Composite Nanosheets Research Articles

SnO2 Quantum Dots Decorated Reduced Graphene Oxide Nanosheets Composites for Electrochemical Supercapacitor Applications

SnO2 Quantum Dots Decorated Reduced Graphene Oxide Nanosheets Composites for Electrochemical Supercapacitor Applications

TiN nanoparticles hybridized with Fe, N co-doped carbon nanosheets composites as highly efficient electrocatalyst for oxygen reduction reaction

Titanium nitride (TiN) nanoparticles hybridized with Fe and N co-doped carbon nanosheets (Fe-N-CNS) composite is constructed by a facile in-situ self-template strategy. During the low-temperature pyrolysis process, uniformly TiO2 nanoparticles were formed and anchored into Fe-doped carbon nitride nanosheets. After further high-temperature pyrolysis, Fe-doped carbon nitride nanosheets as self-template could decompose to form Fe-N co-doped carbon nanosheets and TiO2 nanoparticles were transferred into TiN nanoparticles during the high-temperature nitriding treatment. As a result, TiN nanoparticles hybridized with Fe-N-CNS composites (TiN/Fe-N-CNS) exhibit excellent ORR activity with more positive half-wave potential (0.87 V) and large limiting current density (4.43 mA cm−2) as well as high selectivity (electron transfer number around 4) for ORR in alkaline media. Moreover, it also shows higher stability and better methanol tolerance than those of commercial Pt/C catalyst in both alkaline and acidic media. This excellent ORR performance is attributed to the enhanced specific surface area and synergistically promotion effect of uniformly dispersed TiN on Fe-N-CNS.

Two-dimensional silicene composite nanosheets enable exogenous/endogenous-responsive and synergistic hyperthermia-augmented catalytic tumor theranostics

Silicene as an emerging two-dimensional material (2DM) spurs the broad research interests due to its prominent electronic and physical properties, however, still lacking in exploitation for the biological and medical practices. Herein, we constructed a 2D silicene-based theranostic nanoplatform, MnOx@silicene-BSA (MS-BSA), with tumor microenvironment (TME)-responsive and synergistic hyperthermia-augmented catalytic activity when irradiated by near infrared-II (NIR-II) laser because of the high photothermal-conversion efficiency of 2D silicene matrix. Such MS-BSA nanosheets possess the capability to react with glutathione (GSH) to generate Mn2+ and glutathione disulfide (GSSG) under acidity/reducing TME condition. With the presence/assistance of HCO3−, the released Mn2+ exhibited sensitive catalytic activity towards endogenous H2O2via Fenton-like reaction, enabling the generation of highly toxic hydroxyl radicals (•OH), which finally led to the enhanced nanocatalytic therapeutic efficacy followed by exogenous NIR-II laser exposure, originating from hyperthermia-augmented catalytic activity. Especially, these MS-BSA nanosheets accumulated into the tumor region to enable superb contrast enhancement of TME-responsive T1-weighted magnetic resonance imaging (MRI) and photoacoustic imaging (PAI), and high-efficient in vivo synergistic tumor eradication. Therefore, such an intelligent photothermal-enhanced catalytic theranostic nanoplatform could realize the exogenous/endogenous-responsive and cooperative hyperthermia-augmented tumor treatment and accurate tumor positioning/monitoring.

Metal–Organic-Framework-Derived N-, P-, and O-Codoped Nickel/Carbon Composites Homogeneously Decorated on Reduced Graphene Oxide for Energy Storage

In this work, a type of high-performance electrode material of Ni/C/rGO-n [n = wt % of reduced graphene oxide (rGO)] derived from nickel-based metal–organic framework (Ni-MOF) for supercapacitors is successfully prepared. First, a hydrogen-bonding-assisted approach to continuous growth of Ni-MOFs on graphene oxide (GO) sheets is developed through the application of a hexadentate ligand, hexakis­(4-carboxylphenoxy)­cyclotriphosphazene (CTP-COOH), as the anchor with multiple biting points. The thicknesses of the obtained layer cakelike Ni-MOF/GO-n (n: wt % GO) nanosheet composites with GO as the filling content can be controlled by tuning the ratio between GO and Ni-MOF. During the subsequent process of thermolysis treatment of Ni-MOF/GO-n composites, GO acts as a “hard” template and thus the decomposition of loaded metal–organic frameworks (MOFs) affords highly porous metal/C composites homogeneously embedded on the rGO matrix. This highly porous structure enhances the stability of Ni/C composites profoundly. Besides, both the rGO matrix and porous metal/C composites can provide an expressway for electron transport and shorten ion diffusion paths for greatly enhanced diffusion kinetics within the electrode materials, therefore leading to a superior rate capability. Moreover, application of the hexadentate ligand CTP-COOH with a six-membered ring backbone, which consisted of N and P atoms linked together alternatively, enables self-doping of N, O, and P to the derived materials. It is proven that the electrochemical performances, especially the stability, are remarkably enhanced for the derived Ni/C/rGO-n composites compared with the bare Ni-MOF-derived Ni/C composites. More importantly, this work pioneeringly demonstrates the potential application of MOF derivatives in energy storage devices.

Hydrophobic-Superoleophilic Fluorinated Graphene Nanosheet Composites with Metal–Organic Framework HKUST-1 for Oil–Water Separation

The spills of oils and petroleum byproducts into water bodies cause severe damage to aquatic species and humans along with massive loss to economy. Efficient methods using state of art sorbent mate...

Metallogel-derived 3D porous carbon nanosheet composites as an electrocatalyst for oxygen reduction reaction

The development of low-cost and high-performance non-precious metal electrocatalysts for oxygen reduction reaction (ORR) is of great significance for fuel cell and zinc-air battery applications. Herein, a zinc/cobalt bimetallic organic gel (Zn/Co-MOG) with folate dipotassium salt (FDS) ligands was used as a precursor for pyrolysis synthesis of cobalt/nitrogen dual-doped porous carbon nanosheet composites (Co/N@PCS). The Co/N@PCS exhibits a 3D carbon framework composed of porous carbon nanosheets. Due to hierarchical porous structure and fast ion/electron transport, the Co/N@PCS exhibits an excellent ORR electrocatalytic activity. The half-wave potential of the Co/N@PCS is 0.87 V vs. RHE, and its limiting current density is up to 5.22 mA cm-2. In addition, the Co/N@PCS shows a long-term cycling stability and excellent methanol-tolerant performance.

The research of lead ion detection based on rGO/g-C3N4 modified glassy carbon electrode

Lead-ion (Pb2+) electrochemical sensors were prepared by modified reduced graphene oxide (rGO)/graphite nitride carbon (g-C3N4) nanosheet composite (rGO/g-C3N4) on the surface of glassy carbon electrode (GC). RGO/g-C3N4 composite was prepared by a simple thermal polycondensation process and reduction of hydrationhydrazine method. The as-prepared composite samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), fourier transform infrared (FT-IR),X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET). It is concluded that the GC electrode modified by rGO/g-C3N4 had better electrochemical performance, higher sensitivity and selectivity in Pb2+ detection. Under optimized experimental conditions, there was a linear relationship between the square wave anode stripping voltammetry (SWASV) currents and the concentration of Pb2+(0.01–1000 nmol/L) with the limit of detection (LOD) was 1.07 × 10-12 mol/L (Signal-to-noise ratio is 3). In addition, the recovery experiment of Pb2+ in the practical samples was determined by standard addition method, which was consistent with the results obtained by atomic absorption spectrometry (AAS) method.

One-step fabrication of biomass-derived hierarchically porous carbon/MnO nanosheets composites for symmetric hybrid supercapacitor

In this work, hierarchically porous carbon/manganese monoxide nanosheets (HPC-MnO) composite materials are synthesized by a facile one-step approach, in which chemical activation of biomass precursor (wasted litchi shell) and loading of MnO nanosheets are conducted synchronously. The phase structure, chemical composition, morphology and specific surface area as well as the pores distribution are investigated for the resultant HPC-MnO composite materials. Interestingly, the as obtained HPC-MnO composite materials can serve both as the positive and negative electrodes simultaneously in a hybrid symmetric supercapacitor. High specific capacitances of 162.7F/g at a current density of 0.5 A/g and energy density of 57.7 W h/kg at a power density of 400 W/kg are obtained for the assembled symmetric HPC-MnO//HPC-MnO device, owing to the synergistic effects between electrochemical double-layer capacitance from the hierarchical porous carbons and pseudocapacitance from the redox reaction of manganese oxides. This work provides a facile and scalable strategy to synthesize carbon/metal oxides composites with promising electrochemical performances application for energy storage devices and opens a new gateway to design novel symmetric hybrid supercapacitors.

Chemisorption-Induced and Plasmon-Promoted Photofixation of Nitrogen on Gold-Loaded Carbon Nitride Nanosheets.

Photocatalytic fixation of nitrogen is a promising method for green conversion of solar light, but has been substantially limited by inefficient activation of the nonpolar N≡N bond and the poor utilization of visible light. In this study, carbon nitride nanosheet composites with abundant nitrogen vacancies and strong plasmonic resonance absorption of visible light have been fabricated through the combination of hydrogen treatment and loading of Au nanoparticles. Ammonia yields of 184 μmol g-1 and 93 μmol g-1 are obtained without any sacrificial agent under full-light and visible-light irradiation, respectively. In particular, the visible-light activity is enhanced tenfold with the help of Au. Combining the experimental results and theoretical calculations, both the hydrogen treatment and Au loading help form nitrogen vacancies on the carbon nitride nanosheets, which promote N2 activation by enhancing the chemisorption. Furthermore, the Au loading further improves the nitrogen reduction efficiency through charging the excited hot electrons formed from the surface plasmonic resonance to the adsorbed N2 molecules.

Excellent tribological properties of epoxy\u2014Ti3C2 with three-dimensional nanosheets composites

As a widely used engineering polymer, epoxy resin has been successfully employed in high-performance components and setups. However, the poor thermal and friction properties of traditional epoxy resin greatly limit its application in many extreme environments. In this work, a new kind of epoxy-Ti3C2 with three-dimensional nanosheets (3DNS) composite which was designed by freeze-drying method showed up excellent thermal and friction properties. As a result, the coefficient of thermal expansion (CTE) of epoxy-Ti3C2 3DNS 3.0 composites was 41.9 ppm/K at 40 °C, which was lower than that of the traditional epoxy resin (46.7 ppm/K), and the thermal conductivity (TC) was also improved from 0.176 to 0.262 W/(m·K). Meanwhile, epoxy-Ti3C2 3DNS 1.0 composites showed up the best friction property, with wear rate 76.3% lower than that of epoxy resin. This work is significant for the research of high-performance composite materials.

Solvothermal Synthesis of Humic Acid-Supported CeO₂ Nanosheets Composite as High Performance Adsorbent for Congo Red Removal.

Surface properties and structures of materials are essential for their adsorption of pollutants in water. Humic acids (HA)-supported CeO₂ nanosheet composites are synthesised by solvothermal method. The size of CeO₂ nanosheets are approximately 100-500 nm. The obtained composite exhibits superior adsorption ability for Congo Red (CR) in water, which can be attributed to its unique structure and highly dispersed CeO₂ nanosheet. The composite's adsorption behaviour of CR follows a pseudo-second-order mode and Langmuir adsorption model well, and the maximum adsorptive capacity for CR achieves 260 mg g-1. The presence of CeO₂ nanosheets enhances surface area and enriches the mesoporous structure of the composites, thereby promoting CR adsorption capacity.

Photocatalytic upgrading α-Fe2O3 nanoparticles by incorporating MoS2/rGO nanosheets

α-Fe2O3/MoS2/rGO nanocomposites was prepared by a two-step hydrothermal method and characterized by XRD, FESEM, EDS, FTIR, and UV–vis absorption spectroscopy. The results confirmed the formation of α-Fe2O3/MoS2-rGO (10 wt%) nanocomposites were composed of hematite nanoparticles with particle size of 30 nm and MoS2/rGO composite nanosheets with maximum sheet thickness of ∼ 10 nm. Upon addition of MoS2-rGO (8.0 wt%) nanosheets, the band gap of α-Fe2O3 nanoparticles decreased from 2.3 to 1.7 eV that was accompanied by light absorption enhancement. Owing to synergetic effect between rGO and MoS2 nanosheets leading to suppression of charge carrier recombination, prolongation of charge carrier lifetime, improvement of the interfacial charge transfer and increase in the number of active sites in α-Fe2O3 nanoparticles, as-synthesized α-Fe2O3/MoS2-rGO (10 wt%) nanocomposites nanocomposite showed highly enhanced photocatalytic performance for Rh B degradation under light irradiation so that complete degradation of Rh B organic dye was achieved within 30 min.

Efficient Separation of Photogenerated Charges in Sandwiched Bi2S3−BiOCl Nanoarrays/BiVO4 Nanosheets Composites for Enhanced Photocatalytic Activity

AbstractThe development of cost‐efficient and feasible strategies for producing efficient photocatalysts is crucial to advance photocatalytic pollutants degradation. Herein, we report a high photocatalytic active hierarchical sandwiched Bi2S3−BiOCl nanoarrays/BiVO4 nanosheets composites fabricated using biomass‐derived BiVO4 porous nanosheets as starting substrate material. BiVO4 porous nanosheets were first prepared via an impregnation‐calcination process using biomass template method. Subsequently, the ion exchange reactions during solvothermal reaction realized the in situ nucleation and growth of Bi2S3 nanorods and BiOCl nanoflakes nanoarrays from both sides of BiVO4 porous nanosheets, resulting in the formation of hierarchical sandwiched Bi2S3−BiOCl nanoarrays/BiVO4 nanosheets composites. Specifically, well‐defined Bi2S3 nanorods and BiOCl nanoflakes nanoarrays are vertically grown on the surface of BiVO4 nanosheets to provide plenty of accessible active sites and enable visible light harvesting. The tight contact between different components promises fast electron transfer and excellent durability. Consequently, optimized sandwiched Bi2S3−BiOCl/BiVO4 composite exhibits superior photocatalytic activity for pollutants degradation.

Boosting fast lithium ion storage of Li4Ti5O12 by synergistic effect of vertical graphene and nitrogen doping

The advancement of power-type lithium ion batteries (LIBs) mainly depends on the construction of electrodes with superior electronic & ionic conductivity. In this work, a synergistic combination of nitrogen doped Li 4 Ti 5 O 12 (N-LTO) nanoparticles and highly conductive vertical graphene (VG) skeleton is proposed to obtain ultrafast Li ion storage performance via a facile hydrothermal-nitridation method. The as-synthesized composite nanosheets are composed of interconnected N-LTO shell and VG core to form the final N-LTO/VG core-shell arrays, which are systematically studied as the anodes of LIBs. In virtue of the positive synergistic effect of high conductive VG backbone and nitrogen doping, overwhelming advantages including high specific surface area, superb structural stability and enhanced conductivity are achieved in the well-designed N-LTO/VG electrodes. Accordingly, the as-synthesized N-LTO/VG electrode shows outstanding high rate capacity (142.5 mAh g −1 at 20 C) and superior long-term cycling stability (capacity retention of 98.9% after 10000 cycles at 5 C), better than LTO/VG electrode without N doping. Our research provides a new strategy for the synthesis of high-performance hybrid electrodes for application in power-type LIBs. N-doped Li 4 Ti 5 O 12 (N-LTO) are rationally anchored on highly conductive vertical graphene (VG) skeleton forming N-LTO/VG core-shell arrays and demonstrated with noticeable lithium ion storage performance with superior high-rate capability and good cycling stability.

NixCo1-xS as an effective noble metal-free cocatalyst for enhanced photocatalytic activity of g-C3N4

Solar photocatalysis, as a method of green energy production and sustainable technology, has been regarded as one of the most effective strategies to resolve environmental issues and the current energy crisis. In this work, intimate contact hollow NixCo1-xS polyhedron/g-C3N4 nanosheet composites were prepared in-situ through a facile one-step hydrothermal method. The as-prepared NixCo1-xS/g-C3N4 composites showed superior photocatalytic activity and high stability for H2 generation and methyl orange (MO) degradation under visible light irradiation. The optimized 4 wt.% NixCo1-xS/g-C3N4 composite attained a maximum H2 evolution rate of 1420 μmol g–1 h–1, which was about 157 times higher than that of pure g-C3N4. In addition, the NixCo1-xS/g-C3N4 composite also exhibited greatly improved photocatalytic activity for dye degradation, which for MO was at 98.14 % in 9 min. The outstanding photocatalytic performance was predominantly attributed to the unique architecture of hollow NixCo1-xS polyhedrons, which not only provided more active sites at the edges and surface as convenient charge transfer channels, but also promoted the separation and transport of electron-hole pairs. This work provides some novel ideas for the design and development of highly efficient noble metal-free cocatalyst/semiconductor systems for photocatalytic H2 generation and dye degradation.

Phase and morphology control in the synthesis of Co3O4 nanosphere/α-Co(OH)2 nanosheet hybrids for application in supercapacitors

In this study, we developed a facile chemical precipitation approach for the synthesis of heterogeneous Co3O4 nanosphere/Co(OH)2 nanosheet hybrids in the presence of polyvinylpyrrolidone (PVP) as a phase-controlling reagent. The crystalline phase and morphology of the product varied upon changing the chain length of PVP (from 8k to 120k), with short-chain PVP favoring the formation of Co3O4 nanospheres and long-chain PVP favoring the synthesis of Co(OH)2 nanosheets. Accordingly, heterogeneous Co3O4/Co(OH)2 hybrids of various blending ratios were readily prepared in the presence of PVP of different molecular weights. The molecular weight of PVP also affected the electrochemical properties of the Co3O4 nanosphere/Co(OH)2 nanosheet composites. When using PVP of moderate chain length (58k), the resultant Co3O4/Co(OH)2 composite exhibited the optimal supercapacitive performance, characterized by an excellent specific capacitance of 771.2 F g−1 at 1 A g−1, and retained approximately 68.5% of this capacitance when operated at a high current density of 10 A g−1. Furthermore, this composite displayed an excellent charge/discharge cycling life at a current density of 4 A g−1, with a capacitance retention of 93.3% after 3000 repeated cycles.

Defects Engineering Leads to Enhanced Photocatalytic H2 Evolution on Graphitic Carbon Nitride-Covalent Organic Framework Nanosheet Composite.

Graphitic carbon nitride nanosheet (CNS) represents an attractive candidate for solar fuel production. However, the abundant defects in CNS lead to serious charge recombination and limit the photocatalytic performance. Herein, the synthesis of a CNS-covalent organic framework (CNS-COF) nanosheet composite is presented for the first time. CNS with significantly reduced defects is first obtained by rationally tuning the thermal exfoliation conditions of bulk carbon nitride. Subsequent modification of the CNS with trace COF nanosheet through chemical imine bonding can not only passivate the surface termination of carbon nitride in the boundary region, but also establish strong electronic coupling between these two components. As a consequence, enhanced charge separation and photocatalytic activity are realized on the resulting CNS-COF nanosheet composite. Under optimum conditions, hydrogen is evolved at a rate of 46.4 mmol g-1 h-1 . This corresponds to an apparent quantum efficiency of 31.8% at 425 nm, which is among the best values ever reported for carbon nitride-based materials.

Intercalation of Carbon Nanosheet into Layered TiO2 Grain for Highly Interfacial Lithium Storage.

Interfacial energy storage contributes a new mechanism to the emergence of energy storage devices with not only a high-energy density of batteries but also a high-power density of capacitors. In this study, success was achieved in preparing a highly ordered two-dimensional (2D) carbon/TiO2 (C/TiO2) nanosheet composite using commercially available organic molecules with multifunctional groups and taking advantage of the wedge effects, oxidative polymerization, and carbonization. An experiment was conducted to validate the excellent performance of this 2D composite with respect to interfacial energy storage. The coin cell with 2D C/TiO2 nanosheet composite demonstrates a specific capacity of as high as 510 mAh g-1 and a high specific energy of 390.9 Wh kg-1 at a specific power of 75.9 W kg-1 with a current density of 0.1 A g-1, and it also remains 39.0 Wh kg-1 at a specific power of 8.2 kW kg-1 with a high current density of 12.8 A g-1. The excellent electrochemical performance can be attributed to the superior artificial interface capacitive Li+ storage capability, which would bridge the energy and power density gap between batteries and capacitors. Meanwhile, there are two varieties of carbon derivatives, 2D carbon nanosheet stacks and exfoliated carbon nanosheets, which can be obtained by wet-chemical etching and mechanical peeling. The experimental route is simple from commercially available raw materials, and it could be scalable at a low cost and large scale, which makes it suitable for application in various fields such as energy storage, nanocatalysis, sensors, and so on.

Carbonized wood flour matrix with functional phase change material composite for magnetocaloric-assisted photothermal conversion and storage

Materials for energy collection, conversion and storage are important for overcoming energy-shortage problems. The research reported a nanocomposite containing polyethylene-glycol-10000 (PEG10000) as phase-change-material composite (PCMC) and graphene nanosheets functionalized with Fe3O4 nanoparticles (Fe3O4-GNS) stored and loaded into a porous carbonized-wood-flour (CWF) matrix. The Fe3O4-GNS/CWF/PCMC nanocomposite possessed favorable photothermal and magnetocaloric conversion properties. Introducing Fe3O4-GNS and CWF enhances the inherently low thermal conductivity of the PCMC. Energy was stored by the PCMC and released during the phase transition process. Furthermore, additional magnetothermal conversion and storage via Fe3O4-GNS component could reversely promote photothermal conversion due to continuous thermal energy supply. PEG10000 as biocompatible and nontoxic PCMC could form efficient combination within Fe3O4-GNS/CWF/PCMC and conduct least environmental-related effect. The nanocomposite exhibited favorable thermal conversion performance as temperature rising over 65 °C within 150 s, excellent thermal stability below 300 °C, a high melting enthalpy over 95 J/g and crystallization enthalpy over 85 J/g, good stability over 100 heating-cooling cycles, and efficient synergetic energy conversion. The PCMC with Fe3O4-GNS adsorbed in CWF rapidly converted light and magnetic energy to thermal energy, because of the enhanced thermal conductivity. The Fe3O4-GNS/CWF/PCMC nanocomposite therefore would have great potential in energy collecting, conversion and storage applications.

Wet-adhesive, haemostatic and antimicrobial bilayered composite nanosheets for sealing and healing soft-tissue bleeding wounds

Healing soft-tissue wounds with an irregular, complicated topography in a bleeding environment demands the development of a dressing that is wet-adhesive, haemostatic, and antibacterial. To meet this unmet demand, we designed a flexible nanosheet (~77 nm thick) made of two layers, one is the antibacterial and haemostatic gelatin modified with dopamine (DA) and antimicrobial peptide (AMP) and mixed with Ca2+ ions as coagulation factors, and another is the mechanically strong polycaprolactone (PCL). This flexible nanosheet exhibited robust mechanical strength, continuous and effective adhesion to a topographically irregular tissue surface under a wet condition, and a high platelet adhesion capacity. Moreover, the nanosheet presented a significantly reduced clotting time of 4 min and a high bactericidal rate of nearly 100%. An in vivo evaluation of the nanosheet using both murine dorsal skin and liver models further revealed that the nanosheet could successfully seal and heal the wounds in a bleeding environment, efficiently control haemorrhaging, and exert an excellent antibacterial effect in two weeks. Our work suggests that this nanosheet holds great promise in healing the bleeding soft-tissue wounds for treating acute trauma.