Physical, thermal, and electrochemical characterization of stretched polyethylene separators for application in lithium-ion batteries

The single-layered microporous polyethylene separator is prepared by dry process and has been stretched in uni-axial direction to two different ratios namely 180 and 300 % in order to create high-performance and cost-effective separator for practical application in lithium-ion batteries. In this study, the structures of the microporous polyethylene separator prepared by dry process and uni-axially stretched to two different ratios of 180 and 300 % were characterized. The physical structure of the stretched separator is characterized by key factors such as thickness, mean pore size, porosity, Gurley value, ionic resistivity, MacMullin number and tortuosity. The thermal behavior of the stretched separator is explained by using differential scanning calorimeter (DSC). DSC explains the melting and shutdown behavior of the separator. Electrochemical property is studied by linear sweep voltammetry, electrochemical impedance spectroscopy (EIS) and cyclic performance. EIS is performed to explain, in elaborate, the resistance of separator and the specific discharge capacity is observed using the cyclic performance. Three hundred percent stretched separator is observed to have comparatively less resistance and higher discharge capacity than the 180 % stretched separator.     

Aptamer‐Assisted Gold Nanoparticles/PEDOT Platform for Ultrasensitive Detection of LPS

Neatly arranged gold nanoparticles (AuNPs) were directly electrodeposited on an electrochemically polymerized self‐assembled monolayer (SAM) of thiol‐functionalized 3,4‐ethylenedioxythiophene (EDOT) derivative, EDTMSHA. A thiolated single‐stranded DNA (ssDNA) aptamer with high specificity to LPS was immobilized on the AuNPs/conducting polymer composite film, serving as sensing platform for LPS detection. Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), scanning electron microscope (SEM), and atomic force microscopy (AFM) were utilized to characterize the modification and detection processes. The electron transfer resistance was found to have a linear relationship with LPS concentration from 0.1 pg/mL to 1 ng/mL.     

An All Solid State Potentiometric Sensor for Monohydrogen Phosphate Ions

An all solid state potentiometric sensor using anthracene thiourea derivative as ionophore was developed. It exhibited a near‐Nernstian slope of 30.8±1.0 mV/decade of activity for HPO₄^2? ions in the concentration range of 1.0×10^?7–1.0×10^?3 M at pH 7.4. It displayed excellent selectivity for monohydrogen phosphate over other anions and the selectivity sequence was determined as HPO₄^2?>SO₄^2?>Cl^?>NO₃^?>OAc^?>I^?>ClO₄^?. The developed sensor was evaluated for the analysis of monohydrogen phosphate ions in a standard reference material (SRM 1548) as well as in the potentiometric titration of phosphate ions with a barium chloride solution.     

Fabrication and Properties of Redox Ion Doped Few Monolayer Thick Polyelectrolyte Film for Electrochemical Biosensors at High Sensitivity and Specificity

Redox ions are deposited on a polyelectrolyte‐coated gold electrode by an electric field to fabricate an ion‐selective thin film electrode. The Fe(CN)${{{4- \hfill \atop 6\hfill}}}$ ions are deposited on a few monolayer‐coated polyelectrolyte gold electrode by a slow periodic potential cycle. The deposition process and electrode properties are quantitatively and simultaneously monitored by cyclic voltammetry and a novel technique, using a Scanning Electrometer for Electrical Double‐layers (SEED). No redox properties are obtained without the electric‐field‐deposition. Owing to the redox mediation and net charge due to the redox ion, the electrode is ion‐selective. We demonstrate the principle to detect 1 µM of dopamine in a mixture with 1 mM of ascorbic acid.     

Effect of the residual silanol group protection on the liquid chromatographic resolution of α‐amino acids and proton pump inhibitors on a ligand exchange chiral stationary phase

A new ligand exchange chiral stationary phase (new CSP) containing residual silanol group‐protecting n‐octyl groups on the silica surface was prepared by treating a ligand exchange CSP (original CSP) based on sodium N‐[(R)‐2‐hydroxy‐1‐phenylethyl]‐N‐undecylaminoacetate bonded to silica gel with excess n‐octyltriethoxysilane. The new and original CSPs containing an identical amount of chiral selector were applied to the resolution of α‐amino acids and proton pump inhibitors (PPIs) including omeprazole, pantoprazole, lansoprazole, and rabeprazole. The separation factors (α) and resolutions (R_S) were greater on the new CSP than on the original CSP except for the resolution of asparagine. The trends of the retention factors (k₁) for the resolution of α‐amino acids on the new and original CSPs with the variation of the organic modifier content in aqueous mobile phase were opposite to those for the resolution of PPIs. Removal of the nonenantioselective interactions between the residual silanol groups and the analytes and the improved lipophilicity of the new CSP were proposed to be responsible for the improved chiral recognition ability of the new CSP and the different retention behaviors of the enantiomers between the new and original CSPs.     

Mastoid Obliteration Using Three‐Dimensional Composite Scaffolds Consisting of Polycaprolactone/β‐Tricalcium Phosphate/Collagen Nanofibers: An In Vitro and In Vivo Study

Two different composite scaffolds, solid‐freeform‐fabricated PCL/β‐TCP supplemented with and without collagen nanofibers are fabricated. These scaffolds are evaluated whether a combination of collagen nanofibers with PCL/β‐TCP can promote osteogenesis in a mastoid obliteration. To assess the effects of the cellular activities of osteoblast‐like‐cells (MG63), SEM images and MTT assays are conducted. Experimental mastoid obliteration is performed using guinea pigs that are divided group A (PCL/β‐TCP/collagen‐nanofiber scaffold) and group B (PCL/β‐TCP scaffold). The results reveal that PCL/β‐TCP/collagen scaffold provide much broader cell attachment sites than PCL/β‐TCP scaffold. The µ‐CT and fluorescent microscopy results reveal that the acceleration of early new bone formation within the pores and scaffold itself at week 4 post‐operation is more effective in group A. In addition, based on the results of the histological and µ‐CT at 12 weeks post‐surgery, the effective regeneration of bone in the PCL/β‐TCP/collagen scaffold is appeared.

     

The Effect of Stabilizer on the Mechanical Response of Double‐Emulsion‐Templated Polymersomes

Recent studies have shown that polymersomes templated by microfluidic double‐emulsion possess several advantages such as high monodispersity and encapsulation efficiency compared with those generated based on thin‐film rehydration and electroformation. Stabilizers, including bovine serum albumin (BSA) and polyvinyl alcohol (PVA), have been used to enhance the formation and stability of double emulsions that are used as templates for the generation of polymersomes. In this work, the effect of stabilizers on the mechanical response of double‐emulsion‐templated polymersomes using micropipette aspiration is investigated. It is demonstrated that the existence of stabilizers results in the inelastic response in poly­mersomes in the early stage of solvent removal. However, aged polymersomes that have little residual solvent show elastic behavior. Polymersomes prepared from PVA‐stabilized double emulsions have noticeably lower area expansion moduli than polymersomes prepared from stabilizer‐free and BSA‐stabilized double emulsions, suggesting that PVA is incorporated in the bilayer membrane of polymersomes.

     

Surface anchoring mode‐dependent hydrolysis reactions of hydrazone groups on gold examined by pH‐dependent Raman spectroscopy

We conducted a comparative study of the pH‐dependent anchoring behaviors of 3‐methyl‐2‐benzothiazolinone hydrazone (3M2BH) and benzophenone hydrazone (BPH) on gold nanoparticles (AuNPs) by means of interfacial Raman spectroscopy. We found that several bands of 3M2BH in the highly alkaline pH region disappeared as the colloidal conditions became more neutral and acidic. The vibrational band at 919, 1174, and 1222 cm⁻¹ at pH 10.0 disappeared below pH 9.2, which may be because of the hydrolysis reactions that cleave the labile N―NH₂ group of 3M2BH, indicating a rather perpendicular orientation via the sulfur atom at the surfaces. A fairly high transition pH value was assumed to be because of the interaction of the N―NH₂ group in the vicinity of the surfaces. Several characteristic bands, including 1584 and 1617 cm⁻¹, also exhibited different intensities, suggesting that the adsorbates on Au surfaces underwent structural transformations of the N―NH₂ group after the pH value became neutral or acidic. These changes were not observed for BPH, presumably because of the direct and robust binding of the hydrazone onto Au surfaces. Our results revealed that the pH‐dependent cleavage reactions may vary depending on the surface anchoring modes of the adsorbates. Copyright © 2015 John Wiley & Sons, Ltd.     

Nonenzymatic amperometric sensor for ascorbic acid based on hollow gold/ruthenium nanoshells

We report a new nonenzymatic amperometric detection of ascorbic acid (AA) using a glassy carbon (GC) disk electrode modified with hollow gold/ruthenium (hAu–Ru) nanoshells, which exhibited decent sensing characteristics. The hAu–Ru nanoshells were prepared by the incorporation of Ru on hollow gold (hAu) nanoshells from Co nanoparticle templates, which enabled AA selectivity against glucose without aid of enzyme or membrane. The structure and electrocatalytic activities of the hAu–Ru catalysts were characterized by spectroscopic and electrochemical techniques. The hAu–Ru loaded on GC electrode (hAu–Ru/GC) showed sensitivity of 426 μA mM⁻¹ cm⁻² (normalized to the GC disk area) for the linear dynamic range of <5 μM to 2 mM AA at physiological pH. The response time and detection limit were 1.6 s and 2.2 μM, respectively. Furthermore, the hAu–Ru/GC electrode displayed remarkable selectivity for ascorbic acid over all potential biological interferents, including glucose, uric acid (UA), dopamine (DA), 4-acetamidophenol (AP), and nicotinamide adenine dinucleotide (NADH), which could be especially good for biological sensing.