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Synthesis, characterisation and luminescent properties of lanthanide-organic po...
Girginova, Penka I.; Paz, Filipe A. Almeida; Soares-Santos, Paula C. R.; Ferreira, R. A. Sá; Carlos, Luís D.; Amaral, Vítor S.; Klinowski, JacekThree new lanthanide(III) complexes (Ln = Sm, Tb and Eu) of picolinic and glutaric acid were prepared and characterised. The crystal structure of the complex [Sm(glu)(pic)- (H2O)2] (where Hpic and H2glu stand for picolinic and glutaric acid, respectively) was determined by single-crystal Xray diffraction. All the Ln complexes were characterised by elemental analysis, infrared spectroscopy, X-ray powder diffract...
Luminescent polyoxotungstoeuropate anion-pillared layered double hydroxides
Sousa, Filipa L.; Pillinger, Martyn; Ferreira, Rute A. Sá; Granadeiro, Carlos M.; Cavaleiro, Ana M. V.; Rocha, João; Carlos, Luís D.; Trindade, TitoNovel luminescent polyoxometalate anion-pillared layered double hydroxides (LDHs) were prepared by aqueous ion exchange of a Zn–Al LDH precursor in nitrate form with the europium-containing polyoxotungstate anions [EuW10O36]9–, [Eu(BW11O39)(H2O)3]6– and [Eu(PW11O39)2]11–. The host– guest interaction has a strong influence on the nature of the final intercalated species, as evidenced by elemental analy- Introduc...
Electrospun nanosized cellulose fibers using ionic liquids at room temperature
Freire, Mara G.; Teles, Ana Rita R.; Ferreira, Rute A. S.; Carlos, Luís D.; Lopes-da-Silva, José A.; Coutinho, João A. P.Aiming at replacing the noxious solvents commonly employed, ionic-liquid-based solvents have been recently explored as novel non-volatile and non-flammable media for the electrospinning of polymers. In this work, nanosized and biodegradable cellulose fibers were obtained by electrospinning at room temperature using a pure ionic liquid or a binary mixture of two selected ionic liquids. The electrospinning of 8 w...
Lanthanopolyoxotungstates in silica nanoparticles: multi-wavelength photolumine...
Granadeiro, Carlos M.; Ferreira, Rute A. S.; Soares-Santos, Paula C. R.; Carlos, Luís D.; Trindade, Tito; Nogueira, Helena I. S.Photoluminescent lanthanopolyoxotungstate core/shell nanoparticles are prepared by the encapsulation of lanthanide-containing polyoxometalates (POMs) with amorphous silica shells. The preparation of morphological well-defined core/shell nanoparticles is achieved by the hydrolysis of tetraethoxysilane in the presence of POMs using a reverse microemulsion method. The POMs used are decatungstolanthanoates of [Ln(W...
Nanoencapsulation of luminescent 3-hydroxypicolinate lanthanide complexes
Iwu, Kingsley O.; Soares-Santos, Paula C. R.; Nogueira, Helena I. S.; Carlos, Luis D.; Trindade, TitoWe have synthesized luminescent nanoparticles comprising a core of lanthanide complexes and shells of amorphous silica using reverse micelles as nanoreactors. 3-Hydroxypicolinate complexes of Eu(III), Tb(III), and the corresponding heteronuclear complexes have been investigated as the photoactive cores. The size of the silica particles is within the nanometer scale, which, together with the ability for surface ...
Photoluminescent layered Y/Er silicates
Kostova, Mariya H.; Ananias, Duarte; Carlos, Luís D.; Rocha, JoãoThe synthesis of new layered rare-earth silicates K3[Y1-aEraSi3O8(OH)2] (AV-22 materials) has been reported. The photoluminescence properties of Y/Er-AV-22 and the material resulting from its thermal degradation, K3[Y1-aEraSi3O9] (Y/Er-AV-23), have been studied and compared. Both materials have a similar chemical makeup and structures sharing analogous building blocks, hence providing a unique opportunity for r...
Photoluminescent Layered Lanthanide Silicate Nanoparticles
Ananias, Duarte; Ferdov, Stanislav; Paz, Filipe A. Almeida; Ferreira, Rute A. Sá; Ferreira, Artur; Geraldes, Carlos F. G. C.; Carlos, Luís D.; Lin, ZhiThe first examples of nanoparticles of pure layered Ln2(SiO4H)(OH)2(H2O)Cl (where Ln ) Eu, Gd, and Tb) and mixed microcrystalline layered lanthanide silicates containing different Eu/Gd and Tb/Gd ratios have been reported. The crystal structure of these silicates has been solved from synchrotron powder X-ray diffraction data. These materials display interesting and tuneable photoluminescence (PL) properties, su...
Energy Transfer and Emission Decay Kinetics in Mixed Microporous Lanthanide Sil...
Evans, Rachel C.; Ananias, Duarte; Douglas, Alastair; Douglas, Peter; Carlos, Luis D.; Rocha, JoãoWe have investigated the energy transfer dynamics in mixed lanthanide open-framework silicates, known as Ln-AV-20 materials, with the stoichiometric formula Na1.08K0.5Ln1.14Si3O8.5·1.78H2O (Ln = Gd3+, Tb3+, Eu3+), using steady-state and time-resolved luminescence spectroscopy. Energy transfer between donor and acceptor Ln3+ ions is extremely efficient, even at low molar ratios of the acceptor Ln3+ (<5%). The pr...
Evolution of Photoluminescence across Dimensionality in Lanthanide Silicates
Kostova, Mariya H.; Ananias, Duarte; Paz, Filipe A. Almeida; Ferreira, Artur; Rocha, João; Carlos, Luís D.The dehydratation process of layered lanthanide silicates K3[LnSi3O8(OH)2], Ln = Y, Eu, Tb, and Er, and the structural characterization of the obtained small-pore framework K3LnSi3O9, Ln = Y, Eu, Tb, and Er solids, named AV-23, have been reported. The structure of AV-23 has been solved by single-crystal X-ray diffraction (XRD) methods and further characterized by chemical analysis, thermogravimetry, scanning el...
Structure and properties of Ti4+-ureasil organic-inorganic hybrids
Molina,Celso; Dahmouche,Karim; Hammer,Peter; Bermudez,Verónica de Zea; Carlos,Luís D.; Ferrari,Maurizio; Montagna,Maurizio; Gonçalves,Rogéria R.Hybrid planar waveguides were prepared from Ti4+-acetylacetone (acac)-Ureasil sols deposited on glass substrates. Structural features have been investigated by spectroscopic measurements (Fourier Transform Infrared Spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS) and Raman scattering) and Small Angle X-ray Scattering (SAXS). Addition of Ti4+-acac to the ureasil (Ti:Si molar ratio 1:1) leads to the fo...
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