Hydrophobic Zeolite‐Filled Polymeric Films with High Ethylene Permselectivity for Fresh Produce Packaging Applications

Gas permselective plastic films have been in a great deal of attention in the area of modified atmosphere packaging of fresh produces. Such films must allow transport of the respiring gases, i.e. oxygen and carbon dioxide, in a controlled manner and, moreover, should efficiently remove ethylene gas. Therefore, the development of highly permeable films with high ethylene permselectivity, i.e. high in both permeability and selectivity, was carried out. The concept of ‘mixed matrix membrane’, by which enhanced gas permselectivity can be obtained by incorporation of zeolite particles into the polymeric film, was applied. Fine particles of hydrophobic zeolites, i.e. zeolite beta and ZSM‐5, and the surface‐modified zeolites were used in this study. The films with uniform distribution of zeolite particles (10% w/w) in 70LDPE/30SEBS (styrene‐b‐(ethylene‐ran‐butylene)‐b‐styrene block copolymer) matrix can be prepared by blow film extrusion. Significantly high ethylene permselectivity, i.e. ethylene permeability of 1.78–2.67 × 10³ cm³ ? mm/m² ? day ? atm and ethylene/O₂ selectivity of 4.67–8.26, was obtained from the films containing octyl‐modified and phenyl‐modified zeolites. Particular enhancement was observed on the films containing phenyl‐modified zeolites. Crystallinity of polyethylene, transition temperatures and decomposition temperature were, however, indifferent among the studied films. Nevertheless, elongation at break and toughness of the films containing surface‐modified zeolites were superior. Particle–polymer interface could thus be improved. Copyright © 2014 John Wiley & Sons, Ltd.     

Ethanol sensing properties of CuO nanowires prepared by an oxidation reaction

The ethanol sensing properties of CuO nanowires prepared by oxidation reaction of copper plate have been examined. The characterization of CuO nanowires by FE-SEM, EDS, and TEM revealed diameters of 100–400 nm and a monoclinic structure with a growth direction along 〈1 1 0〉 direction. The ethanol sensing characteristics of CuO nanowires were studied at ethanol concentrations of 100–1000 ppm and working temperatures of 200–280 °C. An increase of resistance was observed under an ethanol vapor atmosphere due to the p-type semi-conducting property of CuO. It was found that the sensitivity, the response and the recovery time depended on the working temperatures and also ethanol concentration. The sensor exhibited the optimum sensitivity of 1.5 to ethanol vapor concentration of 1000 ppm at the working temperature of 240 °C with a response and recovery time of 110 and 120 s, respectively.     

Copper oxide thin film and nanowire as a barrier in ZnO dye-sensitized solar cells

The ZnO dye-sensitized solar cells (DSSCs) with different photoelectrodes were studied on the effect of CuO layer as a barrier layer toward power conversion characteristics. The structures of DSSCs based on ZnO as a photoelectrode, Eosin-Y as a dye sensitizer, iodine/iodide solution as an electrolyte and Pt/FTO as a counterelectrode. CuO powder, nanowire prepared by oxidation reaction of copper powder and CuO thin film prepared by evaporation copper thin film, were used as a layer on the top of ZnO layer to form blocking layer. The photocurrent, photovoltage and power conversion efficiency characteristics for DSSCs were measured under illumination of simulated sunlight obtained from a solar simulator with the radiant power of 100 mW/cm². It was found that ZnO DSSCs with CuO thin film exhibited highest current density of 5.10 mA/cm² and highest power conversion efficiency of 0.92% than those of CuO powder and nanowire. The enhancement of the power conversion efficiency can be explained in terms of the retardation of the interfacial recombination dynamics of CuO blocking layer.