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Publications (10 of 15) Show all publications
Zur, L. Z., Armellini, C., Belmokhtar, S., Bouajaj, A., Cattaruzza, E., Chiappini, A., . . . Enrichi, F. (2019). Comparison between glass and glass-ceramic silica-hafnia matrices on the down-conversion efficiency of Tb3+/Yb3+ rare earth ions. Optical materials (Amsterdam), 87, 102-106
Open this publication in new window or tab >>Comparison between glass and glass-ceramic silica-hafnia matrices on the down-conversion efficiency of Tb3+/Yb3+ rare earth ions
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2019 (English)In: Optical materials (Amsterdam), ISSN 0925-3467, E-ISSN 1873-1252, Vol. 87, p. 102-106Article in journal (Refereed) Published
Abstract [en]

In this paper, the investigation of energy transfer efficiency in Tb3+-Yb3+ co-doped SiO2-HfO2 glass and glass-ceramic waveguides is presented. Cooperative energy transfer between these two ions allows to cut one UV or 488 nm photon in two 980 nm photons and could have important applications in improving the performance of photovoltaic solar cells. Thin films with different molar concentrations of rare earths, up to a total concentration of 21%, were prepared by a sol-gel route, using dip-coating deposition technique on SiO2 substrates. The ratio between Yb3+ and Tb3+ ions in all the prepared thin films is constant and equal to 4. The energy transfer between Tb3+ and Yb3+ ions in glass and glass-ceramic waveguides shows the higher efficiency for glass-ceramic with a maximum quantum transfer efficiency of about 190% for the sample containing 19% of rare earths.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Rare earths, Down-conversion, Energy transfer, Waveguides, Sol-gel
National Category
Other Physics Topics
Research subject
Experimental Physics
Identifiers
urn:nbn:se:ltu:diva-68810 (URN)10.1016/j.optmat.2018.05.008 (DOI)000457505900020 ()2-s2.0-85047221245 (Scopus ID)
Note

Konferensartikel i tidskrift

Available from: 2018-05-21 Created: 2018-05-21 Last updated: 2019-03-08Bibliographically approved
Bortoluzzi, M., Castro, J., Girotto, M., Enrichi, F. & Vomiero, A. (2019). Luminescent copper(I) coordination polymer with 1-methyl-1H-benzotriazole, iodide and acetonitrile as ligands. Inorganic Chemistry Communications, 102, 141-146
Open this publication in new window or tab >>Luminescent copper(I) coordination polymer with 1-methyl-1H-benzotriazole, iodide and acetonitrile as ligands
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2019 (English)In: Inorganic Chemistry Communications, ISSN 1387-7003, E-ISSN 1879-0259, Vol. 102, p. 141-146Article in journal (Refereed) Published
Abstract [en]

The Cu(I) coordination polymer [Cu33-I)3(μ-btzMe)(NCCH3)]n (btzMe = 1-methyl-1H-benzotriazole) was prepared and characterized by X-Ray diffraction. The compound showed strong green emission upon excitation with wavelengths below 475 nm, with lifetime of 47 μs. The emission was attributed to 3(X,M)LCT transition on the basis of experimental data and DFT calculations.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Copper iodide, Coordination polymer, N-donor ligands, Luminescence
National Category
Other Physics Topics
Research subject
Experimental Physics
Identifiers
urn:nbn:se:ltu:diva-73034 (URN)10.1016/j.inoche.2019.02.016 (DOI)000462803900027 ()2-s2.0-85061636648 (Scopus ID)
Available from: 2019-02-27 Created: 2019-02-27 Last updated: 2019-04-17
Enrichi, F., Belmokhtar, S., Benedetti, A., Bouajaj, A., Cattaruzza, E., Coccetti, F., . . . Zur, L. Z. (2018). Ag nanoaggregates as efficient broadband sensitizers for Tb3+ ions in silica-zirconia ion-exchanged sol-gel glasses and glass-ceramics. Optical materials (Amsterdam), 84, 668-674
Open this publication in new window or tab >>Ag nanoaggregates as efficient broadband sensitizers for Tb3+ ions in silica-zirconia ion-exchanged sol-gel glasses and glass-ceramics
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2018 (English)In: Optical materials (Amsterdam), ISSN 0925-3467, E-ISSN 1873-1252, Vol. 84, p. 668-674Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Other Physics Topics
Research subject
Experimental Physics
Identifiers
urn:nbn:se:ltu:diva-70344 (URN)10.1016/j.optmat.2018.07.074 (DOI)000446145200099 ()2-s2.0-85050857389 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-08-13 (andbra)

Available from: 2018-08-13 Created: 2018-08-13 Last updated: 2018-10-22Bibliographically approved
Enrichi, F., Cattaruzza, E., Ferrari, M., Gonella, F., Ottini, R., Riello, P., . . . Zur, L. (2018). Ag-Sensitized Yb3+ Emission in Glass-Ceramics. Micromachines, 9(8), Article ID 380.
Open this publication in new window or tab >>Ag-Sensitized Yb3+ Emission in Glass-Ceramics
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2018 (English)In: Micromachines, ISSN 2072-666X, E-ISSN 2072-666X, Vol. 9, no 8, article id 380Article in journal (Refereed) Published
Abstract [en]

Rare earth doped materials play a very important role in the development of many photonic devices, such as optical amplifiers and lasers, frequency converters, solar concentrators, up to quantum information storage devices. Among the rare earth ions, ytterbium is certainly one of the most frequently investigated and employed. The absorption and emission properties of Yb3+ ions are related to transitions between the two energy levels 2F7/2 (ground state) and 2F5/2 (excited state), involving photon energies around 1.26 eV (980 nm). Therefore, Yb3+ cannot directly absorb UV or visible light, and it is often used in combination with other rare earth ions like Pr3+, Tm3+, and Tb3+, which act as energy transfer centres. Nevertheless, even in those co-doped materials, the absorption bandwidth can be limited, and the cross section is small. In this paper, we report a broadband and efficient energy transfer process between Ag dimers/multimers and Yb3+ ions, which results in a strong PL emission around 980 nm under UV light excitation. Silica-zirconia (70% SiO2-30% ZrO2) glass-ceramic films doped by 4 mol.% Yb3+ ions and an additional 5 mol.% of Na2O were prepared by sol-gel synthesis followed by a thermal annealing at 1000 °C. Ag introduction was then obtained by ion-exchange in a molten salt bath and the samples were subsequently annealed in air at 430 °C to induce the migration and aggregation of the metal. The structural, compositional, and optical properties were investigated, providing evidence for efficient broadband sensitization of the rare earth ions by energy transfer from Ag dimers/multimers, which could have important applications in different fields, such as PV solar cells and light-emitting near-infrared (NIR) devices.

Place, publisher, year, edition, pages
MDPI, 2018
National Category
Other Physics Topics
Research subject
Experimental Physics
Identifiers
urn:nbn:se:ltu:diva-71115 (URN)10.3390/mi9080380 (DOI)000443256300014 ()2-s2.0-85054930887 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-10-05 (johcin)

Available from: 2018-10-05 Created: 2018-10-05 Last updated: 2019-03-27Bibliographically approved
Cailotto, S., Mazzaro, R., Enrichi, F., Vomiero, A., Selva, M., Cattaruzza, E., . . . Perosa, A. (2018). Design of Carbon Dots for Metal-free Photoredox Catalysis. ACS Applied Materials and Interfaces, 10(47), 40560-40567
Open this publication in new window or tab >>Design of Carbon Dots for Metal-free Photoredox Catalysis
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2018 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 10, no 47, p. 40560-40567Article in journal (Refereed) Published
Abstract [en]

The photoreduction potential of a set of four different carbon dots (CDs) was investigated. The CDs were synthesized by using two different preparation methods—hydrothermal and pyrolytic—and two sets of reagents—neat citric acid and citric acid doped with diethylenetriamine. The hydrothermal syntheses yielded amorphous CDs, which were either nondoped (a-CDs) or nitrogen-doped (a-N-CDs), whereas the pyrolytic treatment afforded graphitic CDs, either non-doped (g-CDs) or nitrogen-doped (g-N-CDs). The morphology, structure, and optical properties of four different types of CDs revealed significant differences depending on the synthetic pathway. The photocatalytic activities of the CDs were investigated as such, that is, in the absence of any other redox mediators, on the model photoreduction reaction of methyl viologen. The observed photocatalytic reaction rates: a-N-CDs ≥ g-CDs > a-CDs ≥ g-N-CDs were correlated with the presence/absence of fluorophores, to the graphitic core, and to quenching interactions between the two. The results indicate that nitrogen doping reverses the photoredox reactivity between amorphous and graphitic CDs and that amorphous N-doped CDs are the most photoredox active, a yet unknown fact that demonstrates the tunable potential of CDs for ad hoc applications.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2018
Keywords
carbon dots, carbon nanomaterials, citric acid, methyl viologen, photocatalysis, photoreduction, photosensitizer, structure−reactivity relationship
National Category
Other Physics Topics
Research subject
Experimental Physics
Identifiers
urn:nbn:se:ltu:diva-71591 (URN)10.1021/acsami.8b14188 (DOI)000451932800021 ()30370767 (PubMedID)2-s2.0-85057216827 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-12-04 (inah)

Available from: 2018-11-15 Created: 2018-11-15 Last updated: 2019-03-27Bibliographically approved
Bortoluzzi, M., Castro, J., Enrichi, F., Vomiero, A., Busato, M. & Huang, W. (2018). Green-emitting manganese (II) complexes with phosphoramide and phenylphosphonic diamide ligands. Inorganic Chemistry Communications, 92, 145-150
Open this publication in new window or tab >>Green-emitting manganese (II) complexes with phosphoramide and phenylphosphonic diamide ligands
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2018 (English)In: Inorganic Chemistry Communications, ISSN 1387-7003, E-ISSN 1879-0259, Vol. 92, p. 145-150Article in journal (Refereed) Published
Abstract [en]

Tetrahedral manganese(II) complexes having formulae [MnX2{O = PR(NMe2)2}2] (X = Br, I; R = NMe2, Ph) were isolated and characterized, and in the case of [MnBr2{O = PPh(NMe2)2}2] the structure was ascertained by means of single crystal X-ray diffraction. All the complexes showed intense green emission assigned to the Mn(II) 4T1(4G) → 6A1(6S) transition upon excitation with UV light, with photoluminescence lifetimes in the range 100–1000 μs. Bromo-complexes maintain their luminescence features once dispersed in polycaprolactone matrix.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Other Physics Topics
Research subject
Experimental Physics
Identifiers
urn:nbn:se:ltu:diva-68509 (URN)10.1016/j.inoche.2018.04.023 (DOI)000436883600030 ()2-s2.0-85046357935 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-05-15 (andbra)

Available from: 2018-04-25 Created: 2018-04-25 Last updated: 2018-08-10Bibliographically approved
Scrivanti, A., Bortoluzzi, M., Morandini, A., Dolmella, A., Enrichi, F., Mazzaro, R. & Vomiero, A. (2018). Luminescent europium(III) complexes containing an electron rich 1,2,3-triazolyl-pyridyl ligand. New Journal of Chemistry, 42(13), 11064-11072
Open this publication in new window or tab >>Luminescent europium(III) complexes containing an electron rich 1,2,3-triazolyl-pyridyl ligand
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2018 (English)In: New Journal of Chemistry, ISSN 1144-0546, E-ISSN 1369-9261, Vol. 42, no 13, p. 11064-11072Article in journal (Refereed) Published
Abstract [en]

An improved synthesis of the electron-rich N,N-chelating ligand, 2-(1-t-butyl-1H-1,2,3-triazol-4-yl)pyridine (L), has been developed by coupling t-butyl-azide with ethynylpyridine in the presence of a Cu(I) catalyst. L has been employed in the preparation of lanthanide coordination compounds having formulae [Ln(κ2-NO3)3L2] and [Eu(dbm)3L] (Ln = Eu, Tb; dbm = dibenzoylmethanate). The molecular structure of [Eu(dbm)3L] has been determined by X-ray diffraction studies. All the new complexes exhibit good photoluminescence properties and [Eu(dbm)3L] has been successfully used as the dopant for the preparation of luminescent plastic materials.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2018
National Category
Other Physics Topics
Research subject
Experimental Physics
Identifiers
urn:nbn:se:ltu:diva-69503 (URN)10.1039/C8NJ01390J (DOI)000436517300073 ()2-s2.0-85049158841 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-06-27 (svasva)

Available from: 2018-06-14 Created: 2018-06-14 Last updated: 2018-08-20Bibliographically approved
Enrichi, F., Quandt, A. & Righini, G. C. (2018). Plasmonic enhanced solar cells: Summary of possible strategies and recent results. Renewable & sustainable energy reviews, 82(3), 2433-2439
Open this publication in new window or tab >>Plasmonic enhanced solar cells: Summary of possible strategies and recent results
2018 (English)In: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 82, no 3, p. 2433-2439Article in journal (Refereed) Published
Abstract [en]

Plasmonic structures for light manipulation at sub-wavelength scale have received great interest in the field of photovoltaic (PV) solar cells for their potential to significantly enhance the cell's efficiency.

The performance of any solar cell is determined by the capability to absorb incoming light and produce electric charges, which, in turn, has a number of limiting factors. One is related to the ever-reducing size and acceptance angle of the active region. Another is the limited spectral sensitivity of the active material, which cannot make use of significant parts of the solar spectrum.

Correspondingly, the energy harvesting may be improved in two ways, namely by adopting light trapping schemes and by exploiting spectral modification processes to shift frequencies of the solar spectrum, which are initially not absorbed, into the region of maximum absorption of the cell.

Plasmonic nanoparticles (NPs) can give a significant boost to both these aspects, by scattering and concentrating the electromagnetic field into the active region of the device, and by doing that within specific spectral regions, which can be properly tuned by optimizing the size, shape, distribution of the plasmonic NPs, and by choosing the right surrounding medium.

During the last ten years, many papers have been published on very specific issues, but also on general properties of plasmonics applied to solar cells, with a strong increase between 2006 and 2012, followed by a period of significant, but stable, literature productivity. Given these premises, an organized and schematic summary of the main strategies and of the recent results on the field is given in this review, where different plasmonic approaches are compared and discussed, also by recalling specific examples from the literature and providing a few key conclusions to understand the main aspects and the future perspectives of the field.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Other Physics Topics
Research subject
Experimental physics
Identifiers
urn:nbn:se:ltu:diva-65525 (URN)10.1016/j.rser.2017.08.094 (DOI)000418574800033 ()
Note

Validerad;2018;Nivå 2;2018-01-25 (andbra)

Available from: 2017-09-07 Created: 2017-09-07 Last updated: 2018-02-02Bibliographically approved
Ouafi, M. E., Belmokhtar, S., Bouajai, A., Britel, M., Enrichi, F., Armellini, C., . . . Ferrari, M. (2018). Rare Earth Ions Doped Down-conversion Materials for Third Generation Photovoltaic Solar Cells. In: Proceedings of 2017 International Renewable and Sustainable Energy Conference, IRSEC 2017: . Paper presented at 5th International Renewable and Sustainable Energy Conference, IRSEC 2017, Tangier, Morocco, 4-7 December 2017. IEEE, Article ID 8477416.
Open this publication in new window or tab >>Rare Earth Ions Doped Down-conversion Materials for Third Generation Photovoltaic Solar Cells
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2018 (English)In: Proceedings of 2017 International Renewable and Sustainable Energy Conference, IRSEC 2017, IEEE, 2018, article id 8477416Conference paper, Published paper (Refereed)
Abstract [en]

In order to enhance the efficiency of photovoltaic solar cells and overcome their limitations, a matching between solar spectrum and semiconductor band gap is needed using luminescent materials. The following work present in this paper is mainly based on the adjustment of the solar spectrum to the cell bandgap by developing downconverting materials. Down conversion process is exploited to modify the solar spectrum due to a cooperative energy transfer between Tb 3+ and two Yb 3+ rare earth ions in silica-hafnia waveguides. Tb 3+ /Yb 3+ -codoped SiO 2 -HfO 2 planar waveguides have been prepared by sol gel route, using a dip-coating deposition on SiO 2 substrates. The waveguides were obtained with different concentrations and the total amount was [Tb 3+ +Yb 3+ ] = 5%, 7%, 9%, keeping constant the molar ratio [Yb]/[Tb]=4. The comparison between the glass and the glass-ceramic structures demonstrated that the energy transfer is more efficient in glass ceramic since it combines the good optical properties of glasses with the optimal spectroscopic properties of crystals activated by luminescent species. A maximum quantum transfer efficiency of 154.6% was found for the highest rare earth doping concentration.

Place, publisher, year, edition, pages
IEEE, 2018
Keywords
Rare earth, Down conversion, Energy transfer, Solar cells, Optical waveguides
National Category
Other Physics Topics
Research subject
Experimental Physics
Identifiers
urn:nbn:se:ltu:diva-72224 (URN)10.1109/IRSEC.2017.8477416 (DOI)2-s2.0-85055887124 (Scopus ID)978-1-5386-2847-8 (ISBN)
Conference
5th International Renewable and Sustainable Energy Conference, IRSEC 2017, Tangier, Morocco, 4-7 December 2017
Available from: 2018-12-19 Created: 2018-12-19 Last updated: 2018-12-19Bibliographically approved
Bortoluzzi, M., Reolon, A., Scrivanti, A. & Enrichi, F. (2018). The conjugate base of malonaldehyde as antenna-ligand towards trivalent europium and terbium ions. Paper presented at XXVI International Conference on Coordination and Bioinorganic Chemistry (ICCBiC), Smolenice Castle, Slovakia, June 4-6, 2017. Chemické zvesti, 72(4), 809-819
Open this publication in new window or tab >>The conjugate base of malonaldehyde as antenna-ligand towards trivalent europium and terbium ions
2018 (English)In: Chemické zvesti, ISSN 0366-6352, E-ISSN 1336-9075, Vol. 72, no 4, p. 809-819Article in journal (Refereed) Published
Abstract [en]

Coordination compounds having formulae [M(MA)3]n and M(MA)(Me2Tp)2 (M = Y, Eu, Tb; MA = conjugate base of malonaldehyde; Me2Tp = tris(3,5-dimethyl-pyrazol-1-yl)borate) were synthesized and characterized. The photoluminescence features of the europium and terbium derivatives were investigated. By comparing the herein reported photoluminescence data with those relative to analogous nitro- and bromomalonaldehyde derivatives, it appears that the conjugate base of malonaldehyde is a more efficient antenna-ligand for the sensitization of Tb(III) luminescence. The experimental data were rationalized on the basis of DFT calculations. Tb(MA)(Me2Tp)2 was used as dopant for the preparation of luminescent plastic materials based on poly(methyl methacrylate).

Place, publisher, year, edition, pages
Springer, 2018
National Category
Other Physics Topics
Research subject
Experimental physics
Identifiers
urn:nbn:se:ltu:diva-63259 (URN)10.1007/s11696-017-0182-z (DOI)000428254500004 ()
Conference
XXVI International Conference on Coordination and Bioinorganic Chemistry (ICCBiC), Smolenice Castle, Slovakia, June 4-6, 2017
Note

2018-03-23 (rokbeg);konferensartikel i tidskrift

Available from: 2017-05-05 Created: 2017-05-05 Last updated: 2018-04-12Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-3443-3707

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