Sulfonated poly(arylene ether nitrile)-based composite membranes enhanced with Ca2+ bridged carbon nanotube-graphene oxide networks

As the core component of proton exchange membrane fuel cell, proton exchange membranes (PEM) have attracted much attention of researchers. To trade-off the proton conduction, dimensional stability and anti-oxidation ability, graphene oxide (GO) and acidized multi-walled carbon nanotubes (MWCNT) using calcium ion as coordination bridge (GO-Ca2+-MWCNT) was synthesized, and then incorporating into sulfonated poly(arylene ether nitrile) (SPEN) to fabricate SPEN/GO-Ca2+-MWCNT organic-inorganic composite membranes by solution-casting method and explore the influence of varying loading on performances as PEM. It was found that the proton conductivity of the composite membranes was higher than that of SPEN, while maintaining better dimensional stability, excellent anti-oxidation ability and good mechanical properties. All of these were attributed to the formation of three-dimensional structure between GO and MWCNT bridged by Ca2+. Particularly, the SPEN/GO-Ca2+-MWCNT-1 composite membrane exhibited excellent tensile strength of 71.45 MPa, better thermal stability as well as high proton conductivity (0.054 S/cm at 30 ℃, and 0.193 S/cm at 90 ℃), above 10-2 S/cm, satisfying the requirement of fuel cells. All in all, the results indicate that the filler with three-dimensional network structure can effectively improve the performances of SPEN, and the prepared composite membranes show potential applications in many fields.

Electrospun Nanofibrous Membranes Based on Citric Acid-Functionalized Chitosan Containing rGO-TEPA with Potential Application in Wound Dressings

The present research work is focused on the design and investigation of electrospun composite membranes based on citric acid-functionalized chitosan (CsA) containing reduced graphene oxide-tetraethylene pentamine (CsA/rGO-TEPA) as materials with opportune bio-properties for applications in wound dressings. The covalent functionalization of chitosan (CS) with citric acid (CA) was achieved through the EDC/NHS coupling system and was checked by 1H-NMR spectroscopy and FTIR spectrometry. The mixtures to be electrospun were formulated by adding three concentrations of rGO-TEPA into the 1/1 (w/w) CsA/poly (ethylene oxide) (PEO) solution. The effect of rGO-TEPA concentration on the morphology, wettability, thermal stability, cytocompatibility, cytotoxicity, and anti-biofilm activity of the nanofibrous membranes was extensively investigated. FTIR and Raman results confirmed the covalent and non-covalent interactions that appeared between the system’s compounds, and the exfoliation of rGO-TEPA sheets within the CsA in the presence of PEO (CsA/P) polymer matrix, respectively. SEM analysis emphasized the nanofibrous architecture of membranes and the presence of rGO-TEPA sheets entrapped into the CsA nanofiber structure. The MTT cellular viability assay showed a good cytocompatibility with the highest level of cell development and proliferation registered for the CsA/P composite nanofibrous membrane with 0.250 wt.% rGO-TEPA. The designed nanofibrous membranes could have potential applications in wound dressings, given that they showed a good anti-biofilm activity against Gram-negative Pseudomonas aeruginosa and Gram-positive Staphylococcus aureus bacterial strains.

A smart and responsive crystalline porous organic cage membrane with switchable pore apertures for graded molecular sieving

Membranes with high selectivity offer an attractive route to molecular separations, where technologies such as distillation and chromatography are energy intensive. However, it remains challenging to fine tune the structure and porosity in membranes, particularly to separate molecules of similar size. Here, we report a process for producing composite membranes that comprise crystalline porous organic cage films fabricated by interfacial synthesis on a polyacrylonitrile support. These membranes exhibit ultrafast solvent permeance and high rejection of organic dyes with molecular weights over 600 g mol−1. The crystalline cage film is dynamic, and its pore aperture can be switched in methanol to generate larger pores that provide increased methanol permeance and higher molecular weight cut-offs (1,400 g mol−1). By varying the water/methanol ratio, the film can be switched between two phases that have different selectivities, such that a single, ‘smart’ crystalline membrane can perform graded molecular sieving. We exemplify this by separating three organic dyes in a single-stage, single-membrane process.

A Dual-Function Cobalt Metal-Organic Framework for High Proton Conduction and Selective Luminescence Sensing of Histidine

Proton exchange membrane (PEM) is a key component of proton exchange membrane fuel cells (PEMFCs). In recent years, metal organic framework (MOF) and its composite membranes have become the research hotspots. [Co(L-Glu)(H2O)•H2O]n (Co-MOF, L-Glu = L-glutamate) was synthesized by hydrothermal method. Co2+ ions are coordinated with L-Glu ligands and water molecules to form one-dimensional chains extending along the a-axis, which are further bridged by L-Glu ligands to form a three-dimensional network structure. AC impedance analysis shows that the proton conductivity of Co-MOF reaches 3.14×10-4 S•cm-1 under 98% relative humidity (RH) and 338 K. To improve proton conductivity, different contents of Co-MOF were added in chitosan (CS) to form composite membranes Co-MOF@CS-X (mass fraction X= 5%, 10%, 15% wt). The results show the proton conductivity of the Co-MOF@CS-10 composite membrane is 1.73×10-3 S•cm-1 at 358 K and 98% RH, which is more than 5 times that of Co-MOF. As far as we known, this is the first composite made of amino acid MOFs and CS as proton exchange membrane. Furthermore, Co-MOF has an obvious quenching effect on L-histidine in aqueous solution, which can detect the content of L-histidine in water with high sensitivity, and the detection limit is 1×10-7 M.

Effect of Different Preparation Conditions On The Properties of Bamboo Fiber-Based Bioactive Composite Membrane

A novel nano-hydroxyapatite/bamboo fiber (n-HA/BF) bioactive composite membrane was obtained by a simple casting technique. The membrane forming mechanism and the effects of different forming membrane methods, drying methods and n-HA amounts on the properties of n-HA/BF membrane were investigated by Fourier Transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), contact angle, electromechanical universal tester, in vitro soaking in simulated body fluid (SBF) and in vitro cell cultureexperiment. The results demonstrated that the n-HA dispersity in BF matix was not affected by the prepartion condition, however, the morphologies of membrane was determined by the different preparation conditions owing to different hydrogen bond shrinkage. Moreover, the hydrophilicity of the composite membrane was improved under the condition of the membrane formation in oven, freeze drying and high addition content of n-HA, and the mechanical properties of composite membrane depended on n-HA content. In vitro soaking behavior indicated that the degradability and bone-like apatite deposition could be controled by differentpreparation conditions. And the cell proliferation experiment showed that the n-HA/BF composite membranes obtained under different preparation conditions were all non-toxic. The above results indicated that the n-HA/BF composite membrane could be obtained by a simple casting technique, and the properties could be controlled by adopting different preparation conditions, which would have a great promising as guide bone tissue regeneration (GBR) membrane, and the study would provide a new application for BF in biomedical field.