Photoluminescence study of type-II InGaPN/GaAs quantum wells

Nearly lattice-matched In(0.528)Ga(0.472)P(1-y)Ny bulk layer and In(0.528)Ga(0.472)P(1-y)Ny/GaAs and GaAs/ In(0.528)Ga(0.472)P(1-y)Ny quantum wells with higher N content, y = 0.027, were grown on GaAs(001) substrates by metalorganic vapor phase epitaxy. High-resolution X-ray diffraction results demonstrated the high quality of both the layer and quantum wells with fairly flat interfaces. Temperature dependent photoluminescence results showed that a near-band-edge emission is dominant in the bulk In(0.528)Ga(0.472)P(0.973)N(0.027) layer, which at low temperature (T < 100 K) is associated with localized emissions centered at approximately 1.73 eV. Bandgap of In(0.528)Ga(0.472)P(0.973)N(0.027) was examined to be 1.81 and 1.78 eV at 10 K and room-temperature, respectively. Low temperature (10 K)-photoluminescence spectrum obtained from the GaAs/InxGa(1-x)P(1-y)Ny quantum well also exhibited red emission at 1.73 eV attributed to the emission from the InGaPN barrier. In addition, there are the extra weak peaks appear in a near-infrared energy range at 1.357 and 1.351 eV for InxGa(1-x)P(1-y)Ny/GaAs and GaAs/InxGa(1-x)P(1-y)Ny quantum wells, respectively. Such optical transitions are considered as an indirect transition between electrons located in the InGaPN and holes located in the GaAs regions. This situation suggested that both the In(0.528)Ga(0.472)P(0.973)N(0.027)/GaAs and GaAs/In(0.528)Ga(0.472)P(0.973)N(0.027) quantum wells exhibits a type-II quantum structure. This interpretation is justified when the valence and conduction band offsets of the type-II band alignment, which are relatively approximated to be 450 and 160 meV, are properly taken into account.     

Titanium nitride promoted Ni-based SBA-15 catalyst for dry reforming of methane

Titanium nitride (TiN) promoted nickel catalysts were synthesized and employed as an alternative catalyst in dry reforming of methane (DRM). The series of this catalyst containing various amount of Ni and TiN was prepared in two steps, direct synthesis of SBA-15 in the presence of TiN and the impregnation of Ni. The influence of Ni and TiN loading on DRM reaction was investigated using a feed ratio of CH₄/CO₂ = 1, at 700 °C and atmospheric pressure for a duration of 4 h. The promising catalysts, that gave the highest feed conversions and product yields, were selected for further investigation, compared to non-promoted Ni catalyst using the same conditions but for 12 h of reaction. The results showed that the performance of Ni catalyst was improved by the incorporation of TiN. The modified catalysts provided not only high catalytic activity but also enhancement of coke resistance.     

Zeolite A‐polypropylene and silver‐zeolite A‐polypropylene composite films for antibacterial and breathable applications

Polypropylene (PP) composite films were successfully prepared using melt blending by directly mixing PP pellets with zeolite A or silver‐zeolite A powder and then blowing. All the prepared films were characterized in terms of their physical, mechanical, optical, and gas permeability properties. The structure of each composite film was similar to that of the pure PP film. The crystallinity and glossy quality of the composite films were increased by the addition of silver, zeolite, and maleic anhydride grafted PP (PP‐g ‐MA). The composite PP film with zeolite A and PP‐g ‐MA exhibited a level of oxygen and carbon dioxide permeation (6438 and 15,087 cc m^?2 day^?1 atm^?1, respectively). Finally, all the films were evaluated for their antibacterial activity and fruit packaging applications. Silver‐zeolite A‐PP composite films exhibited a bactericidal activity of 79% against Staphylococcus aureus and 52% against Escherichia coli , while the zeolite A‐PP film could extend the shelf‐life of bananas for over a week. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45450.