New PP/PLA/cellulose composites: effect of cellulose functionalization on accelerated weathering behavior (accelerated weathering behavior of new PP/PLA/cellulose composites)

Polylactic acid (PLA) was used as partial replacement for conventional thermoplastic matrix, new composites comprising cellulose, polypropylene (PP), and PLA being realized. In order to obtain a compatible interface between cellulosic pulp and polymeric matrix, two chemical modifications of cellulose with stearoyl chloride and toluene di‐isocyanate (TDI) were performed, structural changes being evidenced by X‐ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The composite materials were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, dynamic scanning calorimetry, impact, tensile and melt rheological tests, surface tension, and dynamic vapor sorption. Because promising results for impact strength and Young modulus were recorded when replacing 15% of PP with PLA in blends of PP with the same cellulosic pulp load, the aim of our study was to assess the behavior to accelerate weathering of composites comprising PP, cellulosic pulp, and PLA. Although the slight decrease in the mechanical properties was recorded after accelerated weathering, the use of functionalized cellulose successfully prevented the deterioration of surface materials, especially for composite comprising stearoyl chloride treated cellulose pulp. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis,characterization of nanosized CoAl<Subscript>2</Subscript>O<Subscript>4</Subscript> and its electrocatalytic activity for enhanced sensing application

Nanosized cobalt aluminate (CoAl₂O₄) was prepared by thermolysis of heteronuclear coordination compound, namely [Al₂Co(C₂O₄)₄(OH₂)₆]. The synthesized precursor was characterized by chemical analysis, vibrational spectra and thermal analysis. The cobalt aluminate obtained after a heating treatment of the precursor at 700 °C was characterized by IR, XRD, TEM coupled with SAED measurements. Two types of carbon-based electrodes, glassy carbon and boron-doped diamond electrodes were decorated with the obtained cobalt aluminate in order to enhance the electroanalytical performance for the tetracycline (TC) detection in the aqueous solutions. Cyclic voltammetry technique was used to determine the effect of the nanosized CoAl₂O₄ on the electrochemical oxidation of TC and as consequence, for TC detection at both carbon-based electrodes. The obtained cobalt aluminate exhibited the electrocatalytic activity toward TC detection in direct relation with the type of the carbon substrate, which allowed enhancing the electroanalytical parameters of TC detection in the aqueous solution.     

Ultrahigh-throughput screening system for directed glucose oxidase evolution in yeast cells

A compartmentalized tyramide labeling system (CoaTi) employing flow cytometry for sorting of yeast cells was developed as ultrahigh-throughput screening for Glucose oxidase (GOx) from Aspergillus niger. CoaTi combines in vitro compartmentalization technology with the CARD reporter system which uses fluorescein tyramide labels for detection of peroxidase activity. Physical connection between cells and fluorescein tyramide radicals was achieved by compartmentalization of yeast cells inside microdroplets of single water-in-oil emulsions. After reaction cells were recovered from single emulsions and sorted by flow cytometry, an error prone PCR mutant library of Glucose oxidase (GOx) containing 10(7) cells and ~10(5) of different GOx variants was screened. Mutagenic conditions of GOx mutant library were selected to generate <1 % of active GOx population in order to explore influence of high mutation frequency on GOx activity. GOx variant Mut12 that contains 5 mutations (N2Y, K13E, T30V, I94V, K152R) showed a 1.2 times decreased K(m) (22.0 vs 18.1 mM) and a 2.7 fold increased k(cat) (150 s(-1) vs 54.8 s(-1)) compared to wt GOx. Compared to the employed parent B11 GOx (16 mM, 80 s(-1)) it has a slightly increased K(m) and 1.8 times increased k(cat).     

Heterogeneous reactivity of chlorine atoms with sodium chloride and synthetic sea salt particles

The uptake of chlorine atoms on sodium chloride (NaCl) and synthetic sea salt (SSS) particles was studied using a discharge flow reactor coupled to a molecular beam mass spectrometer. The reactive surfaces were prepared by coating the inner surface of the reactor using two different methods: either by depositing size-selected particles on halocarbon wax or by spray depositing thin films using a constant output atomizer. The observed uptake coefficients of Cl˙ on NaCl particles are γ(NaCl)(Cl) ≈ 2 × 10(-2) for size-selected particles or γ(NaCl)(Cl) ≈ 5 × 10(-2) for thin films and for SSS particles γ(SSS)(Cl) ≈ 4 × 10(-3). Heterogeneous recombination of Cl atoms to Cl(2) molecules was observed for the two solid surfaces. The study was performed over the temperature range 258 to 353 K. The temperature dependence of the uptake was observed and the heat of adsorption of Cl˙ on NaCl particles was estimated at Q(ads) = 63 kJ mol(-1) assuming an Eley-Rideal mechanism. The role of surface adsorbed water has also been shown. The atmospheric implications of these findings are discussed briefly.     

Effect of the interface on separation in multicapillary gas chromatography-based hyphenated techniques for speciation analysis of organometallic compounds

This paper reports the effect of transfer line (TL) internal diameter (i.d.) on gas chromatographic separation characteristics such as efficiency and speed, when a multicapillary (MC) column is used for speciation analysis of mercury. Five different TL consisting of fused-silica capillaries with 0.15, 0.20, 0.25, 0.32, and 0.53 mm i.d. are compared. The separation efficiency and total chromatographic run time are critically affected by the i.d. of the TL. Narrow capillaries (i.d.0.20 mm) produce minimum peak dispersion whereas wide capillaries result in narrow peaks and shorter chromatographic analysis times. A thermodynamic approach is proposed to describe the motion of the analytes through the separation column and TL. The model provides good agreement with the experimental data for high pressures (35 psig) and wide TL (0.25 mm i.d.).Dedicated to the memory of Wilhelm Fresenius