Levels Of Pr3 Research Articles

Systemic Resistance to Powdery Mildew in Brassica napus (AACC) and Raphanus alboglabra (RRCC) by Trichoderma harzianum TH12.

Trichoderma harzianum TH12 is a microbial pesticide for certain rapeseed diseases. The mechanism of systemic resistance induced by TH12 or its cell-free culture filtrate (CF) in Brassica napus (AACC) and Raphanus alboglabra (RRCC) to powdery mildew disease caused by ascomycete Erysiphe cruciferarum was investigated. In this study, we conducted the first large-scale global study on the cellular and molecular aspects of B. napus and R. alboglabra infected with E. cruciferarum. The histological study showed the resistance of R. alboglabra to powdery mildew disease. The growth of fungal colonies was not observed on R. alboglabra leaves at 1, 2, 4, 6, 8, and 10 days post-inoculation (dpi), whereas this was clearly observed on B. napus leaves after 6 dpi. In addition, the gene expression of six plant defense-related genes, namely, PR-1, PR-2 (a marker for SA signaling), PR-3, PDF 1.2 (a marker for JA/ET signaling), CHI620, and CHI570, for both genotypes were analyzed in the leaves of B. napus and R. alboglabra after treatment with TH12 or CF and compared with the non-treated ones. The qRT-PCR results showed that the PR-1 and PR-2 expression levels increased in E. cruciferarum-infected leaves, but decreased in the TH12-treated leaves compared with leaves treated with CF. The expression levels of PR-3 and PDF1.2 decreased in plants infected by E. cruciferarum. However, expression levels increased when the leaves were treated with TH12. For the first time, we disclosed the nature of gene expression in B. napus and R. alboglabra to explore the resistance pathways in the leaves of both genotypes infected and non-infected by powdery mildew and inoculated or non-inoculated with elicitor factors. Results suggested that R. alboglabra exhibited resistance to powdery mildew disease, and the application of T. harzianum and its CF are a useful tool to facilitate new protection methods for resist or susceptible plants.

Enhanced luminous efficiency in Pr3+ activated Ca0.5La(MoO4)2 red phosphor with blue excitation for WLED applications

In this article, we have investigated the down-conversion luminescence properties of Ca0.5La(MoO4)2 doped with trivalent Pr3+ (substitute for La3+ site) and codoped with Mn2+ (substitute for Ca2+ site). The powder X-ray diffraction patterns confirm that the single crystalline phosphor powders belong to the scheelite-type tetragonal crystal structure. The photoluminescence (PL) excitation spectra of Ca0.5La(MoO4)2:Pr3+ exhibits a charge transfer band centered at 276 nm along with three intense sharp absorption bands identified at 449, 475, and 488 nm which are attributed to the f–f electronic transitions of 3H 4 (1) → 3P2, 3H 4 (1) → 3P1, 3H 4 (1) → 3P0 of Pr3+, respectively. Upon optical excitation, the depopulation of excited 3P0 level into the 3F2 lower levels of Pr3+ is governed by radiative transfer of energy, as a result, high intense red emission peak was observed at 647 nm. The change in PL emission intensity as a function of Pr3+ concentrations, Mn2+ concentrations, and different excitation wavelengths have been investigated in detail. Further, the codoping of alkali metal chlorides MCl (M = Na, K, Li) into the Ca0.5La(MoO4)2:Pr3+ phosphor greatly improves the luminescence intensity of the transition 3P0 → 3F2 which can be explained by charge compensation effect. To ensure the colour richness and quality of its emission, the photometric parameters were estimated using spectral energy distribution functions of Ca0.5La(MoO4)2:Pr3+. The luminous efficacy of radiation for NaCl codoped Ca0.5La(MoO4)2:Pr3+ phosphor was estimated to be 154 lm/W and the percentage of luminous efficiency is 23 %.

The down-conversion and up-conversion photoluminescence properties of Na0.5Bi0.5TiO3:Yb3+/Pr3+ ceramics

Na0.5Bi0.5−x−yYbxPryTiO3 (NBT:xYb/yPr) ceramics with different Yb and Pr contents are prepared. Both the down-conversion (DC) and up-conversion (UC) photoluminescence (PL) of the ceramics via 453 and 980 nm excitation, respectively, are investigated. The effect of Yb3+ and Pr3+ doping contents on the DC and UC PL is significantly different from each other. Furthermore, the UC PL of the ceramics as a function of temperatures is measured to investigate the UC process in detail. Based on energy level diagram of Pr3+ and Yb3+ ions and the DC and UC PL spectra, the DC and UC PL mechanisms of Pr3+ and Yb3+ ions are discussed. Especially, the UC PL mechanism is clarified, which is different from the previously reported literature. Also, the temperature sensing properties of the ceramics are studied based on the photoluminescence ratio technique, using the thermal coupling energy levels of Pr3+.

Luminescence Quenching of [M]NbO4:Pr3+ [M=La, Lu, Gd] Under UV Excitation

We report on the luminescence properties of three Pr3+-doped niobate systems (LaNbO4, LuNbO4, and LaNbO4) in the temperature range between 7K and 500K. These systems are d0 oxides that exhibit a metal-to-metal charge transfer state lying just below the conduction band. Pumping in the UV, the system exhibits the typical sharp line emission from the 3P0 and 1D2 levels of Pr3+. The emission intensities from these levels are temperature and host dependent, with the 1D2 emission showing strong quenching at higher temperatures. In addition to the Pr emission, we also observe broad-band emission from the niobate complex. Using results from steady state luminescence and kinetic studies, we discuss the flow of energy in these systems following uv excitation, and also consider the quenching mechanism of the luminescence from these systems.

Near Infrared Emission at 1000 nm from Nanostructured Pr3+/Yb3+Co-doped SiO2-Nb2O5for Solar Cell Application

Energy conversion, involving UV and Vis absorption to generate near infrared (NIR) emission at 1000 nm from nanostructured Pr3+/Yb3+ co-doped SiO2-Nb2O5 for solar cell application was the main focus of this work. The synthesis, structural and optical characterization of Pr3+/Yb3+ co-doped 70SiO2-30Nb2O5 nanocomposites and planar waveguides prepared by the sol gel method are reported. The influence of the rare earth content and thermal annealing on the crystallization process and the luminescence properties was studied. The excitation spectra revealed the energy transfer between the Pr3+ and Yb3+, involving mainly the 3P2 level of Pr3+ ions. Multiphonon decay and cross relaxation processes take place at higher rare earth concentration and annealing temperature, which increases the 1D2 level population and consequently the NIR emission from the Pr3+ ions. The nanostructured Pr3+/Yb3+ co-doped SiO2-Nb2O5 nanocomposites and waveguides show interesting NIR emission and optical properties for photonic applications.

Luminescent Properties and Energy Transfer in Pr3+ Doped and Pr3+-Yb3+ Co-doped ZnO Thin Films

Embedding luminescent rare earth ions into transparent oxides such as ZnO is a well-known approach to functionalize the material by adding photon-management properties. In this paper we present a detailed study of the luminescence properties and energy level structure of Pr3+ and Yb3+ ions embedded in ZnO thin films deposited by magnetron reactive sputtering. Careful study of the photoluminescence and excitation spectra allowed identifying and locating almost all excited levels of Pr3+ and Yb3+ ions. Thus, an almost complete electronic energy level diagram of these ions in the ZnO crystal lattice can be drawn for the first time. In particular, we show that the crystal field of ZnO strongly modifies the energy level structure of the Pr3+ and Yb3+ ions creating energy mismatches between the transitions useful for cooperative down conversion. Finally, we demonstrate that light emission from Pr3+ ions can be induced both by direct excitation of the ions and indirectly by energy transfer from the ZnO matrix.

Studies on optimizing sesquioxide contents to enhance luminescence efficiency of Pr3+ ions in PbO−PbF2−B2O3 glass system

Pr3+ doped lead oxy fluoro borate glasses mixed with three sesquioxides (M2O3) viz. Y2O3, Sc2O3, Al2O3 of different concentrations (0–10mol%) have been synthesized. The preliminary understanding over the structural modifications due to the insertion of the sesquioxides in the glass network could be obtained by IR spectral investigations. The optical absorption, luminescence spectra and fluorescence decay curves of these glasses were studied as functions of concentration of M2O3. The luminescence spectra of these glasses have exhibited the bands due to 3P0→3F2, 3F3, 3H6, 3H4, 3H5 transitions of Pr3+ ions. From these spectra, the radiative parameters viz., spontaneous emission probability A, the total emission probability AT, the radiative lifetime τ, the fluorescent branching ratio β of different transitions originated from 3P0 level of Pr3+ ions have been evaluated. A considerable enhancement in the luminescence emission corresponding to 3P0→3H6, 3F2 transitions has been observed with increase in the concentraion of M2O3 up to 8.0mol%. The increase has been attributed to the possible declusterization of Pr3+ ions by M3+ ions in the glass network. The comparison of emissive characteristics of the glasses mixed with three sesquioxides indicated the highest luminescence efficiency for Y2O3 mixed glasses among the three series glasses studied and this has been explained in terms of different degrees of variations in the structural modifications in the vicinity of Pr3+ ion in the glass network.

Near ultraviolet and visible-to-near-infrared spectral converting properties and energy transfer mechanism of Sr_2SiO_4:Ce^3+, Pr^3+ phosphor

A visible-to-near-infrared spectral converting phosphor Ce3+, Pr3+ co-doped Sr2SiO4 was synthesized by a solid-state reaction, and was developed as a potential solar spectral convertor for Si solar cells. The diffuse reflection, photoluminescence excitation and emission spectra at room temperature and at 3K were investigated. The visible and near infrared luminescent properties and energy levels of Pr3+ were investigated in detail. These results demonstrate that the absorption of Pr3+ was greatly broaden and enhanced in UV-Vis through efficient energy feeding by allowed 4f-5d absorption of Ce3+. The energy transfer mechanism including downshift and quantum cutting process is also proposed.

Investigation on the magnetic and magnetocaloric properties of PrNi2

The magnetic properties of some magnetic materials are influenced by the exchange interaction between magnetic ions and the spin fluctuations of magnetic ions. By use of the exchange interaction-effective field including the spin fluctuations of magnetic ions Hm= n0(1+γ T +β eω T)M, the Zeeman splitting of crystal field energy levels of Pr3+ ions in PrNi2 and the variation of the magnetic moments with the applied field in a temperature range of 3.8 K≤ T ≤ 30 K are calculated. The thermal variation of the reciprocal susceptibility of Pr3+ ions is calculated as well for the applied magnetic field H=5000 Oe. The calculated results are in good agreement with the experimental data. The magnetic entropy changes are obtained theoretically in a magnetic field range of 0H<50000 Oe, and the results are similar to those reported in the literature. It is indicated that the exchange interaction-effective field containing the spin fluctuations is applicable not only to the ferrimagnetic crystals, but also to the paramagnets.

Luminescent properties and quenching effects of Pr3+ co-doping in SiO2:Tb3+/Eu3+ nanophosphors

Luminescence properties of Pr3+ single doped SiO2 and Pr3+ co-doped SiO2:Tb3+/Eu3+ nanophosphors synthesized using sol–gel method were investigated. X-ray diffraction (XRD), and scanning electron microscope (SEM) were used to study the phase structure and particle morphology, respectively. The photoluminescence (PL) and cathodoluminescence (CL) properties of SiO2:Pr3+ and Pr3+ co-doped SiO2:Tb3+/Eu3+ were investigated. The concentration quenching effects at high concentrations of Pr3+ were observed from both PL and CL data. The PL and CL intensities from SiO2:Eu3+/Tb3+ nanophosphors were shown to decrease significantly with Pr3+ co-doping and the possible causes for the decrease are discussed Fluorescence lifetimes of the 1D2 emitting level of Pr3+ were determined from luminescence decay curves of SiO2:Pr3+ at different Pr3+ concentrations.

NaLaF4:Pr3+,Yb3+, an efficient blue to near infra-red quantum cutter

In order to reduce the thermalization losses in solar cells, down-conversion of blue photons into near infra-red photons is a promising solution. In the present paper, we analyse the energy transfer processes between Pr3+ and Yb3+ in NaLaF4 and we show that an efficient quantum-cutting process occurs. Nevertheless, we also show that a back transfer from Yb3+ toward the 1G4 level of Pr3+ ion leading to emission beyond 1 μm reduces the potentiality of this material as a quantum cutter for Si solar cells.

Quantitative characterization on multichannel transition emissions originating from 3P0 and 1D2 levels of Pr3+ in fluorotellurite glasses

Multichannel transition emissions in Pr3+-doped fluorotellurite (4BaF2–4AlF3–16BaO–6La2O3–70TeO2, BABLT) glasses have been quantitatively characterized. Broadband ∼1.48 µm near-infrared (NIR) emission due to 1D2 → 1G4 transition covering a 1.28–1.68 µm wavelength region possesses a full-width at half-maximum of 120 nm, along with the spontaneous emission probability (Aij) and maximum stimulated emission cross-section (σem) are calculated to be 693 s−1 and 8.97 × 10−21 cm2, respectively. Intense visible fluorescence originating from 3P0 and 1D2 levels has been observed and the radiant flux for the visible fluorescence of Pr3+ is solved to be 299 µW under commercial blue LED excitation. Quantitative characterization reveals that Pr3+-doped BABLT glasses exhibit a quantum yield (QY) as high as 14.9%, which is 3.1% higher than that in Pr3+-doped heavy metal germanium tellurite glasses. High QY and broadband ∼1.48 µm emission illustrate great advantages of Pr3+-doped BABLT glasses as fibre luminescence sources in photodynamic therapy treatment and gain media for tunable lasers and NIR optical amplifiers.

Sensitization of Pr3+ ions by Eu2+ ions in CaF2 thin films deposited by evaporation

In the present article, we analyse the possibility of sensitizing the 3Pj levels of Pr3+ ion with Eu2+ ion in CaF2 thin film deposited by evaporation. Indeed, the forbidden nature of the 4f-4f transition of Pr3+ ion makes its absorption too weak for thin film applications, while materials doped with the Pr3+-Yb3+ couple are promising candidates for the achievement of efficient down-converter systems and could allow strong reduction of thermalization losses in silicon solar cells.

Pr3+ doped lead tungsten tellurite glasses for visible red lasers

Lead tungsten tellurite (LTT) glasses doped with Pr3+ (0.01, 0.1, 0.5, 1.0 and 1.5mol%) ions were prepared by the conventional melt quenching technique. The glasses were characterized by X-ray diffraction, optical absorption and photoluminescence spectra. The glassy nature of LTT host glass has been confirmed through XRD measurements. From the measured intensities of various absorption bands of these glasses, the three phenomenological Judd–Ofelt (J–O) intensity parameters (Ω2, Ω4 and Ω6) have been evaluated by using the standard as well as modified J–O theory. The J–O parameters measured from the modified J–O theory were used to characterize the absorption and luminescence spectra of these glasses. From this theory, various radiative properties like radiative transition probability (AR), total transition probability (AT), branching ratio (βR) and radiative lifetime (τR) have been evaluated for the fluorescent levels of Pr3+ in these glasses. The emission spectra show five emission bands in visible region for which the effective band widths (ΔλP) and emission cross-sections (σse) have been evaluated. Among all the five emission transitions, a transition 3P0→3F2 is more intense and falls in red region. The visible emission spectra, stimulated emission cross-sections and branching ratios observed for all these glasses suggest the feasibility of using these glasses as lasers in red region. The CIE chromaticity co-ordinates were also evaluated from the emission spectra to understand the suitability of these materials for red emission. From the absorption, emission and CIE chromaticity measurements, it was found that 1mol% of Pr3+ ion concentration is quite suitable for LTT glasses to develop bright red lasers from these glasses.

Theoretical Study of Energy Levels Splitting of Praseodymium-Doped Trichloride

A 91×91 complete energy matrix of 4f2configuration ion Pr3+in triagonal crystal fieldC3hhas been constructed based upon the combination of Racahs irreducible tensor with Slaters wavefunctions. Thus, the Stark energy levels of Pr3+in trichlorides LaCl3have been calculated. The calculation result shows that the complete energy matrix method is effective to analyze the energy levels splitting of the doped entity by rare earth ions. We also know that the consideration to the sixth-order crystal field parameters is indispensable and the ionic radius of the replaced ion will play an important role in the energy levels splitting of the doped systems.

Energy transfer and radiative recombination processes in (Gd, Lu)3Ga3Al2O12:Pr3+ scintillators

(GdxLu3−x)Ga3Al2O12:0.3at.%Pr (x=0.025, 0.05, 0.1, 0.2, 0.4, 0.6) (GLGAG:Pr) polycrystalline powders are prepared by solid-state reaction method. To better understand the luminescence mechanism, the optical diffuse reflectance, photoluminescence emission and excitation, X-ray excited luminescence spectra and decay kinetics of GLGAG:Pr were investigated in detailed, allowing the determination of energy transfer from 5d state of Pr3+ to 4f state of Gd3+, and the non-radiative relaxation from 5d to 4f state of Pr3+. Besides, the former process plays more negative role in the emission quenching of GLGAG:Pr than later one. Pr3+ ion is regarded as an ineffective activation ion in Gd-based multicomponent aluminate garnets. In addition, the wavelength-resolved thermoluminescence spectra of GLGAG:Pr were studied after UV and X-ray irradiation. It is revealed that the localized recombination processes from electron traps to lower lying 4f levels of Pr3+ occurs without populating the higher 5d levels of Pr3+.

Near-infrared quantum cutting in Pr3+-Yb3+ Co-doped oxyfluoride glass ceramics containing CaF2 nanocrystals

The Pr3+-Yb3+ co-doped oxyfluoride glass-ceramics containing CaF2 nanocrystals were obtained by thermal treatment on the as-made glasses. The structure of fluoride nanocrystals was investigated. The light-emitting mechanism of Pr3+-Yb3+ in the near infrared region was proposed and the fluorescence lifetime and quantum efficiency was calculated. The results indicate that the main phase in the oxyfluoride glassceramics is CaF2 nanocrystal sized at 30 nm. Energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) have proved the incorporation of Pr3+ and Yb3+ into CaF2 nanocrystal lattice. Near-infrared quantum cutting involving Yb3+ 980 nm and 1 015 nm (2F5/2→2 F 7/2) emission has been achieved upon the excitation of the 3 P 0 energy level of Pr3+ at 482 nm. The fluorescence lifetime decreases sharply and quantum efficiency increases with increasing Yb3+ concentration, and the optimal quantum efficiency reaches 191%.

Spectroscopic properties of ytterbium, praseodymium-codoped fluorozirconate glass for laser emission at 36 μm

Excitation of the F27/2→F25/2 transition of the Yb3+ ion in Yb3+, Pr3+-doped fluorozirconate glass at 974 nm results in efficient excitation of the G41 level of Pr3+ ion that in turn emits in the middle infrared at ∼3.6  μm. The energy transfer (ET) process Yb3+(F25/2)→Pr3+(G41) is assisted by fast excitation migration among the Yb3+ ions. An upconversion process involving ET from the F25/2 level to the G41 excited state populates the P03 excited state that produces emission at 481, 521, 603, 636, and 717 nm. A study of the behavior of the fluorescence from the G41 level at 1325 nm and from the P03 level at 603 nm allowed the estimation of the ET rate constants for the processes involved after short-pulsed laser excitation at 974 nm. A rate-equation model was employed to evaluate the population inversion relating to the G41→F43 transition of the Pr3+ ion at 3.6 μm under continuous wave pumping.

Influence of Al declustering on the photoluminescent properties of Pr3 + ions in PbO–SiO2 glasses

Pr3+ doped lead alumino silicate glasses with varying concentrations of Al2O3 (from 5 to 10mol%) have been synthesized. The IR and Raman spectral studies of these glasses have indicated that there is a gradual increase in the depolymerization of the glass network with an increase in the concentration of Al2O3. The optical absorption, luminescence spectra and fluorescence decay curves of these glasses were recorded at room temperature. The luminescence spectra of these glasses have exhibited the bands due to 3P0→3F2, 3F3, 3H6, 3H4,3H5 transitions. From these spectra, the radiative parameters viz., spontaneous emission probability A, the total emission probability AT, the radiative lifetime τ, the fluorescent branching ratio β of different transitions that originated from the 3P0 level of Pr3+ ions have been evaluated. A considerable enhancement in the luminescence emission, especially in the red region corresponding to 3P0→3H6, 3F2 transitions has been observed. The increase has been attributed to the possible admixing of wavefunctions of opposite parities and due to the declusterization of Pr3+ ions by Al3+ ions in the glass network. The branching ratio β has been observed to be the highest for the transition 3P0→3F2 and it is found to be ~50% for the glass mixed with 10mol% of Al2O3. The CIE color coordinates for three glasses have been evaluated and found to be in the bright red region.

Red enhanced YAG:Ce, Pr nanophosphor for white LEDs

Rare earth ion Pr3+ was co doped in yellow emitting YAG:Ce nanophosphor to introduce red emission for improving colour rendering property of white LED. Nanocrystalline YAG:Ce, YAG:Ce, Pr was synthesised by a single step auto combustion process. Photoluminescence (PL) emission spectra of YAG:Ce, Pr nanophosphor, when excited by 460 nm blue light, exhibited sharp red emission peaks at 610 nm from Pr3+ ions in addition to broad yellow emission from Ce3+ peaking at 540 nm due to charge transfer from excited Ce3+ 5d band to 3P J /1D2 level of Pr3+. Ce3+ (yellow) and Pr3+ (red) emission decays in tens of nanoseconds and microseconds, respectively. Electroluminescence spectra of blue LED with developed phosphor layer shows colour coordinates (0.30, 0.39) close to ideal white light.