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Auteur : Grafiati
Publié le 25 mai 2024

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1

OWENS, JOHN W., et MARSHA ROBINS. « Phthalocyanine photophysics and photosensitizer efficiency on human embryonic lung fibroblasts ». Journal of Porphyrins and Phthalocyanines 05, no 05 (mai 2001) : 460–64. http://dx.doi.org/10.1002/jpp.340.

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This study correlates the photophysical properties of aluminum phthalocyanine tetrasulfonate (AlPcTs), zinc phthalocyanine tetrasulfonate (ZnPcTs), and phthalocyanine tetrasulfonate (PcTs) with their ability to kill human embryonic lung (HEL) cells. Photofrin, a proven anti-cancer drug, was used for comparison. The photophysical properties include fluorescence emission spectra, fluorescence quantum yields, singlet state and radiative lifetimes, quantum yield for triplet formation, and fluorescence rate constants. Results indicate that photodynamic efficacy correlates inversely with fluorescence quantum yield and fluorescence lifetime and directly with quantum yield for triplet formation.
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2

MUKOYAMA, TAKESHI, HIROHIDE NAKAMATSU et HIROHIKO ADACHI. « CHEMICAL EFFECT ON X-RAY FLUORESCENCE YIELDS FOR CARBON ». International Journal of PIXE 06, no 03n04 (janvier 1996) : 447–52. http://dx.doi.org/10.1142/s012908359600048x.

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The chemical effect on K-shell fluorescence yields for carbon compounds has been estimated in a simple model based on the discrete-variational Xα molecular orbital calculations and the statistical scaling method. The calculated results show that there is a relation between the fluorescence yield and the effective number of 2p electrons in carbon, n2p. The behavior of the fluorescence yield as a function of n2p is in qualitatively agreement with the experimental data by proton impact. The present values for fluorescence yields of carbon oxides agree with other theoretical values.
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3

Kempe, Daryan, Antonie Schöne, Jörg Fitter et Matteo Gabba. « Accurate Fluorescence Quantum Yield Determination by Fluorescence Correlation Spectroscopy ». Journal of Physical Chemistry B 119, no 13 (24 mars 2015) : 4668–72. http://dx.doi.org/10.1021/acs.jpcb.5b02170.

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4

Li, Tongtong, Baosheng Liu, Shaotong Duan et Mengmeng Cui. « Fluorescence spectra, fluorescence quantum yield and dissociation constant of sarafloxacin ». Luminescence 32, no 4 (10 octobre 2016) : 545–48. http://dx.doi.org/10.1002/bio.3211.

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5

Hott, J. L., et R. F. Borkman. « The non-fluorescence of 4-fluorotryptophan ». Biochemical Journal 264, no 1 (15 novembre 1989) : 297–99. http://dx.doi.org/10.1042/bj2640297.

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The derivative 4-fluorotryptophan was confirmed to have negligible fluorescence at 25 degrees C and 285 nm (tryptophan/4-fluorotryptophan quantum-yield ratio greater than 100:1). However, photolysis experiments on tryptophan and 4-fluorotryptophan, in which loss of starting material was measured by reverse-phase h.p.l.c., demonstrated that 4-fluorotryptophan was significantly more photochemically active than the parent tryptophan, with the 4-fluorotryptophan photolysis quantum yield being 7 times larger than that of tryptophan at 25 degrees C and 285 nm. In addition, at 77 K and 275 nm 4-fluorotryptophan displayed strong fluorescence and phosphorescence, with emission quantum yields comparable with those of tryptophan at 77 K and 275 nm.
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Sen, Pinar, Nnamdi Nwahara et Tebello Nyokong. « Photodynamic antimicrobial activity of benzimidazole substituted phthalocyanine when conjugated to Nitrogen Doped Graphene Quantum Dots against Staphylococcus aureus ». Main Group Chemistry 20, no 2 (22 juillet 2021) : 175–91. http://dx.doi.org/10.3233/mgc-210030.

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In this study, peripherally benzimidazole unit substituted ZnPc (1) and its conjugation to nitrogen doped graphene quantum dot (NGQD) as potential phthalocyanine support via π-π stacking have been presented and fully characterized. The bottom-up solution-based synthesized NGQDs was conjugated non-covalently to zinc phthalocyanine to form NGQDs-Pc nanoconjugates. The photophysical and photochemical properties of both such as absorption, fluorescence, fluorescence life time, singlet oxygen quantum yields, triplet state quantum yields and exited state lifetimes were investigated in solutions. We observed a decrease in the fluorescence quantum yields with a corresponding increase in the triplet quantum yield and singlet oxygen quantum yield of the nanoconjugates in comparison to the phthalocyanine complex alone. Photodynamic antimicrobial chemotherapy activities (PACT) of ZnPc alone and its nanoconjugate were determined towards Staphylococcus aureus.
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7

Silva, Gustavo T. M., Cassio P. Silva, Karen M. Silva, Renan M. Pioli, Tássia S. Costa, Vinícius V. Marto, Adilson A. Freitas et al. « Fluorescence and Phosphorescence of Flavylium Cation Analogues of Anthocyanins ». Photochem 2, no 2 (8 juin 2022) : 423–34. http://dx.doi.org/10.3390/photochem2020029.

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Fluorescence spectra and lifetimes were determined for 16 synthetic flavylium cation analogues of anthocyanin plant pigments in dry acetonitrile acidified with trifluoroacetic acid (TFA). Phosphorescence was also observed from the lowest excited triplet state for all of the flavylium cations at 77 K in a rigid TFA-acidified isopropanol glass. The fluorescence quantum yields and lifetimes depend in a systematic manner on the nature and position of the substituents on the flavylium chromophore and three specific substitution patterns associated with significant decreases in the fluorescence quantum yield were identified. A 4′-bromo or 4′-iodo substituent in the B-ring of the flavylium cation produced a small but normal heavy-atom effect, reducing the fluorescence quantum yield and the phosphorescence lifetime relative to analogues without the halogen atom. In contrast, three flavylium cations with a 3′-bromo substituent exhibited an “inverse” heavy atom effect, i.e., an increase in the fluorescence quantum yield rather than a decrease, which was rationalized on the basis of the nodal properties of the natural transition orbitals (NTOs) involved in the S0→S1 radiative transition.
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8

Falkowski, Paul G., Hanzhi Lin et Maxim Y. Gorbunov. « What limits photosynthetic energy conversion efficiency in nature ? Lessons from the oceans ». Philosophical Transactions of the Royal Society B : Biological Sciences 372, no 1730 (14 août 2017) : 20160376. http://dx.doi.org/10.1098/rstb.2016.0376.

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Constraining photosynthetic energy conversion efficiency in nature is challenging. In principle, two yield measurements must be made simultaneously: photochemistry, fluorescence and/or thermal dissipation. We constructed two different, extremely sensitive and precise active fluorometers: one measures the quantum yield of photochemistry from changes in variable fluorescence, the other measures fluorescence lifetimes in the picosecond time domain. By deploying the pair of instruments on eight transoceanic cruises over six years, we obtained over 200 000 measurements of fluorescence yields and lifetimes from surface waters in five ocean basins. Our results revealed that the average quantum yield of photochemistry was approximately 0.35 while the average quantum yield of fluorescence was approximately 0.07. Thus, closure on the energy budget suggests that, on average, approximately 58% of the photons absorbed by phytoplankton in the world oceans are dissipated as heat. This extraordinary inefficiency is associated with the paucity of nutrients in the upper ocean, especially dissolved inorganic nitrogen and iron. Our results strongly suggest that, in nature, most of the time, most of the phytoplankton community operates at approximately half of its maximal photosynthetic energy conversion efficiency because nutrients limit the synthesis or function of essential components in the photosynthetic apparatus. This article is part of the themed issue ‘Enhancing photosynthesis in crop plants: targets for improvement’.
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9

Ma, Lihua. « The Investigation of Fluorescence Spectra and Fluorescence Quantum Yield of Enrofloxacin ». Journal of Chemical, Environmental and Biological Engineering 2, no 1 (2018) : 11. http://dx.doi.org/10.11648/j.jcebe.20180201.13.

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10

Hurtubise, R. J., et S. M. Ramasamy. « Comparison of Fluorescence-to-Phosphorescence Quantum Yield Ratios in Solid-Matrix Luminescence as a Function of Temperature ». Applied Spectroscopy 47, no 3 (mars 1993) : 283–86. http://dx.doi.org/10.1366/0003702934066587.

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An equation that relates the ratio of fluorescence to phosphorescence quantum yields as function of temperature to basic photophysical parameters is considered. The quantum yields were obtained from three compounds on three different solid matrices. Fluorescence quantum yields did not change much with temperature, while phosphorescence quantum yields changed more substantially with temperature. For some of the systems considered, it was possible to show that, as the temperature was lowered, the quantum yield ratio was only a function of the phosphorescence lifetime of the phosphor. However, with other systems, the quantum yield ratio was dependent on both the rate constant of intersystem crossing from the singlet state to the triplet state and the phosphorescence lifetime. The equation discussed is important in defining the fundamental parameters that cause the luminescence quantum yield ratio to change as temperature is lowered.
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11

Boyko, T. D., R. J. Green, A. Moewes et T. Z. Regier. « Measuring partial fluorescence yield using filtered detectors ». Journal of Synchrotron Radiation 21, no 4 (12 juin 2014) : 716–21. http://dx.doi.org/10.1107/s160057751401073x.

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Typically, X-ray absorption near-edge structure measurements aim to probe the linear attenuation coefficient. These measurements are often carried out using partial fluorescence yield techniques that rely on detectors having photon energy discrimination improving the sensitivity and the signal-to-background ratio of the measured spectra. However, measuring the partial fluorescence yield in the soft X-ray regime with reasonable efficiency requires solid-state detectors, which have limitations due to the inherent dead-time while measuring. Alternatively, many of the available detectors that are not energy dispersive do not suffer from photon count rate limitations. A filter placed in front of one of these detectors will make the energy-dependent efficiency non-linear, thereby changing the responsivity of the detector. It is shown that using an array of filtered X-ray detectors is a viable method for measuring soft X-ray partial fluorescence yield spectra without dead-time. The feasibility of this technique is further demonstrated using α-Fe2O3as an example and it is shown that this detector technology could vastly improve the photon collection efficiency at synchrotrons and that these detectors will allow experiments to be completed with a much lower photon flux reducing X-ray-induced damage.
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12

Campbell, J. L., G. Cauchon, T. Lakatos, M.-C. Lépy, L. McDonald, T. Papp, J. Plagnard, P. Stemmler et W. J. Teesdale. « Experimental K-shell fluorescence yield of silicon ». Journal of Physics B : Atomic, Molecular and Optical Physics 31, no 21 (14 novembre 1998) : 4765–79. http://dx.doi.org/10.1088/0953-4075/31/21/009.

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13

Katoh, Ryuzi, Kengo Suzuki, Akihiro Furube, Masahiro Kotani et Katsumi Tokumaru. « Fluorescence Quantum Yield of Aromatic Hydrocarbon Crystals ». Journal of Physical Chemistry C 113, no 7 (27 janvier 2009) : 2961–65. http://dx.doi.org/10.1021/jp807684m.

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14

Nawara, Krzysztof, et Jacek Waluk. « Improved Method of Fluorescence Quantum Yield Determination ». Analytical Chemistry 89, no 17 (16 août 2017) : 8650–55. http://dx.doi.org/10.1021/acs.analchem.7b02013.

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15

Tsin, Andrew T. C., Hugo A. Pedrozo-Fernandez, James M. Gallas et James P. Chambers. « The fluorescence quantum yield of vitamin A2 ». Life Sciences 43, no 17 (janvier 1988) : 1379–84. http://dx.doi.org/10.1016/0024-3205(88)90304-9.

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16

Qu, Jianan Y., Zhijian Huang et Jianwen Hua. « Mapping the fluorescence yield on turbid media ». Applied Physics Letters 76, no 8 (21 février 2000) : 970–72. http://dx.doi.org/10.1063/1.125908.

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17

Kakimoto, F., E. C. Loh, M. Nagano, H. Okuno, M. Teshima et S. Ueno. « A measurement of the air fluorescence yield ». Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment 372, no 3 (avril 1996) : 527–33. http://dx.doi.org/10.1016/0168-9002(95)01423-3.

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18

BINDHU, C. V., S. S. HARILAL, V. P. N. NAMPOORI et C. P. G. VALLABHAN. « SOLVENT EFFECT ON ABSOLUTE FLUORESCENCE QUANTUM YIELD OF RHODAMINE 6G DETERMINED USING TRANSIENT THERMAL LENS TECHNIQUE ». Modern Physics Letters B 13, no 16 (10 juillet 1999) : 563–76. http://dx.doi.org/10.1142/s0217984999000725.

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Dual beam thermal lens technique is successfully employed for the determination of absolute fluorescence quantum yield of rhodamine 6G laser dye in different solvents. A 532 nm radiation from a Q-switched Nd:YAG laser was used for the excitation purpose. The fluorescence quantum yield values are found to be strongly influenced by environmental effects. It has been observed that fluorescence yield is greater for rhodamine 6G in ethylene glycol system than in water or in methanol. Our results also indicate that parameters like concentration of the dye solution, aggregate formation and excited state absorption affect the absolute values of fluorescence yield significantly.
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19

Dragan, Anatoliy I., et Chris D. Geddes. « Metal-enhanced fluorescence : The role of quantum yield, Q0, in enhanced fluorescence ». Applied Physics Letters 100, no 9 (27 février 2012) : 093115. http://dx.doi.org/10.1063/1.3692105.

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20

DING, Yiren, Shizhe QIN, Lulu MA, Xiangyu CHEN, Qiushuang YAO, Mi YANG, Yiru MA, Xin LV et Ze ZHANG. « A study on cotton yield prediction based on the chlorophyll fluorescence parameters of upper leaves ». Notulae Botanicae Horti Agrobotanici Cluj-Napoca 50, no 3 (22 septembre 2022) : 12775. http://dx.doi.org/10.15835/nbha50312775.

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The early and accurate monitoring of crop yield is important for field management, storage needs, and cash flow budgeting. Traditional cotton yield measurement methods are time-consuming, labor-intensive, and subjective. Chlorophyll fluorescence signals originate from within the plant and have the advantages of being fast and non-destructive, and the relevant parameters can reflect the intrinsic physiological characteristics of the plant. Therefore, in this study, the top four functional leaves of cotton plants at the beginning of the flocculation stage were used to investigate the pattern of the response of chlorophyll fluorescence parameters (e.g., F0, Fm, Fv/F0, and Fv/Fm) to nitrogen, and the cumulative fluorescence parameters were constructed by combining them with the leaf area index to clarify the correlation between chlorophyll fluorescence parameters and cotton yield. Support vector machine regression (SVM), an artificial neural network (BP), and an XGBoost regression tree were used to establish a cotton yield prediction model. Chlorophyll fluorescence parameters showed the same performance as photosynthetic parameters, which decreased as leaf position decreased. It showed a trend of increasing and then decreasing with increasing N application level, reaching the maximum value at 240 kg·hm-2 of N application. The correlation between fluorescence parameters and yield in the first, second, and third leaves was significantly higher than that in the fourth leaf, and the correlation between fluorescence accumulation and yield in each leaf was significantly higher than that of the fluorescence parameters, with the best performance of Fv/Fm accumulation found in the second leaf. The correlation between Fv/Fm accumulation and yield in the top three leaves combined was significantly higher than that in the top four leaves. The correlation coefficient between Fv/Fm accumulation and yield was the highest, indicating the feasibility of applying chlorophyll fluorescence to estimate yield. Based on the machine learning algorithm used to construct a cotton yield prediction model, the estimation models of Fv/F0 accumulation and yield of the top two leaves combined as well as top three leaves combined were superior. The estimation model coefficient of determination of the top two leaves combined in the BP algorithm was the highest. In general, the Fv/F0 accumulation of the top two leaves combined could more reliably predict cotton yield, which could provide technical support for cotton growth monitoring and precision management.
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STRAZZERI, E., O. CATALANO et B. SBARUFATTI. « AN EMPIRICAL MODEL OF PRODUCTION AND ATTENUATION OF FLUORESCENCE LIGHT IN ATMOSPHERE FOR SATELLITE-BASED ULTRA HIGH ENERGY COSMIC RAY EXPERIMENTS ». International Journal of Modern Physics D 20, no 03 (mars 2011) : 299–317. http://dx.doi.org/10.1142/s0218271811018822.

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In the context of detection of Ultra High Energy Cosmic Ray (UHECR) showers from space the details of fluorescence light production and transmission in the atmosphere are given. An analytical model of the fluorescence yield, in dependence on nitrogen molecular parameters and the atmospheric conditions, is presented. Seasonal and geographical variations of the total fluorescence photon yield between 300 nm and 400 nm in air excited by 0.85 MeV electrons are shown as a function of the altitude, using different atmospheric models. In the frame of a satellite-based UHECR experiment the fluorescence yield has been corrected by the overall atmospheric transmission which takes into account, in the simplest approximation, the wavelength-dependent scattering and absorption of the fluorescence light from air molecules, from stratospheric ozone, and from aerosol. The effect of the atmospheric attenuation on the fluorescence yield is shown as a function of the altitude of the emission point of light.
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Hale, S. J., et L. A. Melton. « Absolute Quantum Yields for Exciplex Fluorescence ». Applied Spectroscopy 44, no 1 (janvier 1990) : 101–5. http://dx.doi.org/10.1366/0003702904085895.

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The absolute quantum yields for exciplex fluorescence in four solutions which have potential as exciplex-based vapor/liquid visualization systems have been measured. The room-temperature absolute quantum yields for 10% dibutyl-aniline/0.4%, 1-cyanonaphthalene, 12.5% 1-methyl-naphthalene/0.5% N,N,N′,N′-tetramethyl- p-phenylenediamine (TMPD), 10% trihexylamine/1.0% 1-cyanonaphthalene, and 10% naphthalene/1.0% TMPD in hexadecane or cyclohexane are 0.03 ± 0.005, 0.05 ± 0.002 (308 nm), 0.02 ± 0.001, and 0.16 ± 0.021, respectively. The temperature dependence of the absolute quantum yield for the 10% naphthalene/1% TMPD in the hexadecane system was measured over the range of 23 to 260°C and was found to decrease by 20–30% at 260°C.
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Bhunia, Asamanjoy, Dolores Esquivel, Subarna Dey, Ricardo Fernández-Terán, Yasutomo Goto, Shinji Inagaki, Pascal Van Der Voort et Christoph Janiak. « A photoluminescent covalent triazine framework : CO2 adsorption, light-driven hydrogen evolution and sensing of nitroaromatics ». Journal of Materials Chemistry A 4, no 35 (2016) : 13450–57. http://dx.doi.org/10.1039/c6ta04623a.

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24

Biermann, L., C. Guinet, M. Bester, A. Brierley et L. Boehme. « An optimised method for correcting quenched fluorescence yield ». Ocean Science Discussions 11, no 3 (9 mai 2014) : 1243–64. http://dx.doi.org/10.5194/osd-11-1243-2014.

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Abstract. Under high light intensity, phytoplankton protect their photosystems from bleaching through non-photochemical quenching processes. The consequence of this is suppression of fluorescence emission, which must be corrected when measuring in situ yield with fluorometers. Previously, this has been done using the limit of the mixed layer, assuming that phytoplankton are uniformly mixed from the surface to this depth. However, the assumption of homogeneity is not robust in oceanic regimes that support deep chlorophyll maxima. To account for these features, we correct from the limit of the euphotic zone, defined as the depth at which light is at ~1% of the surface value. This method was applied to fluorescence data collected by eleven animal-borne fluorometers deployed in the Southern Ocean over four austral summers. Six tags returned data showing evidence of deep chlorophyll features. Using the depth of the euphotic layer, quenching was corrected without masking subsurface fluorescence signals.
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Соколовская, Ю. Г., А. А. Жильцова, Е. Д. Краснова, Д. А. Воронов et С. В. Пацаева. « Спектрально-люминесцентные характеристики растворенного органического вещества в меромиктических водоемах Кандалакшского залива Белого моря ». Оптика и спектроскопия 131, no 6 (2023) : 872. http://dx.doi.org/10.21883/os.2023.06.55924.111-23.

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The optical properties of chromophoric dissolved organic matter (CDOM) of natural water have been studied by fluorescence spectroscopy and absorption spectroscopy. Samples of natural water from various depths from the meromictic lakes Trekhtzvetnoe and Elovoe were taken. The dependences of the quantum yield and the maximum of fluorescence emission on the excitation wavelength in a wide range of excitation wavelength variation (250...500 nm) for different horizons of stratified reservoirs are obtained. It is shown that the dependences of the maximum of the fluorescence emission on the excitation wavelength and the dependences of fluorescence quantum yield on the excitation wavelength in both lakes and at all depths studied are similar. On the other hand, the absolute value of the quantum yield differs in different layers of water. For example, the values of the fluorescence quantum yield took values from 1.4% to 2.4% at an excitation wavelength of 340 nm. The similar nature of the dependence of the fluorescence intensity on the excitation wavelength is explained by the common origin of DOM fluorophores in the studied horizons of stratified lakes. The different values of the fluorescence quantum yield are due to the difference in the proportion of aromatic compounds in the composition of the CDOM and are associated with differences in the hydrochemical characteristics of water at different horizons.
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26

Ralston, Corie Y., Xu Wu et Oliver C. Mullins. « Quantum Yields of Crude Oils ». Applied Spectroscopy 50, no 12 (décembre 1996) : 1563–68. http://dx.doi.org/10.1366/0003702963904601.

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Fluorescence quantum yield measurements are reported for visible and UV excitation for neat and dilute crude oil solutions, extending earlier work with excitation in the long wavelength visible and the NIR. Large and monotonically increasing quantum yields are found with shorter wavelength excitation (to 325 nm), and all crude oils are shown to have nearly the same relative dependence of quantum yield on excitation wavelength. These observations are explained by the energy dependence of internal conversion. Dilute solutions of light crude oils exhibit higher quantum yields than those of heavy crude oils because of their lack of large chromophores. The fraction of fluorescence emission resulting from electronic energy transfer (with subsequent fluorescence emission) for neat crude oils was previously shown to vary from ∼100% for ultraviolet excitation to ∼0% for near-infrared excitation; this large variation correlates well with and is explained by the very large variation in quantum yields with excitation wavelength. Comparison of quantum yields from neat and dilute solutions shows that quenching is the other major process which occurs with chromophore interactions. The quantum yields of a maltene and resin are large and similar, while the asphaltene exhibits much smaller quantum yields because of its lack of small chromophores.
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Shi, Lei, Jian Hai Yang, Hai Bo Zeng, Yong Mei Chen, Sheng Chun Yang, Chao Wu, Hao Zeng, Osada Yoshihito et Qiqing Zhang. « Carbon dots with high fluorescence quantum yield : the fluorescence originates from organic fluorophores ». Nanoscale 8, no 30 (2016) : 14374–78. http://dx.doi.org/10.1039/c6nr00451b.

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Zhang, Xian-Fu, George Q. Zhang et Jiale Zhu. « Methylated Unsymmetric BODIPY Compounds : Synthesis, High Fluorescence Quantum Yield and Long Fluorescence Time ». Journal of Fluorescence 29, no 2 (23 janvier 2019) : 407–16. http://dx.doi.org/10.1007/s10895-019-02349-5.

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Toh, K. C., Emina A. Stojković, Ivo H. M. van Stokkum, Keith Moffat et John T. M. Kennis. « Fluorescence quantum yield and photochemistry of bacteriophytochrome constructs ». Physical Chemistry Chemical Physics 13, no 25 (2011) : 11985. http://dx.doi.org/10.1039/c1cp00050k.

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30

Thompson, C. I., E. E. Barritt et C. Shenton-Taylor. « Predicting the air fluorescence yield of radioactive sources ». Radiation Measurements 88 (mai 2016) : 48–54. http://dx.doi.org/10.1016/j.radmeas.2016.02.013.

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31

HRIBAR, M., A. KODRE et D. GLAVIĆ. « FLUORESCENCE YIELD OF DOUBLE K VACANCIES IN KRYPTON ». Le Journal de Physique Colloques 48, no C9 (décembre 1987) : C9–625—C9–628. http://dx.doi.org/10.1051/jphyscol:19879105.

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32

Goedkoop, J. B., N. B. Brookes, Michel van Veenendaal et B. T. Thole. « Soft X-ray fluorescence yield XMCD sum rules ». Journal of Electron Spectroscopy and Related Phenomena 86, no 1-3 (août 1997) : 143–50. http://dx.doi.org/10.1016/s0368-2048(97)00060-1.

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33

Arqueros, F., F. Blanco, A. Castellanos, M. Ortiz et J. Rosado. « The yield of air fluorescence induced by electrons ». Astroparticle Physics 26, no 4-5 (novembre 2006) : 231–42. http://dx.doi.org/10.1016/j.astropartphys.2006.06.006.

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Stepanov, S. A. « Fluorescence Yield under X-Ray Surface Back Diffraction ». Physica Status Solidi (a) 132, no 1 (16 juillet 1992) : 9–16. http://dx.doi.org/10.1002/pssa.2211320102.

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35

Girgis, Adel S., Altaf H. Basta, Houssni El-Saied, Mohamed A. Mohamed, Ahmad H. Bedair et Ahmad S. Salim. « Synthesis, quantitative structure–property relationship study of novel fluorescence active 2-pyrazolines and application ». Royal Society Open Science 5, no 3 (mars 2018) : 171964. http://dx.doi.org/10.1098/rsos.171964.

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A variety of fluorescence-active fluorinated pyrazolines 13–33 was synthesized in good yields through cyclocondensation reaction of propenones 1–9 with aryl hydrazines 10–12 . Some of the synthesized compounds provided promising fluorescence properties with quantum yield ( Φ ) higher than that of quinine sulfate (standard reference). Quantitative structure–property relationship studies were undertaken supporting the exhibited fluorescence properties and estimating the parameters governing properties. Five synthesized fluorescence-active pyrazolines ( 13 , 15 , 18 , 19 and 23 ) with variable Φ were selected for treating two types of paper sheets (Fabriano and Bible paper). These investigated fluorescence compounds, especially compounds 19 and 23 , provide improvements in strength properties of paper sheets. Based on the observed performance they can be used as markers in security documents.
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Peloso, Anelisa Figueiredo, Sandro Dan Tatagiba, Francisco José Teixeira Amaral, Paulo César Cavatte et José Eduardo Macedo Pezzopane. « PYRACLOSTROBIN PRESERVES PHOTOSYNTHESIS IN ARABICA COFFEE PLANTS SUBJECTED TO WATER DEFICIT ». REVISTA ENGENHARIA NA AGRICULTURA - REVENG 28 (7 février 2020) : 109–19. http://dx.doi.org/10.13083/reveng.v28i.939.

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The objective of this study was to investigate the effect of pyraclostrobin on the photosynthetic performance of rabica coffee plants subjected or not to a water deficit, using the parameter of gas exchange (net CO2 assimilation, stomatal conductance, transpiration rate, and internal CO2 concentration and nocturnal respiration), chlorophyll fluorescence a parameters (minimum fluorescence, maximum fluorescence, maximum quantum yield of photosystem II, effective quantum yield of PSII, quantum yield of regulated energy dissipation and quantum yield dissipation non-regulated) as well as the concentrations of chloroplast pigments. In the plants maintained without water deficit, pyraclostrobin did not cause any alteration on the parameters of chlorophyll a fluorescence; however, it contributed to an increase in the level of chlorophyll a + b, CO2 assimilation and CO2 influx for the carboxylation sites of the stroma. Decreases in nocturnal respiration in plants treated with pyraclostrobin, submitted or not to water deficit seems to be a common strategy in reducing energy waste in the maintenance metabolism. Under water deficit, pyraclostrobin contributed to increase the photochemical yield, enabling plants to effectively prevent the capture, use and dissipation of light energy.
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37

Kawski, A., G. Piszczek et A. Kubicki. « Fluorescence Properties of p-Quaterphenyl and p-Quinquephenyl Derivatives in Liquid Solvents ». Zeitschrift für Naturforschung A 51, no 8 (1 août 1996) : 905–9. http://dx.doi.org/10.1515/zna-1996-0804.

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Abstract Absorption, fluorescence and emission anisotropy spectra, as well as quantum yields and fluores-cence decay times of p-quaterphenyl (PQP), 4,4"'-bis-(2-butyloctyloxy)-p-quaterphenyl (BBQ), 2,5,2"",5""-tetramethyl-p-quinquephenyl (TMI) and 3,5,3"",5""-tetra-f-butyl-p-quinquephenyl (QUI) were investigated in several nonpolar and polar solvents. It was found that high quantum yield is accompanied by a short (not exceeding 1 ns) lifetime and considerable emission anisotropy in low viscosity solvents. For TMI and QUI, which incorporate as many as 5 phenyl groups, the quantum yield in dioxane is 0.98 and 0.97, respectively. In the case of molecules with 4 phenyl groups, the quantum yield is slightly lower, amounting to 0.91. Rotational motions of terminal phenyl groups cause a lower deactivation of the excitation energy of the singlet state S p the longer the linear molecule.
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38

Malkin, T. L., A. Goddard, D. E. Heard et P. W. Seakins. « Measurements of OH and HO<sub>2</sub> ; yields from the gas phase ozonolysis of isoprene ». Atmospheric Chemistry and Physics Discussions 9, no 4 (25 août 2009) : 17579–631. http://dx.doi.org/10.5194/acpd-9-17579-2009.

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Abstract. The reactions of ozone with alkenes are an important source of hydroxyl (OH) radicals; however, quantification of their importance is hindered by uncertainties in the absolute OH yield. Hydroxyl radical yields for the gas-phase ozonolysis of isoprene are determined in this paper by four different methods: (1) The use of cyclohexane as an OH scavenger, and the production of cyclohexanone, (2) The use of 1,3,5-trimethylbenzene as an OH tracer, and the diminution in its concentration, (3) A kinetic method in which the OH yield was obtained by performing a series of pseudo-first-order experiments in the presence or absence of an OH scavenger (cyclohexane), (4) The OH and HO2 yields were determined by fitting the temporal OH and HO2 profiles following direct detection of absolute OH and HO2 concentrations by laser induced fluorescence at low pressure (Fluorescence Assay by Gas Expansion-FAGE). The following OH yields for the ozonolysis of isoprene were obtained, relative to alkene consumed, for each method: (1) Scavenger (0.25 ± 0.04), (2) Tracer (0.25 ± 0.03), (3) Kinetic study (0.27 ± 0.02), and (4) Direct observation (0.26 ± 0.02), the error being one standard deviation. An averaged OH yield of 0.26 ± 0.02 is recommended at room temperature and atmospheric pressure and this result is compared with recent literature determinations. The HO2 yield was directly determined for the first time using FAGE to be 0.26 ± 0.03.
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39

Malkin, T. L., A. Goddard, D. E. Heard et P. W. Seakins. « Measurements of OH and HO<sub>2</sub> ; yields from the gas phase ozonolysis of isoprene ». Atmospheric Chemistry and Physics 10, no 3 (10 février 2010) : 1441–59. http://dx.doi.org/10.5194/acp-10-1441-2010.

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Abstract. The reactions of ozone with alkenes are an important source of hydroxyl (OH) radicals; however, quantification of their importance is hindered by uncertainties in the absolute OH yield. Hydroxyl radical yields for the gas-phase ozonolysis of isoprene are determined in this paper by four different methods: (1) The use of cyclohexane as an OH scavenger, and the production of cyclohexanone, (2) The use of 1,3,5-trimethylbenzene as an OH tracer, and the diminution in its concentration, (3) A kinetic method in which the OH yield was obtained by performing a series of pseudo-first-order experiments in the presence or absence of an OH scavenger (cyclohexane), (4) The OH and HO2 yields were determined by fitting the temporal OH and HO2 profiles following direct detection of absolute OH and HO2 concentrations by laser induced fluorescence at low pressure (Fluorescence Assay by Gas Expansion- FAGE). The following OH yields for the ozonolysis of isoprene were obtained, relative to alkene consumed, for each method: (1) Scavenger (0.25±0.04), (2) Tracer (0.25±0.03), (3) Kinetic study (0.27±0.02), and (4) Direct observation (0.26±0.02), the error being one standard deviation. An averaged OH yield of 0.26±0.02 is recommended at room temperature and atmospheric pressure and this result is compared with recent literature determinations. The HO2 yield was directly determined for the first time using FAGE to be 0.26±0.03.
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40

Markwardt, Michele L., Gert-Jan Kremers, Catherine A. Kraft, Krishanu Ray, Paula J. C. Cranfill, Korey A. Wilson, Richard N. Day, Rebekka M. Wachter, Michael W. Davidson et Megan A. Rizzo. « An Improved Cerulean Fluorescent Protein with Enhanced Brightness and Reduced Reversible Photoswitching ». PLoS ONE 6, no 3 (29 mars 2011) : e17896. http://dx.doi.org/10.1371/journal.pone.0017896.

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Cyan fluorescent proteins (CFPs), such as Cerulean, are widely used as donor fluorophores in Förster resonance energy transfer (FRET) experiments. Nonetheless, the most widely used variants suffer from drawbacks that include low quantum yields and unstable flurorescence. To improve the fluorescence properties of Cerulean, we used the X-ray structure to rationally target specific amino acids for optimization by site-directed mutagenesis. Optimization of residues in strands 7 and 8 of the β-barrel improved the quantum yield of Cerulean from 0.48 to 0.60. Further optimization by incorporating the wild-type T65S mutation in the chromophore improved the quantum yield to 0.87. This variant, mCerulean3, is 20% brighter and shows greatly reduced fluorescence photoswitching behavior compared to the recently described mTurquoise fluorescent protein in vitro and in living cells. The fluorescence lifetime of mCerulean3 also fits to a single exponential time constant, making mCerulean3 a suitable choice for fluorescence lifetime microscopy experiments. Furthermore, inclusion of mCerulean3 in a fusion protein with mVenus produced FRET ratios with less variance than mTurquoise-containing fusions in living cells. Thus, mCerulean3 is a bright, photostable cyan fluorescent protein which possesses several characteristics that are highly desirable for FRET experiments.
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41

Journal, Baghdad Science. « Study the Effect of thickness on the Optical Properties Performance of active polymeric laser media ». Baghdad Science Journal 5, no 2 (1 juin 2008) : 211–16. http://dx.doi.org/10.21123/bsj.5.2.211-216.

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The paper include study the effect thickness of the polymeric sample which is manufactured by thermo press way. The sample was used as an active tunable R6G laser media. The remarks show that, when the thickness of the samples is increased, with the same concentration, the spectrum will shift towards the short wavelength, & the quantum fluorescence yield will increased. The best result we obtained for the quantum fluorescence yield is (0.68) at the sample, with thickness (0.304mm) in Ethanol solvent, while when we used the Pure Water as a solvent, we found that the best quantum fluorescence yield is (0.63) at (0.18mm) thickness of the sample.
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42

Journal, Baghdad Science. « Study the Effect of solvent on the Optical Properties Performance of active polymeric laser media ». Baghdad Science Journal 4, no 3 (2 septembre 2007) : 387–92. http://dx.doi.org/10.21123/bsj.4.3.387-392.

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The paper include studies the effect of solvent of dye doped in polymeric laser sample which manufactured in primo press way, which is used as an active (R6G) tunable dye lasers. The remarks show that, when the viscosity of the solvent (from Pure Water to Ethanol), for the same concentration and thickness of the performance polymeric sample is increased, the absorption spectrum is shifts towards the long wave length (red shift), & towards short wave length (blue shift) for fluorescence spectrum, also increased the quantum fluorescence yield. The best result we obtained for the quantum fluorescence yield is (0.882) with thickness (0.25mm) in Ethanol solvent in concentration (2*10-3mole/liter), while when we used the Pure Water as a solvent, we found that the best quantum fluorescence yield is (0.72) at the same thickness & concentration of the sample.
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43

BINDHU, C. V., S. S. HARILAL, RIJU C. ISSAC, V. P. N. NAMPOORI et C. P. G. VALLABHAN. « PULSED PHOTOACOUSTIC DETERMINATION OF ABSOLUTE FLUORESCENT QUANTUM YIELD OF THE LASER DYE RHODAMINE B ». Modern Physics Letters B 10, no 22 (20 septembre 1996) : 1103–10. http://dx.doi.org/10.1142/s0217984996001255.

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Pulsed photoacoustic technique which is found to be a very convenient and accurate method, is used for the determination of absolute fluorescence quantum yield of laser dye rhodamine B. Concentration and power dependence of quantum yield of rhodamine B in methanol for excitation at 532 nm is reported here. Results show that a rapid decrease in quantum yield as the concentration is increased and finally it reaches the limit corresponding to fluorescence quenching.
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44

Stepanenko, Olesya V., Olga V. Stepanenko, Olesya G. Shpironok, Alexander V. Fonin, Irina M. Kuznetsova et Konstantin K. Turoverov. « Near-Infrared Markers based on Bacterial Phytochromes with Phycocyanobilin as a Chromophore ». International Journal of Molecular Sciences 20, no 23 (2 décembre 2019) : 6067. http://dx.doi.org/10.3390/ijms20236067.

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Biomarkers engineered on the basis of bacterial phytochromes with biliverdin IXα (BV) cofactor as a chromophore are increasingly used in cell biology and biomedicine, since their absorption and fluorescence spectra lie within the so-called optical “transparency window” of biological tissues. However, the quantum yield of BV fluorescence in these biomarkers does not exceed 0.145. The task of generating biomarkers with a higher fluorescence quantum yield remains relevant. To address the problem, we proposed the use of phycocyanobilin (PCB) as a chromophore of biomarkers derived from bacterial phytochromes. In this work, we characterized the complexes of iRFP713 evolved from RpBphP2 and its mutant variants with different location of cysteine residues capable of covalent tetrapyrrole attachment with the PCB cofactor. All analyzed proteins assembled with PCB were shown to have a higher fluorescence quantum yield than the proteins assembled with BV. The iRFP713/V256C and iRFP713/C15S/V256C assembled with PCB have a particularly high quantum yield of 0.5 and 0.45, which exceeds the quantum yield of all currently available near-infrared biomarkers. Moreover, PCB has 4 times greater affinity for iRFP713/V256C and iRFP713/C15S/V256C proteins compared to BV. These data establish iRFP713/V256C and iRFP713/C15S/V256C assembled with the PCB chromophore as promising biomarkers for application in vivo. The analysis of the spectral properties of the tested biomarkers allowed for suggesting that the high-fluorescence quantum yield of the PCB chromophore can be attributed to the lower mobility of the D-ring of PCB compared to BV.
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45

Downare, Taggart D., et Oliver C. Mullins. « Visible and Near-Infrared Fluorescence of Crude Oils ». Applied Spectroscopy 49, no 6 (juin 1995) : 754–64. http://dx.doi.org/10.1366/0003702953964462.

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Fluorescence emission spectra and absolute quantum yields have been measured for ten diverse crude oils at various concentrations over a broad range of excitation and emission wavelengths in the visible and the near-infrared. Energy transfer produces large red shifts and large widths in the fluorescence emission spectra for shorter wavelength excitation particularly for heavier crude oils. However, the effects of energy transfer are nearly absent for near-infrared excitation; all crude oils exhibit nearly the same emission spectra for long wavelength excitation. In addition, the fraction of emission resulting from collisional energy transfer relative to nascent emission is almost independent of oil type; it is governed by quantum yield characteristics. Absolute fluorescence quantum yields of ten crude oils (and three rhodamine dyes for validation) were measured with respect to scattering of latex microspheres in distilled water. Fluorescence quantum yields vary systematically with crude oil type as well as excitation wavelength; quantum yields are lower for high fluorophore concentrations (heavy crude oils) and for longer wavelength excitation. Stern-Volmer analyses of the quantum yields indicate that simple models apply and show the relative quenching rates for different excitation wavelengths.
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46

Genty, B., et S. Meyer. « Quantitative Mapping of Leaf Photosynthesis Using Chlorophyll Fluorescence Imaging ». Functional Plant Biology 22, no 2 (1995) : 277. http://dx.doi.org/10.1071/pp9950277.

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A method has been developed for routine, non-invasive monitoring of the topography of leaf photochemistry. The method uses video images of leaf chlorophyll fluorescence, taken during steady-state photosynthesis and during a transitory saturation of photochemistry, to construct, pixel by pixel, an image of the photochemical yield of photosystem II (PSII). The photochemical yield of PSII was estimated according to Genty et al. (1989) (Biochimica et Biophysica Acta 990, 87-92). The effectiveness of the method was shown by mapping the heterogeneous distribution of photosynthetic activity after treatment with either a herbicide (DCMU), abscisic acid, or during the course of the induction of photosynthesis. Leaf CO2 assimilation was simultaneously monitored under non- photorespiratory conditions to estimate the average quantum yield of linear electron transport. A unique proportional relationship was found between the mean photochemical yield of PSII calculated from images of the photochemical yield of PSII, and the average quantum yield of linear electron transport in three plant species exposed to a wide range of treatments or conditions. This new ability to quantitatively visualise leaf photochemistry provides a powerful tool to probe the spatial distribution of leaf photosynthesis. Possible errors in estimating the photochemical yield of PSII from mean fluorescence measurements are discussed.
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47

Enoki, Masami, et Ryuzi Katoh. « Estimation of quantum yields of weak fluorescence from eosin Y dimers formed in aqueous solutions ». Photochemical & ; Photobiological Sciences 17, no 6 (2018) : 793–99. http://dx.doi.org/10.1039/c7pp00465f.

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48

Larsen, M. A. B., A. B. Stephansen, E. Alarousu, M. Pittelkow, O. F. Mohammed et T. I. Sølling. « Solvent-dependent dual fluorescence of the push–pull system 2-diethylamino-7-nitrofluorene ». Physical Chemistry Chemical Physics 20, no 8 (2018) : 5942–51. http://dx.doi.org/10.1039/c8cp00235e.

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49

Mahmoud, Sahar F., et Stephen E. Bialkowski. « Laser-Excited Fluorescence of Dityrosine ». Applied Spectroscopy 49, no 11 (novembre 1995) : 1669–76. http://dx.doi.org/10.1366/0003702953965678.

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In this research, laser-excited fluorescence was examined for sensitive detection of aqueous dityrosine. Samples were excited with a 6.3-mW, 325-nm helium-cadmium laser focused into a small volume-fluorescence cell with a 10-cm lens. The resulting fluorescence emission was collected perpendicular to the excitation and detected with two different schemes. An optical bandpass filter was used with a photomultiplier tube for sensitive quantitative measurement, while a photodiode array detector was used in conjunction with a spectrograph for qualitative characterization of fluorescence emission spectra. Dityrosine detection on the order of 2 × 10−11 M was obtained with the use of the photomultiplier tube with bandpass optical filter. The dityrosine fluorescence yield is found to vary with the solution pH, the relative concentrations of ferric and ferrous iron, and the amount of dissolved oxygen. A maximum fluorescence yield is observed for iron-free, oxygen-free alkaline solutions. Fluorescence quenching by oxygen is a cumulative photolysis effect that diminished fluorescence yield with increased irradiation time. Flowing the solutions minimized photolysis effects in oxygenated solutions. Quenching by ferrous and ferric iron is found to be due primarily to complex formation. The ferrous iron complex appears to have a fluorescence efficiency of ∼20% of the free dityrosine. The ferric iron dityrosine complex appears to have two ferric ions per molecule at low iron concentration. Other complexes may form at different concentrations. Solvent effects on dityrosine absorption and fluorescence spectra were also investigated. A red shift in dityrosine fluorescence maximum was observed in 1 M trichloroacetic acid and in N, N-dimethylformamide. The fluorescence emission maximum was shifted to the blue in acetonitrile and glacial acetic acid. These shifts were attributed to typical solvochromic behavior.
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Chen, Xuejuan, Xingguo Mo, Shi Hu et Suxia Liu. « Relationship between fluorescence yield and photochemical yield under water stress and intermediate light conditions ». Journal of Experimental Botany 70, no 1 (8 octobre 2018) : 301–13. http://dx.doi.org/10.1093/jxb/ery341.

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