Entity

Time filter

Source Type


Corricelli M.,CNR Institute for Chemical and Physical Processes | Enrichi F.,Coordinamento Interuniversitario Veneto per le Nanotecnologie | Altamura D.,CNR Institute of Crystallography | De Caro L.,CNR Institute of Crystallography | And 6 more authors.
Journal of Physical Chemistry C | Year: 2012

PbS colloidal nanocrystal (NC) assemblies with monomodal and bimodal size distribution have been fabricated by slow evaporation of solvent on silicon substrates. The interparticle distances of the assembled structures have been carefully defined, both in the plane and in the z direction, perpendicular to the substrate, thanks to the combination of small and wide-angle X-ray diffraction and TEM measurements. The spectroscopic characteristics of PbS NCs, both in solution and organized in a superlattice, have been investigated by steady-state and time-resolved photoluminescence measurements. The optical results reveal the occurrence of a Förster resonant energy transfer (FRET) mechanism between closed-packed neighboring PbS NCs. The occurrence of FRET is dependent on NC assembly geometry, and thus on their interparticle distance, suggesting that only when NCs are close enough, as in the close-packed arrangement of the monomodal assembly, the energy transfer can be promoted. In bimodal assemblies, the energy transfer between large and small NCs is negligible, due to the low spectral overlap between the emission and absorption bands of the different sized nanoparticles and to the large interparticle distance. Moreover, recombination lifetimes on the microsecond time scale have been observed and explained in terms of dielectric screening effect, in agreement with previous findings on lead chalcogenide NC optical properties. © 2012 American Chemical Society. Source


Dhahri A.,Center National des Recherches en science des Materiaux | Horchani-Naifer K.,Center National des Recherches en science des Materiaux | Benedetti A.,University of Venice | Enrichi F.,Coordinamento Interuniversitario Veneto per le Nanotecnologie | Ferid M.,Center National des Recherches en science des Materiaux
Optical Materials | Year: 2012

Eu3+ doped LaAlO3 nanophosphors were successfully synthesized by a combustion process using concentrated solution of lanthanum nitrates and aluminate as oxidiser, and glycine acid as fuel. The powders were characterized by infrared spectroscopy (IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and fluorescence spectroscopy. Pure LaAlO3 phase was obtained at 800°C heated for 4 h, without formation of any intermediate phase, with an average crystal size, as determined by TEM, of 60 nm. Intense photoluminescence emission is reported at 616 nm, allowing the use of this material as red phosphor. © 2012 Elsevier B.V. All rights reserved. Source


Back M.,University of Venice | Boffelli M.,Kyoto Institute of Technology | Massari A.,University of Venice | Marin R.,University of Venice | And 2 more authors.
Journal of Nanoparticle Research | Year: 2013

Tb3+ and Eu3+ co-doped Y2O3 nanoparticles with a volume-weighted average size of about 30 nm were synthesized via simple Pechini-type sol-gel process. The growth of monocrystalline nanoparticles is investigated via XRD and TEM analysis. The study of energy transfer between Tb3+ and Eu3+ ions was carried out by means of PL, PLE, and photoluminescence decay analyses. The energy transfer from Tb3+ to Eu3+ is efficient and we show how a resonant type via a dipole-dipole interaction is the most probable mechanism. We compared the energy-transfer efficiencies calculated from the intensities and from the lifetimes of 5 D4 7 {F} 5 5 D 4 ⟠7 F 5 transition of Tb, showing the presence of two populations of Tb, with different local surroundings, in the matrix. Furthermore, the critical distance between Tb3+ and Eu3+ ions has been calculated by means of different theories, from a new probabilistic approach based on the discretization of the theory of Chandrasekhar about the distribution of the nearest neighbors in a random distribution of particles, and from the PL data, suggesting a value of about 7 Å. © 2013 Springer Science+Business Media Dordrecht. Source


Canton G.,Coordinamento Interuniversitario Veneto per le Nanotecnologie | Canton G.,University of Padua | Ricco R.,Coordinamento Interuniversitario Veneto per le Nanotecnologie | Marinello F.,University of Padua | And 2 more authors.
Journal of Nanoparticle Research | Year: 2011

Dye-doped silica nanoparticles (NPs) have been demonstrated to be sensitive labeling markers for biosensing and bioimaging. Their flexible conjugation, excellent photostability and ultrasensitivity make them a powerful tool in biological analysis. Although there have been many reports on the basic research and application of these NPs, they are far from reaching their full potential. Silica NPs can be obtained through two principal approaches: the Stöber synthesis and the microemulsion method. The Stöber synthesis has the advantage of being easily scaled up for commercial applications and the possibility to effortlessly transfer the NPs into aqueous solutions (typical of bioanalysis). However, further investigation on the impact of the synthesis parameters on the particles size and on the doping process are needed in order to obtain highly luminescent particles. In this study a modified Stöber synthesis is proposed and a systematic study of the different reagents is reported, which provides a better picture on the influence of ethanol, ammonia, water, silica precursors, and dye concentration on the final morpho-optical properties. As a result, samples of luminescent silica NPs from 10 to 300 nm have been synthesized and optimized to be highly promising labels for biological applications. © Springer Science+Business Media B.V. 2011. Source


Dhahri A.,Center National des Recherches en science des Materiaux | Horchani-Naifer K.,Center National des Recherches en science des Materiaux | Benedetti A.,University of Venice | Enrichi F.,Coordinamento Interuniversitario Veneto per le Nanotecnologie | And 2 more authors.
Optical Materials | Year: 2013

Terbium doped lanthanum aluminate (LaAlO3) nanophosphors were successfully synthesized by a combustion process using concentrated solution of lanthanum nitrates and aluminate as oxidiser, and glycine acid as fuel. The powders were characterized by infrared spectroscopy (IR), X-ray diffraction (XRD), Rietveld refinement, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and fluorescence spectroscopy. Pure LaAlO3 phase was obtained at 800 °C heated for 4 h, without formation of any intermediate phase, with an average crystal size, as determined by TEM, of 60 nm. Intense green emission is reported at 542 nm, from the 5D 4 level, which intensity depends on Tb concentration. © 2013 Elsevier B.V. All rights reserved. Source

Discover hidden collaborations