Mechanically tough large‐area hierarchical porous graphene films are fabricated by blade‐casting of graphene oxide hydrogel and postcasting reduction. The as‐prepared graphene films, which consist of ...well‐exfoliated graphene nanosheets, possess interpenetrating 3D hierarchical porous structures, high strength and modulus, large specific area, and high electrical conductivity. Flexible film supercapacitors fabricated with the graphene electrodes show superior areal capacitance, good rate performance, and excellent mechanical stability.
Plants are exposed to increasingly severe drought events and roots play vital roles in maintaining plant survival, growth, and reproduction. A large body of literature has investigated the adaptive ...responses of root traits in various plants to water stress and these studies have been reviewed in certain groups of plant species at a certain scale. Nevertheless, these responses have not been synthesized at multiple levels. This paper screened over 2000 literatures for studies of typical root traits including root growth angle, root depth, root length, root diameter, root dry weight, root-to-shoot ratio, root hair length and density and integrates their drought responses at genetic and morphological scales. The genes, quantitative trait loci (QTLs) and hormones that are involved in the regulation of drought response of the root traits were summarized. We then statistically analyzed the drought responses of root traits and discussed the underlying mechanisms. Moreover, we highlighted the drought response of 1-D and 2-D root length density (RLD) distribution in the soil profile. This paper will provide a framework for an integrated understanding of root adaptive responses to water deficit at multiple scales and such insights may provide a basis for selection and breeding of drought tolerant crop lines.
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•Porous BiVO4 microtubes photocatalysts are multiply modified with inorganic acids.•The modified sample carries more surface negative charges compared with pristine ...one.•Chlortetracycline degradation rate could be enhanced by ~3 times, up to 88% in 2 h.•It is due to promoted ·OH generation by negative field according to degradation path.
Photocatalysis is generally considered as a promising candidate to treat antibiotics in wastewater. The weak adsorption of target molecule makes the degradation largely depend on the dissociative hydroxyl radical oxidation pathway. In this work, porous BiVO4 microtubes were co-modified with H3PO4 and H3BO3 by using glycerol as a “bridge” to increase their surface polarity which was supposed to accelerate the generation rate of hydroxyl radical in chlortetracycline degradation. Our results show that the co-modified BiVO4 microtubes showed obviously enhanced efficiency in chlortetracycline degradation, its reaction rate is 2.0 and 3.8 times of solely modified with H3PO4 and pristine BiVO4 microtubes. We attributed this enhancement to the accelerated generation of free hydroxyl radicals by the ionization of hydroxyl groups in modifying inorganic acid, which increases the intensity of surface electric field. The surface electric field will result in tendentious migration of holes to the surface of BiVO4 microtubes to take catalytic reactions, and thus improve the separation rate of photogenerated charges. The degradation pathway of chlortetracycline was analyzed to reveal the mechanism underlying the enhanced catalytic activity. This work provides a feasible strategy to improve the catalytic degradation efficiency of photocatalysts to weak-adsorbed organic pollutant through surface polarization.
Highly flexible porous carbon nanofibers (P-CNFs) were fabricated by electrospining technique combining with metal ion-assistant acid corrosion process. The resultant fibers display high conductivity ...and outstanding mechanical flexibility, whereas little change in their resistance can be observed under repeatedly bending, even to 180°. Further results indicate that the improved flexibility of P-CNFs can be due to the high graphitization degree caused by Co ions. In view of electrode materials for high-performance supercapacitors, this type of porous nanostructure and high graphitization degree could synergistically facilitate the electrolyte ion diffusion and electron transportation. In the three electrodes testing system, the resultant P-CNFs electrodes can exhibit a specific capacitance of 104.5 F g–1 (0.2 A g–1), high rate capability (remain 56.5% at 10 A g–1), and capacitance retention of ∼94% after 2000 cycles. Furthermore, the assembled symmetric supercapacitors showed a high flexibility and can deliver an energy density of 3.22 Wh kg–1 at power density of 600 W kg–1. This work might open a way to improve the mechanical properties of carbon fibers and suggests that this type of freestanding P-CNFs be used as effective electrode materials for flexible all-carbon supercapacitors.
The recombination of photocarriers is a crucial factor that affects the performance of photocatalysts. Rationally designing the architecture of heterojunction photocatalysts is an effective strategy ...to inhibit the recombination through boosting photocarrier separation and transport. Herein, a Z-scheme WS2/In2S3 photocatalyst with a bi-layered sheet-like structure was synthesized and investigated by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, electron paramagnetic resonance, and Mott–Schottky measurements. The characterization results demonstrated that the unique architecture can reduce the charge transfer distance and provide more surface area to promote the photocatalytic reaction. Moreover, the Z-scheme structure effectively separates photocarriers while retaining their strong redox capability. Thus, a remarkable photocatalytic activity for H2 generation and tetracycline hydrochloride degradation has been achieved. The results showed that the optimal 50 wt% Z-scheme WS2/In2S3 composite exhibited the highest H2 generation rate of 592.9 μmol g−1 h−1, and the best tetracycline hydrochloride degradation efficiency of 90% within 60 min. In addition, the bi-layered Z-scheme photocatalyst also exhibited excellent stability and recyclability. This work provides a new idea to promote the separation and transfer of photocarriers by building Z-scheme composite photocatalysts with appropriate nano building blocks, like nanosheets.
Hydrogen production over nano-sized BiVO4 is achieved benefiting from elevated conduction band, enlarged specific surface area and promoted charge separation.
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Owing to excellent light ...absorption and high activity for oxygen evolution, monoclinic bismuth vanadate (BiVO4) is regarded as an ideal candidate for photocatalytic water splitting. However, its application is limited by the large particle size in micrometer scale, as well as the slightly positive conduction band. In this work, we successfully synthesized nano-BiVO4 with particle size ranged from 27 nm to 57 nm by wet chemical method based on electrostatic spinning method. Unlike bulk BiVO4, the nano-sized BiVO4 possesses the ability to generate hydrogen by water splitting, and the activity could reach up to 1.66 μmol h−1 g−1 with the assistance of Pt. The enhanced activity is mainly attributed to the improvements resulted from reduced particle size, which includes elevated conduction band, enlarged specific surface area and promoted charge separation. This work provides a simple method for synthesizing photocatalyst with small particle size and high yield.
In this paper, a silicon rich nitride–lithium niobate on insulator hybrid platform with waveguides and several key components is proposed. The propagation loss of the silicon rich nitride–lithium ...niobate rib-loaded waveguide (300 × 300 nm2) is 0.86 dB/cm at 1550 nm. Passive devices, including adiabatic power splitters, multimode interferometer-based splitters, asymmetrical Mach–Zehnder interferometers, and Bragg grating filters, are fully designed and characterized. Moreover, we report a Mach–Zehnder modulator with high-speed modulation up to 120 GBaud without digital compensation. The electro-optical response with 1 dB roll-off at 40 GHz is obtained, and the 3-dB modulation bandwidth is predicted to be >100 GHz. Hence, the proposed platform enables high-performance passive and active devices with low loss and high integration density, making it a promising candidate for emerging photonics integrated circuits.
A stretchable and semi-transparent epidermal thin film heater (TFH) has been fabricated by using silver nanowire (Ag NW) networks as a Joule heat generator and polydimethylsiloxane (PDMS) as a ...stretchable and transparent matrix. The device is a conductive layer of interconnected Ag NWs sandwiched with two layers of PDMS. The output power and transparency of the device were rationally tuned by adjusting the Ag NW amount. Our results show that the device transparency at 600 nm decreases from 70% to 46% when we tuned the sheet resistance of Ag NW layer from 30.0 Ω/□ to 5.4 Ω/□. The TFH shows a favorable stretchability, and it can almost completely recover when we applied a strain up to 200% or after a fatigue test of 1000 cycles, 50% in strain. The ultimate temperature in air reached up to 81 °C when we applied an electric field of 1.0 V/cm. Its epidermal heating performance was simulated by warming a piece of pork, and it can make the subcutaneous temperature increase 12 °C. A model to evaluate the heating performance of TFHs with thermal capacity per-unit area, device resistance and energy conversion efficiency was also proposed, which will fatally determine their heating rate and ultimate temperature.
One of the most exciting new developments in energy storage technology is flexible Zn‐ion hybrid supercapacitors (f‐ZIHSCs), which combine the high energy of Zn‐ion batteries with high‐power ...supercapacitors to satisfy the needs of portable flexible electronics. However, the development of f‐ZHSCs is still in its infancy, and there are numerous barriers to overcome before they can be widely implemented for practical applications. This review gives an up‐to‐date description of recent achievements and underlying concepts in energy storage mechanisms of f‐ZIHSCs and emphasizes the critical role of cathode, anode, and electrolyte materials systems in speeding the prosperity of f‐ZIHSCs. The innovative nanostructured‐based cathode materials for f‐ZIHSCs include carbon (e.g., porous carbon, heteroatom‐doped carbon, biomass‐derived porous carbon, graphene, etc.), metal‐oxides, MXenes, and metal/covalent‐organic frameworks, and other materials (e.g., activated carbon, phosphorene, etc.) are mainly focused. Afterward, the latest developments in flexible anode and electrolyte frameworks and impacts of electrolyte compositions on the electrochemical properties of f‐ZIHSC are elaborated. Subsequently, the advancements based on fabrication designs, including quasi‐solid‐state, micro, fiber‐shaped, and all climate‐changed f‐ZIHSCs, are discussed in detail. Lastly, a summary of current challenges and recommendations for the future progress of advanced f‐ZIHSC are addressed. This review article is anticipated to further understand the viable strategies and achievable approaches for assembling high‐performance f‐ZIHSCs and boost the technical revolutions on cathode, anode, and electrolytes for f‐ZIHSC devices.
This review gives an up‐to‐date description of recent achievements and underlying concepts in energy storage mechanisms of flexible Zn‐ion hybrid supercapacitors (f‐ZIHSCs) and emphasizes the critical role of cathode, anode, and electrolyte materials systems in speeding the prosperity of f‐ZIHSCs. Subsequently, the advancements based on fabrication designs, including quasi‐solid‐state, micro, fiber‐shaped, and all climate‐changed f‐ZIHSCs, are discussed in detail.
Strain-gated piezotronic transistors have been fabricated using vertically aligned ZnO nanowires (NWs), which were grown on GaN/sapphire substrates using a vapor–liquid–solid process. The gate ...electrode of the transistor is replaced by the internal crystal potential generated by strain, and the control over the transported current is at the interface between the nanowire and the top or bottom electrode. The current–voltage characteristics of the devices were studied using conductive atomic force microscopy, and the results show that the current flowing through the ZnO NWs can be tuned/gated by the mechanical force applied to the NWs. This phenomenon was attributed to the piezoelectric tuning of the Schottky barrier at the Au–ZnO junction, known as the piezotronic effect. Our study demonstrates the possibility of using Au droplet capped ZnO NWs as a transistor array for mapping local strain. More importantly, our design gives the possibility of fabricating an array of transistors using individual vertical nanowires that can be controlled independently by applying mechanical force/pressure over the top. Such a structure is likely to have important applications in high-resolution mapping of strain/force/pressure.
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