Anchoring vertically grown CoMn-LDH nanosheets on 3D hierarchical porous N,P co-doped graphene aerogel frameworks forms an sufficient bifunctional oxygen electrocatalyst for rechargeable zinc-air ...battery.
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Exploiting the low-cost and high-efficiency bifunctional oxygen electrocatalysts to substitute platinum-group metals is highly desirable but challenging for energy storage/conversion technologies. Herein, we develop a combined gelation/self-assemble/freeze drying process to fabricate a free-standing porous architectures through vertical anchoring two-dimensional (2D) CoMn-LDH nanosheets on three-dimensional (3D) hierarchical N,P co-doped graphene aerogels (NPGA) framework. This unique configuration endows CoMn-LDH/NPGA outstanding catalytic activity toward both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) with a potential difference of ca. 0.72 V between the OER potential at 10 mA cm−2 and the ORR potential at −3 mA cm−2, which is comparable to commercial Pt/C + IrO2 benchmarks, and therefore renders the CoMn-LDH/NPGA assembled zinc-air battery a superior rechargeable performance and cycling stability. In-depth structure-to-property correlation indicates that the prominent bifunctional activity of CoMn-LDH/NPGA are ascribed to large electrochemical active surface area, the rapid mass/charge transfers, the increased exposure and full utilization of active sites originated from the synergistic effect between the uniformly dispersed 2D CoMn-LDH nanosheets and the 3D hierarchical porous NPGA framework.
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•Natural bornite, a kind of Fe-Cu bimetallic sulfide mineral, was used as a cost-effective persulfate activator.•Reductive sulfur in natural bornite could enhance the regeneration of ...Fe2+.•The dominant reactive oxygen species responsible for TC degradation were OH, SO4− and O2−.•The catalytic mechanism and degradation pathways of TC was proposed.
Natural bornite (NBo), a kind of Fe-Cu bimetallic sulfide mineral, was selected as an efficient activator for persulfate (PS) to degrade a typical antibiotic, tetracycline (TC). The removal percentage of TC got up to 81.6% in 180 min in the NBo/PS system with a mineralization efficiency of 48.7%. Experiment results showed that the released Fe had played a more important role than Cu in the degradation process. Reductive sulfur in the NBo catalyst could enhance the regeneration of Fe2+ and thus improve the degradation efficiency of TC by activated PS. The results of radical-quenching and electron paramagnetic resonance tests demonstrated that the dominant reactive oxygen species responsible for TC degradation were OH, SO4− and O2− in the NBo/PS system. The generated O2− was originated from dissolved oxygen rather than PS, but PS could accelerate the reduction process of O2 to O2− by NBo. NBo dosage, PS concentration, initial solution pH and common inorganic anions (Cl− and H2PO4−) all had significant effects on TC removal. NBo was considerable stable in catalyzing PS for TC degradation. This work demonstrates an efficient and cost-effective catalyst towards PS for organic pollutant removal and provides new insight into the mechanism of heterogeneous activation of PS by Fe-Cu bimetallic sulfide.
Sodium and calcification roasting processes are traditional technologies to recover vanadium from vanadium slag. However, these processes are associated with many drawbacks, including high energy ...consumption, serious environment pollution, and the inability to simultaneously extract associated titanium resources. In this paper, a novel technology for simultaneous extraction of vanadium and titanium from vanadium slag was proposed, in which the vanadium slag was roasted with recyclable (NH4)2SO4 (AS) at moderately high temperatures followed by dilute H2SO4 leaching. To enhance the extraction, an activation pretreatment of the vanadium slag through high-temperature water quenching was employed. The results demonstrated that the activation significantly accelerated the extraction, with the vanadium and titanium extraction increasing by 16% and 12%, respectively, compared with the raw vanadium slag. The extraction of vanadium and titanium were 91% and 77%, respectively, after roasting at an AS-to-vanadium slag mass ratio of 4:1 and 370 °C followed by leaching in a 6% H2SO4 solution. X-ray diffraction analysis indicated that the spinel phases in the vanadium slag, such as FeV2O4, Fe2TiO3, and Fe2MnO4, began to transform into (NH4)3V(SO4)3, (NH4)3Fe(SO4)3, (NH4)2Mn(SO4)2, and TiSO4 at 320 °C and a nearly complete conversion could be achieved at 370 °C. The mass ratio of AS to vanadium slag significantly affected the extraction of both vanadium and titanium, which increased with the increasing mass ratio until an 8:1 ratio was achieved, after which, the extraction decreased. A stratification phenomenon of the vanadium slag and ammonium bisulfate at high AS/slag mass ratios was observed, which could be responsible for the decreasing extraction.
•V and Ti were extracted simultaneously from vanadium slag.•Water quenching process was employed to activate vanadium slag.•Transformation rules of vanadium slag were confirmed during AS roasting process.•The mechanism of efficient extraction of V and Ti was confirmed.
All‐dielectric metasurfaces provide a powerful platform for a new generation of flat optical devices, in particular, for applications in telecommunication systems, due to their low losses and high ...transparency in the infrared. However, active and reversible tuning of such metasurfaces remains a challenge. This study experimentally demonstrates and theoretically justifies a novel scenario of the dynamical reversible tuning of all‐dielectric metasurfaces based on the temperature‐dependent change of the refractive index of silicon. How to design an all‐dielectric metasurface with sharp resonances by achieving interference between magnetic dipole and electric quadrupole modes of constituted nanoparticles arranged in a 2D lattice is shown. Thermal tuning of these resonances can cause drastic but reciprocal changes in the directional scattering of the metasurface in a spectral window of 75 nm. This change can result in a 50‐fold enhancement of the radiation directionality. This type of reversible tuning can play a significant role in novel flat optical devices including the metalenses and metaholograms.
Via controlling the temperature and employing the right combination of the electric and magnetic resonant responses of the metasurfaces, drastic and reciprocal interchanges in directional scattering are demonstrated experimentally and theoretically. At 1425 nm forward to backward ratio variation from 1 to >50 can be obtained. The results provide an important step toward tunable nanophotonic components and all‐optical circuitry on a chip.
Iron oxyhydroxide (FeOOH) as heterogeneous catalyst has been widely used in Fenton-like advanced oxidation processes due to its attractive properties such as wide-operating pH range and controllable ...iron leaching into solution. However, little is known about the Fe3+/Fe2+ transformation of supported FeOOH catalyst under the external electrical field condition, which is of the essence in electro-Fenton-like oxidation reactions. In this study, activated carbon-supported nano-FeOOH (FeOOH/AC) catalysts were prepared by the air oxidation of ferrous hydroxide suspension method. The as-prepared catalyst was characterized with various characterization techniques and identified as goethite and lepidocrocite mixed crystals. Adsorption and electrochemically assisted oxidation of amaranth with the FeOOH/AC heterogeneous catalysts were investigated at pH 4.0 using graphite felt as cathode. Under weak acidic and external electric field conditions, the supported nano-FeOOH catalyst undergoes proton-promoted dissolution and electrochemical reductive dissolution processes, which facilitates Fe3+/Fe2+ transformation and produces a beneficial enhancement of the heterogeneous/homogeneous electro-Fenton reaction rates. Experimental results demonstrated that the FeOOH/AC heterogeneous catalyst possesses admirable adsorbability, and the electrochemically assisted oxidation of amaranth takes place not only through the heterogeneous Fenton reaction on catalyst/solution interface but also through the homogeneous Fenton reaction in bulk solution due to iron liberation from the supported nano-FeOOH. In addition, a possible electrochemically assisted oxidation mechanism is also proposed.
This study aimed to explore if viable
avirulent Nine Mile phase II (NMII) can elicit protective immunity against virulent NM phase I (NMI) infection. Interestingly, mice immunized with viable NMII ...elicited significant protection against NMI infection at different time points post-immunization. Viable NMII induced a dose-dependent NMI-specific IgG response in mice, but all doses of NMII-immunized mice conferred a similar level of protection. Comparing different routes of immunization indicated that intranasally immunized mice showed significantly higher levels of protection than other immunization routes. The observation that viable NMII induced a similar level of long-term protection against NMI challenge as the formalin-inactivated NMI vaccine (PIV) suggests that viable NMII bacteria can induce a similar level of long-term protection against virulent NMI challenge as the PIV. Viable NMII also induced significant protection against challenge with virulent Priscilla and Scurry strains, suggesting that viable NMII can elicit broad protection. Immune sera and splenocytes from viable NMII-immunized mice are protective against NMI infection, but immune serum-receiving mice did not control NMI replication. Additionally, viable NMII conferred a comparable level of protection in wild-type, CD4
T cell-deficient, and CD8
T cell-deficient mice, and partial protection in B cell-deficient mice. However, NMII-immunized T cell-deficient mice were unable to prevent
replication. Thus, both B cells and T cells are required for viable NMII-induced protective immunity but T cells may play a critical role. Collectively, this study demonstrates the feasibility of using avirulent NMII as a live attenuated vaccine against human Q fever.
Non‐volatile memory cells using Co‐doped BaTiO3 as an active layer exhibit high‐performance unipolar resistive switching characteristics, with a resistance ratio over 104, retention time longer than ...7 × 104 s, endurance over 105 cycles, and switching speed less than 10 ns/70 ns for SET/RESET. Under high electric field and large Joule heating, the easily varied valence of Co ions, the pre‐existing oxygen vacancies with sufficiently high density, and the local itinerant electrons introduced by the Co‐doping all favor the local metal‐insulator phase transition and therein the formation/rupture of conductive filaments, contributing to the stable resistive switching.
► The activity of anammox bacteria can be enhanced in dose-dependent manner of GO. ► The maximum 10.26% increase in activity is obtained at a GO dose of 0.1 g L-1. ► The appropriate GO dose can ...efficiently stimulate the increase of EPS. ► GO can be used as a scaffold for anammox bacteria attachment.
Graphene oxide (GO) was applied in this study to enhance the activity of anaerobic ammonium oxidation (anammox) bacteria for nitrogen removal. A GO dose-dependent effect on anammox bacteria was observed through batch tests. The results showed that the activity increased as the GO dose was varied within 0.05–0.1gL−1. A maximum 10.26% increase of anaerobic ammonium oxidizing activity was achieved at 0.1gL−1 GO. Analysis of extracellular polymeric substances (EPS) indicated that the highest carbohydrate, protein, and total EPS contents (42.5, 125.7, and 168.2mg (g volatile suspended solids)−1, respectively) were obtained with 0.1gL−1 GO. Appropriate GO dose stimulated EPS production to promote the activity of anammox bacteria. Transmission electron microscopy showed the large surface area of GO benefited cell attachment. These findings proved that the application of GO was an effective approach to enhancing the activity of anammox bacteria.
The multivesicular liposome (MVL) provides a potential delivery approach to avoid the destruction of the structure of drugs by digestive enzymes of the oral cavity and gastrointestinal system. It ...also serves as a sustained-release drug delivery system. In this study, we aimed to incorporate a water-soluble substance into MVLs to enhance sustained release, prevent the destruction of drugs, and to expound the function of different components and their mechanism. MVLs were prepared using the spherical packing model. The morphology, structure, size distribution, and zeta potential of MVLs were examined using an optical microscope (OM), confocal microscopy (CLSM), transmission electron cryomicroscope (cryo-EM) micrograph, a Master Sizer 2000, and a zeta sizer, respectively. The digestion experiment was conducted using a bionic mouse digestive system model in vitro. An in vitro release and releasing mechanism were investigated using a dialysis method. The average particle size, polydispersity index, zeta potential, and encapsulation efficiency are 47.6 nm, 1.880, -70.5 ± 2.88 mV, and 82.00 ± 0.25%, respectively. The studies on the controlled release in vitro shows that MVLs have excellent controlled release and outstanding thermal stability. The angiotensin I-converting enzyme (ACE) inhibitory activity of ACE-inhibitory peptide (AP)-MVLs decreased only 2.84% after oral administration, and ACE inhibitory activity decreased by 5.03% after passing through the stomach. Therefore, it could serve as a promising sustained-release drug delivery system.
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