Nanotubes of Polyethyleneimine (PEI) and Poly(styrene-alt-maleic anhydride) (PSMA) based on the layer-by-layer (LbL) technique and template method through covalent bond have been fabricated. The combination of LbL assembly and the template method can well control the length, wall thickness, outside, and inner diameters of the resulting nanotubes. The formation of covalent between PEI and PSMA enables the nanotubes with a good mechanical stability. The uniform tubular structure has been characterized by scanning electron microscopy (SEM) and transmission Electron Microscopy (TEM). Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) measurements confirms the formation of covalent bond in the assembled nanotubes.
The physisorption of nonionic surfactant poly(ethylene glycol) (PEG) series and the chemisorption of carboxyl-terminated alkanethiols on surface of gold nanoparticles (AuNPs) were investigated. The physical adsorption of oligo(ethylene glycol) moieties introduced a tiny red shift of surface plasmon resonance (SPR) of AuNPs, indicating the formation of a protective layer of PEG molecules around gold surface. The subsequent chemisorption of omega-carboxyl alkanethiols was performed under the protection of PEG molecules, and the aggregation of metal nanoparticles did not appear by TEM observation. The successful adsorption of omega-carboxyl alkanethiol on gold surface was demonstrated according to FT-IR spectrum and the prior adsorbed PEG molecules could be washed out by centrifugation. Furthermore, the presence of nonionic surfactant even displayed a protective role in centrifugal process. The dispersity of modified AuNPs with peripheral functional groups was enhanced under the protection of PEG molecules as an important advantage in further biological applications.
In this paper, we fabricated a bionanocomposite film of glucose oxidase/Pt nanoparticles/graphene-chitosan (GOD/PtNPs/GR-Chit) for glucose sensing. The hybrid bionanocomposites modified GCE were characterized by scanning electron microscopy (SEM), cyclic voltammetry, and amperometric i-t curve. It was found that the PtNPs were uniformly deposited on the surface of GR-Chit hybrid film. The resultant PtNPs/GR-Chit/GCE exhibited a high electrochemical catalytic ability to hydrogen peroxide (H2O2), due to the electrocatalytic synergy of GR and PtNPs. The redox behavior of the GOD/PtNPs/GR-Chit/GCE is a surface-controlled process. Finally, we obtained the amperometric response of the GOD/PtNPs/GR-Chit/GCE toward different concentration of glucose, and also achieved a sensitive glucose oxidase biosensor with a detection limit of 4.6μM glucose.
The effects of pH adjustment method, pH value, UV light, catalase and Fenton reagent on the degradation efficiency of enzyme-Fenton reagent for methyl orange (MO) were investigated, and the synergetic catalytic effects of catalase and Fenton reagent on the catalytic oxidation for methyl orange were found. When under no UV-light, the enzyme can enhance the degradation efficiency of Fenton reagent. The optimum conditions for degrading methyl orange simulated wastewater whose concentration is 0.1 g/L at room temperature are obtained as follows: the pH is tuned with H2SO4, pH is 3.0, concentration of catalase is 5 μg / mL, concentration of H2O2is 0.01%, concentration of FeSO4is 1.8μmol / L. The degradation rate can reach 98% in 60min. When under UV light at the same condition, the degradation rate can reach 94% in only 15min.
2.5-Dimension hollow silica fiber reinforced nitride (2.5D HSFRN) composites were fabricated by repeated infiltration and pyrolysis from hybrid polyborosilazane precursor. The effects of precursor infiltration and pyrolysis (PIP) cycles on densification behavior, mechanical properties, dielectric properties, and microstructures of the composites were investigated. With increasing PIP cycles, the density of 2.5D HSFRN composites increases, the mechanical properties increase accordingly, however, the dielectric properties decrease. The composites prepared after three PIP cycles, which have moderate flexural strength of 77.4MPa and elastic modulus of 20.7GPa, low dielectric constant of 2.98 and loss angle tangent of 3.9×10-3, exhibit suitable mechanical and dielectric properties. The calculation results of dielectric performance show that 2.5D HSFRN composites have good broadband wave-transparent properties, which result from high purity hollow silica fibers with excellent dielectric properties and low density nitride matrix.
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