144 research outputs found

    Sulfonated Graphene Nanosheets as a Superb Adsorbent for Various Environmental Pollutants in Water

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    Graphene nanosheets, as a novel nanoadsorbent, can be further modified to optimize the adsorption capability for various pollutants. To overcome the structural limits of graphene (aggregation) and graphene oxide (hydrophilic surface) in water, sulfonated graphene (GS) was prepared by diazotization reaction using sulfanilic acid. It was demonstrated that GS not only recovered a relatively complete sp<sup>2</sup>-hybridized plane with high affinity for aromatic pollutants but also had sulfonic acid groups and partial original oxygen-containing groups that powerfully attracted positively charged pollutants. The saturated adsorption capacities of GS were 400 mg/g for phenanthrene, 906 mg/g for methylene blue and 58 mg/g for Cd<sup>2+</sup>, which were much higher than the corresponding values for reduced graphene oxide and graphene oxide. GS as a graphene-based adsorbent exhibits fast adsorption kinetic rate and superior adsorption capacity toward various pollutants, which mainly thanks to the multiple adsorption sites in GS including the conjugate π region sites and the functional group sites. Moreover, the sulfonic acid groups endow GS with the good dispersibility and single or few nanosheets which guarantee the adsorption processes. It is great potential to expose the adsorption sites of graphene nanosheets for pollutants in water by regulating their microstructures, surface properties and water dispersion

    Scalable and Environmentally Friendly Synthesis of Hierarchical Magnetic Carbon Nanosheet Assemblies and Their Application in Water Treatment

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    Large-scale assembling of graphitic carbon nanosheets to a three-dimensional hierarchical structure is a great challenge. Herein we report a facile synthesis of hierarchical magnetic carbon nanosheet assemblies (MCNSAs) via an ambient-pressure chemical vapor deposition method. To explore the formation mechanism, the as-prepared MCNSAs as well as the intermediates of synthesis were extensively characterized. It was revealed that two different carbon deposition processes, i.e., the dissolution–precipitation process and graphitic defects triggered catalytic decomposition of methane, were involved in the formation of MCNSAs. The disclosed method is simple and environmentally friendly, which is favorable for large-scale production. The resulting MCNSAs possess large surface areas, bimodal pore structures, abundant defective sites, excellent chemical stability, and sufficient magnetism. Such features afford significant advantages for application in water cleaning. As a proof of concept, the sorption performance of MCNSAs is demonstrated by using Congo red and Pb<sup>2+</sup> as model pollutants. The characteristics of the sorption process including kinetics, isotherms, recovery, regeneration, and recycling are investigated. The results indicate that the MCNSAs are a promising sorbent for water cleaning

    Environmental Applications of Three-Dimensional Graphene-Based Macrostructures: Adsorption, Transformation, and Detection

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    Just as graphene triggered a new gold rush, three-dimensional graphene-based macrostructures (3D GBM) have been recognized as one of the most promising strategies for bottom-up nanotechnology and become one of the most active research fields during the last four years. In general, the basic structural features of 3D GBM, including its large surface area, which enhances the opportunity to contact pollutants, and its well-defined porous structure, which facilitates the diffusion of pollutant molecules into the 3D structure, enable 3D GBM to be an ideal material for pollutant management due to its excellent capabilities and easy recyclability. This review aims to describe the environmental applications and mechanisms of 3D GBM and provide perspective. Thus, the excellent performance of 3D GBM in environmental pollutant adsorption, transformation and detection are reviewed. Based on the structures and properties of 3D GBM, the removal mechanisms for dyes, oils, organic solvents, heavy metals, and gas pollutants are highlighted. We attempt to establish “structure–property–application” relationships for environmental pollution management using 3D GBM. Approaches involving tunable synthesis and decoration to regulate the micro-, meso-, and macro-structure and the active sites are also reviewed. The high selectivity, fast rate, convenient management, device applications and recycling utilization of 3D GBM are also emphasized

    Constructing Three-Dimensional Hierarchical Architectures by Integrating Carbon Nanofibers into Graphite Felts for Water Purification

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    Developing high-performance nanostructured sorbents for water treatment is of great importance. Herein, we report a facile strategy to fabricate three-dimensional hierarchical architectures by integrating carbon nanofibers (CNFs) into macroscopic graphite felt (GF) supports. The physicochemical properties of CNF@GF monoliths including surface areas, densities, porosities, and pore structures could be conveniently tuned by varying reaction time. The CNF@GF monoliths were utilized as advanced sorbents for the removal of Pb<sup>2+</sup>, Congo red, organic solvents, and oils from aqueous solutions. The characteristics of adsorption processes including kinetics, isotherms, and regeneration were investigated. It is demonstrated that the CNF@GF exhibits outstanding performance for water treatment in terms of adsorption capacities, recovering, and recyclability. As such, the versatile CNS@GF monoliths show great application potential for water treatment

    Ternary Platinum–Copper–Nickel Nanoparticles Anchored to Hierarchical Carbon Supports as Free-Standing Hydrogen Evolution Electrodes

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    Developing cost-effective and efficient hydrogen evolution reaction (HER) electrocatalysts for hydrogen production is of paramount importance to attain a sustainable energy future. Reported herein is a novel three-dimensional hierarchical architectured electrocatalyst, consisting of platinum–copper–nickel nanoparticles-decorated carbon nanofiber arrays, which are conformally assembled on carbon felt fabrics (PtCuNi/CNF@CF) by an ambient-pressure chemical vapor deposition coupled with a spontaneous galvanic replacement reaction. The free-standing PtCuNi/CNF@CF monolith exhibits high porosities, a well-defined geometry shape, outstanding electron conductivity, and a unique characteristic of localizing platinum–copper–nickel nanoparticles in the tips of carbon nanofibers. Such features render PtCuNi/CNF@CF as an ideal binder-free HER electrode for hydrogen production. Electrochemical measurements demonstrate that the PtCuNi/CNF@CF possesses superior intrinsic activity as well as mass-specific activity in comparison with the state-of-the-art Pt/C catalysts, both in acidic and alkaline solutions. With well-tuned composition of active nanoparticles, Pt<sub>42</sub>Cu<sub>57</sub>Ni<sub>1</sub>/CNF@CF showed excellent durability. The synthesis strategy reported in this work is likely to pave a new route for fabricating free-standing hierarchical electrodes for electrochemical devices

    In Situ Assembly of Ultrathin PtRh Nanowires to Graphene Nanosheets as Highly Efficient Electrocatalysts for the Oxidation of Ethanol

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    One-dimensional (1D) anisotropic platinum-based nanowires are promising electrocatalysts in polymer electrolyte membrane fuel cells owing to the inherent structural merits. Herein, we report an in situ growth of ultrathin PtRh nanowires (diameters of 2–3 nm) on graphene nanosheets via the oriented attachment pathway. Mechanistic studies reveal that graphene nanosheets play a critical role in the nucleation and growth of PtRh nanowires. The resulting hybrid of PtRh nanowire decorated graphene nanosheets shows outstanding activity and durability toward ethanol electro-oxidation. It exhibits a specific current density of 2.8 mA cm<sup>–2</sup> and a mass-normalized current density of 1 A mg<sup>–1</sup> metal, which are 5.4 and 3.1 times those of the state-of-the-art Pt/C catalyst, respectively. After 2000 cyclic tests, it maintains 86% of the initial electrochemically active surface area, which is larger than that of 63% obtained from the Pt/C catalyst. The superior performance is attributed to the combination of the advantageous 1D morphological motif with the synergistic effects of PtRh alloys and graphene nanosheet support

    Photocaged Nanoparticle Sensor for Sensitive MicroRNA Imaging in Living Cancer Cells with Temporal Control

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    Sensitive imaging of microRNA in living cells is of great value for disease diagnostics and prognostics. While signal amplification-based strategies have been developed for imaging low-abundance disease-relevant microRNA molecules, precise temporal control over sensor activity in living cells still remains a challenge, and limits their applications for sensing microRNA concentration dynamics. Herein, we report a class of photocaged nanoparticle sensors for highly sensitive imaging of microRNA in living cells with temporal control. The sensor features a DNA-templated gold nanoparticle-quantum dot satellite nanostructure which is temporarily inactivated by a photocaged DNA mask. Upon UV light irradiation, the sensor restores its activity for catalytic sensing of microRNA in living cells via entropy-driven two-step toehold-mediated strand displacement reactions. We show that the sensor exhibits quick response to UV light, robust intracellular stability, and high specificity and sensitivity for the microRNA target. On the basis of this strategy, precise control over sensor activity is achieved using an external light trigger, where on-demand sensing could be potentially performed with spatiotemporal control

    Quantum Yield Regeneration: Influence of Neutral Ligand Binding on Photophysical Properties in Colloidal Core/Shell Quantum Dots

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    This article describes an experiment designed to identify the role of specific molecular ligands in maintaining the high photoluminescence (PL) quantum yield (QY) observed in as-synthesized CdSe/CdZnS and CdSe/CdS quantum dots (QDs). Although it has been possible for many years to prepare core/shell quantum dots with near-unity quantum yield through high-temperature colloidal synthesis, purification of such colloidal particles is frequently accompanied by a reduction in quantum yield. Here, a recently established gel permeation chromatography (GPC) technique is used to remove weakly associated ligands without a change in solvent: a decrease in ensemble QY and average PL lifetime is observed. Minor components of the initial mixture that were removed by GPC are then added separately to purified QD samples to determine whether reintroduction of these components can restore the photophysical properties of the initial sample. We show that among these putative ligands trioctylphosphine and cadmium oleate can regenerate the initial high QY of all samples, but only the “L-type” ligands (trioctyphosphine and oleylamine) can restore the QY without changing the shapes of the optical spectra. On the basis of the PL decay analysis, we confirm that quenching in GPC-purified samples and regeneration in ligand-introduced samples are associated chiefly with changes in the relative population fraction of QDs with different decay rates. The reversibility of the QY regeneration process has also been studied; the introduction and removal of trioctylphosphine and oleylamine tend to be reversible, while cadmium oleate is not. Finally, isothermal titration calorimetry has been used to study the relationship between the binding strength of the neutral ligands to the surface and photophysical property changes in QD samples to which they are added

    Constructing Three-Dimensional Hierarchical Architectures by Integrating Carbon Nanofibers into Graphite Felts for Water Purification

    No full text
    Developing high-performance nanostructured sorbents for water treatment is of great importance. Herein, we report a facile strategy to fabricate three-dimensional hierarchical architectures by integrating carbon nanofibers (CNFs) into macroscopic graphite felt (GF) supports. The physicochemical properties of CNF@GF monoliths including surface areas, densities, porosities, and pore structures could be conveniently tuned by varying reaction time. The CNF@GF monoliths were utilized as advanced sorbents for the removal of Pb<sup>2+</sup>, Congo red, organic solvents, and oils from aqueous solutions. The characteristics of adsorption processes including kinetics, isotherms, and regeneration were investigated. It is demonstrated that the CNF@GF exhibits outstanding performance for water treatment in terms of adsorption capacities, recovering, and recyclability. As such, the versatile CNS@GF monoliths show great application potential for water treatment

    Occurrence of the TFs and miRNAs in pan-cancer and prostate cancer FFLs.

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    <p>Occurrence of the TFs and miRNAs in pan-cancer and prostate cancer FFLs.</p
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