Zongjie Li

Fabrication of a polyvinylidene fluoride tree-like nanofiber web for ultra high performance air filtration

A novel polyvinylidene fluoride (PVDF) tree-like nanofiber web was successfully fabricated via one-step electrospinning. The effect of the tree-like structure on the pore size distribution and specific surface area were measured, and the filtration properties of the tree-like nanofiber webs with different basis weights were investigated. The results showed that the tree-like structure significantly decreased the pore size and narrowed the range of pore size distribution, and dramatically enhanced the specific surface area. In comparison with common PVDF nanofiber webs, the tree-like nanofiber webs exhibited excellent filtration performance. The filtration efficiency of the tree-like nanofiber webs with the basis weight of 1 g m−2 to 0.26 μm NaCl particles was 99.999% and the pressure drop was only 124.2 Pa which was comparable to ultra low penetration air filters (ULPA). The tree-like nanofiber webs will be widely used in the field of high efficiency and precision filter materials and medical protective materials.

Preparation of a polyvinylidene fluoride tree-like nanofiber mat loaded with manganese dioxide for highly efficient lead adsorption

A novel polyvinylidene fluoride/tetrabutylammonium chloride (PVDF/TBAC) tree-like nanofiber mat loaded with manganese dioxide (MnO2) as a highly efficient lead adsorbent was successfully fabricated. The adsorbent was prepared by in situ polymerization of pyrrole monomer on the surface of the PVDF/TBAC tree-like nanofiber mat, and subsequently reacted with KMnO4 solution to deposit MnO2. The morphology and structure of the as-prepared adsorbent were measured by field emission scanning electron microscopy (FE-SEM) and the tree-like structures can be clearly seen from the FE-SEM images. Fourier transform infrared spectroscopy (FT-IR) results confirmed the presence of PPy and MnO2 layers on the surface of PVDF/TBAC tree-like nanofibers. Thermo-gravimetric analysis (TGA) results exhibited that MnO2 accounted for about 43.27% in the PVDF/TBAC–polypyrrole–MnO2 (PVDF/TBAC–PPy–MnO2) nanofiber mat. The kinetics of Pb2+ adsorption was found to follow a pseudo-second-order rate model. The adsorption isotherms were fitted best with the Langmuir isotherm model. The thermodynamic analysis confirmed that the adsorption process was endothermic and spontaneous. The regeneration experiments showed that the obtained tree-like PVDF/TBAC–PPy–MnO2 nanofiber mat also exhibited high recyclable removal efficiency. XPS analysis showed that ion exchange was the main mechanism for Pb2+ adsorption.

Preparation and characterization of tree-like cellulose nanofiber membranes via the electrospinning method

A novel tree-like cellulose nanofiber membrane was controllably fabricated via the electrospinning method by adding certain amount of tetra butyl ammonium chloride (TBAC) into the cellulose acetate solution followed by a deacetylation treatment process. The morphological structure, material structure and air filtration performance of both the cellulose and the cellulose acetate tree-like nanofiber membranes were characterized. Water contact angles, mechanical properties, and air filtration properties were also evaluated. The air filtration efficiency of cellulose acetate tree-like nanofiber membrane can reached 99.58%, and the eventually cellulose tree-like membrane still maintain 98.37%. The eventual cellulose tree-like nanofiber membranes exhibited small pore size, excellent hydrophilicity, good solvent resistance and preferable mechanical property. The small average pore size caused by the tree-like structure and the strong resistance to organic solvent can make it a potential candidate for the membrane separation.

Electrospun SiO2/PMIA nanofiber membranes with higher ionic conductivity for high temperature resistance lithium-ion batteries

The nanofiber membrane prepared by electrospinning has been widely applied in lithium-ion batteries. A powerful strategy for designing, fabricating and evaluating Poly-m-phenylene isophthalamide (PMIA) nanofiber membrane with SiO2 nanoparticles was developed by electrospinning in this paper. The morphology, crystallinity, thermal shrinkage, porosity and electrolyte uptake, and electrochemical performance of the SiO2/PMIA nanofiber membranes were investigated. It was demonstrated that the nanofiber membrane with 6 wt% SiO2 possessed notable properties, such as better thermal stability, higher porosity and electrolyte uptake, resulting in higher ionic conductivity (3.23×10-3 S·cm-1) when compared with pure PMIA nanofiber membrane. Significantly, the SiO2/PMIA nanofiber membrane based Li/LiCoO2 cell exhibited more excellent cycling stability with capacity retention of 95 % after 50 cycles. The results indicated that the SiO2-doped PMIA nanofiber membranes had a potential application as separator in high temperature resistance lithium-ion batteries.

A Novel Polyvinylidene Fluoride Tree-Like Nanofiber Membrane for Microfiltration

A novel polyvinylidene fluoride (PVDF) tree-like nanofiber membrane (PVDF-TLNM) was fabricated by adding tetrabutylammonium chloride (TBAC) into a PVDF spinning solution via one-step electrospinning. The structure of the prepared membranes was characterized by field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FT-IR) and pore size analysis, and the hydrophilic property and microfiltration performance were also evaluated. The results showed that the tree-like nanofiber was composed of trunk fibers and branch fibers with diameters of 100–500 nm and 5–100 nm, respectively. The pore size of PVDF-TLNM (0.36 μm) was smaller than that of a common nanofiber membrane (3.52 μm), and the hydrophilic properties of the membranes were improved significantly. The PVDF-TLNM with a thickness of 30 ± 2 μm showed a satisfactory retention ratio of 99.9% against 0.3 μm polystyrene (PS) particles and a high pure water flux of 2.88 × 104 L·m−2·h−1 under the pressure of 25 psi. This study highlights the potential benefits of this novel PVDF tree-like nanofiber membrane in the membrane field, which can achieve high flux rates at low pressure.

Catalytic performance of metal oxide modified SiMCM-41 catalysts in diphenyl carbonate synthesis

Decomposition of CCl4 into diphenyl carbonate (DPC) was examined over metal oxides modified SiMCM-41. ZnO/SiMCM-41 and Fe2O3/SiMCM-41 showed high activity in DPC synthesis. Although many other metal oxides, such as La2O3, CuO, Al2O3 and alkali or alkaline earth oxide, were success in destruction of CCl4, they displayed nearly no activity on DPC synthesis. ZnO/SiMCM-41 and Fe2O3/SiMCM-41 were characterized by X-ray diffraction (XRD), UV-Raman, 29Si MAS NMR and N2 adsorption-desorption isotherms, and results showed that ferric and zinc oxide were supported onto SiMCM-41. The well ZnO dispersion in SiMCM-41 channels and the weak electrostatic interaction between chlorine anion and Zn2+ play an important role for the high activity of ZnO/SiMCM-41 in decomposition of CCl4 into DPC.

Coaxial solution blowing of modified hollow polyacrylonitrile (PAN) nanofiber Fe complex (Fe-AO-CSB-HPAN) as a heterogeneous Fenton photocatalyst for organic dye degradation

As a novel photocatalyst supporting material, one-dimensional hollow PAN nanofiber mat (HPAN) was successfully fabricated via coaxial solution blowing method (CSB), which we named CSB-HPAN. Then modified hollow PAN Fe complex (Fe-AO-CSB-HPAN) was prepared by the amidoximation and Fe coordination of AO-CSB-HPAN which used for the heterogeneous Fenton degradation of textile dyes. SEM, TEM and the digital photo revealed that CSB-HPAN has hollow structure, three-dimensional curly and loosely fibrous morphologies, which is beneficial for Fe3+ complexation, dye adsorption and degradation. The experiments of photocatalytic activity indicated that Fe-AO-CSB-HPAN showed excellent photocatalytic performance in the degradation of textile dyes in the presence of H2O2 under light irradiation. Meanwhile, 99% of RR195 molecules were decomposed by Fe-AO-CSB-HPAN in 35 min, which was faster than by conventional modified electrospinning PAN nanofiber Fe complex (Fe-AO-ES-PAN), due to the large surface area and loosely fibrous structure of Fe-AO-CSB-HPAN.

Fabrication and catalytic behavior of hierarchically-structured nylon 6 nanofiber membrane decorated with silver nanoparticles

A hierarchically-structured nylon 6 (PA6) nanofiber membrane decorated with silver nanoparticles (Ag NPs) was fabricated by electrospinning and impregnation methods. The as-fabricated hierar-chically-structured Ag/PA6 nanofiber membrane (HS-Ag/PA6 NM) exhibits a morphology in which Ag NPs are deposited on the surfaces of both thick fibers and thin fibers. The content and size of the Ag NPs can be controlled by varying the concentration of the silver colloid solution. Compared with the non-hierarchically-structured Ag/PA6 nanofiber membrane, HS-Ag/PA6 NM has a higher spe-cific surface area and exhibits a higher degradation rate for methylene blue of 81.8%-98.1% within 2 h. HS-Ag/PA6 NM can be easily recycled and exhibits good reusability. It retains a degradation rate for methylene blue of 83.5% after five consecutive cycles. The hierarchically-structured nano-fiber membrane is therefore a potential nanocatalyst.

Characterization and antibacterial properties of Ag NPs doped nylon 6 tree-like nanofiber membrane prepared by one-step electrospinning

A hierarchically Ag/nylon 6 tree-like nanofiber membrane (Ag/PA6 TLNM) was fabricated by adding tetrabutylammonium chloride (TBAC) and silver nitrate (AgNO3) into spinning solution via one-step electrospinning. TBAC presented in PA6/formic acid (HCOOH) spinning solution was able to cause the formation of a tree-like structure due to its space steric structure and the increasing of solution conductivity. Electrospinning solvent acted as a reducing agent for in situ conversion of AgNO3 into silver nanoparticles (Ag NPs) during the solution preparation. SEM, TEM, FT-IR XPS and XRD confirmed that Ag NPs were doped in the prepared nanofiber membrane successfully and the mechanical properties, pore size distribution and hydrophilicity of the membranes were investigated. The results showed that the tree-like structure improved the mechanical properties and hydrophilicity of the membrane while ensuring high specific surface area and small pore size. And the Ag/PA6 TLNM showed superior antibacterial properties against both E. coli and S. aureus compared with common Ag/PA6 nanofiber membranes (Ag/PA6 NMs). All of the results show that the Ag/PA6 TLNM would have potential applications in water purification.

Preparation and characterization of crosslinked electrospun pullulan nanofiber membrane as a potential for biomaterials

Abstract Pullulan nanofiber membrane (Pull-NM) was prepared by electrospinning method and its stability in the water was improved by a chemical crosslinking with mixed solution of ethylene glycol diglycidyl ether (EGDE) and ethanol absolute as crosslinking agent. The effect of crosslinked pullulan nanofiber membrane (C-l-Pull-NM) with different process conditions was studied and the excellent crosslinking reaction condition is proved to be 1:70 (EGDE: ethanol absolute) for 24 h. The analytical methods, including SEM, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and differential scanning calorimetry, were used to study morphology, structure, and thermal performance of the nanofiber membrane. In addition, the swelling behavior and tensile were also discussed. The results showed that the water resistance of crosslinked nanofiber membrane had a significant improvement. Furthermore, the maximum water absorption and the strength were reached to about 520 and 192.7%, respectively.