Poly(lactic acid)-based bio-blends and nanocomposites

172 p.

Development of the heterogeneous catalysts for the production of levulinic acid from furfuryl alcohol

207 p.

Sol-gel combustion synthesis and luminescent properties of nanocrystalline YAG : Eu3+ phosphors

EU3+ -doped Y3Al5O12 (YAG:Eu3+) phosphors were synthesized by a facile sol-gel combustion method. In this process, citric acid traps the constituent cations and reduces the diffusion length of the precursors. YAG phase is obtained through sintering at 900 degrees C for 2h. There were no intermediate phases such as YAlO3 (YAP) and Y4Al2O9 (YAM) observed. The charge transfer band of nanocrystalline phosphors shows a shift toward the high-energy side, compared with that of amorphous ones due to lower covalency of Eu-O bond for nanocrystalline phosphors. The higher concentration quenching in YAG:EU3+ nanophosphors may be caused by the confinement effect on resonant energy transfer of nanocrystalline. It also indicates that the sol-gel combustion synthesis method provides a good distribution of Eu3+ activators in YAG host. (c) 2005 Elsevier B.V. All rights reserved.

Structural and optical properties of YAG : Ce3+ phosphors by sol-gel combustion method

High-quality Ce3+-doped Y3Al5O12 (YAG:Ce3+) phosphors were synthesized by a facile sol-gel combustion method. In this sol-gel combustion process, citric acid acts as a fuel for combustion, traps the constituent cations and reduces the diffusion length of the precursors. The XRD and FT-IR results show that YAG phase can form through sintering at 900 degrees C for 2 h. This temperature is much lower than that required to synthesize YAG phase via the solid-state reaction method. There were no intermediate phases such as YAlO3 (YAP) and Y4Al2O9 (YAM) observed in the sintering process. The average grain size of the phosphors sintered at 900-1100 degrees C is about 40 nm. With the increasing of sintering temperature, the emission intensity increases due to the improved crystalline and homogeneous distribution of Ce3+ ions. A blue shift has been observed in the Ce3+ emission spectrum of YAG:Ce3+ phosphors with increasing sintering temperatures from 900 to 1200 degrees C. It can be explained that the decrease of lattice constant affects the crystal field around Ce3+ ions. The emission intensity of 0.06Ce-doped YAG phosphors is much higher than that of the 0.04Ce and 0.02Ce ones. The red-shift at higher Ce3+ concentrations may be Ce-Ce interactions or variations in the unit cell parameters between YAG:Ce3+ and YAG. It can be concluded that the sol-gel combustion synthesis method provides a good distribution of Ce3+ activators at the molecular level in YAG matrix. (c) 2005 Elsevier B.V. All rights reserved.

Enhancement of ferromagnetic properties in In1.99Co0.01O3 by additional Cu doping

This paper reports room-temperature ferromagnetism in Co- and Cu-doped In2O3 samples synthesized by a solid-state reaction method. Structure and composition analyses revealed that Co and Cu were incorporated into the In2O3 lattices. Photoluminescence measurement revealed an additional emission at 520 urn from these doped samples. The magnetic measurement showed that additional Cu doping greatly enhanced the ferromagnetism of In1.99Co0.01O3 bulk samples. The implication of the effects of additional Cu doping is also discussed. (c) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Influences of Al doping concentration on structural, electrical and optical properties of Zn0.95Ni0.05O powders

Nanocrystalline Zn0.95 - xNi0.05AlxO (x = 0.01, 0.02, 0.05 and 0.10) diluted magnetic semiconductors have been synthesized by an auto-combustion method. X-ray diffraction measurements indicate that all Al-doped Zn0.95Ni0.05O samples have the pure wurtzite structure. Transmission electron microscope analyses show that the as-synthesized powders are of the size 40 - 45 nm. High-resolution transmission electron microscope, energy dispersive spectrometer and X-ray photoemission spectroscope analyses indicate that Ni2+ and Al3+ uniformly substitute Zn2+ in the wurtzite structure without forming any secondary phases. The Al doping concentration dependences of cell parameters (a and c), resistance and the ratio of green emission to UV emission have the similar trends. (c) 2007 Elsevier B.V. All rights reserved.

Estudo estrutural e funcional das proteínas ligadoras de ácidos graxos (FABP- Fatty Acid Binding Proteins) de Fasciola hepatica

As proteínas ligadoras de ácidos graxos (Fatty Acid Binding Proteins, FABPs) de parasitos têm um papel importante no processo de infecção por estes organismos. Por este motivo, estas proteínas são antígenos candidatos para vacina contra a infecção por Schistosoma mansoni e Fasciola hepatica. No presente trabalho foram caracterizadas FABPs de F. hepatica e comparadas com a proteína Sm14 de S. mansoni, a FABP de parasito melhor caracterizada, mediante análise de sequências e estruturas modeladas. Também foram clonadas, expressas e purificadas as FABPs tipo 1 e tipo 3 de F. hepatica. Os resultados do presente estudo indicam que a FABP tipo 3 de F. hepatica é relacionada estrutural, imunológica e funcionalmente com a Sm14, um candidato vacinal amplamente estudado. Devido à importância da Sm14 como alvo para o desenvolvimento de vacina para a esquistossomose, as características apresentadas pela FhFABP3 de F. hepatica apontam esta proteína como um candidato importante também para o desenvolvimento de uma vacina contra a fasciolose