Novel routes to epoxy functionalization of PHA‐based electrospun scaffolds as ways to improve cell adhesion

Straightforward and versatile routes to functionalize the surface of poly(3‐hydroxyalkanoate) (PHA) electrospun fibers for improving cell compatibility are reported under relatively mild conditions. The modification of nanofibrous PHAs is implemented through two different methodologies to introduce epoxy groups on the fiber surface: (1) preliminary chemical conversion of double bonds of unsaturated PHAs into epoxy groups, followed by electrospinning of epoxy‐functionalized PHAs blended with nonfunctionalized PHAs, (2) electrospinning of nonfunctionalized PHAs, followed by glycidyl methacrylate grafting polymerization under UV irradiation. The latter approach offers the advantage to generate a higher density of epoxy groups on the fiber surface. The successful modification is confirmed by ATR‐FTIR, Raman spectroscopy, and TGA measurements. Further, epoxy groups are chemically modified via the attachment of a peptide sequence such as Arg‐Gly‐Asp (RGD), to obtain biomimetic scaffolds. Human mesenchymal stromal cells exhibit a better adhesion on the latter scaffolds than that on nonfunctionalized PHA mats. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 816–824     

Effect of surface on the optical structure and thermal properties of organically capped CdS nanoparticles

Cadmium sulfide (CdS) nanoparticles were synthesized by a novel wet chemical route with various organic thiol stabilizers. Systematic experimental studies, including X-ray diffraction (XRD), ultraviolet–visible (UV–vis) spectroscopy, Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), photoluminescence (PL) spectroscopy, and time-resolved photoluminescence (TRPL), have evidenced that the stability, crystallinity, and optical properties of the CdS nanoparticles are affected by the organic groups which generate significant effects in surface reconstruction. Particle size was evaluated from UV–vis spectroscopy using the effective mass approximation (EMA) method and from XRD patterns based on Scherrer?s formula. The S–H vibrations are not detectable in the infrared (IR) spectra of any of the bound ligands, which are expected for thiols covalently bound to the surface of nanoparticles. PL studies reveal that the emission from the nanostructures is not much influenced by the surface states, indicating a good passivation of the particle?s surface. The time-resolved measurements reveal a biexponential decay behavior. The fast decay component is attributed to the recombination of core states, while the slow decay component of PL is associated with the charge-carrier recombination process with the involvement of surface states.     

The effect of plasma treatment on structure and properties of poly(1-butene) surface

This paper is focused on the chemical and morphology changes in the surface of poly(1-butene) (PB-1) generated by plasma treatment. The radio frequency capacitively coupled plasma (air, argon, argon then allylamine, argon containing ammonia and argon with octafluorocyclobutane) was used. Modified surface of PB-1 was characterized by contact angle measurements, X-ray photoelectron spectroscopy, and atomic force microscopy. The surface hydrophilization by air and argon with ammonia plasmas was evaluated as most sufficient. Oppositely, a high level of hydrophobicity of PB-1 surface was reached by combination of argon with octafluorocyclobutane plasma. Upon plasma modification, hydrophilicity/hydrophobicity of treated surfaces remained stable within three days under air atmosphere and then values of contact angle slowly recovered to those of unmodified PB-1. However, morphology and surface chemical composition of plasma-modified samples remained generally unchanged during observed time. Changes in surface hydrophilicity/hydrophobicity of plasma-treated PB-1 were attributed to variance of conformation of the surface molecules.     

Ion sensing film optodes based on chromogenic calix[4]arene: application to the detection of Hg2+, Ni2+ and Eu3+ ions

The development of sensors for the detection of transition metal ions has attracted a special attention because of the toxic impact of these elements on our environment. Due to their sensitivity, reliable, inexpensive and easy use for on site analysis, optical chemical sensors (optodes) have received an increasing attention for a rapid determination of toxic species in water. A new chromogenic calix[4]arene has been investigated on the basis of the high recognition properties of calixarenes associated to the optical response provided by their functionalization with a phenyl azo group. Thin tetrakis-(phenylazo) calix[4]arene amide derivative layers deposited on a glass suprasil substrate have been characterized by contact angle measurements showing a good surface coverage whereas a uniform morphology of the calixarene membrane in acetonitrile solvent was observed by scanning electron microscopy (SEM). The ability of the tetrakis-(phenylazo) calix[4]arene amide derivative thin film to complex Hg²⁺, Ni²⁺ and Eu³⁺ ions have been demonstrated by the modification of the calixarenes main absorption band at 343?nm and appearance of a new absorption band at 500?nm upon addition of Eu³⁺. The different sensors could be regenerated with hydrochloric acid. The dynamic concentration range, ion selectivity, response time, repeatability and reproducibility are discussed. These results are suitable to the development of optodes for the detection of metal pollutants.     

Low Reynolds number axisymmetric turbulent boundary layer on a cylinder

In the present study, an axisymmetric turbulent boundary layer growing on a cylinder is investigated experimentally using hot wire anemometry. The combined effects of transverse curvature as well as low Reynolds number on the mean and turbulent flow quantities are studied. The measurements include the mean velocity, turbulence intensity, skewness and flatness factors in addition to wall shear stress. The results are presented separately for the near wall region and the outer region using dimensionless parameters suitable for each case. They are also compared with the results available in the open literature.The present investigation revealed that the mean velocity in near wall region is similar to other simple turbulent flows (flat plate boundary layer, pipe and channel flows); but it differs in the logarithmic and outer regions. Further, for dimensionless moments of higher orders, such as skewness and flatness factors, the main effects of the low Reynolds number and the transverse curvature are present in the near wall region as well as the outer region.