•This is the first investigation on supercapacitors derived from water hyacinth.•Water hyacinth has a well-designed three-level hierarchical structure.•The supercapacitors possess a specific capacitance of 344.9 F/g at 0.5 A/g.•The supercapacitors possess 95% of the capacitance retention after 10000 cycles.•This work supports sustainable development and the control of biological invasion.A hierarchical porous water hyacinth-derived carbon (WHC) is fabricated by pre-carbonization and KOH activation for supercapacitors. The physicochemical properties of WHC are researched by scanning electron microscopy (SEM), N2 adsorption-desorption measurements, X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The results indicate that WHC exhibits hierarchical porous structure and high specific surface area of 2276 m2/g. And the electrochemical properties of WHC are studied by cyclic voltammetry (CV), galvanostatic charge-discharge and electrochemical impedance spectroscopy (EIS) tests. In a three-electrode test system, WHC shows considerable specific capacitance of 344.9 F/g at a current density of 0.5 A/g, good rate performance with 225.8 F/g even at a current density of 30 A/g, and good cycle stability with 95% of the capacitance retention after 10000 cycles of charge-discharge at a current density of 5 A/g. Moreover, WHC cell delivers an energy density of 23.8 Wh/kg at 0.5 A/g and a power density of 15.7 kW/kg at 10 A/g. Thus, using water hyacinth as carbon source to fabricate supercapacitors electrodes is a promising approach for developing inexpensive, sustainable and high-performance carbon materials. Additionally, this study supports the sustainable development and the control of biological invasion.

Thermal exfoliation and reduction of graphene oxide (GO) were performed to prepare graphene nanosheets at 300 °C under the ambient atmosphere without any supplementary conditions. The microstructure and morphology of the resulting graphene nanosheets were characterized with scanning electron microscopy, transmission electric microscopy, atomic force microscopy and X-ray photoelectron spectroscopy. The composite films based on poly(1-butene) (PB) and graphene nanosheets were prepared successfully through solution blending and compression molding. The morphological investigation suggested that the graphene nanosheets with nanoscale thickness achieved a homogeneous dispersion in the PB matrix. The composite films exhibited a sharp transition from insulating state to the conducting one with a low percolation threshold, followed by a high electrical conductivity at graphene content higher than 1.6 vol %. The composite films also achieved high dielectric constant with low dielectric loss due to the effective electrical conductive path established by graphene nanosheets in a local range. Moreover, the mechanical evaluation demonstrated that a considerable reinforcement was achieved for the composite films due to the strong interfaces between the graphene nanosheets and PB matrix. The introduction of graphene nanosheets not only enhanced the nucleation capability and crystallinity of PB domain but also improved the thermal stability of the composite films. In addition, the composite films showed an increase in storage modulus and a decrease in loss factors due to the incorporation of graphene nanosheets.

This paper reports the synthesis and antibacterial performance of a novel type of layer-structured montmorillonite (MMT) nanocomposite with cationic silica nanoparticles through an intercalating self-assembly method. The quaternary amine-functionalized SiO2 nanoparticles were first prepared by grafting dimethyloctadecyl [3-(trimethoxysilyl) propyl] ammonium chloride (PQAC) onto the surfaces of silica nanoparticles, and their chemical composition and structure were characterized by Fourier-transform infrared spectroscopy, thermogravimetric analysis and X-ray photoelectron spectroscopy. Then, the reactant PQAC–SiO2 nanoparticles were intercalated into the interlayers of MMT through electrostatic self-assembly to achieve the layer-structured MMT/PQAC–SiO2 nanocomposites. The ordered and layered structural characteristics of the resulting nanocomposites were characterized using X-ray diffraction patterns and N2 adsorption–desorption measurements and then confirmed by scanning electron microscopy and transmission electron microscopy. The optimum weight ratio of MMT/PQAC–SiO2 nanoparticles was also achieved for the self-assembly fabrication of the nanocomposites on the basis of results mentioned above. The MMT/PQAC–SiO2 nanoparticles gained an excellent thermal stability due to the intercalation of PQAC–SiO2 nanocomposites into MMT and their onset degradation temperature was improved by 40 °C compared to that of PQAC–SiO2 nanoparticles. Most of all, the nanocomposites presented a significant antibacterial effect against Escherichia coli and Staphylococcus aureus as the model microorganisms of Gram-negative and Gram-positive bacteria, respectively. This type of layered structural nanocomposite is expected to be applied for food packaging and containment of food materials, medical bandages for wound care, removal of environment pollutants like pesticides and phenol, etc.