Tuning hydrophobicity of a fluorinated terpolymer in differently assembled thin films

In the current report, casting from good solvent (acetone) and casting from mixed solvent and nonsolvent were employed for preparing thin films of terpolymer of T etrafluoroethylene (TFE), H exafluoropropylene (HFP), and V inylidene fluoride (VDF) (THV), on silicon wafers. These films revealed various morphologies and wetting behaviors depending on the solution concentration, temperature, and thin film preparation method. The THV thin films prepared by casting from good solvent showed smooth morphology with holes. The thin film prepared from a 3 wt % THV/acetone solution by casting from good solvent at 15 °C demonstrated spheres in addition to the smooth morphology, while the thin film prepared from a 5 wt % THV/acetone solution at 15 °C by casting from good solvent had a mesh‐like structure with some linked spheres. Casting the thin films from mixed solvent and nonsolvent resulted in various morphologies such as different sphere sizes embedded in a dense film layer, and hexagonal close packed structures. The thin films prepared by casting from good solvent showed a slightly hydrophobic character, with a measured water contact angle of approximately 99°, while the nonsolvent cast films had a water contact angle as high as 145°. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 643–657     

Progress and Prospects on the Fabrication of Graphene-Based Nanostructures for Energy Storage,Energy Conversion and Biomedical Applications

Graphene, a two-dimensional (2D) layered material has attracted much attention from the scientific community due to its exceptional electrical, thermal, mechanical, biological and optical properties. Hence, numerous applications utilizing graphene-based materials could be conceived in next-generation electronics, chemical and biological sensing, energy conversion and storage, and beyond. The interaction between graphene surfaces with other materials plays a vital role in influencing its properties than other bulk materials. In this review, we outline the recent progress in the production of graphene and related 2D materials, and their uses in energy conversion (solar cells, fuel cells), energy storage (batteries, supercapacitors) and biomedical applications.     

Oxygen Barrier LDPE/LLDPE/Organoclay Nano-Composite Films for Food Packaging

Summary: This study intends to replace polyethylene multi-layer films used in food packaging industry with single-layer polyethylene nanocomposites films. Nanocomposites of LDPE/LLDPE/ montmorillonite organoclay were prepared by melt compounding in a twin extruder and then film blown to prepare thin films. LLDPE-g-MA was used as compatibilizer to achieve better interaction between the blend and organoclay. Various compositions of organoclay and compatibilizer were prepared. The structure of nanocomposites was characterized by XRD and TEM. Permeability properties were measured using a permeability measuring set-up and aspect ratio of the particles was evaluated using permeability data. The results showed that addition of organoclay even at low level (below 5 phr) had significant effect on barrier properties of the nanocomposites. Oxygen permeability decreased by 50% by adding only 3 phr of nanoclay into the blend. Crystalline structure of the nanocomposites was studied by DSC. Addition of clay also led to increase in melting point and somewhat decrease in the crystalline level. Given the fact that crystals are effectively non-permeable, the concomitant reduction in crystallinity of the blend with decrease in permeability suggests that barrier properties arise from tortuousity of nanoparticles in the blend.     

On the Second Iterate for Critically Diffusive Active Scalar Equations

We consider an iterative resolution scheme for a class of active scalar equations with a fractional power γ of the Laplacian and focus our attention on the second iterate. In the case of critical diffusivity, we extract information relevant to Well-posedness questions in scale-invariant spaces. Our results are Two-fold: we prove continuity of the bilinear operator in ${\dot{B}^{0}_{\infty,1}}$ ; for equations with an even symbol we show that the ${B^{-1/2}_{\infty,q}}$ -regularity, where q > 2, is in a sense a minimal necessary requirement on the solution.     

High performance two-color one megapixel CMOS ROIC for QWIP detectors

FLIR Systems, Inc. has designed and fabricated the ISC0501 CMOS readout integrated circuit (ROIC) for quantum well infrared photodetectors (QWIPs). The ISC0501 is a two-color 1024 × 1024 format array with a 30 μm pixel pitch. The ROIC contains a separate analog signal path for each wavelength band. Separate signal paths allow the two-colors to have optimized detector biases, integration times, offsets and gains. This architecture also allows both colors to simultaneously sample a scene and readout the pixel data. This paper will describe the interface, design and features of the ROIC as well as a summary of the characterization test results. A sample image is included from a focal plane array (FPA) built by the Jet Propulsion Laboratory (JPL) using the ISC0501 ROIC with QWIP detectors designed by JPL.     

Highly Water‐Soluble,Fluorescent, Conjugated Fluorene‐Based Glycopolymers with Poly(ethylene glycol)‐Tethered Spacers for Sensitive Detection of Escherichia coli

Know your bacteria! Two fluorene‐based, conjugated polymers with oligo(ethylene glycol)‐ and poly(ethylene glycol)‐tethered spacers have been prepared by the Suzuki coupling polymerization reactions. β‐Glucose and α‐mannose residues were covalently attached to the conjugated polymers by post‐polymerization functionalization with thiol‐functionalized carbohydrates under basic conditions. Investigations on their use as biosensing materials for the detection of Escherichia coli are reported (see figure).

     

Headspace solid-phase microextraction–gas chromatography–mass spectrometry for profiling free volatile compounds in Cabernet Sauvignon grapes and wines

The complex aroma of wine is derived from many sources, with grape-derived components being responsible for the varietal character. The ability to monitor grape aroma compounds would allow for better understanding of how vineyard practices and winemaking processes influence the final volatile composition of the wine. Here, we describe a procedure using GC–MS combined with headspace solid-phase microextraction (HS-SPME) for profiling the free volatile compounds in Cabernet Sauvignon grapes. Different sample preparation (SPME fiber type, extraction time, extraction temperature and dilution solvent) and GC–MS conditions were evaluated to optimize the method. For the final method, grape skins were homogenized with water and 8 ml of sample were placed in a 20 ml headspace vial with addition of NaCl; a polydimethylsiloxane SPME fiber was used for extraction at 40 °C for 30 min with continuous stirring. Using this method, 27 flavor compounds were monitored and used to profile the free volatile components in Cabernet Sauvignon grapes at different maturity levels. Ten compounds from the grapes, including 2-phenylethanol and β-damascenone, were also identified in the corresponding wines. Using this procedure it is possible to follow selected volatiles through the winemaking process.     

Reversible Control of Third-Order Optical Nonlinearity of DNA Decorated Carbon Nanotube Hybrids

Positive and negative third-order optical nonlinearities have been investigated in single-stranded DNA wrapped semiconducting single-walled carbon nanotubes. It is found that the redox reactions of hydrogen peroxide can reverse the sign of the third-order nonlinearity. The observation proves that the lowest unoccupied molecular orbital has a lower density of electronic states than that of the highest occupied molecular orbital. A three-energy-level model is used to explain the effect of the redox reactions. Raman spectroscopy has also been used to investigate the interaction between single-walled carbon nanotubes and single-stranded DNA.