Ionic conductivity of PVdF-co-HFP/LiClO4 in terms of free volume defects probed by positron annihilation lifetime spectroscopy

ABSTRACT

Polymers based on ionic conducting materials have important interest because of their potential applications in polymer electrolytes and membranes for fuel cell application. PVdF-co-HFP poly(viniliden-co-hexafluoropropylene) was chosen as a polymer matrix because of its high ionic conductivity and better mechanical properties. Polymer matrix composites were prepared with various amounts of LiClO₄ salt by a solution casting method. The sample-ionic conductivity measurements were recorded by AC impedance analyzer at different frequencies from 0.1?Hz to 20?MHz and at different temperatures from 273 to 373?K.

The changes of nanoscopic free volume and free volume fraction in these materials were investigated in terms of temperature from 273 to 373?K using Positron Annihilation Lifetime Spectroscopy (PALS) and Simha-Somcynsky (SS) Hole Theory. The free volume had a bump at about 3% in weight percentage of the salt and there is a slight increase after 10%. The effects of weight percentages of LiClO₄ and temperature were investigated. The mechanism of the ac ionic conductivity was presented in terms of the free volume models, however thermo-occupancy function justifies the best accurate representation of the data.     

Λ-strongly summable sequence spaces in n-normed spaces defined by ideal convergence and an Orlicz function

In this paper we introduce some certain new sequence spaces via ideal convergence, λ-sequence and an Orlicz function in n-normed spaces and study different properties of these spaces and also establish some inclusion results among them.     

PEG–Anthracene Hydrogels as an On‐Demand Stiffening Matrix To Study Mechanobiology

There is a growing interest in materials that can dynamically change their properties in the presence of cells to study mechanobiology. Herein, we exploit the 365 nm light mediated [4+4] photodimerization of anthracene groups to develop cytocompatible PEG‐based hydrogels with tailorable initial moduli that can be further stiffened. A hydrogel formulation that can stiffen from 10 to 50 kPa, corresponding to the stiffness of a healthy and fibrotic heart, respectively, was prepared. This system was used to monitor the stiffness‐dependent localization of NFAT, a downstream target of intracellular calcium signaling using a reporter in live cardiac fibroblasts (CFbs). NFAT translocates to the nucleus of CFbs on stiffening hydrogels within 6 h, whereas it remains cytoplasmic when the CFbs are cultured on either 10 or 50 kPa static hydrogels. This finding demonstrates how dynamic changes in the mechanical properties of a material can reveal the kinetics of mechanoresponsive cell signaling pathways that may otherwise be missed in cells cultured on static substrates.     

Fractional diffusion-wave problem in cylindrical coordinates

In this Letter, we present analytical and numerical solutions for an axis-symmetric diffusion-wave equation. For problem formulation, the fractional time derivative is described in the sense of Riemann-Liouville. The analytical solution of the problem is determined by using the method of separation of variables. Eigenfunctions whose linear combination constitute the closed form of the solution are obtained. For numerical computation, the fractional derivative is approximated using the Grünwald-Letnikov scheme. Simulation results are given for different values of order of fractional derivative. We indicate the effectiveness of numerical scheme by comparing the numerical and the analytical results for α=1 which represents the order of derivative.     

Ni(II), Cu(II), and Zn(II) complexes of tetradentate schiff base containing two thiadiazoles units: Structural,spectroscopic, magnetic properties,and molecular modeling studies

Four new mononuclear metal complexes with a mononucleating Schiff base ligand containing two thiadiazoles units have been synthesized. The ligand and metal complexes were characterized by elemental analyses, IR, ¹H, and ¹³C NMR, UV–vis, ESR, electrospray ionization mass spectra, and magnetic susceptibility measurements. Electronic spectra, magnetic susceptibility measurement, and molecular modeling studies support octahedral geometry around the Ni(II), Cu(II), and Zn(II) ions. The magnetic properties were investigated, and ferromagnetic coupling is observed in Cu(II) and Ni(II) complexes. In addition, total energy and heat of formation calculated for conformers of the Schiff base ligand by the semiempirical AM1 calculations have shown that E,Z‐isomer of the ligand is more stable (about 5.3 kcal/mol) than E,E‐ and Z,Z‐isomers. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:700–712, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20496     

Electrical and photoelectrical behaviour of heterojunctions based on novel oligomeric metal complexes

Naringenin‐based Schiff base ligands with 4‐aminobenzoic hydrazide were obtained as a unilateral form ( L¹ ). The ligand was oligomerized by oxidative polycondensation reaction with NaOCl as an oxidant in an aqueous alkaline medium at 90 °C to form a functional oligomer ( L² ), and its transition metal complexes such as those with Cu(II), Ni(II) and Zn(II) were prepared. The monomer and the oligomeric compounds were characterized using various techniques. Optical and electrical properties of the complexes were also investigated. All compounds showed indirect band gaps and they can be accepted as being in the semiconductor class. Organic–inorganic hybrid devices were obtained using n‐Si inorganic semiconductor and the complexes. The characteristic parameters of the devices were determined using current–voltage (I–V) and capacitance–voltage measurements in the dark. Photoelectrical properties of the devices were investigated using I–V measurements under a solar simulator with an AM1.5 global filter. Copyright © 2015 John Wiley & Sons, Ltd.     

A High Sensitive,Reproducible and Disposable Immunosensor for Analysis of SOX2

In this study, an ITO (indium tin oxide) based biosensor was constructed to detect SOX2. SOX2 helps the regulation of cell pluripotency and is closely related to early embryonic development, neural and sexual differentiation. SOX2 is amplified and overexpressed in some malignant tumors such as squamous cell, lung, prostate, breast, esophageal cell, colon, ovarian, glioblastoma, pancreatic cancer, gastric cancer, head and neck squamous cell carcinoma. To generate a hydroxylated clean electrode surface, ITO electrodes were treated with NH₄OH/H₂O₂/H₂O. Later, ITO‐PET electrode surfaces were modified with 3‐glycidoxypropyl trimethoxysilane (3‐GOPS). Then, Anti‐SOX2 was covalently immobilized onto the electrode surfaces. 3‐GOPS concentration, Anti‐SOX2 concentration and incubation time, SOX2 incubation time were optimized. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were utilized in order to follow up the immobilization processes and the optimization steps of the biosensor. To characterize the analytical properties of constructed immunosensor; linear range, repeatability, reproducibility and regeneration studies were investigated. The linear range of the immunosensor was detected as 0.625 pg/mL–62.5 pg/mL. Square wave voltammetry technique was also applied to the biosensor. Storage life of the biosensor was determined for identifying the possible usability of the biosensor in clinical field. Finally, the designed biosensor was applied to the real human serum samples. The results obtained with the presented biosensor were also compared with ELISA results.     

A Practical Approach for the Detection of Protein Tau with a Portable Potentiostat

Along with many factors, the change in protein tau isoforms, which has an obvious role in the function of microtubules, is an important biomarker of Alzheimer's disease. The aim of this study is to determine the protein Tau-441 with a portable potentiostat using a practical approach. For this purpose, screen printed electrodes (SPCEs) were first hydroxylated and then functional self-assembled monolayers were formed on the surface with 3-aminopropyltriethoxysilane (APTES). Evidence of anti-Tau being immobilized on to the surface was followed by techniques such as cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and Fourier transform infrared spectroscopy (FTIR). The constructed immunosensor showed a linear response within the concentration range of 0.0064–0.8 ng/mL for the target analyte Tau-441 and the limit of detection was found to be 0.0053 ng/mL. In addition, analytical behaviors such as reproducible measurements and storage life of the developed immunosensor with a portable potentiostat were also investigated. It has been demonstrated that Tau-441 can be captured with the help of portable device with sensitivity in CSF environment.