Enhanced properties of SPEEK with incorporating of PFSA and barium strontium titanate nanoparticles for application in DMFCs

Novel blend nanocomposite proton‐exchange membranes were prepared using sulfonated poly (ether ether ketone) (SPEEK), perfluorosulfonic acid (PFSA), and Ba_0.9Sr_0.1TiO₃ (BST) doped‐perovskite nanoparticles. The membranes were evaluated by attenuated total reflection, X‐ray diffraction spectroscopy, water uptake, proton conductivity, methanol permeability, and direct methanol fuel cell test. The effect of two additives, PFSA and BST, were investigated. Results indicated that both proton conductivity and methanol barrier of the blend nanocomposite membranes improved compared with pristine SPEEK and the as‐prepared blend membranes. The methanol permeability and the proton conductivity of the blend membrane containing 6 wt% BST obtained 3.56 × 10^?7 cm² s^?1 (at 25 °C) and 0.110 S cm^?1 (at 80 °C), respectively. The power density value for the optimum blend nanocomposite membrane (15 wt% PFSA and 6 wt% BST) (54.89 mW cm^‐2) was higher than that of pristine SPEEK (31.34 mW cm^‐2) and SPF15 blend membrane (36.12 mW cm^‐2).     

Recent advances on akermanite calcium-silicate ceramic for biomedical applications

Owing to great biocompatibility and high capacity of apatite formation, bioceramics, especially calcium silicate-based compounds, were extensively employed in orthopedic and dental uses concerning biomedical applications. Lately, akermanite (AK; Ca₂MgSi₂O₇), as a bioceramic containing Ca-, Mg- and Si, has gained an increased level of attention because of its more tunable mechanical characteristics and degradation rate. All studies indicate that this magnesium incorporating Ca-silicate ceramic has a great capacity to use as a bone graft material to fulfill the necessity of bone reconstruction. Despite the rising interest in using these materials in biomedical fields, there has not yet been an extensive overview of this bioceramic property and its potential benefits. Thus, it has been speculated that this concept and the emergence of akermanite bioactive ceramics might lead to significant upcoming advancements in the field of bone tissue engineering (BTE). Definitely, the approach still requires additional advances to considerably better respond to the vital concerns regarding the clinical application. The review tackles the present research trends on akermanite ceramics for biomedical purposes such as bone scaffold, coating materials, bone cement, and treatment of osteoporotic bone defects, commencing with recent status and shifting to upcoming developments.     

Synthesis and characterization of highly crystalline Na‐X zeolite from class F fly ash

The aim of this research is to illustrate the feasibility of transforming a byproduct of coal combustion process (fly ash) into a highly crystalline zeolite with enhanced ion exchange capacity and molecular sieving ability that can be used in various phase separation applications. The main crystalline phases present were: α‐quartz, Mullite, Hematite, Magnetite and Lime. The hydrothermal synthesis process resulted in the formation of a Na‐A in low alkalinity, and Na‐X (Na₈₈Al₈₈Si₁₀₄O₃₈₄ (H₂O)_172.1) in higher alkalinity – classified as FAU (Faujasite). Physisorption analysis using BET method revealed the presence of micropores. Cation exchange capacity increased, as high as 374 meq/g, by increasing the crystallization time. Highly ordered pore structure, enhanced specific surface area and the presence of a negative charge in the framework of Na‐X zeolite (FAU) make it a strong adsorbent and an effective molecular sieve with high shape/size selectivity for various applications, including petroleum refinery catalytic cracking units.     

Thermorheological and mechanical behavior of polylactide and its enantiomeric diblock copolymers and blends

In this study, different compositions of nearly monodispersed diblock copolymers of dl-lactide or d-lactide and l-lactide were synthesized by living ring-opening polymerization with a dinuclear indium catalyst. The effects of molecular weight and block length ratio on the rheological behavior of dl and l-lactide diblock copolymers in the disordered state were investigated. For comparison, blends of PDLLA and PLLA homopolymers of equivalent molecular weights to the diblock copolymers were prepared. We found that the time–temperature (t–T) superposition principle is applicable to the diblock copolymers PLLA-b-PDLLA and blends in the disordered state. However, the t–T superposition failed at low temperatures close to the temperature of crystallization. In contrast, diblock copolymers PLLA-b-PDLA formed stereocomplex crystallites of high melting point (slightly above 200 °C) that causes a viscosity enhancement. The failure of t–T superposition was found due to existing of micro homo or stereocomplex crystallites. The non-isothermal crystallization behavior was investigated using differential scanning calorimetry (DSC). The DSC thermograms of blends exhibited a single glass transition at 50–60 °C followed by melting point of PLLA at 177 °C. With decreasing of the PLLA content in the blends, the intensity of the melting peak decreased. In addition, different crystallization behavior was observed for diblock copolymers compared to their equivalent blends. Specifically, low temperatures and enthalpies of melting peaks were observed for diblock copolymers. These also show improvement in elongation at break and tensile strength as compared to their counterpart homopolymer blends.     

Copper chloride modified copper electrode: Application to electrocatalytic oxidation of methanol

Copper chloride modified copper (CCMC) electrode was prepared as a new electrode. For the preparation of the modified electrode, the polished copper electrode was placed in 0.1 M CuCl₂ solution for 20 s. In this step, a layer of copper (I) chloride was formed at the surface of copper electrode. Then, the electrode was placed in 0.1 M NaOH and the electrode potential was cycled between −250 and 1000 mV (vs. SCE) at a scan rate of 50 mV s⁻¹ for 5 cycles in a cyclic voltammetry regime until a featureless voltammogram was obtained. Surface physical characteristics of the modified electrode were studied by scanning electron micrographs (SEM). Results showed that considerable amounts of microcrystals have been formed on the copper surface during the modification. Surface elemental analysis of electrode were performed by energy dispersive X-ray (EDX) technique. The results showed that in addition to copper and chloride elements, there is also oxygen at the surface of CCMC electrode. This indicates that a layer of (ClCu)₂O was formed at the surface of the modified electrode. The electrocatalytic activity of the modified electrode for the oxidation of methanol, in aqueous basic solution was studied by using cyclic voltammetry. Results showed that, copper chloride modified electrode can improve the activity of Cu towards the oxidation of this small organic molecule, showing the possibility of attaining good electrocatalytic anodes for fuel cells. The modified electrode shows a stable and linear response in the concentration range of 5 × 10⁻³ to 8 × 10⁻² M with a correlation coefficient of 0.9958.     

Green synthesis of AgCl/Ag3 PO4 nanoparticle using cyanobacteria and assessment of its antibacterial,colorimetric detection of heavy metals and antioxidant properties

In this study, the extract of two strains of cyanobacteria was used for the synthesis of silver nanoparticles (NPs). UV–vis spectroscopy, X‐ray diffraction, dynamic light scattering and field emission scanning electron microscopy (FESEM) analyses were carried out to characterise the NPs. The antioxidant activity and heavy metal detection properties were investigated; moreover, their minimum inhibitory concentration and minimum bactericidal concentration against the multi‐drug resistant bacteria were determined. The most abundant materials in these extracts were carbohydrates, so the biosynthesis of NPs using exopolysaccharide (EPS) was also investigated. The surface plasmon resonance of NPs had a peak at 435 nm and EPS NPs at 350–450 nm. The NPs produced by Nostoc sp. IBRC‐M5064 extract revealed the face‐centred cubic (fcc) structure of AgCl, while NPs of N. pruniforme showed the fcc crystalline structure of Ag₃ PO₄ and AgCl. The FESEM showed the spherical shape of these NPs. The AgCl/Ag₃ PO₄ colloid, in comparison with AgCl, showed better antioxidant activity and antibacterial effect. The heavy metal detection analysis of NPs revealed that the NPs of both stains involved in Hg (NO₃)₂ detection.Inspec keywords: drugs, light scattering, silver, biochemistry, surface plasmon resonance, X‐ray diffraction, silver compounds, antibacterial activity, ultraviolet spectra, nanoparticles, visible spectra, colloids, microorganisms, nanofabrication, field emission scanning electron microscopy, chemical sensors, nanosensorsOther keywords: cyanobacteria, antibacterial detection, colorimetric detection, dynamic light scattering, antioxidant activity, heavy metal detection analysis, silver nanoparticle synthesis, field emission scanning electron microscopy analysis, UV‐visible spectroscopy analysis, X‐ray diffraction analysis, inhibitory concentration, exopolysaccharide, surface plasmon resonance, Nostoc sp. IBRC‐M5064 extract, face‐centred cubic crystalline structure, FESEM, spherical shape, antibacterial effect, multidrug resistant bacteria, wavelength 350.0 nm to 450.0 nm, AgCl‐Ag₃ PO₄ , Ag     

Self‐Assembling Peptide as a Potential Carrier for Hydrophobic Anticancer Drug Ellipticine: Complexation,Release and In Vitro Delivery

The self‐assembling peptide EAK16‐II is capable of stabilizing hydrophobic compounds to form microcrystal suspensions in aqueous solution. Here, the ability of this peptide to stabilize the hydrophobic anticancer agent ellipticine is investigated. The formation of peptide‐ellipticine suspensions is monitored with time until equilibrium is reached. The equilibration time is found to be dependent on the peptide concentration. When the peptide concentration is close to its critical aggregation concentration, the equilibration time is minimal at 5 h. With different combinations of EAK16‐II and ellipticine concentrations, two molecular states (protonated or cyrstalline) of ellipticine could be stabilized. These different states of ellipticine significantly affect the release kinetics of ellipticine from the peptide‐ellipticine complex into the egg phosphatidylcholine vesicles, which are used to mimic cell membranes. The transfer rate of protonated ellipticine from the complex to the vesicles is much faster than that of crystalline ellipticine. This observation may also be related to the size of the resulting complexes as revealed from the scanning electron micrographs. In addition, the complexes with protonated ellipticine are found to have a better anticancer activity against two cancer cell lines, A549 and MCF‐7. This work forms the basis for studies of the peptide‐ellipticine suspensions in vitro and in vivo leading to future development of self‐assembling peptide‐based delivery of hydrophobic anticancer drugs.     

A highly selective carbon paste electrode enhanced by Cu-encapsulated poly(amidoamine) for the simultaneous detection of organic and inorganic contaminants

In this study, a copper/poly(amidoamine)/multi-walled carbon nanotube/reduced graphene oxide (Cu/PAMAM/MWCNT/rGO) complex was synthesized for fabricating an electrochemical sensor to simultaneously detect nitrate and nitrite ions as inorganic contaminants, and 4-chlorophenol (4-CP) and 1,2,5,8 tetrahydroxy anthraquinone (THA) as organic pollutants. The prepared Cu/PAMAM/MWCNT/rGO electrode was characterized using scanning electron microscopy (SEM), Fourier-transform infrared (FT-IR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and electrochemical impedance spectroscopy (EIS). Cyclic voltammetry (CV) was performed to investigate the influence of the pH of the solution, concentration of anions, and scan rate on the analytical performance of the electrodes. The simultaneous determination of nitrite/nitrate ions using a Cu/PAMAM/MWCNT/rGO electrode showed sensitivities of 8.030 × 10⁻³ and 5.370 × 10⁻³ μA μM⁻¹ mm⁻², and limits of detection (LODs) of 0.081 and 0.115 μM, respectively. For the simultaneous determination of 4-CP/THA, the sensitivities of the modified electrode were 0.0105 and 9.399 × 10⁻³ μA μM⁻¹ mm⁻², and detection limits were 0.062 and 0.070 μM respectively.     

Statistical factor-screening and optimization in slurry phase bioremediation of 2,4,6-trinitrotoluene contaminated soil

Since slurry phase bioremediation is a promising treatment for recalcitrant compounds such as 2,4,6-trinitrotoluene (TNT), a statistical study was conducted for the first time to optimize TNT removal (TR) in slurry phase. Fractional factorial design method, 2(IV)(7-3), was firstly adopted and four out of the seven examined factors were screened as effective. Subsequently, central composite design and response surface methodology were employed to model and optimize TR within 15 days. A quadratic model (R(2) = 0.9415) was obtained, by which the optimal values of 6.25 g/L glucose, 4.92 g/L Tween 80, 20.23% (w/v) slurry concentration and 5.75% (v/v) inoculum size were estimated. Validation experiments at optimal factor levels resulted in 95.2% TR, showing a good agreement with model prediction of 96.1%. Additionally, the effect of aeration rate (0-4 vvm) on TR was investigated in a 1-liter bioreactor. Maximum TR of 95% was achieved at 3 vvm within 9 days, while reaching the same removal level in flasks needed 15 days. This reveals that improved oxygen supply in bioreactor significantly reduces bioremediation time in comparison with shake flasks.     

Photoinduced oxidation of Hg0(aq) in the waters from the St. Lawrence estuary

The oxidation of volatile aqueous Hg0 in aquatic systems may be important in decreasing the fluxes of Hg out of the water column. Using incubations of natural samples from the St. Lawrence River, we examined some of the parameters that control this oxidation. Hg0 was found to be chiefly mediated by UV radiation since (i) "dark" oxidation was not found to be statistically significant; (ii) visible light induced a significant but slow photooxidation (k = 0.09 h(-1)); and (iii) visible + UV radiation led to a faster photooxidation (k = 0.6-0.7 h(-1)), mainly because of UV-A induced reactions. Doubling UV irradiation did not increase the reaction rate of Hg0 photooxidation in natural water samples, indicating that some factor other than photon flux was rate limiting and suggesting that the reaction involves intermediate photoproduced oxidant(s). The addition of methanol, a *OH scavenger, decreased Hg photooxidation rates by 25% in brackish waters and by 19% in artificial saline water containing semiquinones, indicating that *OH may be partly responsible for Hg0 oxidation. Photooxidation rates were not affected by oxygen concentrations and did not decrease when samples were heat-sterilized, treated with chloroform, or filtered prior to exposure to light.