The Experts below are selected from a list of 180 Experts worldwide ranked by ideXlab platform
Alfons Penzkofer - One of the best experts on this subject based on the ideXlab platform.
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Phosphorescence Quantum Yield determination with time-gated fluorimeter and Tb(III)-acetylacetonate as luminescence reference
Chemical Physics, 2013Co-Authors: Alfons PenzkoferAbstract:Abstract Phosphorescence Quantum Yield measurements of fluorescent and phosphorescent samples require the use of time-gated fluorimeters in order to discriminate against the fluorescence contribution. As reference standard a non-fluorescent luminescent compound is needed for absolute Phosphorescence Quantum Yield determination. For this purpose the luminescence behavior of the rare earth chelate terbium(III)-acetylacetonate (Tb(acac)3) was studied (determination of luminescence Quantum Yield and luminescence lifetime). The luminescence Quantum Yield of Tb(acac)3 was determined by using an external light source and operating the fluorimeter in chemo/bioluminescence mode with a fluorescent dye (rhodamine 6G in methanol) as reference standard. A procedure is developed for absolute luminescence (Phosphorescence) Quantum Yield determination of samples under investigation with a time-gated fluorimeter using a non-fluorescent luminescent compound of known luminescence Quantum Yield and luminescence lifetime.
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room temperature Phosphorescence lifetime and Quantum Yield of erythrosine b and rose bengal in aerobic alkaline aqueous solution
Journal of Luminescence, 2012Co-Authors: Alfons Penzkofer, Max Simmel, Dieter RiedlAbstract:Abstract The room-temperature Phosphorescence behavior of erythrosine B (ER) and rose bengal (RB) in aerobic aqueous solution at pH 10 (10−4 M NaOH) is investigated. The samples were excited with sliced second harmonic pulses of a Q-switched Nd:glass laser. A gated photomultiplier tube was used for instantaneous fluorescence signal discrimination and a digital oscilloscope was used for signal recording. For Phosphorescence lifetime measurement the oscilloscope response time was adjusted to appropriate time resolution and sensitivity by the ohmic input resistance. In the case of Phosphorescence Quantum Yield determination the gated photomultiplier – oscilloscope arrangement was operated in integration mode using 10 MΩ input resistance. Phosphorescence Quantum Yield calibration was achieved with erythrosine B and rose bengal doped starch films of known Quantum Yields. The determined Phosphorescence lifetimes (Quantum Yields) of ER and RB in 0.1 mM NaOH are τP=1.92±0.1 μs (ϕP=(1.5±0.3)×10−5) and 2.40±0.1 μs ((5.7±0.9)×10−5), respectively. The results are discussed in terms of triplet state deactivation by dissolved molecular oxygen.
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Photoluminescence properties of fluorone dyes in bio-related films at low temperatures
Journal of Photochemistry and Photobiology A-chemistry, 2011Co-Authors: Taiju Tsuboi, Alfons Penzkofer, E. A. Slyusareva, A. SizykhAbstract:Abstract The fluorescence and Phosphorescence behavior of the fluorone dyes disodium fluorescein (uranine), 4,5-dibromofluorescein, eosin Y, erythrosine B, and rose bengal in biofilms of chitosan, gelatin, and starch was studied in the temperature range from 293 K to 12 K. Luminescence Quantum Yields, fluorescence Quantum Yields, and triplet Quantum Yields were determined. The fluorescence Quantum Yield generally increased with lowering the temperature at a high level of absolute Quantum Yield, while the Phosphorescence Quantum Yield increased with decreasing temperature at a low level of absolute Quantum Yield. The strongest Phosphorescence was found for erythrosine B in starch where the Phosphorescence Quantum Yield increased from 6% at 293 K to 25% at 12 K. The temperature dependent luminescence behavior is discussed considering radiative and non-radiative transitions in a spectroscopic-state potential energy surface scheme.
Lixiang Wang - One of the best experts on this subject based on the ideXlab platform.
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Room-temperature Phosphorescence from a purely organic tetraphenylmethane derivative with formyl groups in both solution and crystalline states
Journal of Materials Chemistry C, 2020Co-Authors: Haiyang Shu, Jiancheng Rao, Liang Chen, Xin Wang, Hongkun Tian, Hui Tong, Lixiang WangAbstract:Room-temperature Phosphorescence of most purely organic compounds can hardly be observed in their solutions. Here, we report a tetraphenylmethane derivative with four aldehyde groups, which exhibits clear blue Phosphorescence in its solution at room temperature. Furthermore, its crystal displays a nearly 7-fold higher Phosphorescence Quantum Yield as compared to the solution.
Takao Itoh - One of the best experts on this subject based on the ideXlab platform.
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Excitation-energy dependence of the Phosphorescence Quantum Yields of pyridinecarboxaldehyde vapors.
Spectrochimica acta. Part A Molecular and biomolecular spectroscopy, 2008Co-Authors: Takao ItohAbstract:Emission and excitation spectra of 3- and 4-pyridinecarboxaldehyde vapors have been measured at different pressures down to 10(-2)Torr. The Phosphorescence Quantum Yield measured at low pressure as a function of excitation energy is nearly constant in the range of excitation energy corresponding to the S1(n, pi*) state, but it decreases abruptly at the S2(pi, pi*) threshold. The onset of the abrupt decrease of the Yield corresponds to the location of the S2 absorption origin of each molecule, indicating that the nonradiative pathway depends on the type of the excited singlet state to which the molecule is initially excited. The relaxation processes are discussed based on the pressure and excitation-energy dependence of the Phosphorescence Quantum Yield.
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Photophysical processes in quinoxaline vapor at low pressure.
Spectrochimica acta. Part A Molecular and biomolecular spectroscopy, 2003Co-Authors: Takao ItohAbstract:Abstract Excitation and pressure dependence of fluorescence and Phosphorescence Quantum Yields has been reinvestigated in detail for quinoxaline in the static vapor phase at pressure range from 10 −3 to 10 −1 Torr. It is shown that the ratio of the nonradiative rate from T 1 (π, π*) to the rate of the S 1 (n, π*)∼→T 1 (π, π*) intersystem crossing decreases with increasing the excitation energy in the S 0 →S 1 excitation region. The Phosphorescence Quantum Yield measured as a function of the excitation energy at low pressure shows an abrupt decrease on going the excitation from S 0 →S 1 to S 0 →S 2 , indicating the slow vibrational energy redistribution between the S 1 levels optically populated and those populated through the internal conversion from S 2 to S 1 .
Haiyang Shu - One of the best experts on this subject based on the ideXlab platform.
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Room-temperature Phosphorescence from a purely organic tetraphenylmethane derivative with formyl groups in both solution and crystalline states
Journal of Materials Chemistry C, 2020Co-Authors: Haiyang Shu, Jiancheng Rao, Liang Chen, Xin Wang, Hongkun Tian, Hui Tong, Lixiang WangAbstract:Room-temperature Phosphorescence of most purely organic compounds can hardly be observed in their solutions. Here, we report a tetraphenylmethane derivative with four aldehyde groups, which exhibits clear blue Phosphorescence in its solution at room temperature. Furthermore, its crystal displays a nearly 7-fold higher Phosphorescence Quantum Yield as compared to the solution.
A. Sizykh - One of the best experts on this subject based on the ideXlab platform.
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Photoluminescence properties of fluorone dyes in bio-related films at low temperatures
Journal of Photochemistry and Photobiology A-chemistry, 2011Co-Authors: Taiju Tsuboi, Alfons Penzkofer, E. A. Slyusareva, A. SizykhAbstract:Abstract The fluorescence and Phosphorescence behavior of the fluorone dyes disodium fluorescein (uranine), 4,5-dibromofluorescein, eosin Y, erythrosine B, and rose bengal in biofilms of chitosan, gelatin, and starch was studied in the temperature range from 293 K to 12 K. Luminescence Quantum Yields, fluorescence Quantum Yields, and triplet Quantum Yields were determined. The fluorescence Quantum Yield generally increased with lowering the temperature at a high level of absolute Quantum Yield, while the Phosphorescence Quantum Yield increased with decreasing temperature at a low level of absolute Quantum Yield. The strongest Phosphorescence was found for erythrosine B in starch where the Phosphorescence Quantum Yield increased from 6% at 293 K to 25% at 12 K. The temperature dependent luminescence behavior is discussed considering radiative and non-radiative transitions in a spectroscopic-state potential energy surface scheme.