Augmented reality display with high eyebox uniformity over the full field of view based on a random mask grating.

Ensuring uniform illuminance in waveguide-based augmented reality (AR) display devices is crucial for providing an immersive and comfortable visual experience. However, there is a lack of a straightforward and efficient design method available to achieve illuminance uniformity over the full field of view. To address this issue, we propose a novel design that utilizes random mask gratings (RMGs) as the folding grating and the out-coupling grating. Unlike traditional approaches that modify the grating structure, we control the diffraction efficiency distribution by adjusting the filling factor of the mask while keeping the grating structure unchanged in one RMG. The grating structures are designed and optimized based on rigorous coupled wave analysis and particle swarm optimization. The feasibility of our method is verified by the simulation results in Lighttools. In the FOV range of 20°×15°, the eyebox uniformities of all fields are greater than 0.78, which can provide a good visual experience for users.

Sodium lignosulfonate/graphene composites for efficient desalination by incorporating CoS to control pore size.

The phenomenon of overlapping double layers due to micropores inhibits capacitive deionization performance, which is improved by increasing the pore size. In this study, a novel ternary composite electrode (sodium lignosulfonate/reduced graphene oxide/cobalt sulfide, LGC) was designed using a two-step hydrothermal method. CoS with high pseudocapacitance modifies sodium lignosulfonate and graphene connected by hydrogen bonding, benefiting from the constitutive steric structure. The electrochemical performance was significantly enhanced, and the desalination capacity substantially improved. The LGC electrode specific capacitance was as high as 354.47 F g-1 at a 1 A g-1 current density. The desalination capacity of the capacitive deionization device comprising LGC and activated carbon in 1 M NaCl electrolyte reached 28.04 mg g-1 at an operating condition of 1.2 V, 7 mL min-1. Additionally, the LGC electrodes degraded naturally post the experiment by simply removing the CoS, suggesting that the LGC composites are promising material for capacitive deionization electrodes.

Sodium alginate/sodium lignosulfonate hydrogel based on inert Ca2+ activation for water conservation and growth promotion.

Soil degradation has become a major global problem owing to the rapid development of agriculture. The problems of soil drought and decreased soil fertility caused by soil degradation severely affect the development of the agricultural and forestry industries. In this study, we designed sodium alginate (SA)/sodium lignosulfonate (SLS) hydrogel based on the activation and crosslinking of inert Ca2+. CaCO3 and SA were mixed, and then, inert Ca2+ was activated to prepare a gel with a stable structure and a uniform interior and exterior. The crosslinking activated by inert Ca2+ enhanced the stability of the hydrogel, and the optimal swelling rate of the hydrogel reached 28.91 g/g, thereby effectively improving the water-holding capacity of the soil (77.6-108.83 g/kg). SLS was degraded into humic acid (HA) and gradually released, demonstrating a positive growth-promoting effect in plant growth experiments. The SA/SLS hydrogel can be used for soil water retention and mitigation to significantly decrease the water loss rate of soil. This study will assist in addressing soil drought and fertility loss.

Custom-designed polyphenol lignin for the enhancement of poly(vinyl alcohol)-based wood adhesive.

Adhesives are used extensively in the wood industry. As resource and environmental issues become increasingly severe, the development of green and sustainable biomass-based adhesives has attracted increasing attention. In this work, a green wood adhesive is developed from poly(vinyl alcohol) and lignin with molecular designs of lignin extending beyond those in nature. The lignin undergoes extraction from corncob residue, aldehydration, and phenolisation (phenol, resorcinol, and catechol) to significantly increase the phenolic hydroxyl groups (over 7.92 mmol/g), which has the effect of enhancing the hydrogen bonding force between the adhesive and the wood, thereby greatly improving adhesive performance. Compared with pure PVA, polyphenol lignin-containing PVA showed improved adhesion strength and hydrophobicity. PVA/resorcinol-lignin has the significantly improved wood lap shear strength (6.27 MPa, 77.6 % improvement) and hydrophobicity (almost 100 % increase in wet shear strength). This research not only provides a green and high-performance alternative raw material for wood adhesives but also broadens the path for large-scale application of biomass.

Fan-in/fan-out for heterogeneous 19-core fibers based on metasurfaces with nonuniform phase plates.

In space-division-multiplexed transmission systems, it is essential to realize fan-in/fan-out devices that connect the cores between multicore fibers and single-mode fibers. In this Letter, we propose a metasurface-based fan-in/fan-out device with nonuniform phase plates for heterogeneous 19-core fibers across the full C band. Our results show that an average insertion loss of 0.85 dB and a maximum crosstalk of -25.5 dB can be achieved at 1550 nm. Across the C band, the insertion loss and crosstalk are better than 2.78 dB and -19.96 dB, respectively. The proposed concept can flexibly handle various fiber configurations without additional complexity.

RGO-Induced Flower-like Ni-MOF In Situ Self-Assembled Electrodes for High-Performance Hybrid Supercapacitors.

Currently, the primary bottlenecks that hinder the widespread application of supercapacitors are low energy density and narrow potential windows. Herein, the hybrid supercapacitor with high energy density and wide potential window is constructed via an in situ self-assembly method employing RGO-induced flower-like MOF(Ni). Benefiting from the synergistic effect between RGO and MOF(Ni), the interfacial interactions are effectively improved, and the contact area with the electrolyte is enhanced, which increases the ion transfer kinetics and overall electrochemical performance. The MOF(Ni)@RGO electrode exhibits a specific capacitance of 1267.73 F g-1 at a current density of 1 A g-1. Crucially, the assembled MOF(Ni)@RGO//BC with a broad potential window and good stability employing a MOF(Ni)@RGO anode and biomass carbon cathode, combined with a 2 M PVA-KOH gel-electrolyte, achieves a maximum energy density of 70.16 Wh kg-1 at a power density of 2200.09 W kg-1, outperforming most reported supercapacitors. This hybrid supercapacitor exhibits excellent stability and high energy density, providing a novel strategy for further large-scale applications.

Hybrid waveguide based augmented reality display system with extra large field of view and 2D exit pupil expansion.

For a waveguide display device, the field of view (FOV) is a key parameter for evaluating its optical performance. To address this issue, we propose a hybrid waveguide system, which is composed of two projectors, two in-couplers, two half-mirror arrays and an out-coupler. We use two projectors to generate the left and right parts of the output image separately, which can increase the upper limit of the FOV significantly. Unlike conventional waveguide-based system, we use half-mirror arrays instead of folding gratings to realize 2D exit pupil expansion. By doing so, the total internal reflection condition can always be met during the pupil expansion process. To solve the difficulty in designing collimating optical system with large FOV, we propose a method of tilting the projection system. The hybrid waveguide system can realize a FOV of 88°(H) × 53°(V).

Bandgap engineering control bifunctional MnxCd1-xS photocatalysts selectively reforming xylose to C3 organic acids and efficient hydrogen production.

The simultaneous reforming of biomass into high value-added chemicals and H2 production by water splitting in a green and environmentally clean way is a very challenging task. Herein, we demonstrate the design of bifunctional MnxCd1-xS photocatalyst with a controllable band gap by bandgap engineering. Bandgap engineering effectively regulates the oxidation and reduction capacity of materials. The design of photocatalysts with suitable conduction bands and valence bands makes the targeted conversion of xylose possible. Innovative conversion of xylose to glyceric acid, lactic acid, and propanoic acid. The optimized Mn0.7Cd0.3S catalyst showed excellent performance in the production of H2 (14.06 mmol·gcat-1·h-1, 29.9 times more than CdS and 351.5 times more than MnS), xylose conversion (90%), and C3 organic acid yield (59.2%) without cocatalyst and any scavengers under visible light irradiation. This work shows that a rational photocatalyst design can achieve efficient simultaneous production of high value-added chemicals and clean energy.

Constructing 3D hierarchical TiO2 microspheres with enhanced mass diffusion for efficient glucose photoreforming under modulated reaction conditions.

Three-dimensional (3D) TiO2 hierarchical microspheres (THMs) were successfully prepared via a facial template-free hydrothermal approach. The possible growth mechanism of THM was also investigated by TiCl4 concentration-, time-, and temperature-dependent experiments. The results indicate that the formation of an urchin-like hierarchical structure may follow a "nucleation-dissolution and recrystallization-assembly" process. THM was employed for photoreforming under various catalyst and glucose concentrations, solvent compositions, and pH values. The H2 production rate, glucose conversion, arabinose and formic acid selectivity reached 9.44 mmol gcat.-1h-1, 86.35%, 11.32%, and 46.87%, respectively, under the modulated condition with Pt as cocatalyst; this is attributed to the enhanced mass diffusion caused by the 3D hierarchical morphology as well as the interaction between unsaturated Ti atoms (or oxygen vacancies) in THM and the hydroxyl oxygen atoms on glucose. In addition, the enhanced light absorption induced by defects also exerts a positive effect. In this work, we present an emerging sustainable strategy for the coproduction of H2 and value-added chemicals from biomass-based glucose with economic photocatalysts under mild conditions.

Rapid fabrication of tough sodium alginate/MXene/poly(vinyl alcohol) dual-network hydrogel electrolytes for flexible all-solid-state supercapacitors.

With the rapid development of flexible portable devices, polymer-based hydrogel electrolytes have drawn tremendous attention and widespread interest to replace conventional liquid electrolytes. Herein, an eco-friendly, low cost and fast method was adopted to synthesize novel cross-linked dual-network hydrogel electrolytes (PVA/SA/MXene-NaCl) within 5 min due to the formation of borate bonds. The unique dual-network structure of hydrogel enabled hydrogel electrolytes to efficiently dissipate energy under deformation and the formation of borate bonds endowed hydrogel with self-healing ability. Benefited from the introduction of NaCl and MXene, the hydrogels displayed a high ionic conductivity (40.8 mS/cm) and enhanced mechanical strength (650 kPa). Notedly, the flexible supercapacitor with low concentration of NaCl (0.3 mol L-1) delivered a superior areal capacitance of 130.8 mF cm-2 at 1 mA cm-2 and 106.2 mF cm-2 at 3 mA cm-2, and simultaneously offered remarkable capacitance retention under the state of bending, self-healing (five cycles), compression and stretching. Moreover, as-assembled supercapacitor maintained about 88.9 % of its original capacitance and 90.5 % of Coulombic efficiency after 5000 charge-discharge cycles. Our research presented a simple and universally pathway to prepare flexible energy storage devices with excellent mechanical and electrochemical properties.

Bidirectional wide-angle waveguide grating antennas with flat-top far-field patterns for optical phased arrays.

To build advanced all solid-state LiDAR, optical phased arrays (OPAs) with a large field of view are highly desirable. As a critical building block, a wide-angle waveguide grating antenna is proposed here. Instead of aiming at the elimination of downward radiation of waveguide grating antennas (WGAs) to improve efficiencies, we in turn utilize the downward radiation and double the range of beam steering. In addition to widened field of views, the steered beams in two directions come from a common set of power splitters, phase shifters and antennas, which greatly reduces chip complexity and power consumption, especially for large-scale OPAs. Beam interference and power fluctuation in the far field due to downward emission can be decreased by specially designed SiO2/Si3N4 antireflection coating. The WGA exhibits balanced emissions in both the upward and downward directions, in which the field of view in each direction is more than 90°. The normalized intensity remains almost the same with a small variation of 10% from -39° to 39° for the upward emission and from -42° to 42° for the downward emission. This WGA is featured by a flat-top radiation pattern in far field, high emission efficiency and good tolerance to device fabrication errors. It holds good potential to achieve wide-angle optical phased arrays.

Sodium alginate-based gel electrodes without binder for high-performance supercapacitors.

Binder use results in an expansion of the dead volume of the active material and a decline in the active sites, which will lead to a decrease in the electrochemical activity of the electrode. Therefore, the construction of electrode materials without the binder has been the research focus. Here, a novel ternary composite gel electrode without the binder (reduced graphene oxide/sodium alginate/copper cobalt sulfide, rGSC) were designed using a convenient hydrothermal method. Benefiting from the dual-network structure of rGS via the hydrogen bonding between rGO and sodium alginate not only better encapsulates CuCo2S4 with high pseudo-capacitance, but also simplifies the electron transfer path, and reduces the electron transfer resistance, which leads to a remarkable enhanced electrochemical performance. The rGSC electrode exhibits a specific capacitance of up to 1600.25 F g-1 when the scan rate is 10 mV s-1. The asymmetric supercapacitor was constructed with rGSC and activated carbon as the positive and negative electrode in a 6 M KOH electrolyte. It has a large specific capacitance and high energy/power density (10.7 Wh kg-1/1329.1 W kg-1). This work proposes a promising strategy for designing gel electrodes for higher energy density and larger capacitance without the binder.

Composite film with adjustable number of layers for slow release of humic acid and soil remediation.

In this study, to improve the soil amendment performance of film materials, composite films with the adjustable number of layers and controlled slow-release time were prepared using sodium alginate (SA), chitosan (CS) and activated charcoal (AC) as raw materials. The prepared multilayer films exhibited a wide pH response range and excellent slow-release time. The cumulative release of humic acid (HA) increased from 19.87 ± 0.98% to 66.72 ± 1.06% with increasing the pH from 4.0 to 10.0 after 700 h of slow-release. In addition, after 50 d of remediation in red soil, plantation soil, and saline soil, the NH4+-N, Olsen-P, Olsen-K, and organic matter contents in the three soils were increased by 2.91-28.62 mg/kg, 46.97-70.43 mg/kg, 55.89-77.01 mg/kg, and 12.47-22.52 g/kg, respectively, and were able to provide sustained crop growth promotion effect. This study demonstrates the promising application of multilayer film in soil remediation and agricultural production.

Biomass-derived carbon dots regulating nickel cobalt layered double hydroxide from 2D nanosheets to 3D flower-like spheres as electrodes for enhanced asymmetric supercapacitors.

Layered double hydroxides (LDHs) often require the use of carbon materials to improve their stability, conductivity, and specific surface area to accommodate new directions in the development of high-performance energy storage materials. Herein, 2D nickel cobalt layered double hydroxide (NCLDH) nanosheets are regulated to form 3D flower-like spheres by fungus bran-derived carbon dots (CDs) via an in situ growth method. The prepared sample (CDs/NCLDH) shows abundant accessible active sites and favorable electrical conductivity, which is aided by strong interactions between CDs and NCLDH. The optimized CDs/NCLDH exhibits significantly enhanced electrochemical performances, including ultrahigh specific capacitance (2100F g-1 at 1 A g-1) and a great rate capability, which are two times higher than those of the NCLDH electrode. Additionally, the asymmetric supercapacitor device assembled with the CDs/NCLDH positive electrode and the fungus bran-derived activated carbon (FBC) negative electrode achieves a superior energy density of 52.5 Wh kg-1 at an ultrahigh powder density of 750 W kg-1. With their simple synthesis method and excellent electrochemical performance, the role of the CDs provides new insights for the development of LDHs with improved performance.

Effective enhancement of electron migration and photocatalytic performance of nitrogen-rich carbon nitride by constructing fungal carbon dot/molybdenum disulfide cocatalytic system.

To find a cocatalyst that can replace noble metals, fungal carbon dot (CD) modified molybdenum disulfide (MoS2) cocatalyst system was designed. The composites were prepared by hydrothermal and calcination methods with different ratios of CDs, MoS2 and nitrogen-rich carbon nitride (p-C3N5). p-C3N5 has excellent electronic properties, and MoS2 modified by CDs (D-MoS2) can significantly enhance the photocatalytic performance of p-C3N5 by improving the photogenerated electron migration efficiency. The experiments showed that the developed CDs/MoS2/C3N5 composites exhibited excellent performance in both photocatalytic hydrogen (H2) evolution and methylene blue (MB) degradation, with CMSCN5 (D-MoS2 with 5% mass fraction) showing the best photocatalytic activity. The corresponding H2 evolution rate of CMSCN5 was 444 µmol g-1h-1 and 1.45 times higher than that of unmodified p-C3N5, by 120 min, the removal rate of MB was up to 93.51%. The 5 cycle tests showed that CMSCN5 had great stability. The high charge mobility and high density of H2 evolution active sites of MoS2 nanosheets, together with the electron storage and transfer properties of CDs can obviously improve electron migration and reduce the photogenerated carrier recombination on the p-C3N5 surface. The design and preparation of such composites offer broad prospects for the development of photocatalytic systems with noble metal-free cocatalysts.

Biomimetic nitrogen-rich photocatalyst based on cadmium sulfide for photocatalytic hydrogen evolution.

A novel N-rich sugarcane-like photocatalyst CdS/C3N5 (CCN) was prepared by a thermal polymerization method and tested for generating H2 and realizing antiphotocorrosive performance. The best photocatalytic H2 evolution is obtained for a CdS to C3N5 mass ratio of 1:1 (CCN3), which is nearly 33 and 3 times higher than that of pure C3N5 and CdS, respectively. CCN3 can be used to effectively reduce CdS photocorrosion and increase stability because of its N-rich performance and sugarcane-like structure, which can affect electron transport and enhance the internal binding force, respectively. CCN3 can maintain a high H2 evolution ability after 5 cycles, while still maintaining the original sugarcane-like shape, which has an anti-photocorrosive ability.

Integrated Instillation Technology for the Synthesis of a pH-Responsive Sodium Alginate/Biomass Charcoal Soil Conditioner for Controlled Release of Humic Acid and Soil Remediation.

In this work, pH-responsive gel spheres for controlled release of humic acid (CSGCHs) were prepared by an integrated instillation technology using a composite material of sodium alginate (SA) and charcoal activated carbon (CAC) as a carrier, and their slow-release performance, pH-responsive performance, and soil amendment performance were investigated. The results showed that the prepared CSGCH was uniform in size with obvious base responsiveness. Soil remediation experiments revealed that CSGCH could play a good role in the remediation of different types of soils. After 50 days of remediation, the content of nutrients and organic matter in the soil increased significantly and the pH and salt content of saline soils decreased by 15.2 and 29.8%, respectively. The plant experiment showed that CSGCH could effectively promote the growth of crops. Therefore, the prepared soil conditioner has a great potential value for improving soil conditions and promoting crop growth in agricultural applications.

Polarization-controlled efficient and unidirectional surface plasmon polariton excitation enabled by metagratings in a generalized Kretschmann configuration.

In this paper, we propose a generalized Kretschmann configuration that employs a metagrating to replace the prism, realizing polarization-controlled efficient and unidirectional surface plasmon polariton (SPP) excitation. This dielectric phase gradient metagrating on the top surface of a silica substrate is designed to deflect incident light, which subsequently launches SPP wave by means of momentum matching on the metal film coated on the bottom surface. A series of metagratings is designed to enable the SPP excitation by circularly or linearly polarized incident light. The flexibility and tunability of this design to efficiently control SPPs show potential to find wide applications in diverse integrated optics and SPP devices.

Constructing CeO2/nitrogen-doped carbon quantum dot/g-C3N4 heterojunction photocatalysts for highly efficient visible light photocatalysis.

Ternary CeO2/nitrogen-doped carbon quantum dot (NCQD)/graphitic carbon nitride (g-C3N4) heterojunction nanocomposites were prepared by a high-temperature calcination and hydrothermal method and tested for degrading tetracycline (TC) and generating H2. Compared with CeO2 and g-C3N4, the Z-scheme CeO2/NCQDs/g-C3N4 (CSNx, where x represents the amount of CeO2 in wt%) nanoparticles showed a higher TC photodegradation capacity and H2 evolution ability owing to enhanced efficient charge separation and photocatalytic stability. CSN5 showed the best photodegradation activity for TC degradation (100 mL, 20 mg L-1; 100% degradation in 60 min; λ≥ 420 nm) and the highest H2 evolution rate of 1275.42 µmol h-1 g-1 was approximately 3.73- and 32.25-times higher than those of pristine g-C3N4 (341.85 µmol h-1 g-1) and pure CeO2 (39.55 µmol h-1 g-1), respectively. Superoxide (˙O2-) and hydroxyl (˙OH) radicals were also confirmed to be formed on the sample surface for TC photocatalytic degradation. As an electronic medium, NCQDs transferred electrons between the g-C3N4 and CeO2 interface to promote the electron-hole separation. This work affords a helpful perspective for synthesizing efficient charge separation and environmentally friendly photocatalysts by controlling the surface heterostructure.