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1.
An energy transfer process from Ce3+ to Tb3+ ions was successfully achieved in a Li2SO4–Al2(SO4)3 mixed‐sulphate system. A wet‐chemical synthesis was employed to prepare the Li2SO4–Al2(SO4)3 system by doping Ce3+ and Tb3+ ions individually as well as collectively. The phases were identified using X‐ray diffraction studies. The as‐prepared samples were characterized by FT‐IR and photoluminescence measurements. Green‐light emission was exhibited by Ce3+, Tb3+ co‐doped Li2SO4–Al2(SO4)3 system, thus, indicating its potential as a material for display devices or in the lamp industry. 相似文献
2.
In the present study, Na3(SO4)X (X = F or Cl) halosulphate phosphors have been synthesized by the solid‐state diffusion method. The phase formation of the compounds Na3(SO4)F and Na3(SO4)Cl were confirmed by X‐ray powder diffraction (XRD) measurement. Photoluminescence (PL) excitation spectrum measurement of Na3(SO4)F:Ce3+ and Na3(SO4)Cl:Ce3+ shows this phosphor can be efficiently excited by near‐ultraviolet (UV) light and presents a dominant luminescence band centred at 341 nm for Ce3+, which is responsible for energy transfer to Dy3+and Mn2+ ions. The efficient Ce3+ → Dy3+ energy transfer in Na3(SO4)F and Na3(SO4)Cl under UV wavelength was observed due to 4 F9/2 to 6H15/2 and 6H13/2 level, while Ce3+ → Mn2+ was observed due to 4 T1 state to 6A1. The purpose of the present study is to develop and understanding the photoluminescence properties of Ce3+‐, Dy3+‐ and Mn2+‐doped fluoride and chloride Na3(SO4)X (X = F or Cl) luminescent material, which can be the efficient phosphors in many applications, such as scintillation applications, TL dosimetry and the lamp industry, etc. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
3.
Sushant Rajendra Bargat Yatish Ratn Parauha Nayana Sudhakar Shirbhate Girish Mishra Sanjay Janaraoji Dhoble 《Luminescence》2022,37(3):463-471
In the recent few years, Eu2+- and Mn4+-activated phosphors are widely used as potential colour converters for indoor plant cultivation lighting application due to their marvellous luminescence characteristics as well as low cost. In this investigation, we synthesized novel red colour-emitting Ca(2−x)Mg2(SO4)3:xmol% Eu2+ (x = 0–1.0 mol%) phosphors via a solid-state reaction method in a reducing atmosphere. The photoluminescence (PL) excitation spectra of synthesized phosphors exhibited a broad excitation band with three excitation bands peaking at 349 nm, 494 nm, and 554 nm. Under these excitations, emission spectra exhibited a broad band in the red colour region at ~634 nm. The PL emission intensity was measured for different concentrations of Eu2+. The maximum Eu2+ doping concentration in the Ca2Mg2(SO4)3 host was observed for 0.5 mol%. According to Dexter theory, it was determined that dipole–dipole interaction was responsible for the concentration quenching. The luminous red colour emission of the sample was confirmed using Commission international de l'eclairage colour coordinates. The results of PL excitation and emission spectra of the prepared phosphors were well matched with excitation and emission wavelengths of phytochrome PR. Therefore, from the entire investigation and obtained results it was concluded that the synthesized Ca0.995Mg2(SO4)3:0.5mol%Eu2+ phosphor has huge potential for plant cultivation application. 相似文献
4.
A new halophosphor K3Ca2(SO4)3 F activated by Eu or Ce and K3Ca2(SO4)3 F:Ce,Eu co‐doped halosulfate phosphor has been synthesized by the co‐precipitation method and characterized for its photoluminescence (PL). The PL emission spectra of the K3Ca2(SO4)3 F :Ce phosphor show emission at 334 nm when excited at 278 nm due to 5d → 4f transition of Ce3+ ions. In the K3Ca2(SO4)3 F:Eu lattice, Eu2+ (440 nm) as well as Eu3+ (596 nm and 615 nm) emissions have been observed showing 5D0 → 7 F1 and 5D0 → 7 F2 transition of the Eu3+ ion, which is in the blue and red region of the visible spectrum respectively. The trivalent europium ion is very useful for studying the nature of metal coordination in various systems owing to its non‐degenerate emitting 5D0 state. K3Ca2(SO4)3 F:Ce,Eu is suitable for Ce3+ → Eu2+ → Eu3+ energy transfer in which Ce3+and Eu2+ play the role of sensitizers and Eu2+ and Eu3+ act as the activators. The observations presented in this paper are relevant for lamp phosphors. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
5.
This paper deals with the complex issue of reversing long‐term improvements of fertility in soils derived from heathlands and acidic grasslands using sulfur‐based amendments. The experiment was conducted on a former heathland and acid grassland in the U.K. that was heavily fertilized and limed with rock phosphate, chalk, and marl. The experimental work had three aims. First, to determine whether sulfurous soil amendments are able to lower pH to a level suitable for heathland and acidic grassland re‐creation (approximately 3 pH units). Second, to determine what effect the soil amendments have on the available pool of some basic cations and some potentially toxic acidic cations that may affect the plant community. Third, to determine whether the addition of Fe to the soil system would sequester PO4? ions that might be liberated from rock phosphate by the experimental treatments. The application of S0 and Fe(II)SO4? to the soil was able to reduce pH. However, only the highest S0 treatment (2,000 kg/ha S) lowered pH sufficiently for heathland restoration purposes but effectively so. Where pH was lowered, basic cations were lost from the exchangeable pool and replaced by acidic cations. Where Fe was added to the soil, there was no evidence of PO4? sequestration from soil test data (Olsen P), but sequestration was apparent because of lower foliar P in the grass sward. The ability of the forb Rumex acetosella to apparently detoxify Al3+, prevalent in acidified soils, appeared to give it a competitive advantage over other less tolerant species. We would anticipate further changes in plant community structure through time, driven by Al3+ toxicity, leading to the competitive exclusion of less tolerant species. This, we suggest, is a key abiotic driver in the restoration of biotic (acidic plant) communities. 相似文献
6.
Enhanced luminescence and white light emission from Eu3+‐co‐doped K3Ca2(SO4)3Cl:Dy3+ phosphor with near visible ultraviolet excitation for white LEDs
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The luminescent properties of europium (Eu)‐ and dysprosium (Dy)‐co‐doped K3Ca2(SO4)3Cl halosulfate phosphors were analyzed. This paper reports the photoluminescence (PL) properties of K3Ca2(SO4)3Cl microphosphor doped with Eu and Dy and synthesized using a cost‐effective wet chemical method. The phosphors were characterized by X‐ray diffraction and scanning electron microscopy. The CIE coordinates were calculated to display the color of the phosphor. PL emission of the prepared samples show peaks at 484 nm (blue), 575 nm (yellow), 594 nm (orange) and 617 nm (red). The emission color of the Eu,Dy‐co‐doped K3Ca2(SO4)3Cl halophosphor depends on the doping concentration and excitation wavelength. The addition of Eu in K3Ca2(SO4)3Cl:Dy greatly enhances the intensity of the blue and yellow peaks, which corresponds to the 4 F9/2 → 6H15/2 and 4 F9/2 → 6H13/2 transitions of Dy3+ ions (under 351 nm excitation). The Eu3+/Dy3+ co‐doping also produces white light emission for 1 mol% of Eu3+, 1 mol% of Dy3+ in the K3Ca2(SO4)3Cl lattice under 396 nm excitation, for which the calculated chromaticity coordinates are (0.35, 0.31). Thus, K3Ca2(SO4)3Cl co‐doped with Eu/Dy is a suitable candidate for NUV based white light‐emitting phosphors technology. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
7.
A new Na3Ca2(SO4)3F: Ce3+ phosphor synthesized by a solid state diffusion method is reported. The photoluminescence study showed a single high intensity emission peak at 307 nm wavelength when excited by UV light of wavelength 278 nm. An unresolved peak of comparatively less intensity was also observed at 357 nm along with the main peak. The characteristic emission of dopant Ce in Na3Ca2(SO4)3F phosphor clearly indicated that it resides in the host lattice in trivalent form. The emission peak can be attributed to 5d → 4f transition of rare earth Ce3+. The prepared sample is also characterized for its thermoluminescence properties. The TL glow curve of prepared sample showed a single broad peak at 147°C. The trapping parameters are also evaluated by Chen's method. The values of trap depth (E) and frequency factor (s) were found to be 0.64 ± 0.002 eV and 1.43 × 107 s–1 respectively. The study of PL and TL along with evaluation of trapping parameters has been undertaken and discussed for the first time. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
8.
Summary Application of gypsum (tagged Ca45SO4.2H2O) caused a considerable increase in dry matter yield and content of Ca, Ca45, Mg and K and Ca:Na and (Ca+Mg): (Na+K) ratios and a decrease in the content of Na, N and P in dhaincha tops. There was a
considerable increase in the total uptake of Ca, Mg, Na, K, N, P and Ca45 by plant tops in response to gypsum. Contribution of Ca from applied Ca45SO4 varied from 78.3 to 84.7 per cent of the total Ca in plant tops, whereas, its uptake from this source varied from 52.18 to
98.73 me per 100 g plant tops. re]19720705 相似文献
9.
Tian-lei Zhang Xin-guang Lan Ming-jie Wen Yong-qi Zhang Rui Wang 《Molecular simulation》2013,39(18):1544-1553
ABSTRACTIn this article, we report a theoretical investigation on the role of several catalysts in the isomerisation mechanisms of HON(O)NNO2 to ON(OH)NNO2 by theoretical method of CBS-QB3. The isomerisation reactions with catalyst X (X?=?H2O, (H2O)2, HCOOH and H2SO4) are multi-hydrogen atom transfer reactions. Compared to the isomerisation mechanisms and rate constant of HON(O)NNO2 to ON(OH)NNO2 without catalysts, incorporation of the catalyst X shows different positive catalytic effects on affecting the reaction processes, with the H2SO4-assisted reaction being the most favourable. Such different catalytic effects are mainly related to the size of the ring structure in X-assisted transition states and the different values of pKa and proton affinities for HCOOH and H2SO4. Besides, compared with the barrier height of the isomerisation process from HON(O)NNO2 to ON(OH)NNO2 with HN(NO2)2 and HON(O)NNO2, the barrier of H2SO4-assisted reaction is lower by 9.3 and 4.5?kcal?·mol?1, meanwhile, the rate constant of H2SO4 catalyzed is larger than water and water dimer–assisted by 3–5 and 2–3 orders of magnitude, respectively. So, H2SO4-assisted reaction is the most favourable. 相似文献
10.
Summary The photosynthetic processes of two ecologically-matched, herbaceous Atriplex species differed in their response to SO2 fumigations. Atriplex triangularis, a C3 species, was more sensitive than the C4 species, A. sabulosa. This difference in sensitivity can be attributed in part to the higher conductance of the C3 species in normal air and saturating light as well as greater stimulation of stomatal opening following exposure to SO2. In addition, photosynthetic mechanisms of the C3 species had higher intrinsic SO2 sensitivity than the C4 species. Differences between photosynthetic responses of these two species may also reflect differences in morphological configuration of mesophyll tissues and greater SO2 sensitivity of the initial photosynthetic carboxlating enzyme of the C3 species. It is likely that certain of the differences in photosynthetic SO2 sensitivity of these contrasting C3 and C4
Atriplex species are characteristic of C3 and C4 plants in general.Abbreviations PEP carboxylase
phosphoenolpyruvate carboxylase
- RuBP carboxylase
ribulose-1,5-bisphosphate carboxylase 相似文献
11.
In this article we report Eu3+ luminescence in novel K3Ca2(SO4)3Cl phosphors prepared by wet chemical methods. The Eu3+ emission was observed at 594 nm and 615 nm, keeping the excitation wavelength constant at 396 nm nearer to light‐emitting diode excitation, Furthermore, phosphors were characterized by X‐ray diffraction for the confirmation of crystallinity. The variation of the photoluminescence intensity with impurity concentration has also been discussed. Thus, prominent emission in the red region makes prepared phosphors more applicable for white light‐emitting diodes. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
12.
Summary Rock phosphates from Udaipur (India), North Carolina, Florida, Tennessee and Missouri (USA) were acidulated with HCl or H2SO4, to the extent of 25, 50, 75 or 100 per cent of the requirement for complete conversion into single superphosphate. Partial
acidulation resulted in the formation of a mixture of water- and citrate-soluble and -insoluble phosphates, the proportion
of the first two increasing with increasing degree of acidulation, at the expense of the insoluble phosphate. For a given
degree of acidulation, the P compounds formed with HCl or H2SO4 were of comparable composition, except that the HCl-acidulated products were hygroscopic. Pot experiments with acid P-deficient
soils showed that the behaviour of the HCl- or H2SO4- acidulated products in respect of P availability in soil, grain yield response and P uptake by rice was more or less similar.
Partially acidulated rock phosphate to the extent of 50 per cent with either of the acids was found to be suitable for growing
rice under flooded soil conditions. There is thus scope for the use of HCl- acidulated rock phosphate as a substitute for
the H2SO4- acidulated product, for growing rice in acid soils. The scope for use of lower degree HCl-acidulated product in an upland
crop — rice rotation in acid soils is also discussed. 相似文献
13.
Effect of Dy3+ or Eu2+ co‐activator on a BaCa(SO4)2:Ce3+ mixed alkaline earth sulfate phosphor
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The individual emission and energy transfer between Ce3+ and Eu2+ or Dy3+ in BaCa(SO4)2 mixed alkaline earth sulfate phosphor prepared using a co‐precipitation method is described. The phosphor was characterized by X‐ray diffraction (XRD) and photoluminescence (PL) studies and doped by Ce;Eu and Dy rare earths. All phosphors showed excellent blue–orange emission on excitation with UV light. PL measurements reveal that the emission intensity of Eu2+ or Dy3+ dopants is greater than when they are co‐doped with Ce3+. An efficient Ce3+ → Eu2+ [2T2g(4f65d) → 8S7/2(4f7)] and Ce3+ → Dy3+ (4 F9/2 → 6H15/2 and 4 F9/2 → 6H13/2) energy transfer takes place in the BaCa(SO4)2 host. A strong blue emission peak was observed at 462 nm for Eu2+ ions and an orange emission peak at 574 nm for Dy3+ ions. Hence, this phosphor may be used as a lamp phosphor. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
14.
Summary Six early successional plant species with differing photosynthetic pathways (3 C3 species and 3 C4 species) were grown at either 300, 600, or 1,200 ppm CO2 and at either 0.0 or 0.25 ppm SO2. Total plant growth increased with CO2 concentration for the C3 species and varied only slightly with CO2 for the C4 species. Fumigation with SO2 caused reduced growth of the C3 species at 300 ppm CO2 but not at the higher concentrations of CO2. Fumigation with SO2 reduced growth of the C4 species at high CO2 and increased growth at 300 ppm CO2. Leaf area increased with increasing CO2 for all plant species. Fumigation with SO2 reduced leaf area of C3 plants more at low CO2 than at high CO2 while leaf area of C4 plants was reduced more at high CO2 than at low CO2. These results support the notion that C3 species are more sensitive to SO2 fumigation than are C4 species at concentrations of CO2 equal to that found in normal ambient air. However, the difference in sensitivity to SO2 between C3 and C4 species was found to be reversed at higher concentrations of CO2. A possible explanation for this reversal based upon differences in stomatal response to elevated CO2 between C3 and C4 species is discussed. 相似文献
15.
A green chemical precipitation route was used to yield a hydrated basic sulfate precursor upon calcination at 1000°C into a series of (Y,Gd)2O2SO4:Dy particles. The phosphors exhibited characteristic Dy3+ emissions from 4F9/2→6HJ (J = 15/2, 13/2, 11/2) transitions under ultraviolet light excitation; the quenching concentration of Dy3+ was determined to be 2.5 at.%. Substitution of Gd3+ for Y3+ led to an additional strong sharp band at ~277 nm (8S7/2→6IJ transition of Gd3+) in the photoluminescence excitation spectra, upon which the (Gd0.975Dy0.025)2O2SO4 phosphor achieved a ~2.8-fold higher photoluminescence intensity via an effective energy transfer from Gd3+ to Dy3+ compared with the 354 nm excitation of Dy3+. Both the photoluminescence and photoluminescence excitation intensities of (Y,Gd)2O2SO4:Dy phosphors increased with rising Gd3+ concentration and calcination temperature in the range 750–1000°C. A higher Gd3+ concentration slightly prolonged the effective fluorescence lifetime. 相似文献
16.
A series of efficient Li3Al2(PO4)3:Eu2+ novel phosphors were synthesized by the facile combustion method. The effects of dopant on the luminescence behavior of Li3Al2(PO4)3 phosphor were also investigated. The phosphors were characterized by X‐ray diffraction, field emission scanning electron microscope and photoluminescence techniques. The result shows that all samples can be excited efficiently by near‐ultraviolet excitation under 310 nm. The emission was observed for Li3Al2(PO4)3:Eu2+ phosphor at 425 nm, which corresponded to the d → f transition. The concentration quenching of Eu2+ was observed in Li3Al2(PO4)3:Eu2+ when the Eu concentration was at 0.5 mol%. The prepared powders exhibited intense blue emission at the 425 nm owing to the Eu2+ ion by Hg‐free excitation at 310 nm (i.e., solid‐state lighting excitation). Consequently, the availability of such a phosphor will significantly help in the development of blue‐emitting solid‐state lighting applications. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
17.
Ulrich E. Grauer 《Plant and Soil》1993,157(2):319-331
There is good evidence for the ameliorating effect of SO4
2- and F- on the expression of Al phytotoxicity in acidic solutions. The role of OH-, in both shifting Al speciation towards hydroxy-Al species and decreasing activities of H+ with increasing pH, is still controversially discussed. Grauer and Horst (1992) proposed a model based on the assumption that Al phytotoxicity is a function of the Al saturation (AlS) of exchange sites in the root apoplast and analyzed the predictions of the model in the case of cation amelioration, with special emphasis on H+. In this study the model is further developed by considering, in addition to Al3+, the complexation of Al with the anions OH-, F-, SO4
2-, and Cl- to form potentially toxic Al species. Association constants of these Al complexes with a ligand (L
-) which is assumed to simulate the cation exchange sites in the root apoplast, were estimated. Affinity factors for binding to L
- compared to Al3+ were derived from these estimated association constants, and values were, in a first approach, 0.79 for AlOH2+, 0.02 for Al(OH)2
+, and 0.13 for Al(OH)3
0 (or 0.03 choosing another hydrolysis constant). High toxicity of Al13 (AlO4Al12(OH)24(H2O)12
7+) could be explained by diminished H+ amelioration and a high association constant to L
-. From estimated association constants for Al-Cl complexes, low affinity factors for L
- for these complexes were derived. Since the formation of these Al-Cl complexes is not favoured, Cl- is predicted to have very little ameliorating effect. In the case of SO4
2– and F- complexes with Al, the derived affinity factors never exceeded 0.05 and, since formation of these complexes is favoured by high association constants, are thus in agreement with experimental results on ameliorating effects. The ranking of the anions for ameliorative effectiveness was estimated to be in the order of OH->F->SO4
2–>Cl-. Hydroxy amelioration in this context is restricted to the speciation effect, which is only significant above pH 4. 相似文献
18.
Rajan Singh Mohit Manhas Ankush Kumar Bedyal Fahim Durani Hendrick C. Swart Vinay Kumar 《Luminescence》2024,39(2):e4665
The present study investigates the impact of the ligand environment on the luminescence and thermometric behavior of Sm3+ doped A3(PO4)2 (A = Sr, Ca) phosphors prepared by combustion synthesis. The structural and luminescent properties of Sm3+ ions in the phosphate lattices were investigated using powder X-ray diffraction (PXRD) and photoluminescence (PL) techniques. PXRD results of the synthesized phosphors exhibit the expected phases that are in agreement with their respective standards. Fourier-transform infrared (FTIR) spectroscopy confirms the presence of PO4 vibrational bands. Upon excitation with near ultraviolet light, the PL studies indicated that Sr3(PO4)2:Sm3+ phosphors exhibit a yellow light emission, whereas Ca3(PO4)2:Sm3+ phosphors exhibit an emission of orange light. The PL emission results are in accordance with the CIE coordinates, with the Sr3(PO4)2:Sm3+ phosphors showing coordinates of (0.56, 0.44), and the Ca3(PO4)2:Sm3+ phosphors displaying coordinates of (0.60, 0.40). Thermal analysis shows improved stability of Ca3(PO4)2:Sm3+ based on lower weight reduction in thermogravimetric analysis. The effect of temperature on the luminescence properties of the phosphor has been examined upon a 405 nm excitation. By using the fluorescence intensity ratio (FIR) method, the temperature responses of the emission ratios from the Sm3+: the 4F3/2 → 6H5/2 transition to the 4G5/2 → 6H7/2 and 4F3/2 → 6H5/2 transition to the 4G5/2 → 6H9/2 emissions are characterized. The Ca3(PO4)2:Sm3+ phosphors are more sensitive as compared with the Sr3(PO4)2:Sm3+ phosphors. The earlier research findings strongly indicate that these phosphors hold great promise as ideal candidates for applications in non-invasive optical thermometry and solid-state lighting devices. 相似文献
19.
M. J. Kropff 《Plant and Soil》1991,131(2):235-245
The impact of SO2 on the ionic balance of plants and its implications for intracellular pH regulation was studied to find explanations for long-term effects of SO2. When sulphur, taken up as SO2 by the shoots of plants, is not assimilated in organic compounds, but stored as sulphate, an equivalent amount of H+ is produced. These H+ ions are not buffered chemically, but removed by metabolic processes.On the basis of knowledge on metabolic buffering mechanisms a conceptual model is proposed for the removal of shoot-generated H+ by (i) OH- ions, produced in the leaves when sulphate and nitrate are assimilated in organic compounds and/or by (ii) OH- ions produced by decarboxylation of organic anions (a biochemical pH stat mechanism). The form in which nitrogen is supplied largely determines the potential of the plant to neutralize H+ in the leaves during SO2 uptake by the proposed mechanisms.In field experiments with N2 fixing Vicia faba L. crops, the increase of sulphate in the shoots of SO2-exposed plants was equivalent in charge to the decrease of organic anion content, calculated as the difference between inorganic cation content (C) and inorganic anion content (A), indicating that H+ ions produced in the leaves following SO2 uptake were partly removed by OH- from sulphate reduction and partly by decarboxylation of organic anions.The appearance of chronic SO2 injury (leaf damage) in the field experiment at the end of the growing period is discussed in relation to the impact of SO2 on the processes involved in regulation of intracellular pH. It is proposed that the metabolic buffering capacity of leaf cells is related to the rates of sulphate and nitrate reduction and the import rate of organic anions, rather than to the organic anion content in the vacuoles of the leaf cells. 相似文献
20.
The physical parameters of cellulose such as surface area and porosity are important in the development of cellulose composites which may contain valuable additives which bind to cellulose. In this area, the use of acid hydrolyzed nano-dimensional cellulose nanowhiskers (CNWs) has attracted significant interest, yet the surface area and porosity of these materials have not been explored experimentally. The objective of this work was to characterize the surface area and porosity of CNWs from different origins (plant cotton/bacterium Gluconacetobacter xylinus) and different acid treatments (H2SO4/HCl) by N2 adsorption; as well as to compare surface area and porosity of bacterial cellulose synthesized by static and agitated cultures. Our results showed that CNWs produced from H2SO4/HCl exhibited significantly increased surface area and porosity relative to starting material cotton fiber CF11. Micropores were generated in HCl hydrolyzed CNWs but not in H2SO4 hydrolyzed CNWs. Bacterial CNWs exhibited larger surface area and porosity compared to plant CNWs. Cellulose synthesized by G. xylinus ATCC 700178 from agitated cultures also exhibited less surface area and porosity than those from static cultures. 相似文献