Proton conducting composite membranes from crosslinked poly(vinyl alcohol) and poly(styrene sulfonic acid)-functionalized silica nanoparticles

Proton conducting membranes based on crosslinked poly(vinyl alcohol) (PVA) and poly (styrene sulfonic acid)-functionalized silica particles (PSSA-Si) were reported. Two-step crosslinking process involving sulfosuccinic acid (SSA) and glutaraldehyde as crosslinking agents was conducted to provide additional proton source and to enhance hydrolytic and mechanical stabilities. PSSA-Si was synthesized from vinyltrimethoxysilane via Stöber method, followed by radical polymerization of sodium 4-vinylbenzenesulfonate on the silica particle. The obtained PSSA-Si was characterized by thermogravimetric analysis (TGA), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FTIR). The effects of PSSA-Si loading (0, 2.5, 5, and 10%) and PSSA content in PSSA-Si (2, 5, 8, and 12%) on membrane properties including surface morphology, water vapor absorption, water uptake, ion exchange capacity, mechanical and oxidative stabilities, and proton conductivity were investigated and discussed. Proton conductivities of these composite membranes were found to increase with PSSA-Si loading and PSSA content. Promising proton conductivities of ～0.072 S/cm were obtained from PVA-8%PSSA-Si-10 and PVA-12%PSSA-Si-10 membranes, having PSSA-Si loading of 10%, and PSSA contents of 8%, and 12%, respectively. In addition, these membranes showed good hydrolytic and oxidative stabilities with high storage moduli.     

Determination of silver nanoparticle release from antibacterial fabrics into artificial sweat

Silver nanoparticles have been used in numerous commercial products, including textiles, to prevent bacterial growth. Meanwhile, there is increasing concern that exposure to these nanoparticles may cause potential adverse effects on humans as well as the environment. This study determined the quantity of silver released from commercially claimed nanosilver and laboratory-prepared silver coated fabrics into various formulations of artificial sweat, each made according to AATCC, ISO and EN standards. For each fabric sample, the initial amount of silver and the antibacterial properties against the model Gram-positive (S. aureus) and Gram-negative (E. coli) bacteria on each fabric was investigated. The results showed that silver was not detected in some commercial fabrics. Furthermore, antibacterial properties of the fabrics varied, ranging from 0% to greater than 99%. After incubation of the fabrics in artificial sweat, silver was released from the different fabrics to varying extents, ranging from 0 mg/kg to about 322 mg/kg of fabric weight. The quantity of silver released from the different fabrics was likely to be dependent on the amount of silver coating, the fabric quality and the artificial sweat formulations including its pH. This study is the unprecedented report on the release of silver nanoparticles from antibacterial fabrics into artificial sweat. This information might be useful to evaluate the potential human risk associated with the use of textiles containing silver nanoparticles.     

Soil hydraulic parameters estimated from satellite information through data assimilation

Leaf area index (LAI) and actual evapotranspiration (ET_a) from satellite observations were used to estimate simultaneously the soil hydraulic parameters of four soil layers down to 60 cm depth using the combined soil water atmosphere plant and genetic algorithm (SWAP–GA) model. This inverse model assimilates the remotely sensed LAI and/or ET_a by searching for the most appropriate sets of soil hydraulic parameters that could minimize the difference between the observed and simulated LAI (LAI_sim) or simulated ET_a (ET_asim). The simulated soil moisture estimates derived from soil hydraulic parameters were validated using values obtained from soil moisture sensors installed in the field. Results showed that the soil hydraulic parameters derived from LAI alone yielded good estimations of soil moisture at 3 cm depth; LAI and ET_a in combination at 12 cm depth, and ET_a alone at 28 cm depth. There appeared to be no match with measurement at 60 cm depth. Additional information would therefore be needed to better estimate soil hydraulic parameters at greater depths. Despite this inability of satellite data alone to provide reliable estimates of soil moisture at the lowest depth, derivation of soil hydraulic parameters using remote sensing methods remains a promising area for research with significant application potential. This is especially the case in areas of water management for agriculture and in forecasting of floods or drought on the regional scale.     

Characterization of Cobalt Dispersed on Various Micro- and Nanoscale Silica and Zirconia Supports

Cobalt dispersion on various micro- and nanoscale SiO₂ and ZrO₂ was investigated. It revealed that Co/SiO₂ (M) exhibited higher activity than Co/SiO₂ (N) due to strong support interaction. However, Co/ZrO₂ behaved oppositely. In addition, Co dispersed on the nanoscale SiO₂ and ZrO₂ gave the similar activity for CO hydrogenation because of more uniform species.     

Effects of gamma irradiation with and without compatibilizer on the mechanical properties of polypropylene/wood flour composites

In this study, polypropylene/wood flour (Hevea brasiliensis) composites at 40 wt% filler content were prepared using a twin-screw extruder and an injection moulding machine. The effects of gamma irradiation with and without maleic anhydride graft polypropylene (PP-g-MA) compatibilizer (3% relative to the wood flour content) on the flexural properties, tensile properties, and creep behavior were investigated. The irradiation in nitrogen and air atmospheres was performed at various radiation doses (i.e. 5, 10, 20 and 30 kGy). The results revealed the improvement of mechanical properties and creep behavior was found in the presence of gamma irradiation at low radiation doses (5 and 10 kGy), while the composites irradiated at radiation doses over 10 kGy rendered the decrease of mechanical properties. Furthermore, at the same radiation dose, the composites irradiated in nitrogen atmosphere tended to provide significantly higher mechanical properties than the ones irradiated in air atmosphere. Interestingly, the great enhancement of creep resistance was observed, i.e. the tensile strains (6 h of static loading) of the irradiated composites (at 10 kGy) with and without compatibilizer were approximately 36% and 19% lower than that of the untreated composite, respectively. In addition, the Burger’s creep model is applied in order to determine the creep parameters of the composites.     

Local Structure of Magnetoelectric BiFeO3–BaTiO3 Ceramics Probed by Synchrotron X-Ray Absorption Spectroscopy

The novel Cu- and Mn-doped and Cu/Mn codoped 0.75BiFeO₃–0.25BaTiO₃ magnetoelectric ceramics were successfully prepared by a solid-state reaction method. The dielectric, ferroelectric, ferromagnetic, and magnetoelectric properties were determined and all the results suggested that Cu and Mn dopants occupied different B-site lattices in the 0.75BiFeO₃–0.25BaTiO₃ structure. To identify the preferential sites of Cu and Mn in the lattice, Synchrotron X-ray Absorption Spectroscopy (SXAS) measurements were carried out. A combination of both measured and simulated XAS results with a linear combination fitting (LCF) revealed that in Cu- and Mn-doped 0.75BiFeO₃–0.25BaTiO₃ ceramics both Mn and Cu substituted at Fe-site and Ti-site with slightly different proportion. On the other hand, both dopants were found to occupied different sites in Cu/Mn codoped 0.75BiFeO₃–0.25BaTiO₃ ceramics.     

Enhancing performance of optical sensor through the introduction of polystyrene and porous structures

Simple and promising approaches for developing high‐performance Fe³⁺ sensors were proposed. Polyvinyl chloride (PVC) membrane containing pyrene as a fluorescent indicator was prepared via solvent‐cast method. Upon immersion into 1.0 mM Fe³⁺ solution, the fluorescence emission of the membrane decreased with the ratio of fluorescence intensities before and after (F₀/F) immersion of 1.25. The sensitivity enhancement was achieved through the introduction of polystyrene (PS) onto PVC and the introduction of porous structures. Polyvinyl chloride‐graft‐polystyrene copolymers (PVC‐g‐PS) were synthesized via Atom Transfer Radical Polymerization using PVC as macroinitiator. The grafting percentages of PS on PVC calculated from Nuclear Magnetic Resonance Spectroscopy were 17 and 41. The membrane prepared from low molecular weight copolymer showed higher sensing ability than that from PVC with the F₀/F value of 1.39. The increase in PS chain length did not significantly affect the fluorescence quenching. A Stern–Volmer quenching relationship was found with K_sv of 3.96 × 10² M^?1. The effect of porous structures on fluorescence quenching was studied by introducing Triton X‐100 as a porogen to PVC/pyrene solution. Attenuated total reflection Fourier transform infrared spectroscopy and Scanning Electron Microscopy analyses confirmed a complete removal of Triton X‐100 after 3 days of immersion in water. The porous membrane demonstrated an enhanced sensing performance with the F₀/F value of 1.46. PVC‐g‐PS/pyrene membrane exhibited highly sensitive and selective responses toward Fe³⁺ over Cu²⁺, Mg²⁺, Co²⁺, Zn²⁺, Ni²⁺, and Ag⁺. In addition, a good reversibility after five cycles of quenching and regeneration was obtained. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41759.     

Magnetic and Cytotoxicity Properties of La1−x Sr x MnO3 (0 ≤ x ≤ 0.5) Nanoparticles Prepared by a Simple Thermal Hydro-Decomposition

This study reports the magnetic and cytotoxicity properties of magnetic nanoparticles of La_1−x Sr _x MnO₃ (LSMO) with x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5 by a simple thermal decomposition method by using acetate salts of La, Sr, and Mn as starting materials in aqueous solution. To obtain the LSMO nanoparticles, thermal decomposition of the precursor was carried out at the temperatures of 600, 700, 800, and 900 °C for 6 h. The synthesized LSMO nanoparticles were characterized by XRD, FT-IR, TEM, and SEM. Structural characterization shows that the prepared particles consist of two phases of LaMnO₃ (LMO) and LSMO with crystallite sizes ranging from 20 nm to 87 nm. All the prepared samples have a perovskite structure with transformation from cubic to rhombohedral at thermal decomposition temperature higher than 900 °C in LSMO samples of x ≤ 0.3. Basic magnetic characteristics such as saturated magnetization (M _S) and coercive field (H _C) were evaluated by vibrating sample magnetometry at room temperature (20 °C). The samples show paramagnetic behavior for all the samples with x = 0 or LMO, and a superparamagnetic behavior for the other samples having M _S values of ~20–47 emu/g and the H _C values of ~10–40 Oe, depending on the crystallite size and thermal decomposition temperature. Cytotoxicity of the synthesized LSMO nanoparticles was also evaluated with NIH 3T3 cells and the result shows that the synthesized nanoparticles were not toxic to the cells as determined from cell viability in response to the liquid extract of LSMO nanoparticles.     

Polyacrylonitrile‐based proton conducting membranes containing sulfonic acid and tetrazole moieties

Proton conducting membranes based on polymers containing sulfonic acid and tetrazole moieties were developed. Successful syntheses of poly(acrylonitrile‐co ‐styrene sulfonic acid) (PAN‐co ‐PSSA), poly(acrylonitrile‐co ‐5‐vinyl tetrazole) (PAN‐co ‐PVTz), and poly(acrylonitrile‐co ‐5‐vinyl tetrazole‐co ‐styrene sulfonic acid) (PAN‐co ‐PVTz‐co ‐PSSA) were confirmed by ¹H‐nuclear magnetic resonance spectroscopy, elemental analysis, and Fourier transform infrared spectroscopy. Two approaches were performed to study the effects of molar ratio of sulfonic acid to tetrazole and tetrazole content on membrane properties. In the first approach, PAN‐co ‐PSSA was blended with PAN‐co ‐PVTz at three molar ratios. The second approach focused on PAN‐co ‐PVTz‐co ‐PSSA membranes with various tetrazole contents. PAN‐co ‐PSSA membrane was also prepared. All solution‐cast membranes were hydrolytically stable, except for PAN‐co ‐PVTz‐co ‐PSSA with 71% tetrazole. Surface morphologies of blend membranes were studied using scanning electron microscopy, and no phase separation was observed. Water uptake was shown to increase with increasing tetrazole. All membranes exhibited high thermal stability (up to 250 °C) and high storage moduli. Proton conductivity was found to depend significantly on relative humidity. The influences of sulfonic acid to tetrazole ratio and tetrazole content on proton conduction were observed and discussed. A maximum proton conductivity of 7.1 × 10^?3 S/cm at 26 °C was obtained from PAN‐co ‐PSSA membrane. In addition, all tested membranes showed relatively good oxidative stability after treatment in Fenton's reagent. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45411.