7 research outputs found

    Partial Conversion of Current Collectors into Nickel Copper Oxide Electrode Materials for High-Performance Energy Storage Devices

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    A novel substrate sacrifice process is proposed and developed for converting part of a current collector into supercapacitor active materials, which provides a new route in achieving high energy density of supercapacitor device. Part of a copper foam current collector is successfully converted into highly porous nickel copper oxide electrode for light- and high-performance supercapacitors. Remarkably, this strategy circumvents the problem associated with poor contact interface between electrode and current collector. Meanwhile, the overall weight of the supercapacitor could be minimized. The charge transfer kinetics is improved while the advantage of the excellent mechanical properties of metal current collector is not traded off. By virtue of this unique current collector self-involved architecture, the material derived from the current collector manifests large areal capacitance of 3.13 F cm<sup>–2</sup> at a current density of 1 A g<sup>–1</sup>. The capacitance can retain 2.97 F cm<sup>–2</sup> at a much higher density (4 A g<sup>–1</sup>). Only a small decay of 6.5% appears at 4 A g<sup>–1</sup> after 1600 cycles. The strategy reported here sheds light on new strategies in making additional use of the metal current collector. Furthermore, asymmetric supercapacitor using both solid-state gel electrolyte and liquid counterpart are obtained and analyzed. The liquid asymmetric supercapacitor can deliver a high energy density up to 0.5 mWh cm<sup>–2</sup> (53 Wh kg<sup>–1</sup>) at a power density of 13 mW cm<sup>–2</sup> (1.4 kW kg<sup>–1</sup>)

    Nanoparticle-Mediated Mechanical Destruction of Cell Membranes: A Coarse-Grained Molecular Dynamics Study

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    The effects of binding mode, shape, binding strength, and rotational speed of actively rotating nanoparticles on the integrity of cell membranes have been systematically studied using dissipative particle dynamics simulations. With theoretical analyses of lipid density, surface tension, stress distribution, and water permeation, we demonstrate that the rotation of nanoparticles can provide a strong driving force for membrane rupture. The results show that nanoparticles embedded inside a cell membrane via endocytosis are more capable of producing large membrane deformations under active rotation than nanoparticles attached on the cell membrane surface. Nanoparticles with anisotropic shapes produce larger deformation and have a higher rupture efficiency than those with symmetric shapes. Our findings provide useful design guidelines for a general strategy based on utilizing mechanical forces to rupture cell membranes and therefore destroy the integrity of cells

    Direct Z‑Scheme TiO<sub>2</sub>/NiS Core–Shell Hybrid Nanofibers with Enhanced Photocatalytic H<sub>2</sub>‑Production Activity

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    Photocatalytic water splitting to generate hydrogen (H<sub>2</sub>) is a sustainable approach for solving the current energy crisis. A novel TiO<sub>2</sub>/NiS core–shell nanohybrid was fabricated where few-layer NiS nanoplates were deposited on TiO<sub>2</sub> skeletons via electrospinning and hydrothermal methods. The NiS nanoplates with a thickness of ca. 28 nm stood vertically and uniformly upon the TiO<sub>2</sub> nanofibers, guaranteeing intimate contact for charge transfer. XPS analysis and DFT calculation imply that the electrons in NiS would transfer to TiO<sub>2</sub> upon hybridization, which creates a built-in electric field at the interfaces and thus facilitates the separation of useful electron and hole upon photoexcitation. <i>In-situ</i> XPS analysis directly proved that the photoexcited electrons in TiO<sub>2</sub> migrated to NiS under UV–visible light irradiation, suggesting that a direct Z-scheme heterojunction was formed in the NiS/TiO<sub>2</sub> hybrid. This direct Z-scheme mechanism greatly promotes the separation of useful electron–hole pairs and fosters efficient H<sub>2</sub> production. The hybrid nanofibers unveiled a high H<sub>2</sub>-production rate of 655 μmol h<sup>–1</sup> g<sup>–1</sup>, which was 14.6-fold of pristine TiO<sub>2</sub> nanofibers. Isotope (<sup>4</sup>D<sub>2</sub>O) tracer test confirmed that H<sub>2</sub> was produced from water, rather than from any H-containing contaminants. This work provides an alternative approach to rationally design and synthesize TiO<sub>2</sub>-based photocatalysts with direct Z-scheme pathways toward high-efficiency photogeneration of H<sub>2</sub>

    Rupture of Lipid Membranes Induced by Amphiphilic Janus Nanoparticles

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    The surface coatings of nanoparticles determine their interaction with biomembranes, but studies have been limited almost exclusively to nanoparticles with a uniform surface chemistry. Although nanoparticles are increasingly made with complex surface chemistries to achieve multifunctionalities, our understanding of how a heterogeneous surface coating affects particle–biomembrane interaction has been lagging far behind. Here we report an investigation of this question in an experimental system consisting of amphiphilic “two-faced” Janus nanoparticles and supported lipid membranes. We show that amphiphilic Janus nanoparticles at picomolar concentrations induce defects in zwitterionic lipid bilayers. In addition to revealing the various effects of hydrophobicity and charge in particle–bilayer interactions, we demonstrate that the Janus geometrythe spatial segregation of hydrophobicity and charges on particle surfacecauses nanoparticles to bind more strongly to bilayers and induce defects more effectively than particles with uniformly mixed surface functionalities. We combine experiments with computational simulation to further elucidate how amphiphilic Janus nanoparticles extract lipids to rupture intact lipid bilayers. This study provides direct evidence that the spatial arrangement of surface functionalities on a nanoparticle, rather than just its overall surface chemistry, plays a crucial role in determining how it interacts with biological membranes

    Dopamine Modified g‑C<sub>3</sub>N<sub>4</sub> and Its Enhanced Visible-Light Photocatalytic H<sub>2</sub>‑Production Activity

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    Photocatalytic water splitting is a promising strategy to convert solar energy into chemical energy. Herein, a series of g-C<sub>3</sub>N<sub>4</sub>/polydopamine (g-C<sub>3</sub>N<sub>4</sub>/PDA) composites were successfully fabricated by in situ polymerization of dopamine on the g-C<sub>3</sub>N<sub>4</sub> surface. Among all the as-prepared composites, the best photocatalytic hydrogen evolution rate of the as-prepared composites was up to 69 μmol h<sup>–1</sup> under the irradiation of visible light (λ > 420 nm), which was about 4.5 times than that of pristine g-C<sub>3</sub>N<sub>4</sub> (16 μmol h<sup>–1</sup>). The enhancement of photocatalytic H<sub>2</sub> evolution is reasonably attributed to the markedly enhanced light harvesting, broadened spectral response range and low onset potential of H<sub>2</sub> production, as well as effective separation and rapid transportation of photogenerated charge carriers. More importantly, the surface modification of g-C<sub>3</sub>N<sub>4</sub> by a small amount of PDA can effectively inhibit the overgrowth of Pt nanoparticles (NPs) during the photocatalytic reactions, which promotes the photoelectron injection and better photocatalytic activity. This work should provide a new insight into preparing metal-free polymer–polymer composites with effective solar energy conversion

    Rupture of Lipid Membranes Induced by Amphiphilic Janus Nanoparticles

    No full text
    The surface coatings of nanoparticles determine their interaction with biomembranes, but studies have been limited almost exclusively to nanoparticles with a uniform surface chemistry. Although nanoparticles are increasingly made with complex surface chemistries to achieve multifunctionalities, our understanding of how a heterogeneous surface coating affects particle–biomembrane interaction has been lagging far behind. Here we report an investigation of this question in an experimental system consisting of amphiphilic “two-faced” Janus nanoparticles and supported lipid membranes. We show that amphiphilic Janus nanoparticles at picomolar concentrations induce defects in zwitterionic lipid bilayers. In addition to revealing the various effects of hydrophobicity and charge in particle–bilayer interactions, we demonstrate that the Janus geometrythe spatial segregation of hydrophobicity and charges on particle surfacecauses nanoparticles to bind more strongly to bilayers and induce defects more effectively than particles with uniformly mixed surface functionalities. We combine experiments with computational simulation to further elucidate how amphiphilic Janus nanoparticles extract lipids to rupture intact lipid bilayers. This study provides direct evidence that the spatial arrangement of surface functionalities on a nanoparticle, rather than just its overall surface chemistry, plays a crucial role in determining how it interacts with biological membranes

    Enhanced Performance of Planar Perovskite Solar Cell by Graphene Quantum Dot Modification

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    In organic–inorganic halide perovskite solar cells (PSCs), the perovskite layer is the main source of photogenerated electron–hole pairs. Therefore, the premier concern in PSCs is to improve the quality of the perovskite film (PF). In the present research, graphene quantum dots (GQDs) were prepared and incorporated in the perovskite precursor, and due to the merits of dangling bonds, quantum size, and excellent electronic conductivity of GQDs, PF of higher-quality with flat surface and pinhole-free hallmarks was garnered. It is delightful that the PFs with GQDs exhibit higher light absorption and faster charge extraction. Consequently, the power conversion efficiency (PCE) of PSCs incorporating GQDs achieves an improvement of 11% compared with the pristine ones. Our work confirms that incorporating GQDs is a viable approach to obtain high-quality PF with more efficient charge extraction for superior planar PSCs
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