| 1. |
- Nunes, S. C., et al.
(författare)
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Structure and photoluminescent features of di-amide cross-linked alkylene-siloxane hybrids
- 2005
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 1364-5501 .- 0959-9428. ; 15:35-36, s. 3876-3886
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Tidskriftsartikel (refereegranskat)abstract
- Novel amide cross-linked alkylene-siloxane hybrid materials (di-amidosils) synthesized by the sol-gel process have been investigated. Two samples identified by the notation d-A(x) with x = 4 and 8 (where x is the number of methylene groups of the alkylene chain) have been produced as transparent, amorphous, rigid monoliths. The d-A(8) material is thermally stable up to approximately 245°C. In this hybrid the siliceous framework is mainly composed of [-(CH2)Si(OSi)3)] and [-(CH 2)Si(OSi)2(OH)] substructures. Structural unit distances of 4.1 and 4.2 Å and average interparticle distances of 12 and 17 A have been determined for d-A(4) and d-A(8), respectively. In these compounds the alkylene chains are disordered and adopt gauche conformations. While a negligible proportion of the amide linkages remain non-bonded, the great majority of these groups belong to highly disordered strong hydrogen-bonded amide-amide associations. The hybrids introduced are room temperature white light emitters, presenting an intense, broad emission band in the blue/purplish-blue spectral region. The origin of such a band has been ascribed to the convolution of donor-acceptor pair (D-A) recombinations that occur in the NH groups of the amide linkages and in the siliceous nanodomains. The maximum quantum yield value of the d-A(8) di-amidosil is 5.4%.
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| 2. |
- Nunes, S. C., et al.
(författare)
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Structure and photoluminescence of di-amidosil nanohybrids incorporating europium triflate
- 2006
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Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388. ; 451:1-2, s. 510-515
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Konferensbidrag (refereegranskat)abstract
- The sol-gel process was used to prepare amorphous di-amide cross-linked alkyl/siloxane hybrid materials (di-amidosils) incorporating europium triflate (Eu(CF3SO3)(3)). Samples with 200 F-7(0-4) transitions. Photoluminescence data suggest that in the dilute di-amidosil with n = 100 the Eu3+ ions occupy the same type of chemical local environment. (C) 2007 Elsevier B.V. All rights reserved.
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| 3. |
- Pawłów, J., et al.
(författare)
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Influence of ionic liquid and oleic acid assisted methods on the spectroscopic properties of Nd3+-doped GdPO4 nano-particles
- 2023
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Ingår i: Journal of Materials Chemistry C. - 2050-7526 .- 2050-7534. ; 11:22, s. 7227-7242
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Tidskriftsartikel (refereegranskat)abstract
- We report a detailed analysis of both the structural and spectroscopic properties of Nd3+-doped GdPO4 nano-powders obtained via various wet synthesis methods. This type of material may be useful in optoelectronics, bioimaging and biomedicine. Three series of Nd3+-doped nano-materials with different concentrations of the optical activator (1–10 mol%) were obtained via ionic liquid assisted classical hydrothermal (IL HT) and microwave (IL MW) methods as well as via an oleic acid assisted hydrothermal (OA HT) method. A powder X-ray diffraction (PXRD) technique confirmed that the obtained GdPO4 nano-powders crystallize in a monoclinic system (P21/n) with the average grain size ranging from 40 to 100 nm; the smallest grains are obtained via the ionic liquid assisted microwave method, and no other phase has been detected for any of the materials obtained. Electron microscopy techniques i.e. SEM and TEM were used to demonstrate the differences in the morphology and grain size, which resulted in the spectroscopic properties of nano-materials. The nine-fold coordinated Gd3+ ion in GdPO4 is easily substituted by the Nd3+ one with the C1 symmetry due to their similar ionic radii, so that high-resolution low-temperature absorption and emission spectra do not show any structural distortion. The 4F3/2 excited state dynamics studied at 77 K showed abnormal behavior, similar to that already observed for Nd3+ ions embedded in the YPO4 and LuPO4 tetragonal orthophosphates crystallizing in a xenotime-type crystal system.
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| 4. |
- Prokop, K. A., et al.
(författare)
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Nano-crystalline Nd3+-doped LuPO4 optical materials obtained by ionic liquid assisted synthesis route
- 2022
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Ingår i: Materials Science & Engineering. - : Elsevier BV. - 0921-5107 .- 1873-4944. ; 275
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Tidskriftsartikel (refereegranskat)abstract
- LuPO4 in the form of nano-powders can find potential application in bio-imaging and luminescence thermometry. To enable development of functional materials there is a need to acquire basic information about the effect of morphology and grain size on spectroscopic properties. So, we investigated a series of Nd3+-doped LuPO4 nanoparticles prepared with task-specific ionic liquid as the reactant and in-situ stabilizer. Thus, fast and facile preparation of the desired well-crystallized single-phase phosphate nanomaterials was possible. The XRD patterns and TEM analysis revealed the influence of the synthesis conditions on the morphology and nanoparticles size, which is reflected in their spectroscopic properties. Low-temperature high-resolution techniques i.e. absorption spectroscopy at 4.2 K and laser site-selective spectroscopy at 77 K with Nd3+ ion as structural probe were used. Micro-powdered Nd3+-doped LuPO4 obtained by a solid-state reaction was applied as a reference. The possible application of this material as an optical thermometer was considered.
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