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101.
Ashish Akojwar K. N. Shinde Roshani Singh S. J. Dhoble N. S. Kokode 《Luminescence》2016,31(1):305-308
A series of phosphors KAl1‐xPO4Cl:Eux3+ (0.1 ≤ x ≤ 1.0) was synthesized using a facile combustion method using urea as a fuel and their structural, morphological and photoluminescence properties were investigated. It was found that the particle size was in the range of 1–2 µm with an irregular shape. The f–f transitions of Eu3+ in the host lattice were assigned and discussed. The excitation and emission spectra indicated that this phosphor can be efficiently excited by ultraviolet (395 nm), and exhibit reddish orange emission corresponding to the 5D0→7FJ (J = 0, 1, 2) transitions of Eu3+. The impact of the Eu3+ concentration on the relative emission intensity was investigated, and the best doping concentration is 0.5. The present study suggests that the KAl0.5PO4Cl: Eu0.53+ phosphor is a strong candidate as a red component for phosphor‐ converted white light‐emitting diodes (LEDs). Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
102.
Eu3+‐activated Y(P,V)O4 phosphors were prepared by the EDTA sol‐gel method, and the corresponding morphologies and luminescent properties were investigated. The sample particles were relatively spheroid with size of 2–3 µm and had a smooth surface. The excitation spectra for Y(P,V)O4:Eu3+ consisted of three strong excitation bands in the 200–350 nm range, which were attributed to a Eu3+‐ O2? charge‐transfer band and 1A1?1 T1/1 T2 transitions in VO43?. The as‐synthesized phosphors exhibited a highly efficient red luminescence at 613 nm due to the Eu3+ 5D0?7 F2 electric dipole transition. With the increase in the V5+/P5+ ratio, the luminescence intensity of the red phosphor under UV excitation was greatly improved due to enhanced VO43? → Eu3+ energy transfer. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
103.
We have studied possibilities for constructing Escherichia coli strains capable of producing stable light. Light production in E. coli is achieved by cloning the genes encoding bacterial luciferase from Vibrio harveyi. To gain the advantage of sensitive detection of light we transferred the genes under the control of a strong, regulatable promoter system. Stabilization of light produced by E. coli clones was accomplished by finding the optimal plasmid construction and growth conditions as well as suitable measuring buffers. The adjustment of the luciferase synthesis for bioluminescence measurements to a high but not harmful level gives healthy cells and stable luciferase. Cultivation at 30 °C in an uninduced state was found to be the most important factor in getting stable-light production. The overall cell metabolism being unstressed gives us the possibility of monitoring cell physiology and factors affecting it via bioluminescence reactions in vivo. To make the results easy to interpret the light emission has to be stable during a measurement period of one to several hours. In the case of the original light-producing bacteria, Vibrio and Photobacterium strains it has not thus far been possible to find conditions where light emission would be stable for several hours. Based on our findings an automated biosensor system can be developed to monitor the effects of biologically active compounds against stable-light-producing bacteria. 相似文献
104.
H. Reiber 《Luminescence》1989,4(1):245-248
Cellular low-level luminescence was measured after various disintegrative processes in brain cell preparations. In addition to known origins of low-level luminescence, e.g. oxygen radical reactions or enzymatic and non-enzymatic redox systems, a further source of photon emission is reported which is independent of external oxygen, oxygen radicals and enzyme activities. Vital cells from rat brain homogenates or pig oligodendrocytes could be kept for hours at 37 °C without any photon emission. Only after disintegrative processes a cellular photon emission could be induced. The maximal intensity of about 400 impulses/s/mg protein and a total radiation of about 6 × 106 I/mg depended on the type of cells. The signal could be retained completely at 4 °C or in frozen samples. Heating (10 min, 90 °C) did not suppress the photon emission. Luminol and lucigenin did not amplify the signal as is usually observed in oxygen radical-producing cells. Non-specific radical scavengers as well as detergents suppressed the cellular photon emission completely. It is suggested that this cellular luminescence represents a biophysical radiation which originates from the interruption of an intermolecular radiationless energy transfer. 相似文献
105.
106.
Luca Lanzanò Li Sui Evelina Costanzo Marisa Gulino Agata Scordino Salvatore Tudisco Francesco Musumeci 《Luminescence》2009,24(6):409-415
Delayed luminescence from a single dry soybean seed was investigated in both spectral and time domains, under different excitation wavelengths. Emission spectra were collected, under 337 nm laser excitation, from native and artificially deteriorated seeds and the time‐dependence of different spectral components was analyzed in detail. The single seed viability was evaluated through observation of germination properties after imbibition and compared with different parameters related to the luminescence kinetics. The significant correlation found between single seed delayed luminescence parameters and germination capability strongly validates the connection of this phenomenon with the functional state of the system and suggests the development of a non‐invasive technique for seed quality determination. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
107.
Optical absorption, photoluminescence, thermoluminescence (TL) and photostimulated luminescence (PSL) studies on RbI:Tb(3+) crystals irradiated with gamma-rays is reported. Photoluminescence of these crystals exhibits characteristic Tb(3+) emissions, due to transitions from the (5)D(3) and (5)D(4) levels to various levels of the (7)F septet. On F-bleaching the gamma-irradiated crystals, Z(3) centres are observed. The TL glow curve indicates a two-step thermal annihilation process for the radiatively created defects. The presence of the characteristic emissions due to terbium ions in the photostimulation at the F-band, and TL emissions under both glow peaks, confirm the participation of Tb ions in the defect production and recombination processes. Trap parameters for the TL process are calculated and presented. The low temperature glow peak is attributable to Z(3) centres. 相似文献
108.
A solid‐state reaction route‐based LiTi2 ? xEux(PO4)3 was phosphor synthesized for the first time to evaluate its luminescence performance by excitation, emission and lifetime (τ) measurements. The LiTi2 ? xEux(PO4)3 phosphor was excited at λexci. = 397 nm to give an intense orange–red (597 nm) emission attributed to the 5D0 → 7F1 magnetic dipole (ΔJ = ±1) transition and red (616 nm) emission (5D0 → 7F2), which is an electric dipole (ΔJ = ±2) transition of the Eu3+ ion. Beside this, excitation and emission spectra of host LiTi2(PO4)3 powder were also reported. The effect of Eu3+ concentration on luminescence characteristics was explained from emission and lifetime profiles. Concentration quenching in the LiTi2 ? xEux(PO4)3 phosphor was studied from the Dexter's model. Dipole–quadrupole interaction is found to be responsible for energy transfer among Eu3+ ions in the host lattice. The LiTi2 ? xEux(PO4)3 phosphor displayed a reddish‐orange colour realized from a CIE chromaticity diagram. We therefore suggest that this new phosphor could be used as an optical material of technological importance in the field of display devices. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
109.
110.
Helena Brunckova Lucas Alonso Rocha Eduardo Jose Nassar Susane Bonamin Moscardini Hristo Kolev 《Luminescence》2022,37(4):642-655
Thin films of lanthanide orthoniobate LnNbO4 (LnNO) and orthotantalate LnTaO4 (LnTO), (Ln = Nd, Sm, Eu) were fabricated using the sol–gel method with subsequent spin-coating on the PbZrO3/Al2O3 substrate and annealing at 1000°C. X-ray diffraction patterns showed monoclinic M-LnNbO4 or M´-LnTaO4, which coexists with the orthorhombic or tetragonal phase. X-ray photoelectron spectroscopy demonstrated the presence of Nd3+, Sm3+/Sm2+ and Eu3+/Eu2+ ions. The luminescence properties of polymorphic films were investigated. Excitation spectra of PbZrO3 interlayer represented broad bands at 410 and 550 nm that were assigned to charge transfer bands (CTB). In all films, the CTB broad band at ~275 nm related to charge transfer transition of Ln3+→O2− and NbO43− or TaO43− groups. In excitation spectra, 4I9/2→4G5/2 (Nd3+), 6H5/2→6P3/2 (Sm3+) and 7F0→5L6 (Eu3+) transitions (at 585, 402 and 395 nm), respectively were found to be more intense than any other Ln3+ transition. The emission spectra showed narrow and intense bands at 1065, 600, and 614 nm that were ascribed to Nd3+, Sm3+, and Eu3+ 4f–f intraconfigurational transitions 4F3/2→4I11/2, 4G5/2→6H7/2, and 5D0→7F2, respectively. The excellent luminescence properties of films make them new potential groups for visible and/or near-infrared applications such as sensors and imaging equipment. 相似文献