| 1. |
- Enrichi, Francesco, et al.
(författare)
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Effect of the crystal structure on the optical properties and Ag sensitization of Tb3+/Yb3+ ions in silica-zirconia glasses and glass-ceramics
- 2022
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Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 49:24 Part B
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Tidskriftsartikel (refereegranskat)abstract
- The role of the material structure in the energy transfer between Ag and Tb3+/Yb3+ ions is studied in silica-soda-zirconia sol-gel glasses and glass-ceramics. The preparation of Tb3+ and Yb3+ doped silica-soda-zirconia layers was carried out by sol-gel and dip-coating, followed by thermal annealing. The precipitation of zirconia nanocrystals was obtained by controlling the annealing temperature: from a full amorphous glass at 700 °C into a glass-ceramic at 1000 °C. A different crystalline structure of zirconia nanocrystals, tetragonal or cubic, was controlled by the rare-earth doping and investigated in relation to the Tb3+/Yb3+ optical properties. Moreover, Ag codoping was introduced by ion-exchange, obtaining a significant photoluminescence enhancement, both in the intensity and in the broadness of the excitation band, covering the whole UV region and part of the violet-blue region. Ag-sensitized Tb3+/Yb3+ doped silica-soda-zirconia glass-ceramics were attested to be potential candidates for energy-related applications, such as spectral conversion layers for solar cells, lasers and light-emitting devices (LEDs) in the visible and NIR spectral regions.
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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)
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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. |
- Zaman, Quaid, et al.
(författare)
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Water Diffusion Effectsat Gold-Graphene Interfaces Supporting Surface Plasmon Polaritons
- 2022
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Ingår i: The Journal of Physical Chemistry C. - : AMER CHEMICAL SOC. - 1932-7447 .- 1932-7455. ; 126:32, s. 13905-13919
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Tidskriftsartikel (refereegranskat)abstract
- We present a detailed investigation on the effects of water diffusion at the different interfaces of gold-graphene plasmonic sensors on the propagation of the supported surface plasmon polaritons (SPPs). The substrate/metal interfacial chemical reactions are investigated by monitoring the full width at half-maximum of the SPR reflectivity curve. Although protection by single-layer graphene (SLG) grown by chemical vapor deposition inhibits the chemical reactions happening at the metal-dielectric interfaces, SPR experimental results confirm that water diffusion paths through the borders of graphene domains are still present into the plasmonic sensors. Density functional theory calculations show that the doping level of SLG after the transfer on gold as well as interfacial charge transfer can be tuned in the presence of water molecules. On these bases, we propose a simplified effective medium approach for heterogeneous metal-carbon interfaces, where the interaction between the surface atomic layers of the gold thin film, water molecules, and the SLG induces the creation of an extended charge density difference region crossing the Au/H2O/SLG/H2O heterointerface. The latter is modeled as an ultrathin effective medium with a thickness and extraordinary optical susceptivity and conductivity that are different from those of the free-standing graphene. In this context, the extraordinary refractive index and thickness of the graphene-gold effective medium are measured in the near-infrared on the low-damping SPR platforms by applying the two-medium SPR method. The results are coherent with graphene n-doping in water environment, showing that the optically excited electrons along the extraordinary axis have a substantial bonding character and that the enhancement of the sensitivity of the gold-graphene plasmonic sensors is not related to a shift in the plasma frequency of the metal layer but to the changes in the extraordinary polarizability of graphene. The research highlights the importance of the SLG-substrate and SLG-environment interactions in graphene-protected plasmonics and optoelectronics.
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