LUIZ ANTONIO DE OLIVEIRA NUNES

LUIZ ANTONIO DE OLIVEIRA NUNES

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Tuneable luminescence in multicolour films
2010 - KAI, JIANG; NUNES, LUIZ A.O.; FELINTO, MARIA C.F.C.; MALTA, OSCAR L.; BRITO, HERMI F.
Trivalent Rare Earth (RE3+) β-diketonate complexes and polymethylmetacrylate (PMMA) have been widely employed in the productions of luminescent materials. In this work, preparation, characterization and photoluminescence studies for a series of stand-free polymer thin films incorporating RE3+-β-diketonate complexes into PMMA were reported. The PMMA matrix not only immobilizes the luminescent RE3+ species via physical and chemical interactions, but also operates as co-sensitizer and enhances the characteristic monochromatic emissions arising from the 4f–4f intraconfigurational transitions of the RE3+ ions. Furthermore, it was observed colour-tuneable luminescence with the polymeric systems. Therefore, they are potentially attractive for the production of advanced photonic applications such as multicolour anti-falsification optical markers, λex.= 254 nm full range UV sensors etc. Moreover, the observation of intermolecular energy transfer from the emitter level (5D4) of Tb3+ ions to the triplet state (T1) of the Eu3+ species was unprecedented in literature.
Low temperature synthesis of Ysub(2)Osub(3):Eusup(3+) nanophosphor using tricarboxylate precursor
2010 - BRITO, H.F.; RODRIGUES, L.C.V.; SILVA, I.G.N.; SOUZA, E.R.; KAL, J.; FELINTO, M.C.F.C.; NUNES, L.A.O.
Persistent luminescence mechanism of the CdSiOsub(3):Tbsup(3+) phosphors
2011 - RODRIGUES, L.C.V.; BRITO, H.F.; HOLSA, J.; STEFANI, R.; FELINTO, M.C.F.C.; LASTUSAARI, M.; MALKAMAKI, M.; NUNES, L.A.O.
Synthesis, characterization and spectroscopic studies of tin/titanium mixed oxide nanoparticles doped with europium for use in biomarkers
2012 - PAGANINI, PAULA P.; RODRIGUES, LUCAS C.V.; HOLSA, JORMA; NUNES, LUIZ A.O.; MALTA, OSCAR L.; BRITO, HERMI F.; FELINTO, MARIA C.F.C.
Biolabeling with nanoparticles based on Ysub(2)Osub(3):Ndsup(3+) and luminescence detection in the near-infrared
2011 - KODAIRA, CLAUDIA A.; LOURENCO, ANA V.S.; FELINTO, MARIA C.F.C.; SANCHEZ, EDUARDO M.R.; RIOS, FRANCISCO J.O.; NUNES, LUIZ A.O.; GIDLUND, MAGNUS; MALTA, OSCAR L.; BRITO, HERMI F.
Spectroscopic properties and quantum cutting in Tb3+-Yb3+ co-doped ZrO2 nanocrystals
2013 - TERRA, I.A.A.; BORRERO GONZALEZ, L.J.; CARVALHO, J.M.; TERRILE, M.C.; FELINTO, M.C.F.C.; BRITO, H.F.; NUNES, L.A.O.
Ultraviolet-visible to near-infrared quantum cutting (QC) materials are a promising tool to enhance the efficiency of conventional crystalline silicon solar cells. The spectroscopic properties of Tb3þ–Yb3þ co-doped ZrO2 nanocrystals are presented, and the QC mechanisms in these nanocrystals are investigated. The materials were fabricated using the sol gel method and characterized using X-ray powder diffraction, X-ray absorption near edge structure, and luminescence spectroscopy. The incorporation of Yb3þ ions into the host induced a crystalline phase change of ZrO2 from monoclinic to tetragonal to cubic symmetry and influenced the Tb valence state. The Tb3þ visible emission, excitation intensity (monitored by the Tb3þ: 5 D4 emission), decay time of the Tb3þ: 5 D4 emitter level, and down-conversion (DC) emission intensity increased with Yb3þ concentration. Furthermore, a sublinear dependence of the DC intensity on the excitation power at the Tb3þ: 5 D4 level indicated the coexistence of two different QC mechanisms from Tb3þ ! Yb3þ. The first one is a linear process in which one Tb3þ ion transfers its energy simultaneously to two Yb3þ ions, known as cooperative energy transfer, and the second one is a non-linear process involving an intermediated virtual level in the Tb3þ ion.