Here, we present a facile technique to design self-supported 3D N-doped graphene foam (NGF) via simply annealing in chemical vapor deposition furnace which used powder metallurgy nickel template and ...melamine as both carbon and nitrogen source. The NGF possesses highly conductive and interconnected mesoporous network. Particularly nitrogen-doping provided strong polysulfide immobilization ability, significantly suppressing the shuttle effect. The NGF was directly used as binder-free electrode which delivered a high initial discharge capacity of 987 mA h g−1 and maintains at 819 mA h g−1 after 200 cycles at 0.2 C, corresponding to 82.9% capacity retention. Specifically, even at high current density of 2 C, it still possesses a good long life cycle performance (from 633.8 mA h g−1 to 440.3 mA h g−1 after 500 cycles, with ultralow capacity fading rate of 0.061% per cycle). 7Li nuclear magnetic resonance (7Li NMR) suggested strong interaction between NGF and polysulfide. Moreover, X-ray photoelectron spectroscopy and density function theory calculation further revealed the strong interaction mostly ascribed to chemisorption and physisorption of polysulfide by pyridinic and pyrrolic nitrogen, respectively. As we know this method-based NGF as binder free electrode was first reported, which provided an effective strategy for developing high-performance Li/S batteries.
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The fine structure of the wing scale of a Morpho Peleides butterfly was examined carefully, and the entire configuration was completely replicated by a uniform Al2O3 coating through a low-temperature ...ALD process. An inverted structure was achieved by removing the butterfly wing template at high temperature, forming a polycrystalline Al2O3 shell structure with precisely controlled thickness. Other than the copy of the morphology of the structure, the optical property, such as the existence of PBG, was also inherited by the alumina replica. Reflection peaks at the violet/blue range were detected on both original wings and their replica, while a simple alumina coating shifted the reflection peak to longer wavelength because of the change of periodicity and refraction index. The alumina replicas also exhibited similar functional structures as waveguide and beam splitter, which may be used as the building blocks for photonic ICs with high reproducibility and lower fabrication cost compared to traditional lithography techniques.
When the in vitro research works of biosensing begin to mimic in vivo conditions, some certain three-dimensional (3D) structures of biosensors are needed to accommodate biomolecules, bacteria or even ...cells to resemble the in vivo 3D environment. To meet this end, a novel method of synthesizing CuO nanoflowers on the 3D graphene foam (GF) was first demonstrated. The 3DGF/CuO nanoflowers composite was used as a monolithic free-standing 3D biosensor for electrochemical detection of ascorbic acid (AA). The 3D conductive structure of the GF is favorable for current collection, mass transport and loading bioactive chemicals. And CuO nanoflowers further increase the active surface area and catalyze the redox of AA. Thus, all these features endows 3DGF/CuO composite with outstanding biosensing properties such as an ultrahigh sensitivity of 2.06mAmM−1cm−2 to AA at 3s response time.
•The synthesis of 3D graphene foam (GF)/CuO nanoflowers composite was proposed.•The 3DGF provides vast area and a well-organized conducting freestanding network.•CuO nanoflowers maximize the surface area, transfer electrons between 3DGF and AA.•3DGF/CuO has an ultrahigh sensitivity of 2.06mAmM−1cm−2 to AA.•3DGF/CuO could be a smart sensing platform to support cells and detect analytes.
•The ingenious GOx/p-NiO/n-Bi4Ti3O12 sandwich structure prevents the leakage of enzyme effectively.•A desirable nanostructure of p-n heterojunction contributes to the efficient separation of ...electron-hole pairs.•Co-catalysis of GOx and p-NiO/n-Bi4Ti3O12 heterojunctio plays a synergetic role in gaining performance boosts.•The novel biosensor remedies the limitation of enzyme-based glucose sensor due to its ultrahigh sensitivity.
A glucose oxidase (GOx) based p-NiO/n-Bi4Ti3O12 sandwich heterojunction was fabricated and explored as a glucose electrochemical sensor. The constructed GOx/p-NiO/n-Bi4Ti3O12 sandwich structure effectively prevents the leakage of GOx. Dandelion-like Bi4Ti3O12 nanowires were directly grown on the titanium foil substrates, and dense NiO nanoparticles were deposited by employing pulsed laser deposition at room temperature. Amperometric measurements towards glucose were carried out, and efficient direct electron transfer was successfully achieved. The enzyme biosensor showed a linear range from 20 μM to 3.55 mM (R = 0.999) with an ultrahigh sensitivity of 215 μA mM−1 cm−2, response time within 2 s, low detection limit of 1.26 μM (S/N = 3) and high specificity. The apparent Michaelis-Menten constant (Km app) was estimated to be 0.22 mM. Intercrossed nanowires and interconnected pores favor the electrons transfer and the massive GOx loading. Binder-free feature leads to a seamless connection between Bi4Ti3O12 nanowires and the substrate. Co-catalysis of GOx and p-NiO/n-Bi4Ti3O12 heterojunction plays a synergetic role in gaining performance boosts. The GOx based p-NiO/n-Bi4Ti3O12 heterojunction biosensor remedies the limitation of enzyme-based glucose sensor and be potentially applied in practice.
Due to the unique properties of room temperature ionic liquids (RTILs), most researchers' interest in RTIL-based electrolytes in electric double-layer capacitors (EDLCs) stems from molecular ...simulations, which are different from experimental scientific research fields. The knowledge of RTIL-based electrolytes in EDLCs began with a supposition obtained from the results of molecular simulations of molten salts. Furthermore, experiments and simulations were promoted and developed rapidly on this topic. In some instances, the achievements of molecular simulations are ahead of even those obtained from experiments in quantity and quality. Molecular simulations offer more information on the impacts of overscreening, quasicrowding, crowding, and underscreening for RTIL-based electrolytes than experimental studies, which can be helpful in understanding the mechanisms of EDLCs. With the advancement of experimental technology, these effects have been verified by experiments. The simulation prediction of the capacitance curve was in good agreement with the experiment for pure RTILs. For complex systems, such as RTIL-solvent mixtures and RTIL mixture systems, both molecular simulations and experiments have reported that the change in capacitance curves is not monotonous with RTIL concentrations. In addition, there are some phenomena that are difficult to explain in experiments and can be well explained through molecular simulations. Finally, experiments and molecular simulations have maintained synchronous developments in recent years, and this paper discusses their relationship and reflects on their application.
It is commonly considered that the morphology and interface of semiconductor–reduced graphene oxide (rGO) composite photocatalysts play a crucial role in determining their photocatalyzing ...performance. Herein, we report on the design and synthesis of BiVO4–rGO nanocomposites with efficient interfacial contact by self-assembly of positively charged amorphous BiVO4 powders with negatively charged graphene oxide (GO), followed by a one-step GO reduction and BiVO4 crystallization via hydrothermal treatment. The as-prepared BiVO4–rGO nanocomposites exhibit high visible light photocatalytic efficiency for the degradation of model dyes, and are significantly superior to bare crystalline BiVO4 and BiVO4–rGO–U that is hydrothermally synthesized using the mixture of GO nanosheets and BiVO4 powders without modification of surface charge. Using multiple characterization techniques, we found that the enhanced photocatalytic performance of BiVO4–rGO arises from the synergistic effects between the microscopic crystal structure of BiVO4 with smaller particle size and more sufficient interfacial interaction between BiVO4 and graphene sheets, leading to increased photocatalytic reaction sites, extended photoresponding range, enhanced photogenerated charge separation, and transportation efficiency. This work may provide a rational and convenient strategy to construct highly efficient semiconductor–rGO nanocomposite photocatalysts with well-contacted interface toward environmental purification and solar energy conversion.
In an era of intense partisanship, there is widespread concern that people are self-sorting into separate online communities which are detached from one another. Referred to as echo chambers, the ...phenomenon is sometimes attributed to the new media landscape and internet ecosystem. Of particular concern is the idea that communication between disparate groups is breaking down due to a lack of a shared reality. In this article, we look to evaluate these assumptions. Applying text and semantic network analyses, we study the language of users who represent distinct partisan political ideologies on Reddit and their discussions in light of the January 6, 2021, Capitol Riots. By analyzing over 58k posts and 3.4 million comments across three subreddits, r/politics, r/democrats, and r/Republican, we explore how these distinct groups discuss political events to understand the possibility of bridging across echo chambers. The findings of this research study provide insight into how members of distinct online groups interpret major political events.
Controlled synthesis of spinel ZnFe2O4 nanoparticle-decorated ZnO nanofiber heterostructures was carried out with regularly varied particle sizes and uniform distribution. The obtained ...heterostructures possessed enhanced intrinsic peroxidase-like activity, and the activities regularly changed as the sizes of ZnFe2O4 nanoparticles varied. The heterostructures were further applied in sensitive colorimetric biosensing of urine glucose.
Gasoline vehicles are a major source of anthropogenic secondary organic aerosols (SOAs). However, current models based on known precursors fail to explain the substantial SOAs from vehicle emissions ...due to the inadequate understanding of the formation mechanism. To provide more information on this issue, the formation of SOAs from ozonolysis of four light-duty gasoline vehicle exhaust systems was investigated with a vacuum ultraviolet photoionization mass spectrometer (VUV-PIMS). Remarkable SOAs formation was observed and the SOAs were primarily aliphatic alkenes. PI mass spectra of the SOAs from all vehicles exhibited similar spectral patterns (a regular mass group with m/z at 98, 112, 126 …). Interestingly, most carbonyl products of aliphatic alkenes observed as major gaseous products have specific molecular weights, and the main formation pathway of SOAs can be explained well using aldol condensation reactions of these carbonyls. This is a direct observation of the aldol condensation as a dominated pathway for SOAs formation, and the first report on the composition and formation mechanism of the SOAs from the ozonolysis of gasoline vehicle exhaust is given. The study reveals that low molecular weight alkenes may play a more significant role in vehicle-induced SOAs formation than previously believed. More importantly, the PI mass spectra of SOAs from vehicles show similarities to the field aerosol sample mass spectra, suggesting the possible significance of the aldol condensation reactions in ambient aerosol formation. Since carbonyls are a major degradation product of biogenic and anthropogenic VOCs through atmospheric oxidation processes, the mechanism proposed in this study can be applied more generally to explain aerosol formation from the oxidation of atmospheric hydrocarbons.
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•Ozonolysis of gasoline vehicle exhausts were on-line monitored with a VUV-PIMS.•Carbonyl derivatives were obtained as major gas-phase products.•Composition of SOA from ozonolysis of vehicle exhausts was analyzed.•Formation mechanism of SOA from ozonolysis of vehicle exhaust was proposed.
Aldol condensation of carbonyls resulting from the oxidation of aliphatic alkenes was proposed to explain SOA formation from vehicle exhaust.
In this study, we examined the fine structure of the compound eyes of a household fly and precisely replicated its entire structure using a low-temperature atomic layer deposition technique. The ...surface of the fly eye is found to be covered by highly packed protuberances, which potentially increases visual efficiency through increased photon capture for a given stimulus. The alumina replica was achieved by removing the fly compound eye template at high temperature, and the alumina coating was crystallized simultaneously. Besides the morphology, the unique antireflection property was also inherited by the alumina replica. By measuring the reflective spectra of the replica, we demonstrated that the alumina replica of a fly eye was an efficient antireflection structure of visible light at an incident angle up to 80°. Such a grating would be particularly useful on a cured corneal surface since it could increase the transmission of incident light through the cornea compared with a smooth surface.
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