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Venezia, Italy

Bouajaj A.,Abdelmalek Essaadi University | Belmokhtar S.,Abdelmalek Essaadi University | Britel M.R.,Abdelmalek Essaadi University | Armellini C.,CNR Institute for Photonics and Nanotechnologies | And 8 more authors.
Optical Materials | Year: 2016

In this paper we present the investigation of the energy transfer efficiency between Tb3+ and Yb3+ ions in silica-hafnia waveguides. Cooperative energy transfer between these two ions allows to cut one 488 nm photon in two 980 nm photons and could have important applications in improving the performance of photovoltaic solar cells. Previous works revealed that for a given concentration of donors (Tb3+), increasing the number of acceptors (Yb3+) located near to the Tb3+ ion can increase the Tb-Yb transfer probability. However, when increasing the density of active ions, some detrimental effects due to cross-relaxation mechanisms become relevant. On the basis of this observation the sample doping was chosen keeping constant the molar ratio [Yb]/[Tb] = 4 and the total rare earths contents were [Tb + Yb]/[Si + Hf] = 5%, 7%, 9%. The choice of the matrix is another crucial point to obtain an efficient down conversion processes with rare earth ions. To this respect a 70SiO2-30HfO2 waveguide composition was chosen. The comparison between the glass and the glass-ceramic structures demonstrated that the latter is more efficient since it combines the good optical properties of glasses with the optimal spectroscopic properties of crystals activated by luminescent species. A maximum transfer efficiency of 55% was found for the highest rare earth doping concentration. © 2015 Elsevier B.V. All rights reserved. Source


Malba C.,University of Venice | Sudhakaran U.P.,University of Pisa | Borsacchi S.,University of Pisa | Geppi M.,University of Pisa | And 8 more authors.
Dalton Transactions | Year: 2014

The encapsulation of [Eu(dbm)3phen] into functionalized mesoporous silica nanoparticles (MSN) has been carried out to study the effect of chemical environments on the photoluminescence properties of the rare-earth complex. Surface functionalization was achieved by the reaction of the silanol groups on the surface of mesoporous silica with different organosilylating agents such as (3-aminopropyl)-triethoxysilane (APTES), (3-mercaptopropyl)-trimethoxysilane (MPTMS), and ethoxytrimethylsilane (ETMS). A change in the luminescence properties of the Eu(dbm)3phen complex has been observed on its encapsulation into surface modified mesoporous silica nanoparticles. The modification of photophysical properties is attributed to the interaction of Eu(dbm)3phen with the different chemical environments in the functionalized mesoporous silica nanoparticles (MSN). The luminescence properties of the rare-earth complex in surface-modified MSN increase in the order MSN < MSN-ETMS < MSN-MPTMS < MSN-APTES. The Eu(dbm)3phen complex encapsulated in the functionalized mesoporous silica nanoparticles shows an enhanced luminescence and an increased lifetime compared to the pure rare-earth complex in the solid state and that in unmodified MSN. This implies that some interactions of the lanthanide complexes take place during their incorporation process into the organically modified mesoporous silica nanoparticles. The organically modified mesoporous silica nanoparticles were characterized by Fourier transform infrared spectroscopy (FTIR) and N2 adsorption desorption measurements. The luminescence properties of the encapsulated Eu(dbm)3phen were studied in detail. Moreover, the effect of functionalized MSNs on the structural behaviour of the Eu(dbm)3phen was investigated by solid state nuclear magnetic resonance (SSNMR) techniques using an analogous diamagnetic model complex, Y(dbm)3phen, encapsulated into functionalized MSNs. These studies indicate that the encapsulated rare-earth complex shows some interactions with the functional groups anchored on the surface of MSNs. © 2014 the Partner Organisations. Source


Bortoluzzi M.,University of Venice | Bianchin E.,University of Venice | Roppa S.,University of Venice | Bertolasi V.,University of Ferrara | And 2 more authors.
Dalton Transactions | Year: 2014

Coordination compounds having formulae [AsPh4][Ln(NMA) 4] (1Ln), Ln(NMA)3(tppo)2 (2 Ln), Ln(NMA)3(bipyO2) (3Ln), Ln(NMA)3(phen) (4Ln) and Ln(NMA)3(terpy) (5Ln) (Ln = Y and some lanthanides; NMA = conjugate base of nitromalonaldehyde; tppo = triphenylphosphine oxide; bipyO2 = 2,2′-bipyridine-N,N′-dioxide; phen = 1,10-phenanthroline; terpy = 2,2′:6′,2′′-terpyridine) were synthesized and characterized and X-ray diffraction data were collected for [AsPh 4][Y(NMA)4] (1Y). The neutral europium derivatives showed appreciable luminescence in the solid state upon excitation with UV light and photoluminescence measurements were carried out. These compounds were used as dopants for the preparation of luminescent poly(methyl methacrylate). Luminescent polyvinylpyrrolidone samples were obtained by reacting the pure polymer with water solutions containing NMA and trivalent europium ions. © 2014 The Royal Society of Chemistry. Source


Back M.,University of Venice | Marin R.,University of Venice | Franceschin M.,University of Venice | Sfar Hancha N.,University of Venice | And 5 more authors.
Journal of Materials Chemistry C | Year: 2016

The development of highly luminescent water-dispersible biocompatible nanoparticles is a hot topic in biomedical research. Here, we report about the study of the energy transfer process between Tb3+ and Eu3+ in calcium fluoride nanoparticles. Water-dispersible RE-doped nanoparticles were prepared by means of a simple synthesis route without the need for high temperature, pressure or additional surface functionalization. The structural and morphological properties were investigated by means of XRPD and TEM analysis. Optical analysis led to information about both the RE ion site symmetry in the crystalline host and the Tb3+ and Eu3+ excited state lifetimes, whose remarkable duration is suitable for biosensing applications. Concerning the energy transfer process, dipole-dipole interaction, with a donor-activator critical distance of about 13 Å, was identified as the most probable mechanism. © The Royal Society of Chemistry 2016. Source


Malba C.M.,University of Venice | Enrichi F.,Laboratorio Nanofab | Enrichi F.,CNR Institute for Photonics and Nanotechnologies | Facchin M.,University of Venice | And 7 more authors.
RSC Advances | Year: 2015

Highly luminescent anionic Ln(III) β-diketonate complexes of the formula [P8,8,8,1][Ln(dbm)4], with Ln = Eu3+ and Sm3+, [P8,8,8,1] = trioctylmethylphosphonium and dbm = 1,3-diphenylpropane-1,3-dione were synthesized. The single crystal X-ray structure of the samarium and europium complexes showed that the metal ion was surrounded by four ligands and that no water or solvent molecules were coordinated. The solid complexes showed good thermal stability up to 250 °C. The complexes easily dissolved in the ionic liquid trioctylmethylphosphonium bis(trifluoromethylsulfonyl)imide [P8,8,8,1][Tf2N], due to the presence of a common phosphonium countercation in the ionic liquid and in the Eu(III) and Sm(III) complexes. The photoluminescence of the complexes was studied in the solid state and in an ionic liquid as well as in acetonitrile (MeCN) as a solvent. © The Royal Society of Chemistry 2015. Source

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