Fengzhu Lv

Fabrication and enhanced dielectric properties of graphene–polyvinylidene fluoride functional hybrid films with a polyaniline interlayer

Graphene–polyvinylidene fluoride hybrid films (GPNs–PVDF) with a polyaniline (PANI) interlayer are fabricated by a facile and effective process. The morphology of the graphene–polyaniline nanoflakes (GPNs) is examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and the interaction between graphene and PANI is investigated by Fourier transform infrared spectroscopy (FTIR), UV-visible spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The GPNs have a layered structure resembling a cake with the graphene sheets sandwiched between the PANI layers. The GPNs have a uniform morphology which can be controlled by adjusting the ratio of PANI to graphene. The PANI inter-layer plays an active role in the dielectric properties of the GPNs–PVDF composites which have low dielectric loss, high breakdown field, and large energy density. The enhanced dielectric performance originates from the insulating PANI layer which not only ensures good dispersion of graphene sheets in the PVDF but also acts as an inter-particle barrier to prevent direct contact with the graphene sheets.

Cuprous oxide created on sepiolite: preparation, characterization, and photocatalytic activity in treatment of red water from 2,4,6-trinitrotoluene manufacturing.

Cuprous oxide is firstly created on acidized sepiolite (AS) by a simple deposition method for photocatalytic degradation of the red water produced from 2,4,6-trinitrotoluene (TNT) manufacturing. X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), ultraviolet-visible diffuse reflection absorptive spectroscopy (UV-vis/DRS), and Fourier transform infrared (FT-IR) spectroscopy are used to characterize the photocatalyst composites. Gas chromatography/mass spectrometry (GC/MS) is employed to determine the organic constituents in the red water. The results show that the cuprous oxide particles can be immobilized on the surface of the AS fibers and the structure of the AS is altered when cuprous oxide interacts with AS via chemical reactions besides physical adsorption. The AS improves the optical properties of cuprous oxide and red-shifts the band gap thereby enhancing the utilization of visible light. The Cu(2)O/AS composites demonstrate excellent photocatalytic performance in the degradation of red water. 87.0% of red water can be photocatalytically degraded by Cu(2)O/AS after illumined for 5h and a majority of organic components of red water except 1,3,5-trinitrobenzene were degraded according to GC-MS analysis.

Layered Double Hydroxide Assemblies with Controllable Drug Loading Capacity and Release Behavior as well as Stabilized Layer-by-Layer Polymer Multilayers

A stable drug release system with magnetic targeting is essential in a drug delivery system. In the present work, layered double hydroxide assemblies stabilized by layer-by-layer polymer multilayers were prepared by alternative deposition of poly(allylamine hydrochloride) and poly(acrylic acid) species on composite particles of Fe3O4 and ZnAl-LDH and then covalent cross-linkage of the polymer multilayers by photosensitive cross-linker. The successful fabrication was recorded by Zeta potential and Fourier transform infrared spectrum measurements. The formed assemblies were stable in high pH solutions (pH > 7). The drug loading capacity and release behavior of the assemblies could be controlled by treatment with appropriate acidic solution, and were confirmed by loading and release of a simulated drug, methylene blue. The formed assemblies possessed enough saturated magnetic strength and were sensitive to external magnetic field which was essential for targeting drug delivery. The formed assemblies were multifunctional assemblies with great potential as drug delivery system.

Structure, molecular simulation, and release of a spirin from intercalated Zn-Al-layered double hydroxides

Aspirin or acetylsalicylic acid (AA), a non-steroidal anti-inflammatory drug, is intercalated into Zn-Al-layered double hydroxides (ZnAl-LDHs) by co-precipitation and reconstruction methods. The composition, structure, and morphology of the intercalated products as well as their release behavior are determined experimentally and theoretically by Material Studio 5.5. Experimental results disclose the strong interaction between the LDHs sheets and AA in the intercalated ZnAl-LDHs produced by co-precipitation and slow release of AA from the intercalated ZnAl-LDHs in both phosphate buffered saline (PBS) and borate buffered saline (BBS) solutions. The percentage of AA released from the ZnAl-LDHs prepared by both methods in PBS (96.87% and 98.12%) are much more than those in BBS (68.59% and 81.22%) implying that both H4BO4(-) and H2PO4(-) can exchange with AA in the ZnAl-LDHs. After AA is released to PBS, ZnAl-LDHs break into small pieces. The experimental results are explained theoretically based on the calculation of the bonding energy between the anions and LDHs sheets as well as the AlO bond length change in the LDHs sheets.

Structure and magnetic properties of soft organic ZnAl-LDH/polyimide electromagnetic shielding composites

The imidization mechanism, structure, and magnetic properties of organic modified Zinc-aluminum layered double hydroxides/polyimide composites are investigated. During imidization, organic modified Zinc-aluminum layered double hydroxides lose the hydroxyl group and sodium dodecyl sulfate modifier decomposes partly resulting in a loose contact between PI and oxidized Zinc-aluminum layered double hydroxides. The thermal properties of composites are slightly decreased with increasing organic modified Zinc-aluminum layered double hydroxides but the wettability varies oppositely. Comparing to organic modified Zinc-aluminum layered double hydroxides, the saturated magnetization of heated organic modified Zinc-aluminum layered double hydroxides is enhanced slightly due to structural improvement in Fe3O4 crystalline domain. Therefore, the magnetic properties are not affected by imidization procedure. The soft magnetic composites have large potential in electromagnetic shielding.

Extraction of organic materials from red water by metal-impregnated lignite activated carbon

Extraction of organic materials from 2,4,6-trinitrotoluene (TNT) red water by lignite activated carbon (LAC) impregnated with Cu(2+), Ba(2+), Sn(2+), Fe(3+), Ca(2+) and Ag(+) was investigated. The affinity to organic materials in red water was found to follow the order: Cu/LAC>Sn/LAC>Ag/LAC>Ba/LAC>Fe/LAC>Ca/LAC, which was explained by the hard and soft acid base (HSAB) theory. Cu(2+) showed the best performance and several parameters were further studied. X-ray photoelectron spectroscopy (XPS) verified effective loading of Cu(2+) on the LAC surface. The water quality before and after treated by Cu/LAC was evaluated using high performance liquid chromatograph, Gas Chromatography/Mass Spectroscopy (GC/MS), UV-vis spectroscopy and other analyses. The extraction performances and mechanism of organic materials on Cu/LAC were investigated through static methods. The experimental results showed that Cu/LAC possessed stronger extraction ability for the sulfonated nitrotoluenes than the non-sulfonated nitrotoluenes, the kinetic data fitted the pseudo-second-order kinetic model well. In addition, the leaching out of Cu(2+) from Cu/LAC was found much lower in the 100 times diluted red water (0.074%) than in the raw water (10.201%). Column adsorptions with more concentrated red water were also studied. Finally, Cu/LAC was observed to possess excellent reusability as well.

Removal of organic pollutants from red water by magnetic-activated coke

AbstractA magnetic adsorbent, magnetic-activated coke (MAC), is incorporated with Fe3O4 particles for removal of organic materials from 2,4,6-trinitrotoluene red water. The MAC is characterized by N2 adsorption, Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscope, and energy dispersive X-ray spectroscopy. Adsorption of organic pollutants is evaluated systematically by varying the adsorbent dosage, exposure time, temperature, pH, and dilution ratios of 2,4,6-trinitrotoluene red water. The equilibrium adsorption data can be better fitted with the Freundlich isotherm than Langmuir isotherm except at 343 K. The adsorption kinetics follows a pseudo-second-order model and thermodynamic analysis indicates an endothermic and spontaneous adsorption process. The settling rate after adsorption suggests that the response of MAC under an external magnetic field is very fast.

Functions of surfactants in the one-step synthesis of surfactant-intercalated LDHs

Surfactant-intercalated Zn and Al layered double hydroxides (ZnAl-LDHs) were synthesized via spontaneous self-assembly of the surfactants (sodium dodecyl sulfate and sodium dodecyl benzene sulfonate) and the LDH salt precursors. To understand the function of the surfactants in the synthesis, the surfactant-modified ZnAl-LDHs and their intermediates before aging were characterized via X-ray diffraction, Fourier transform infrared spectroscopy, Field emission scanning electron microscopy, and thermogravimetric analysis. In addition, fluorescence spectroscopy was used to in situ trace the microenvironmental variations of the reactants in the synthesis. It was found that the anionic surfactants can interact with the LDH precursors to form cooperative micellar assemblies, which increase the concentration of cationic counter ions around the micelles leading to enhanced growth of the LDH sheets along their lamellar surface direction and the stacking of LDH sheets into nanoparticles as the surfactant possesses longer molecular length. Because of the hydrophobicity of the intermediate sheets coated with surfactants, the reaction between the dissolved CO32− and the LDH intermediate sheets can be greatly reduced, and thus no strict N2 protection was necessary in this method. This mechanistic understanding of the effects of the surfactants on the formation of LDHs is critical in successful synthesis of organic-intercalated LDHs in complicated system by void the interruption of competitive ions.

Green dielectric materials composed of natural graphite minerals and biodegradable polymer

Polymeric nanocomposites are a promising dielectric due to their low cost, easy processability and flexibility but most polymers are difficult to treat and recycle leading to “white pollution”. Here, we report an eco-friendly “green” dielectric material made from natural graphite minerals and biodegradable poly(butylene succinate) synthesized by solution casting and hot pressing. Dielectric constant of resulting composite films agreed quite well with percolation theory and a low percolation threshold fc = 5.98% was obtained due to a high aspect ratio of natural graphite minerals. Composite films possessed a high dielectric constant of 113, around 28 times higher than that of pristine PBS (103) when volume fraction reached 5.5%. Furthermore, dynamic mechanical properties of composite films can be improved at the same time. Dielectric constant of composite films can be greatly improved by incorporating natural graphite minerals while mechanical flexibility can be maintained to be as good as that of pure polymer matrix.

Red mud/polypropylene composite with mechanical and thermal properties:

Polypropylene (PP) based composites containing 0, 5, 10, 15, 20, 30, and 50 wt% red mud are granulated by twin-screw extrusion and injection molding. Their mechanical properties such as tensile strength, flexural strength and modulus, impact strength, and thermal properties are determined. After filling with red mud, the flexural strength and modulus, thermal deformation temperature, and Vicat softening temperature increase, whereas the impact strength decreases with increasing red mud contents. The maximum tensile strength is observed from the PP doped with 15 wt% red mud. Scanning electron microscopy (SEM) is used to investigate the dispersion of red mud in the PP matrix.