| 1. |
- Enrichi, Francesco, et al.
(författare)
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Ag nanoaggregates as efficient broadband sensitizers for Tb3+ ions in silica-zirconia ion-exchanged sol-gel glasses and glass-ceramics
- 2018
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Ingår i: Optical materials (Amsterdam). - : Elsevier. - 0925-3467 .- 1873-1252. ; 84, s. 668-674
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we report the study of down-shifting silica-zirconia glass and glass-ceramic films doped by Tb3+ ions and Ag nanoaggregates, which combine the typical spectral properties of the rare-earth-ions with the broadband sensitizing effect of the metal nanostructures. Na-Tb co-doped silica-zirconia samples were obtained by a modified sol-gel route. Dip-coating deposition followed by annealing for solvent evaporation and matrix densification were repeated several times, obtaining a homogeneous crack-free film. A final treatment at 700 °C or 1000 °C was performed to control the nanoscale structural properties of the samples, resulting respectively in a glass (G) or a glass-ceramic (GC), where tetragonal zirconia nanocrystals are surrounded by an amorphous silica matrix. Ag introduction was then achieved by ion-exchange in a molten salt bath, followed by annealing in air to control the migration and aggregation of the metal ions. The comparison of the structural, compositional and optical properties are presented for G and GC samples, providing evidence of highly efficient photoluminescence enhancement in both systems, slightly better in G than in GC samples, with a remarkable increase of the green Tb3+ PL emission at 330 nm excitation: 12 times for G and 8 times for GC samples. Furthermore, after Ag-exchange, the shape of Tb3+ excitation resembles the one of Ag ions/nanoaggregates, with a broad significant absorption in the whole UV-blue spectral region. This broadband enhanced downshifting could find potential applications in lighting devices and in PV solar cells.
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| 2. |
- Enrichi, Francesco, et al.
(författare)
-
Structural and optical properties of Eu3+-doped sol-gel silica-soda glasses
- 2024
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Ingår i: The European Physical Journal Plus. - : Springer Nature. - 2190-5444. ; 139:4
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Tidskriftsartikel (refereegranskat)abstract
- Rare earths (REs) incorporated in glasses, mostly in the form of RE3+ ions, have several applications such as lasers and optical amplifiers, spectral conversion layers for solar cells, light emitters and sensors. In this context, both the composition and the structural properties of the glass, as well as the dopant concentration play an important role in determining the optical properties and the efficiency of the system. Usually, the concentration of REs is small, below 1 at%, to avoid clustering and optical quenching. In this paper, we report the case of sol-gel Eu-doped silica-soda glass films. The addition of soda to silica can reduce RE clustering and precipitation, according to molecular dynamic simulations, but brings structural instabilities to the network. Here, sodium was varied from 10 to 30 at% and Eu from 0 to 8 at%. It was shown that Eu plays a significant role in the stabilization of the matrix, improving the transparency, the refractive index and the thickness of the films. The increase of Eu concentration provides a decrease of site symmetry and an increase of quantum efficiency (QY), reaching 71% for the highest 8 at% Eu doping, with remarkable absence of concentration quenching.
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| 3. |
- Enrichi, Francesco, et al.
(författare)
-
Structural and optical properties of Eu3+-doped sol–gel silica–soda glasses
- 2024
-
Ingår i: The European Physical Journal Plus. - : Springer Nature. - 2190-5444. ; 139:4
-
Tidskriftsartikel (refereegranskat)abstract
- Rare earths (REs) incorporated in glasses, mostly in the form of RE3+ ions, have several applications such as lasers and optical amplifiers, spectral conversion layers for solar cells, light emitters and sensors. In this context, both the composition and the structural properties of the glass, as well as the dopant concentration play an important role in determining the optical properties and the efficiency of the system. Usually, the concentration of REs is small, below 1 at%, to avoid clustering and optical quenching. In this paper, we report the case of sol–gel Eu-doped silica–soda glass films. The addition of soda to silica can reduce RE clustering and precipitation, according to molecular dynamic simulations, but brings structural instabilities to the network. Here, sodium was varied from 10 to 30 at% and Eu from 0 to 8 at%. It was shown that Eu plays a significant role in the stabilization of the matrix, improving the transparency, the refractive index and the thickness of the films. The increase of Eu concentration provides a decrease of site symmetry and an increase of quantum efficiency (QY), reaching 71% for the highest 8 at% Eu doping, with remarkable absence of concentration quenching.
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| 4. |
- Lanza, Roberto, et al.
(författare)
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Effect of Crystalline Phase and Composition on the Catalytic Properties of PdSn Bimetallic Nanoparticles in the PROX Reaction
- 2014
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 118:44, s. 25392-25402
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Tidskriftsartikel (refereegranskat)abstract
- We present a synthetic strategy for the preparation of palladiumtin alloy and intermetallic nanoparticles. Complexes of palladium(II) and tin(IV) precursors in oleylamine were thermally decomposed in an organic solution in the presence of reducing moieties, leading to the formation of monodispersed nanoparticles with varying crystallographic structures. We found that the nanoparticles crystalline structure closely follows the bulk material phase diagram. The nanoparticles were supported on Al2O3 and their reactivity tested as catalysts for the preferential oxidation of CO in excess of hydrogen (PROX). Different Pd/Sn and O-2/CO ratios have been investigated, and the structurereactivity correlation highlighted. With increasing tin content, the CO ignition temperature remarkably lowers and the CO conversion rate increases, up to the formation of intermetallic phases that concurrently determine a reduction in the catalyst activity; the selectivity of the pure palladium references is preserved.
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