Showing papers by "Martin Nikl published in 2023"
01 Jan 2023-Journal of Materials Chemistry C. Materials for Optical, Magnetic and Electronic Devices
TL;DR: Cerium doped rare-earth aluminum garnets represent an important class of scintillation and luminescent materials widely used in different technical fields including the medical imaging and the solid state white light as mentioned in this paper .
Abstract: Cerium doped rare-earth aluminum garnets represent an important class of scintillation and luminescent materials widely used in different technical fields including the medical imaging and the solid state white light...
3 citations
TL;DR: In this article , a set of transparent crystalline hexagonal platelets were synthesized by chemical reaction under a flow of hydrogen sulfide, and their structural, optical, and scintillation properties were investigated thoroughly by means of x-ray powder diffraction, time-resolved luminescence spectroscopy, and decay measurements to assess the spectroscopic properties of the ions in the host.
Abstract: A set of ${\mathrm{Pr}}^{3+}$-doped ${\mathrm{KLuS}}_{2}$ samples with different $\mathrm{Pr}$ concentrations are synthesized in the form of transparent crystalline hexagonal platelets by chemical reaction under a flow of hydrogen sulfide. Their structural, optical, and scintillation properties are investigated thoroughly by means of x-ray powder diffraction, time-resolved luminescence spectroscopy, scintillation light yield, and decay measurements to assess the spectroscopic properties of ${\mathrm{Pr}}^{3+}$ ions in the ${\mathrm{KLuS}}_{2}$ host. Charge-trapping processes are further investigated by electron paramagnetic resonance. The fundamental absorption band edge of the ${\mathrm{KLuS}}_{2}$ host is located at 303 nm, the absorption due to the ${\mathrm{Pr}}^{3+}$ 4f \ensuremath{\rightarrow} 5d transition is found at 347 nm, the emission maximum is given by the $4{f}^{1}5d1$ \ensuremath{\rightarrow} ${}^{3}{H}_{4}$ transition of the ${\mathrm{Pr}}^{3+}$ ion at 380 nm, and the leading photoluminescence and scintillation decay time is around 1 ns at room temperature. The moderate scintillation light yield reaches 7200 ph/MeV. A phenomenological model is fitted to the measured temperature dependences of the photoluminescence emission spectra and photoluminescence decay times to better understand the dynamics of the 5d excited state of the ${\mathrm{Pr}}^{3+}$ center in the ${\mathrm{KLuS}}_{2}$ host. The number of photons emitted in the first nanosecond of the scintillation response is evaluated and found to be considerably higher (1.6--2.5 times) than that in the commercial $(\mathrm{Lu};\mathrm{Y}{)}_{2}({\mathrm{SiO}}_{4})\mathrm{O}$:$\mathrm{Ce},\mathrm{Ca}$ scintillator, which shows the potential of $\mathrm{Pr}$-doped ${\mathrm{KLuS}}_{2}$ for fast-timing scintillator applications.
1 citations
1 citations
TL;DR: In this article , the authors investigated the role of non-radiative energy transfer between the nanoscintillator and conjugated moieties, which is usually considered crucial for the activation of PSs and therefore pivotal to enhance the therapeutic effect.
Abstract: Multicomponent nanomaterials consisting of dense scintillating particles functionalized by or embedding optically active conjugated photosensitizers (PSs) for cytotoxic reactive oxygen species (ROS) have been proposed in the last decade as coadjuvant agents for radiotherapy of cancer. They have been designed to make scintillation-activated sensitizers for ROS production in an aqueous environment under exposure to ionizing radiations. However, a detailed understanding of the global energy partitioning process occurring during the scintillation is still missing, in particular regarding the role of the non-radiative energy transfer between the nanoscintillator and the conjugated moieties which is usually considered crucial for the activation of PSs and therefore pivotal to enhance the therapeutic effect. We investigate this mechanism in a series of PS-functionalized scintillating nanotubes where the non-radiative energy transfer yield has been tuned by control of the intermolecular distance between the nanotube and the conjugated system. The obtained results indicate that non-radiative energy transfer has a negligible effect on the ROS sensitization efficiency, thus opening the way to the development of different architectures for breakthrough radiotherapy coadjutants to be tested in clinics.
1 citations
TL;DR: For the first time hafnia (HfO2) nanoparticles have been produced by photochemical synthesis as mentioned in this paper , and the photochemical route has been proven to be a scalable, affordable, and straightforward to create monoclinic HfO 2 nanoparticles.
Abstract: For the first time hafnia (HfO2) nanoparticles have been produced by photochemical synthesis. The photochemical route has been proven to be a scalable, affordable, and straightforward to create monoclinic HfO2...
TL;DR: In this article , the phase composition, microstructure, luminescence properties, trap state, and performance of HIP post-treated (Sr0.97Eu0.01Dy0.02)Al2O4 PersL ceramics were discussed.
Abstract: (Sr0.97Eu0.01Dy0.02)Al2O4 persistent luminescence (PersL) ceramics were fabricated by solid-state reactive sintering in vacuum combined with hot isostatic pressing (HIP) using H3BO3 as sintering additive. The phase composition, microstructure, luminescence properties, trap state, and PersL performance of HIP post-treated (Sr0.97Eu0.01Dy0.02)Al2O4 PersL ceramics were discussed. For the (Sr0.97Eu0.01Dy0.02)Al2O4 PersL ceramics after HIP post-treatment, the initial luminescence intensity of the ceramics reached over 6400 mcd/m2 with a simulated daylight irradiation of 1000 lx for 5 min, and the persistent emission decay time > 17 h. This is much better than the SrAl2O4:Eu2+,Dy3+ PersL powders and the other luminescent ceramics. In addition, this method is a solid-state reactive sintering method for synthesizing ceramics, which has the advantages of low cost and simple operation, and is suitable for large-scale, high-volume industrial production. This article is protected by copyright. All rights reserved
01 Jan 2023-Journal of Materials Chemistry C. Materials for Optical, Magnetic and Electronic Devices
TL;DR: In this article , the crystal chemical principles related to the incorporation of incompatible atoms into the garnet host lattice were investigated, and these considerations might be used to guide and drive the design of the design.
Abstract: This research investigated the crystal chemical principles related to the incorporation of incompatible atoms into the garnet host lattice. These considerations might be used to guide and drive the design...
TL;DR: In this paper , the results on creation of novel types of composite scintillators based on Ce3+ doped Gd3Al5-xGaxO12 single crystalline films grown by the LPE method using PbO-B2O3 flux onto substrate-scintillator prepared from commercial GdAl2.3Ga2.7O12.
08 Mar 2023
TL;DR: In this paper , the Gd3(Ga,Al)5O12 (GGAG) crystal was grown by Czocharlski method from melt with initial composition Gd2.91Ho0.075Ga2.7Al2.3O12.
Abstract: Holmium-doped solid state lasers are important direct sources of coherent radiation at 2 μm with applications in medicine, spectroscopy, LIDAR technologies, or conversion to mid-infrared wavelengths. Co-doping with Tm3+ sensitizer enables resonant diode-pumping at 1.7 μm with aim to reduce lasing threshold and thermal loading and to increase efficiency and obtainable wavelengths range. The Gd3(Ga,Al)5O12 (GGAG) crystal investigated in this work belongs to a class of mixed or disordered garnets. Such crystals are actively researched host material for rare earth ions due to broadening of dopant spectral lines and preserving good thermal and mechanical properties of crystalline garnet hosts. Spectroscopic and laser properties and their doping concentration dependence of Tm, Ho:GGAG crystal were investigated under 1.7 μm diode pumping. The laser material was Tm3+ and Ho3+ co-doped Gd3(Ga,Al)5O12. It was grown by Czocharlski method from melt with initial composition Gd2.91Ho0.012Tm0.075Ga2.7Al2.3O12. The grown crystal boule was cut into eight face-polished crystal samples 5.4 mm thick and 8–14 mm wide in diameter. Tm3+ and Ho3+ content of samples was between 2.1–3.2 at.% Tm/Gd and 0.3–0.5 at.% Ho/Gd. Crystals were pumped at room temperature by fiber-coupled (NA = 0.22, core diameter = 400 µm) 30 W laser diode emitting at 1.7 µm in quasi-continuous regime. A hemispherical laser cavity was tested with OC curvature of -150 mm and reflectivity of 96.5 % at 2090 nm. All lasers emitted at 2084–2090 nm range in the untuned setup. Threshold absorbed power was in 0.1–0.3 W range and generated beam corresponded to TEM00 mode. Both the highest efficiency w.r.t. absorbed power of 37 % and the highest output power amplitude of 3.8 W were obtained for 3.0 at.% (Tm/Gd) 0.5 at.% (Ho/Gd) crystal. The total wavelength tunability range of 1936–2111 nm was obtained, with lower concentration samples tended to result in broader continuous tuning curves.
TL;DR: In this article , the scintillation, luminescence and optical properties of the multicomponent Gd3Sc2Ga(2+x)Al(1-x)O12:Ce (x = 0, 0.25, 0., 0.75, 1), Gd2.957Sc1.905 Ga(2.138+x), Al( 1-x), O12Ce, Gd1.75Al0.25O12, 0
TL;DR: In this paper , the authors investigated the effect of co-doping with aliovalent ions on the formation of lattice defects in Lutetium oxyorthosilicate Lu2SiO5 (LSO) and pyrosilicate pyrosilecimitriou Lu 2Si2O7 (LPS) powders.
Abstract: Lutetium oxyorthosilicate Lu2SiO5 (LSO) and pyrosilicate Lu2Si2O7 (LPS) activated by Ce3+ or Pr3+ are known to be effective and fast scintillation materials for the detection of X-rays and γ-rays. Their performances can be further improved by co-doping with aliovalent ions. Herein, we investigate the Ce3+(Pr3+) → Ce4+(Pr4+) conversion and the formation of lattice defects stimulated by co-doping with Ca2+ and Al3+ in LSO and LPS powders prepared by the solid-state reaction process. The materials were studied by electron paramagnetic resonance (EPR), radioluminescence spectroscopy, and thermally stimulated luminescence (TSL), and scintillation decays were measured. EPR measurements of both LSO:Ce and LPS:Ce showed effective Ce3+ → Ce4+ conversions stimulated by Ca2+ co-doping, while the effect of Al3+ co-doping was less effective. In Pr-doped LSO and LPS, a similar Pr3+ → Pr4+ conversion was not detected by EPR, suggesting that the charge compensation of Al3+ and Ca2+ ions is realized via other impurities and/or lattice defects. X-ray irradiation of LPS creates hole centers attributed to a hole trapped in an oxygen ion in the neighborhood of Al3+ and Ca2+. These hole centers contribute to an intense TSL glow peak at 450–470 K. In contrast to LPS, only weak TSL peaks are detected in LSO and no hole centers are visible via EPR. The scintillation decay curves of both LSO and LPS show a bi-exponential decay with fast and slow component decay times of 10–13 ns and 30–36 ns, respectively. The decay time of the fast component shows a small (6–8%) decrease due to co-doping.
TL;DR: In this paper , a zero-dimensional Cs4EuBr6 halide scintillators via Sm2+ doping was developed and the energy transfer processes between Eu2+ and Sm2+) were investigated by using photoluminescence (PL) spectra, PL decay kinetics, and soft X-ray excited decay kinetic measurements.
Abstract: Near-infrared (NIR)-emitting scintillators, coupled with high quantum efficiency silicon-based photodetectors, have emerged as a promising solution for highly efficient radiation detection applications. However, the study of efficient NIR-emitting scintillators and their associated luminescence mechanism is still limited. In this work, we developed NIR-emitting zero-dimensional Cs4EuBr6 halide scintillators via Sm2+ doping. Single crystals of Cs4EuBr6 with varying Sm2+ concentrations were grown by the vertical Bridgman method. Under X-ray irradiation, the scintillation emission of highly Sm-doped Cs4EuBr6 single crystals is dominated by the Sm2+ 5d–4f emission peaking at 831 nm with a weak Eu2+ 5d–4f emission peaking at 443 nm. The energy transfer processes between Eu2+ and Sm2+ were investigated by using photoluminescence (PL) spectra, PL decay kinetics, and soft X-ray excited decay kinetics measurements. Based on the temperature-dependent PL decay results, we constructed a configurational coordinate diagram of Sm2+ in the Cs4EuBr6 host. Furthermore, we evaluated the gamma spectroscopy response of Cs4EuBr6:Sm single crystals using an avalanche photodiode detector known for its high sensitivity in the NIR wavelength region.
TL;DR: In this paper , the performance tuning of LuAG via Ce and Ca codoping was analyzed and it was shown that the Fermi level shifts down with ca codoping, which increases the Ce4+ content and decreases the depth of the electron traps (VO), resulting to faster decay.
Abstract: High-energy physics (HEP) community is looking for a hard, fast and low-cost scintillation material, and Ce:Lu3Al5O12 (Ce:LuAG) ceramic is one of the competitive candidates. This work presents Ce,Ca:LuAG scintillation ceramics with good optical quality and the influence of Ce and Ca concentrations on optical and scintillation properties were fully analyzed. At relatively low level of Ce concentration, the less Ca2+ content is needed to achieve a significant intensity increase in fast scintillation component while maintaining a relatively high light yield (LY). The introduction of only 0.1 at% Ca2+ could increase the LY0.5 μs/ LY3.0 μs from 79.9% to 96.1% in Ce,Ca:LuAG ceramics of 0.1 at% Ce. First-principles investigations are further performed to reveal the tuning mechanisms of the scintillation properties of LuAG by Ce and Ca codoping. We show that the Fermi level shifts down with Ca codoping, which increases the Ce4+ content and decreases the depth of the electron traps (VO), resulting to a faster decay. Moreover, the formation preference of Ca-VO complexes over Ce-VO leads to the suppression of the non-radiative decay of Ce via VO. In summary, our study demonstrates the realization of the performance tuning of LuAG via Ce and Ca codoping. This article is protected by copyright. All rights reserved
TL;DR: In this paper , a new Cs4SrI6 :Yb2+,Sm2+ near-infrared (NIR) emitting scintillator was developed using sensitization strategy.
Abstract: In this study, a new Cs4SrI6 :Yb2+,Sm2+ near-infrared (NIR) emitting scintillator was developed using sensitization strategy. It was found that Yb2+ sensitization significantly enhances the NIR radioluminescence (RL) of Sm2+, providing a new approach of designing highly-emissive sensitized NIR scintillators. By studing the optical spectra and decay kinetics of Cs4SrI6:Yb2+,Sm2+, it was revealed that the energy transfer pathways involve both radiative and nonradiative processes. The gamma spectroscopy performance of Cs4SrI6:Yb2+,Sm2+ single crystals was studied by using the high-quantum-efficiency avalanche photodiode (APD) as the readout. Our results highlights the importance of using sensitization strategy of achieving NIR emitting scintillators, and demonstrating the significant potential for radiation detection applications. This article is protected by copyright. All rights reserved