and planning the management of tooth concrescence and may be beneficial for reducing unnecessary complications.

Self-powered asymmetric metal-semiconductor-metal AlN deep ultraviolet detector.

Self-powered ultraviolet detectors may find application in aviation and military fields. Here we demonstrate a self-powered asymmetric metal-semiconductor-metal (MSM) deep ultraviolet (DUV) detector with an Ni/Al electrode contact to AlN, and a photoelectric response current increase from dark current (Id) 2.6 × 10-12 A to 1.0 × 10-10 A after UV illumination (Ip) at 0 V bias. To further improve device performance, trenches are etched in AlN, and the Ni/Al electrodes are deposited in trenches to form a three-dimensional MSM (3D-MSM) structure. The improved performance is attributed to the stronger electric field from the asymmetric electrode and a shorter carrier migration path from the 3D-MSM device configuration. Our work will promote the development and application of DUV self-powered devices.

Enhanced hydrogen generation by reverse spillover effects over bicomponent catalysts.

The contribution of the reverse spillover effect to hydrogen generation reactions is still controversial. Herein, the promotion functions for reverse spillover in the ammonia borane hydrolysis reaction are proven by constructing a spatially separated NiO/Al2O3/Pt bicomponent catalyst via atomic layer deposition and performing in situ quick X-ray absorption near-edge structure (XANES) characterization. For the NiO/Al2O3/Pt catalyst, NiO and Pt nanoparticles are attached to the outer and inner surfaces of Al2O3 nanotubes, respectively. In situ XANES results reveal that for ammonia borane hydrolysis, the H species generated at NiO sites spill across the support to the Pt sites reversely. The reverse spillover effects account for enhanced H2 generation rates for NiO/Al2O3/Pt. For the CoOx/Al2O3/Pt and NiO/TiO2/Pt catalysts, reverse spillover effects are also confirmed. We believe that an in-depth understanding of the reverse effects will be helpful to clarify the catalytic mechanisms and provide a guide for designing highly efficient catalysts for hydrogen generation reactions.

Toward environmentally friendly direct reduced iron production: A novel route of comprehensive utilization of blast furnace dust and electric arc furnace dust.

In this study, a novel method for producing direct reduced iron (DRI) powders based on microwave-assisted self-reduction of core-shell composite pellets composed of blast furnace (BF) dust and hazardous electric arc furnace (EAF) dust followed by magnetic separation was reported. The proper core-shell structure of the composite pellets was designed according to the rule of impedance matching and properties of BF dust and EAF dust by adjusting the thickness of shell (i.e., thickness of impedance matching layer) via controlling the C/O molar ratio of the raw materials from 0.55 to 0.70. The results showed that the EAF dust with high content of CaO was beneficial to the mechanical strength of green, dried, and metallized pellets (collected after reduction), while the BF dust with high content of carbon enabled sufficient microwave-assisted reduction of the pellets, facilitating subsequent magnetic separation and also the removal of zinc from EAF dust. By reduction of the core-shell BF dust-EAF dust composite pellets with the C/O molar ratio of 0.65 at 1050 °C for 15 min, the resulting metallized pellets showed superior reduction and magnetic separation indexes with higher removal percentages of zinc and lead, in comparison with conventional metallized pellets. The DRI powders obtained after magnetic separation had total iron content of 91.2 wt%, iron metallization degree of 95.8%, yield of 68.1%, and iron recovery of 88.0%. This study provided a good example for efficient and environmentally friendly comprehensive utilization of typical and hazardous wastes in the iron and steel industry.

Pixel crosstalk in naked-eye micro-LED 3D display.

Micro-LED display is considered to be the most promising display technology, and naked-eye 3D display represents the most advanced frontier of display. Naked-eye 3D micro-LED display has both the advantages of micro-LED display and the characteristics of naked-eye 3D display. Only conceptual solutions for 3D micro-LED display have been reported so far. The effect of luminescence distribution and the direction of micro-LED devices on crosstalk in the naked-eye 3D display is not clear. In this paper, we first investigated the chip-shaping effect on the emission characteristics, mainly the luminescence distribution and direction of the micro-LED, and then we investigated the influence of luminescence distribution and direction of micro-LED on the pixel crosstalk in naked-eye micro-LEDs 3D display. Our work should advance the micro-LED display, especially the micro-LED 3D display.

Unidirectional-emitting GaN-based micro-LED for 3D display.

Naked-eye 3D micro-LED display combines the 3D characteristics and advantages of micro-LED simultaneously. A conventional micro-LED device emission exhibits Lambertian distribution, and it requires stacking of multiple optical components into a 3D display, resulting in bulky systems, low efficiency, and a limited viewing zone and points. We propose and investigate a single-chip micro-LED with unidirectional emission through an in-situ integrated resonant cavity and metasurface, which has great potential to be used for an efficient naked-eye 3D display with a wide viewing angle and multiple viewpoints. This Letter promotes the application of GaN-based micro-LEDs in a display, especially a 3D display.

Circularly polarized light emission from a GaN micro-LED integrated with functional metasurfaces for 3D display.

This Letter proposes a circularly polarized (CP) light GaN micro-LED which is integrated with functional metasurfaces. The one-dimensional metallic nanograting can achieve a high transverse electric (TE) reflectivity (${{\rm{R}}_{\rm{TE}}}$) and extinction ratio (ER) of TE and transverse magnetic (TM) waves, which is highly polarized output for micro-LEDs. Besides, the nanograting, which is integrated on the bottom of the GaN layer, can also support a resonant cavity, together with the top distributed Bragg reflector, which can shape the radiation pattern. By optimizing the structure parameters of nanograting, the ${{\rm{R}}_{\rm{TE}}}$ achieves over 80%, and the ER reaches higher than 38 dB at 450 nm for the GaN micro-LED. Additionally, the metasurface, which acts as a quarter-wave plate, was investigated to control the phase delay between the polarization state of the electric wave in two orthogonal components. Finally, the circular shape of the transmitted pattern denotes the high performance of the metasurface which is integrated in the micro-LED for CP light emission. The work reported in this Letter might provide potential application in a 3D polarized light display.

Multiplexing multifoci optical metasurfaces for information encoding in the ultraviolet spectrum.

Recently, optical metasurfaces have attracted much attention due to their versatile features in manipulating phase, polarization, and amplitude of both reflected and transmitted light. Because it controls over four degrees of freedom: phase, polarization, amplitude, and wavelength of light wavefronts, optical cryptography is a promising technology in information security. So far, information encoding can be implemented by the metasurface in one-dimensional (1D) mode (either wavelength or polarization) and in a two-dimensional (2D) mode of both wavelength and polarization. Here, we demonstrate multiplexing multifoci optical metasurfaces for information encoding in the ultraviolet spectrum both in the 1D and 2D modes in the spatial zone, composed of high-aspect-ratio aluminum nitride nanorods, which introduce discontinuous phases through the Pancharatnam-Berry phase to realize multifoci in the spatial zone. Since the multiplexed multifocal optical metasurfaces are sensitive to the helicity of the incident light and the wavelength is within the ultraviolet spectrum, the security of the information encrypted by it would be guaranteed.

Understanding homoepitaxial growth of horizontal kinked GaN nanowires.

Epitaxial horizontal nanowires (NWs) have attracted much attention due to their easily large-scale integration. From the reported literature, epitaxial growth is usually driven by minimization of strain between NW and substrate, which governs the growth along with specific crystallographic orientation. Here, we report the first homoepitaxial growth of horizontal GaN NWs from a surface-directed vapor-liquid-solid growth method. The NWs grow along with six symmetry-equivalent 〈1-100〉 (m-axis) directions, exhibiting a random 60°/120° kinked configuration. Owing to homoepitaxial growth, strain could be eliminated. From the obtained results, we suggest that the formation the horizontal NWs, and their growth direction /orientation is not directly related to the strain minimization. A general rule based on the epitaxial relationship and potential low-index growth orientation is proposed for understanding the arrangement of epitaxial horizontal NWs. It is deduced that kinking of the horizontal NWs was attributed to unintentional guided growth determined by the roughness of the substrates' surface. This study provides an insight for a better understanding of the evolution of epitaxial horizontal NWs, especially for the growth direction/orientation.

Sputtering AlN/InxAl1-xN distributed Bragg reflector across the full visible range on Si and SiO2 substrates.

III-nitride-based distributed Bragg reflectors (DBRs) are advantageous in being in-situ integrated in III-nitride devices, and the bandgaps and their other corresponding optical parameters are tunable. However, a growing nitride DBR with low strain and high reflectivity remains a challenge. Here we demonstrate an AlN/InxAl1-xN DBR grown on Si and SiO2 substrates by reactive radio-frequency magnetron sputtering. Reflectance wavelengths covering the whole visible regions of the visible spectrum were achieved by rationally tuning the indium composition in InxAl1-xN and each layer's thickness of an AlN/InxAl1-xN DBR. This Letter should advance the design and fabrication of nitride optical and optoelectrical devices by incorporating an AlN/InxAl1-xN DBR, such as vertical-cavity surface-emitting laser (VCSEL) and RC LEDs.

Amorphous Cr2WO6-Modified WO3 Nanowires with a Large Specific Surface Area and Rich Lewis Acid Sites: A Highly Efficient Catalyst for Oxidative Desulfurization.

The oxidative desulfurization (ODS) of fuel oils is of great significance for environmental protection, and the development of efficient ODS heterogeneous catalysts is highly desired. Herein, we have designed and synthesized a novel material of amorphous Cr2WO6-modified WO3 (a-Cr2WO6/WO3) nanowires (3-6 nm) with a large specific surface area of 289.5 m2·g-1 and rich Lewis acid sites. The formation of such a unique nanowire is attributed to the adsorption of Cr3+ cations on non-(001) planes of WO3. In the ODS process, the a-Cr2WO6/WO3 nanowires can efficiently oxidize benzothiophene (BT), dibenzothiophene (DBT), and 4,6-dimethyldibenzothiophene (4,6-DMDBT) to their corresponding sulfones in a quasi-microemulsion reaction system and possess the highest activity (Ea = 55.4 kJ/mol) for DBT: 99.0% of 15,000 ppm DBT with 2600 ppm S can be removed (70 °C, H2O2 as the oxidant). The improvement in ODS activity from most of WO3 catalysts is owing to the sufficient active sites and enhanced adsorption of DBT on the basis of structural features of a-Cr2WO6/WO3 nanowires. Combined with free radical capture experiments, a possible ODS mechanism of W(O2) peroxotungstate route based on surface -OH groups is reasonably proposed. Moreover, the a-Cr2WO6/WO3 nanowires have good stability and can be synthesized on a large scale, suggesting its potential applications as an efficient heterogeneous catalyst.

Ultrawide bandgap AlN metasurfaces for ultraviolet focusing and routing.

All-dielectric metasurfaces offer a promising way to control amplitude, polarization, and phase of light. However, ultraviolet (UV) component metasurfaces are rarely reported due to significant absorption loss for most dielectric materials and the required smaller footprint or feature size. Here, we demonstrate broadband UV focusing and routing in both transmission and reflection modes in simulations by adopting aluminum nitride (AlN) with ultrawide bandgap and a waveplate metasurface structure. As for experiments, the on-axis, off-axis focusing characteristics in transmission mode have been investigated at representative UVA (375 nm) wavelength for the first time, to the best of our knowledge. Furthermore, we fabricated a UV transmission router for monowavelength, guiding UV light to the designated different spatial positions of the same or different focal planes. Our work is meaningful for the development of UV photonics components and devices and would facilitate the integration and miniaturization of UV nanophotonics.

Three-dimensional metal-semiconductor-metal AlN deep-ultraviolet detector.

Conventional metal-semiconductor-metal (MSM) ultraviolet (UV) detectors have the disadvantage of limited adjustable structural parameters, finite electrical field, and long carrier path. In this Letter, we demonstrate a three-dimensional (3D) MSM structural AlN-based deep-UV (DUV) detector, fabricated through simple trench etching and metal deposition, while flip bonding to the silicon substrate forms a flip-chip 3D-MSM (FC-3DMSM) device. 3D-MSM devices exhibit improved responsiveness and response speed, compared with conventional MSM devices. Time-dependent photoresponse of all devices is also investigated here. The enhanced performance of the 3D-MSM device is to be attributed to the intensified electrical field from the 3D metal electrode configuration and the inhibition of the carrier vertical transport, which unambiguously increases the carrier collection efficiency and migration speed, and thus the responsivity and speed as well. This work should advance the design and fabrication of AlN-based DUV detectors.

Design of AlN ultraviolet metasurface for single-/multi-plane holography.

The metasurface promises an unprecedented way for manipulating wavefronts and has strengths in large information capacity for the hologram. However, strong absorption loss for most dielectric materials hinders the realization of such a metasurface operating in the ultraviolet (UV) spectrum. Herein, aluminum nitride (AlN) with an ultrawide bandgap has been utilized as the material of the UV metasurface for multi-plane holography, increasing the information capacity and security level of information storage simultaneously. The metasurface for multi-plane holography achieving a correlation coefficient of over 0.8 with three reconstructed images has been investigated, and also the single-plane holography at an efficiency of 34.05%. Our work might provide potential application in UV nanophotonics.

Exploring how Chinese adults living with spinal cord injury viewed the prospect of inpatient peer support programs within a hospital-based rehabilitation setting.

STUDY DESIGN: Generic qualitative design. OBJECTIVES: To explore how Chinese adults living with spinal cord injury (SCI) viewed the prospect of inpatient peer support programs within a rehabilitation setting. SETTING: Hospital in China. METHODS: A purposive sample of adult inpatients with SCI (N = 6) currently undergoing rehabilitation was recruited. Each participant was interviewed twice. Twelve interview transcripts were analyzed using a thematic method. RESULTS: Five higher-order themes were developed. First, participants had unique backgrounds and personal lives before and after their SCI and reported frustrations about their lives resulting from their SCI. Second, participants reported varying degrees of satisfaction with their rehabilitation and identified the facilitators and barriers to their rehabilitation. Third, their perspectives on peer support were shaped by their rehabilitation goals. For example, participants who solely focused on the recovery of physical functioning noted that peers could help to supplement existing rehabilitation programming by guiding their rehabilitation exercises. Participants who concentrated on their future lives believed peers could teach them new skills to facilitate their integration in the community. However, some participants felt they could not trust peers' advice because peers are not healthcare providers. Fourth, peer support delivery options varied from online chat groups (i.e., WeChat), in-person conversations, and mentoring lectures. Finally, anticipated outcomes were related to obtaining practical and emotional support from peers, being motivated, and feeling understood. CONCLUSIONS: Participants harbored mixed views on potential use-value and necessity of hospital-based peer support programs, which could inform future utilization of SCI peer support within Chinese hospitals.

CoP/RGO-Pd Hybrids with Heterointerfaces as Highly Active Catalysts for Ethanol Electrooxidation.

The ethanol oxidation reaction is of critical importance to the commercial viability of direct ethanol fuel cell technology. However, owing to the poor C-C bond cleavage capability, almost all ethanol oxidation is incomplete and suffers from low selectivity toward the C1 pathway. Herein, under the support of theoretical calculations that the heterointerfaces between CoP and Pd can reduce the energy barrier of C-C bond cleavage, rich heterointerfaces in CoP/RGO-Pd hybrids were designed to improve ethanol electrooxidation performance through enhancing the selectivity toward the C1 pathway. The experimental results show that the faradaic efficiency of the C1 pathway of CoP/RGO-Pd hybrids is as high as 27.6%, surpassing most reported catalysts in the literature. As a result of this enhancement, CoP/RGO-Pd10 exhibits mass activity as high as 4597 mA·mgPd-1 and specific activity as high as 10 mA·cm-2, which are much higher than those of other Pd-based electrocatalysts.

Removal of trace Cr(VI) from aqueous solution by porous activated carbon balls supported by nanoscale zero-valent iron composites.

In this study, porous activated carbon balls supported by nanoscale zero-valent iron composites (Fe@PACB-700) were used for the first time for the removal of trace Cr(VI) from aqueous solutions. The Fe@PACB-700 composites were prepared by a facile carbothermal reduction method and then characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray diffraction analysis (XRD), and X-ray photoelectron spectroscopy (XPS). The results show that nZVI particles have been successfully loaded onto PACBs. Fe@PACB-700 shows an excellent Cr(VI) removal efficiency of 91.2%. The maximum adsorption capacity of Fe@PACB-700 for Cr(VI) is 22.24 mg/g, which is 4.36 times that of PACB. The residual Cr(VI) concentration is below 20 ppb with the use of 0.15 g of Fe@PACB-700, which is much lower than the allowable concentration for Cr(VI) in drinking water (0.05 mg/L). The adsorption of Cr(VI) can be well described by the Langmuir isotherm model and pseudo-second-order kinetic model. Fe@PACB-700 still has a high removal efficiency of 80% after five cycles. Thus, Fe@PACB-700 has a great potential for Cr(VI) removal from aqueous solution. Graphical abstract.