| 1. |
- Abou Nada, Fahd Jouda, et al.
(författare)
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Investigation of the effect of engine lubricant oil on remote temperature sensing using thermographic phosphors
- 2016
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Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313. ; 179, s. 568-573
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Tidskriftsartikel (refereegranskat)abstract
- Phosphor thermometry, a remote temperature sensing technique, is widely implemented to measure the temperature of different combustion engines components. The presence of engine lubricant can influence the behavior of the applied sensor materials, known as thermographic phosphors, and thus leading to erroneous temperature measurements. The effect of two engine lubricants on decay times originating from six different thermographic phosphors was investigated. The decay time of each thermographic phosphor was investigated as a function of lubricant/phosphor mass ratio. Tests were conducted at temperatures around 293 K and 376 K for both lubricants. The investigations revealed that ZnO:Zn and ZnS:Ag are the only ones that exhibit a change of the decay time as function of the lubricant/phosphor mass ratio. While the remaining thermographic phosphors, namely BaMg2Al16O27:Eu (BAM), Al2O3-coated BaMg2Al16O27:Eu, La2O2S:Eu, Mg3F2GeO4:Mn, displayed no sensitivity of their characteristic decay time on to the presence of lubricant on the porous coating. Biases in the calculated temperature are to be expected if the utilized thermographic phosphor displays decay time sensitivity to the existence of the engine lubricant within the sensor. Such distortions are concealed and can occur undetected leading to false temperature readings for the probed engine component.
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| 2. |
- Echresh, Ahmad, et al.
(författare)
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High photocurrent gain in NiO thin film/M-doped ZnO nanorods (M = Ag, Cd and Ni) heterojunction based ultraviolet photodiodes
- 2016
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Ingår i: Journal of Luminescence. - : ELSEVIER SCIENCE BV. - 0022-2313 .- 1872-7883. ; 178, s. 324-330
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Tidskriftsartikel (refereegranskat)abstract
- The thermal evaporation method has been used to deposit p-type NiO thin film, which was combined with hydrothermally grown n-type pure and M-doped ZnO nanorods (M=Ag, Cd and Ni) to fabricate a high performance p-n heterojunction ultraviolet photodiodes. The fabricated photodiodes show high rectification ratio and relatively low leakage current. The p-NiO/n-Zn0.94Ag0.06O heterojunction photo diode displays the highest photocurrent gain (similar to 1.52 x 10(4)), a photoresponsivity of similar to 4.48 x 10(3) AW(-1) and a photosensitivity of similar to 13.56 compared with the other fabricated photodiodes. The predominated transport mechanisms of the p-n heterojunction ultraviolet photodiodes at low and high applied forward bias may be recombination-tunneling and space charge limited current, respectively. (C) 2016 Elsevier B.V. All rights reserved.
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| 3. |
- Echresh, Ahmad, et al.
(författare)
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Light emitting diode based on n-Zn0.94M0.06O nanorods/p-GaN (M= Cd and Ni) heterojunction under forward and reverse bias
- 2015
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Ingår i: Journal of Luminescence. - : Elsevier. - 0022-2313 .- 1872-7883. ; 160, s. 305-310
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we report on the improvement in the optoelectronic properties of n-ZnO nanorods/p-GaN heterojunction. This was achieved by doping the ZnO with cadmium (Cd) and nickel (Ni). The ZnO and Zn0.94M0.06O nanorods grown hydrothermally on the p-GaN substrate were used to fabricate the light emitting diodes (LEDs). Structural measurement revealed that nanorods with wurtzite structure having a preferential orientation along the (002) c-axis. The UV-vis spectra show that the optical band gap of Zn0.94M0.06O nanorods is decreased in comparison to ZnO nanorods. Electrical measurements of the fabricated LEDs show an obvious rectifying behaviour with low threshold voltage. Electroluminescence (EL) characteristics of LEDs operated at forward and reverse bias were investigated. The EL spectra under forward bias show that doping ZnO nanorods with Cd and Ni led to an intensity enhancement of the broad peak in the visible region while the blue peak originating from the p-GaN substrate remains almost unaffected. The effect of doping was to reduce the valence band offsets and consequently more hole injection has occurred leading to the observed enhancement of the broad band in the visible region. Under reverse bias all heterojunction LEDs show the blue light emission peak originating from the p-GaN substrate.
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| 4. |
- Enrichi, Francesco, et al.
(författare)
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Visible to NIR downconversion process in Tb3+-Yb3+ codoped silica-hafnia glass and glass-ceramic sol-gel waveguides for solar cells
- 2018
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Ingår i: Journal of Luminescence. - : Elsevier. - 0022-2313 .- 1872-7883. ; 193, s. 44-50
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Tidskriftsartikel (refereegranskat)abstract
- The efficiency of photovoltaic solar cells is strongly related to the spectral absorption and photo-conversion properties of the cell's active material, which does not exploit the whole broadband solar spectrum. This mismatch between the spectrum of the solar light and the wavelength dependent cell's response can be partially overcome by using luminescent conversion layers in front or in the back of the solar cell. In this paper, the investigation of Tb3+-Yb3+ co-doped SiO2-HfO2 glass and glass-ceramic waveguides is presented. Due to a down-conversion process based on cooperative energy transfer between one Tb3+ ion and two Yb3+ ions, a blue photon at 488 nm can be divided in two NIR photons at 980 nm. Films with different molar concentrations of rare earths, up to a total amount of [Tb+Yb] = 15%, were prepared by a sol-gel route, using dip-coating deposition on SiO2 substrates. For all the films, the molar ratio [Yb]/[Tb] was taken equal to 4. The comparison of the energy-transfer efficiency between Tb3+ and Yb3+ ions in the glass and in the glass-ceramic materials demonstrated the higher performance of the glass-ceramic, with a maximum quantum transfer efficiency of 179% for the highest rare earth doping concentration. Moreover, experimental results and comparison with proper rate equations modelling showed a linear dependence of the photoluminescence emission intensity for the Yb3+ ions 2F5/2 → 2F7/2 transition at 980 nm on the excitation power, indicating a direct transfer process from Tb3+ to Yb3+ ions. The reported waveguides could find applications not only as downconverting filters in transmission but also as efficient solar concentrators in the near-IR spectral region
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| 5. |
- Ghosh, Sirina, et al.
(författare)
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Effect of the change of heteroatom on phenyl capped benzazole : Photophysical and electrochemical properties from the structural viewpoint
- 2018
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Ingår i: Journal of Luminescence. - : ELSEVIER SCIENCE BV. - 0022-2313 .- 1872-7883. ; 194, s. 164-169
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Tidskriftsartikel (refereegranskat)abstract
- Donor-acceptor-donor type phenyl capped benzazoles were synthesized and their photophysical properties were studied. By changing the heteroatom (N, O, S and Se) of central acceptor benzazole unit, the emission color was varied from blue to green. Phenyl capped benzotriazole (1) and benzooxadiazole (2) were characterized by single crystal X-ray crystallography. The absolute solid state fluorescence quantum yields of these compounds were obtained in the range of 0.05-0.93 by a calibrated integrating sphere method. High solid state quantum yield can be attributed to the non-planarity and absence of strong intermolecular interactions in the solid state. Except phenyl capped benzotriazole (1), all compounds showed reversible reduction peak in cyclic voltammetry experiments which reflects the considerable n-type nature.
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| 6. |
- Khachatourian, Malek Adrine, et al.
(författare)
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Microwave synthesis of Y2O3:Eu3+ nanophosphors : A study on the influence of dopant concentration and calcination temperature on structural and photoluminescence properties
- 2016
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Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313 .- 1872-7883. ; 169, s. 1-8
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Tidskriftsartikel (refereegranskat)abstract
- Red fluorescent emitting monodispersed spherical Y2O3 nanophosphors with different Eu3+ doping concentrations (0-13 mol%) are synthesized by a novel microwave assisted urea precipitation, which is recognized as a green, fast and reproducible synthesis method. The effect of Eu3+ doping and calcination temperature on the structural characteristics and luminescence properties of particles is investigated in detail. The as prepared powders have (Y,Eu)(OH)(CO3) structure which converts to Y2O3:Eu3+ from 500 °C and become crystalline at higher temperatures. The crystallite size of nanophosphors increased from 15 nm to 25 nm as the calcination temperature increased from 700 °C to 1050 °C. The efficient incorporation of Eu3+ ions in cubic Y2O3 host matrix is confirmed by the calculated X-ray Powder diffraction (XRPD) structural parameters. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) micrographs show that the as obtained and calcined particles are spherical, monodispersed and non-agglomerated. The overall size of particles increases from 61±8 nm to 86±9 nm by increasing Eu3+ concentration from 0 mol% to 13 mol%. High resolution TEM revealed polycrystalline nature of calcined particles. The particles exhibit a strong red emission under ultraviolet (UV) excitation. The photoluminescence (PL) intensity of the peaks increases proportionally with Eu3+ concentration and the calcination temperature with no luminescence quenching phenomenon observed even for Y2O3:13%Eu3+. The fluorescent emission properties combined with the monodispersity and narrow size distribution characteristics make the Y2O3:Eu3+ heavy metal free nanophosphors applicable in fluorescence cell imaging and as fluorescence biolabels.
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| 7. |
- Khanin, V., et al.
(författare)
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Variation of the conduction band edge of (Lu,Gd) 3 (Ga,Al) 5 O 12 :Ce garnets studied by thermally stimulated luminescence
- 2019
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Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313. ; 211, s. 48-53
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Tidskriftsartikel (refereegranskat)abstract
- The shift of the conduction band (CB) edge for thirty different (Lu,Gd) 3 (Ga,Al) 5 O 12 :Ce compositions, with simultaneous variation in Lu/Gd and Ga/Al content was studied using thermally stimulated luminescence (TSL). Specific TSL peaks were related to impurities of Ta, Cr, Yb, Ti and Eu in Lu 1 Gd 2 Ga 3 Al 2 O 12 :Ce ceramics. The shift of Yb-related peak positions (in temperature and trap depth) with composition modification was investigated as well. In Gd-containing (Lu,Gd) 3 (Ga,Al) 5 O 12 compositions a non-monotonous shift of the CB edge with increasing Ga content has been affirmed. The difference between thermal trap depths evaluated from our TSL experiments and optical trap depths obtained from the literature was explained by the role of lattice relaxation.
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| 8. |
- Khranovskyy, Volodymyr, et al.
(författare)
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Complementary study of the photoluminescence and electrical properties of ZnO films grown on 4H-SiC substrates
- 2017
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Ingår i: Journal of Luminescence. - : ELSEVIER SCIENCE BV. - 0022-2313 .- 1872-7883. ; 181, s. 374-381
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the photoluminescence and electrical properties of ZnO films grown epitaxially by atmospheric pressure MOCVD on 4H-SiC substrates. The dominating DA line on the low temperature PL spectrum is attributed to the emission of an exciton bound to the neutral donor. The intensity of this line correlates with the electrical properties of the films: the decrease of DA intensity occurs simultaneously with the increase of the carriers mobility. This we explain as donor activation providing free electrons to the conduction band. Based on the comparison of the calculated value of donor binding energy, the literature data and complementary SIMS analysis a suggested donor impurity is aluminum (Al). The exciton localization energy is 16.3 meV, and agrees well with localization energy of 15.3 meV for Al impurity reported by other authors (e.g. Ref. [33]). The thermal activation energy E-D=22 meV, determined from the Hall data and is in agreement with the optical activation energy 20 meV, which is derived from the temperature-dependent PL study. The calculated value of the donor binding energy of 54.3 eV is in agreement with the ionization energy of 53 meV mentioned in earlier reports for Al in ZnO films. Our results prove that the commonly observed line at similar to 3.3599 eV on low temperature PL spectra of ZnO is a neutral donor bound exciton emission due to the Al impurity. (C) 2016 Elsevier B.V. All rights reserved.
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| 9. |
- Pandey, Rampal, et al.
(författare)
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Strong luminescence behavior of mono- and dimeric imidazoquinazolines: Swift OLED degradation under electrical current
- 2017
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Ingår i: Journal of Luminescence. - : ELSEVIER SCIENCE BV. - 0022-2313 .- 1872-7883. ; 181, s. 252-260
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Tidskriftsartikel (refereegranskat)abstract
- Design and synthesis of novel mono-and dimeric quinazoline derivatives (+)-6-methyl-6-pyridin-2-yl-5,6-dihydrobenzo[4,5]imidazo[1,2-c]quinazoline (1) and (+)-6-[(6-methyl-5,6-dihydrobenzo-[4,5]imidazo [1,2-c] quinazolin-6-yl)-pyridin-2-yl]-6-methyl-5,6-dihydro-benzo-[4,5]imidazo-[1,2-c] quinazoline (2) have been described. Both 1 and 2 have been characterized by elemental analyses, FT-IR, H-1 and C-13 NMR, HRMS spectroscopic studies and their structures authenticated by X-ray single crystal analyses. Photophysical properties of these compounds have been studied by UV/VIS absorption and fluorescence spectroscopy and transient photoluminescence analysis in solution, powder, and non-doped (neat) and doped vacuum-deposited films. A broad emission spectrum spanning most of the visible range and good thermal stability indicated promising application of 1 and 2 as OLED emitters. Unfortunately, under current flow we observed rapid device degradation, presumably to be related to free -NH moiety in these compounds. (C) 2016 Elsevier B.V. All rights reserved.
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| 10. |
- Serrano, Diana, et al.
(författare)
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Satellite line mapping in Eu3+-Ce3+ and Pr3+-Ce3+ codoped Y2SiO5
- 2016
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Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313. ; 170, s. 102-107
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Tidskriftsartikel (refereegranskat)abstract
- In this work we perform a high-resolution spectroscopic investigation of Eu3+-Ce3+ and Pr3+-Ce3+ codoped Y2SiO5 crystals. Satellite line spectra were recorded at low temperatures around the Eu3+:F-7(0) -> D-5(0) and the Pr3+:H-3(4) -> D-1(2) transitions. It is observed that the incorporation of Ce3+ as a codopant notably changes the Eu3+ and Pr3+ satellite line patterns. Satellite lines measured in singly doped Eu3+:Y2SiO5 were found at the same spectral positions in Eu3+-Ce3+ codoped crystals. These coincident lines were concluded to be due to pairs of Eu3+ ions. Extra satellite lines appeared in the codoped crystals, which were assigned to Ce3+ related structures such as Ce3+-Eu3+ pairs. The analysis of the Pr3+ satellite line spectra presents further challenges. Satellite lines associated to Pr3+ pairs show weaker intensity, presumably due to the efficient quenching of the Pr3+ D-1(2) emission through cross-relaxation paths (D-1(2) -> (1)G(4); H-3(4) -> F-3(4)). The investigation of the Eu3+ and Pr3+ satellite line patterns in Y2SiO5 is particularly interesting for their exploitation in rare-earth based quantum computation schemes. (C) 2015 Elsevier B.V. All rights reserved.
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