Fluorescein Disodium Salt Research Articles

The Application of Fluorescence Anisotropy for Viscosity Measurements of Small Volume Biological Analytes.

Time-resolved fluorescence anisotropy has been extensively used to detect changes in bimolecular rotation associated with viscosity levels within cells and other solutions. Physiological alterations of the viscosity of biological fluids have been associated with numerous pathological causes. This current work serves as proof of concept for a method to measure viscosity changes in small analyte volumes representative of biological fluids. The fluorophores used in this study were fluorescein disodium salt and Enhanced Green Fluorescent Protein (EGFP). To assess the ability of the method to accurately detect viscosity values in small volume samples, we conducted measurements with 12 μL and 100 μL samples. No statistically significant changes in determined viscosities were recorded as a function of sample volume for either fluorescent probe. The anisotropy of both fluorescence probes was measured in low viscosity standards ranging from 1.02 to 1.31 cP, representative of physiological fluid values, and showed increasing rotational correlation times in response to increasing viscosity. We also showed that smaller fluid volumes can be diluted to accommodate available cuvette volume requirements without a loss in the accuracy of detecting discrete viscosity variations. Moreover, the ability of this technique to detect subtle viscosity changes in complex fluids similar to physiological ones was assessed by using fetal bovine serum (FBS) containing samples. The presence of FBS in the analytes did not alter the viscosity specific rotational correlation time of EGFP, indicating that this probe does not interact with the tested analyte components and is able to accurately reflect sample viscosity. We also showed that freeze-thaw cycles, reflective of the temperature-dependent processes that biological samples of interest could undergo from the time of collection to analyses, did not impact the viscosity measurements' accuracy. Overall, our data highlight the feasibility of using time-resolved fluorescence anisotropy for precise viscosity measurements in biological samples. This finding is relevant as it could potentially expand the use of this technique for in vitro diagnostic systems.

So similar yet so different: The distinct contributions of extrafascicular and fascicular phloem to transport and exudation in cucumber plants

Cucurbits have been used as phloem research models for many decades because their exudates can be accessed with ease. However, cucurbit plants possess two distinct phloem systems known as the fascicular phloem (FP) and extrafascicular phloem (EFP). Therefore, the molecular composition and function of certain exudates can be misinterpreted due to their unclear origin. To characterize the anatomy and function of the different phloem systems more clearly, we generated specific antibodies against marker proteins (PP1 homologs) allowing the clear identification of the EFP at the organ, tissue and cellular levels by immunological staining. We also used detailed microscopy to determine common and unique anatomical features of the FP and EFP sieve elements (SEs) in cucumber (Cucumis sativus). The comparison of exudation rates and the dynamic viscosity, density and sugar content of the exudates from plants grown in the light and dark revealed the consistent composition and behavior of the EFP exudate even when photosynthesis was prevented, thus differing from the properties of the FP exudate. Furthermore, the analysis of phloem transport using a fluorescein disodium salt showed only wound-induced exudation of dye from the EFP, indicating the absence of transport in this tissue. Our results show that it is important to distinguish between the EFP and FP in cucurbits, particularly their differing behaviors in response to wounding.

Использование флуоресценции при определении глубины просаливания крупнокускового цельномышечного мяса индейки

Introduction. Fluorescence is one of the most promising methods of food quality tests. Fluorescein disodium salt is used as a means of diagnostics in medicine and food production. In particular, fluorophore can determine the ripening stage of boneless turkey meat during brining by defining the penetration depth of the brine.
 Study objects and methods. The present research featured samples of brined turkey breast and thigh meat. The experiment was based on standard research methods, e.g. macro- and microscopy, statistical method, etc. It also included an original fluorescence method for determining the penetration depth of sodium chloride brine into turkey muscles.
 Results and discussion. The experimental brine consisted of food salt, white sugar, water, and fluorescein disodium salt, while brine without fluorophore served as control. Regardless of sodium chloride concentration, the changes in the ripening depth of the turkey breast samples were 8 times lower after 5 min, 3 times – after 12 h, and 4 times after 24 h. Complete ripening occurred after 36 h, which was confirmed by visual and fluorophore measurements. The thigh meat samples showed a smaller area of sodium chloride penetration: 8 times lower – after 5 min, 2 times – after 12 and 24 h. Complete salting was also registered after 36 h of brining.
 Conclusion. The fluorescence method proved quite effective in determining the ripening of boneless turkey parts meat.

Molecular Study of Ultrasound-Triggered Release of Fluorescein from Liposomes.

Several investigations have suggested that ultrasound triggers the release of drugs encapsulated into liposomes at acoustic pressures low enough to avoid cavitation or high hyperthermia. However, the mechanism leading to this triggered release as well as the adequate composition of the liposome membrane remains unknown. Here, we investigate the ultrasound-triggered release of fluorescein disodium salt encapsulated into liposomes made of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) or 1,2-distearoylphosphatidyl-ethanolamine (DSPC) lipids with various concentrations of cholesterol (from 0 to 44 mol %). The passive release of encapsulated fluorescein was first characterized. It was observed to be higher when the membrane is in a fluid phase and increased with temperature but decreased upon addition of cholesterol. Next, the release of fluorescein was measured at different acoustic frequencies (0.8, 1.1, and 3.3 MHz) and peak-to-peak pressures (0, 2, 2.5, 5, and 8 MPa). Measurements were performed at temperatures where DOPC and DSPC liposomes were, respectively, in the fluid or gel phase. We found that the release rate did not depend on the ultrasound frequency. For DOPC liposomes, the ultrasound-triggered release of fluorescein decreased with increasing concentration of cholesterol in liposomes, while the behavior was more complex for DSPC liposomes. Overall, the triggered release from DSPC liposomes was up to ten times less than DOPC liposomes. Molecular dynamics simulations performed on a pure DOPC membrane showed that a membrane experiences, under a directional pressure of ±2.4 MPa, various changes in properties such as the area per lipid (APL). An increase in the APL was notably observed when the simulation box was laterally stretched or perpendicularly compressed, which was accompanied by an increase in the number of water molecules crossing the membrane. This suggests that ultrasound most probably enhances the diffusion of encapsulated molecules at small acoustic pressures by increasing the distance between lipids.

A Miniature 3D Printed LED-Induced Fluorescence Detector for Capillary Electrophoresis and Dual-Detector Taylor Dispersion Analysis.

Taylor dispersion analysis (TDA) provides absolute determination of diffusion coefficients for analytes ranging from small molecules to particulate matter. TDA has seen a resurgence in recent years, as modern commercial capillary electrophoresis (CE) instrumentation is well equipped to meet the precision flow requirements of TDA. Discontinuous flow velocities, which occur during sample injection, can lead to substantial inaccuracies in single-point detection TDA. Dual-point detection allows TDA to be carried out under continuous flow in the volume between the detection points, but dual-point fluorescence detection has not previously been feasible within the confines of commercial CE instrumentation. Here, we describe a compact light-emitting diode (LED)-induced fluorescence detector designed for online, dual-point capillary detection within a commercial CE system. The three-dimensional (3D) printed detector houses an inexpensive LED excitation source, a bandpass excitation filter, an integral 3D printed pinhole collimator, and a ball lens, which collects fluorescence emission. Multivariate optimization of operating conditions yielded a detection limit of 613 ± 13 pM for CE of fluorescein disodium salt solution in borate buffer. The miniature size of the device allowed integration of two detectors within a commercial CE system without modification to the instrument, thereby enabling dual-detector assays including TDA and CE-TDA. Monitoring of the bioconjugation reaction between fluorescein isothiocyanate (FITC) and a model protein illustrates the utility of direct, calibration-free size determination, which enabled the resolution of fluorescence originating from free FITC from that of protein-bound FITC. TDA detection coupled to CE enabled the determination of peak identities without the need for standard solutions.

Highly luminescent sensing for nitrofurans and tetracyclines in water based on zeolitic imidazolate framework-8 incorporated with dyes

Antibiotics are one of the emerging contaminants in water, which have a great impact on ecosystems and human health. It has been challenging to simultaneously realize low-cost, rapid, highly sensitive and selective detection of antibiotics with conventional methods. Here, we report luminescent chemosensors for detecting antibiotics in water, based on metal-organic framework (MOF), i.e., zeolitic imidazolate framework-8 (ZIF-8), loaded with rhodamine B (RhB) and fluorescein disodium salt (FSS) dyes. Compared with ZIF-8, the fluorescence signals of RhB@ZIF-8 and FSS@ZIF-8 were significantly improved and presented ultrahigh sensitivity to nitrofurans (NFAs) and tetracyclines (TCs) with fluorescence quenching and fluorescence enhancement in water, respectively. The unique structures and properties of RhB@ZIF-8 and FSS@ZIF-8 lead to outstanding sensitivities in antibiotic detection. For instance, the RhB@ZIF-8 sensor shows the lower limit of detection (LOD) of 0.26 μM to nitrofurantoin (NFT), 0.47 μM to nitrofurazone (NFZ), 0.11 μM to tetracycline (TC), and 0.14 μM to oxytetracycline (OTC); while the FSS@ZIF-8 sensor shows the LOD of 0.31 μM to NFT, 0.35 μM to NFZ, 0.17 μM to TC, and 0.16 μM to OTC. In addition, NFT and TC were also successfully detected by FSS@ZIF-8 in water from real water environment. The results indicate that dye@MOF-based luminescent composites are favorable for antibiotic detection, presenting great potentials in water quality monitoring.

The construction of amorphous metal-organic cage-based solid for rapid dye adsorption and time-dependent dye separation from water

For the first time, an amorphous solid contains large cationic M12L24 metal–organic cage (MOC) based on Pd(II) and 3,5-di-pyridin-4-yl-benzaldehyde (L), namely aMOC-1, was constructed and characterized. Although it is an amorphous structure, regular cavity that created by MOC still exists in the solid and performs excellent dye adsorption and separation ability in water. The aMOC-1 can rapidly adsorb the anionic dyes including methyl orange (MO), fluorescein disodium salt (FS), acid fuchsin (AF) and methyl blue (MB) only in several minutes to about 30 min. The adsorption capacities for them are 359, 464, 116 and 150 mg/g, respectively. On the contrary, the adsorption rate of aMOC-1 towards cationic dyes is significantly slower than that of anionic dyes. The adsorption of cationic dyes shows a size-selectively behavior, in which the adsorption of rhodamine B (RhB) is more favorable than the other selected smaller or bigger cationic dyes. The adsorption capacity of RhB is up to 454 mg/g. According to the differences in the adsorption rates and capacities for different charged dyes, aMOC-1 displays diverse dye separation behaviors. It can selectively adsorb RhB from a mixed solution of MLB and RhB by size selectivity. Moreover, the selective separation of anionic and cationic dyes shows an interesting new time-dependence mode that the anionic dye can be selectively adsorbed from a mixed solution of anionic and cationic dyes by controlling the adsorption time. The good adsorption and separation performance of aMOC-1 is caused by the large cavity and the high positive Zeta potential of the material, which are created by the Pd12L24 metal-organic cages.

Mesoporous Hexanuclear Copper Cluster-Based Metal-Organic Framework with Highly Selective Adsorption of Gas and Organic Dye Molecules.

Despite many advances in the design and assembly of mesoporous metal-organic frameworks (meso-MOFs), it is still a challenge to obtain the desired structure. Here, we utilized an effective cluster cooperative assembly strategy by introducing SO42- ions as chelating binding sites to construct a novel mesoporous MOF, [Cu8(SO4)(TBA)6(OH)2( N,N-dimethylacetamide (DMA))4]·12DMA·12CH3OH [JLU-MOF51, H2TBA = 4-(1 H-tetrazol-5-yl)-benzoic acid]. Remarkably, the cooperative assembly of the infrequent hexanuclear [Cu6SO4(OH)2] cluster and the classical paddlewheel [Cu2(CO2)4] via linear hetero-N, O donor ligand results in an open three-dimensional framework, which possesses one-dimensional nanometer tube channels with the diameter of 24 and 28 Å. Fascinatingly, JLU-MOF51 displays an exceptionally large Langmuir surface area (5443 m2 g-1) and exhibits a high capacity for selective adsorption of C3H8 (C3H8: 348 cm3 g-1 at 273 K; C3H8/CH4 = 220 at 298 K). In addition, JLU-MOF51 can selectively adsorb fluorescein disodium salt dye among numerous organic dyes. An extremely high surface area and unique structural characteristics make JLU-MOF51 a promising meso-MOF material for the adsorption and separation of hydrocarbon gases and organic dyes. Moreover, this strategy will provide an effective means for constructing meso-MOFs via one-step synthesis.

Photophysics and photochemistry of mercurochrome in reverse micelles

Abstract The photophysics of the xanthene dye 2′,7′-Dibromo-5′-(hydroxymercurio)fluorescein disodium salt (merbromine, mercurochrome) (MCr) was studied in reverse micelles (RMs) of sodium 1,4-bis (2-ethylhexyl) sulfosuccinate (AOT) and benzylhexadecyldimethylammonium chloride (BHDC). In the reverse micellar media both the absorption and emission spectra of the dye present a red shift with respect to water. It is concluded that MCr in both reverse micellar systems is localized in the interface. In BHDC due to the positive charge at the interface and the negative charge of the dye, it remains anchored to the interface irrespective of the water content of the RMs. On the other hand in the case of the negative interface of AOT the photophysical properties tend to those in homogeneous water solution as the water content increases. For small size AOT RMs the dye resides in the interface co-micellizing with the surfactant, although more exposed to water than in the case of BHDC. Special interest was assigned to the effect of confinement on the triplet state properties. The triplet state decay kinetics and absorption spectra were determined by laser flash photolysis. The triplet lives longer in RMs than in homogeneous solvents. The compartmentalization of the dye precludes the auto-quenching which shorts the lifetime in homogeneous solvents. Furthermore, the quenching by electron donors and acceptors was investigated. Two aliphatic amines were used as electron donors. The hydrophilic triethanolamine (TEOA) is localized in the water pool, and the triplet quenching is more efficient than in homogeneous solvents. The apparent quenching rate constant for TEOA in AOT is one order of magnitude higher than BHDC. On the other hand the quenching by dipropylamine (DPA) which is located in the bulk organic solvent is much less efficient. The quenching by TEOA in RMs can be understood in terms of an exchange mechanism between micelles. As electron acceptor 1,4-benzoquinone (BQ) was employed, and the value in BHDC is two orders of magnitude higher than in AOT. These divergences most likely arise from different partitions of the quenchers in the reverse micellar systems.

Preconcentration of diluted biochemical samples using microchannel with integrated nanoscale Nafion membrane.

A microfluidic preconcentration device comprising a microchannel and a surface-patterned nanoscale Nafion membrane is proposed. Given the application of an electric field across the chip, the nanopore within Nafion membrane becomes ion selective due to an overlapping of the electric double layer. The resulting difference in flux of the co- and counter-ions within the membrane nanopore prompts the formation of a concentration gradient and leads to a gradual accumulation of the co-ions at the micro-nano junction. It is shown experimentally that the rate of concentration and the preconcentration factor both increase with an increasing electrical field intensity. The preconcentration performance in a straight microchannel is compared with that in a convergent microchannel using fluorescein disodium salt dehydrate and Fluorescein isothiocyanate (FITC)-labeled bovine serum albumin samples. The results show that the reduced cross-sectional area of the convergent microchannel increases the preconcentration factor compared to that obtained in a straight microchannel and yields a significant reduction in the preconcentration time.

Poly(propylene imine) dendrimer caps on mesoporous silica nanoparticles for redox-responsive release: smaller is better

To elucidate the importance of the size of capping agents in stimulus-induced release systems from mesoporous silica nanoparticles (MSNs), the effectiveness of poly(propylene imine) dendrimers in controlling the model drug release was studied. MCM-41-type MSNs were synthesized and characterized. Fluorescent compounds (fluorescein disodium salt and carboxyfluorescein) were loaded in the porous structure of the MSNs and entrapped in the silica matrix with the dendrimers of generations I through V by anchoring dendrimers on the MSN surface through disulfide bonds. Stimulus-induced release of the cargo was studied in the presence of dithiothreitol (DTT). Dendrimers of generations I and II were found to be more effective in model drug retention and subsequent release than higher generations. Moreover, MSNs modified with larger amounts of dendrimers lowered the cargo release in the presence of DTT. These findings are of importance for optimizing drug delivery systems based on responsive MSNs as they enable tuning of the amount of the released cargo by choosing the capping agent of appropriate size.

Non-emissive plastic colour filters for fluorescence detection

We report the fabrication of non-emissive short- and long-pass filters on plastic for high sensitivity fluorescence detection. The filters were prepared by overnight immersion of titania-coated polyethylene terephthalate (PET) in an appropriate dye solution - xylene cyanol for short-pass filtering and fluorescein disodium salt for long-pass filtering - followed by repeated washing to remove excess dye. The interface between the titania and the dye molecule induces efficient quenching of photo-generated excitons in the dye molecule, reducing auto-fluorescence to negligible values and so overcoming the principal weakness of conventional colour filters. Using the filters in conjunction with a 505 nm cyan light-emitting diode and a Si photodiode, dose-response measurements were made for T8661 Transfluosphere beads in the concentration range 1 × 10(9) to 1 × 10(5) beads μL(-1), yielding a limit of detection of 3 × 10(4) beads μL(-1). The LED/short-pass filter/T8661/long-pass filter/Si-photodiode combination reported here offers an attractive solution for sensitive, low cost fluorescence detection that is readily applicable to a wide range of bead-based immunodiagnostic assays.

Surface Uptake and Intercalation of Fluorescein Anions into Zn−Al−Hydrotalcite. Photophysical Characterization of Materials Obtained

The xanthene dye fluorescein was immobilized, via anion-exchange reactions, in the interlayer region and/or on the surface of a synthetic Zn−Al hydrotalcite, prepared by the thermal hydrolysis of urea. Surface uptake was investigated by equilibrating [Zn0.67Al0.33(OH)2] [CO3]0.165 0.4 H2O with diluted solutions of fluorescein disodium salt. Only carbonates present on the surface of microcrystals were exchanged by fluoresceinate anions to reach a maximum uptake of 50 μmol/g. Intercalation compounds were obtained by equilibrating the perchlorate form of hydrotalcite [Zn0.67Al0.33(OH)2] [ClO4]0.33 0.6 H2O (interlayer distance 11.0 A) with 10-2 mol/dm3 fluorescein disodium salt solution. Intercalation of fluoresceinate anions occurs with a first-order phase transition from the ClO4- phase to a phase containing 0.11 mol of fluoresceinate per mol of the host and an interlayer distance of 16.5 A. The materials were characterized by chemical and thermal analysis and by X-ray powder diffraction and FT-IR technique...

Thermal transitions of poly(vinyl alcohol) hydrogel sensed by a fluorescent probe

Fluorescence from the fluorescein molecule has been used to study of phase transition processes in five poly(vinyl alcohol) (PVA) hydrogels in the temperature range 75–350 K. These hydrogels were prepared with PVA with molecular weight = 124,000–186,000, 99+% hydrolyzed, by repeated freezing–thawing cycles in five compositions: 9.9, 11.1, 13.3, 16.5, and 20.9 PVA w/w %. Plots of total fluorescence intensity versus temperature, normalized with the fluorescence signal at 75 K, and of the emission wavelength maximum versus temperature indicated that the dynamic of the guest deactivation was dependent on the hydrogel thermal transitions. These thermal transition processes were compared to three model systems: uranine (fluorescein di-sodium salt) in water, fluorescein in water/ethanol (85%/15% v/v), and fluorescein/PVA homopolymer. Small spectral shifts were obtained for these model systems over the entire temperature range attributed to the hot band effect. Nevertheless, larger spectral shifts were obtained for hydrogels, indicating that shifts of the chemical dissociation equilibrium was occurring in this last case. Slope changes of both intensity and wavelength maximum plots versus temperature occurred at the same temperature values, and we attributed the onset of the hydrogel thermal transition as the sol–gel transition occurring at T ≅ 370 K; at 320 K we observed the glass transition temperature of PVA plasticized by water molecules; at T ≅ 240 ± 5 K we attributed the melting point of water molecules bonded to the PVA chains (freezable bond molecules); at T ≅ 270 ± 5 K we observed the melting point of free water molecules (bulk water); and, at 135–145 K the water glass transition. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 815–824, 2000

Mercurochrom can be used for the histochemical demonstration and microphotometric quantitation of both protein thiols and protein (mixed) disulfides.

Mercurochrom [2,7-dibromo-4-(hydroxymercuri)-fluorescein disodium salt] used for staining of protein thiols in addition binds to other groups of proteins. Experimental evidence is provided that mercurochrom bound to non-thiol groups forms a 1:1 adduct with protein (mixed) disulfides. The disulfide contents of three different types of cells determined biochemically correlated with the corresponding mean integrated optical densities determined microphotometrically after mercurochrom staining of groups other than thiols. Intracellular disulfide exchange has been studied, leading to a transformation of protein mixed disulfides to protein disulfides and an equimolar loss of protein thiols. Protein mixed disulfides were generated from protein thiols using both methyl methanethiosulfonate (MMTS) and 2,2'-dihydroxy-6,6'-dinaphthyldisulfide (DDD). Loss of thiols as well as the equimolar increase of protein mixed disulfides were followed using both mercurochrom staining for thiols and for disulfides. Generation of protein mixed disulfides due to the DDD reaction was also followed by azocoupling with Fast blue B. On the basis of the observed stoichiometry between the loss of protein thiols and the quantity, increase or conversion of protein disulfides determined microphotometrically using both mercurochrom staining and DDD Fast blue B staining, we conclude that: (1) 1 mol of mercurochrom is bound per mol of protein (mixed) disulfide; and (2) the molar absorptivity of mercurochrom bound to disulfides is epsilon 520 = 34940. This study demonstrates that mercurochrom can be used for the quantitative determination of the oxidative status of protein thiols in cells.

Effect of β-cyclodextrin on the fluorescence, absorption and lasing of rhodamine 6G, rhodamine B and fluorescein disodium salt in aqueous solutions

The fluorescence, absorption and lasing of three xanthene dyes, rhodamine 6G, rhodamine B and the disodium salt of fluorescein were examined in aqueous solutions with and without added β-cyclodextrin. β-cyclodextrin enhances both fluorescence and lasing for all three dyes in concentrated (10 −3 M) aqueous dye solutions. In dilute (10 −5 to 10 −8 M) aqueous dye solutions, β-cyclodextrin can induce either enhancement or quenching of fluorescence and absorption depending on the nature and concentration of the dye. Deaggregation in concentrated solutions and variable complex formation in dilute solutions are proposed to account for the β-cyclodextrin-induced effects.

Photoelectron microscopy and photoelectron quantum yields of the fluorescent dyes flourescein and rhodamine

Photoelectric properties of the dyes fluorescein and rhodamine were determined with the aim of assessing the usefulness of these compounds as labels in photoelectron microscopy. The photoelectron quantum yields were measured over the wavelength range 180–230 nm. At 230 nm the quantum yields for fluorescein disodium salt, rhodamine B free base and rhodamine B HCl salt are approximately 10 -5 electrons per incident photon. At 180nm these values rise to approximately 10 -3 electrons per incident photon. All forms of fluorescein do not have the same quantum yield. The neutral form of fluorescein has a quantum yield an order of magnitude lower than the disodium salt. Beam current measurements were performed on labeled and unlabeled proteins to determine the effect of the high light intensity employed in the photoelectron microscope. The initial beam current measurements and the quantum yield curves are consistent and demonstrate that there is significant contrast between labeled and unlabeled proteins. However, after several minutes in the photoelectron microscope, the proteins become more photoemissive and the contrast diminishes. This change in contrast explains several puzzling observations in the literature.

Gain studies on a uranine-damc dye mixture laser under nitrogen laser pumping

The radiative and Forster type of energy transfer processes in a dye mixture laser of 7-diethylamino-4-methyl coumarin (donor) and fluorescein disodium salt (acceptor) under nitrogen laser pumping were investigated. The Forster transfer rate calculated from the absorption and emission spectra of acceptor and donor is 1.3 × 10 11 liter mole −1 sec −1. The gain of acceptor at 550 nm was measured for acceptor concentrations N A from 10 −3 M to 3 × 10 −3 M for a fixed ratio F = 1 of donor to acceptor concentrations at different pump powers. The results agreed with the rate equation model proposed for the dye mixture laser. The radiative rate constant calculated from these results is 3.1 × 10 10 liter mole −1 sec −1. Numerical simulation of the rate equations showed that the acceptor reaches peak emission with a time lag of 3 ns with respect to the donor peak emission for F = 0.998, N A = 10 −5 M. This time lag decreases with increasing N A and becomes zero for N A = 10 −1 M, F = 0.048.

Effect of pH on dye-laser output power

Experiments have been performed to measure the output power of stimulated emission from acidified or basified solutions of xanthene dyes pumped by a N2 laser. The results showed the laser output power was improved for rhodamine 6G, rhodamine B, pyronin B, fluorescein disodium salt, and fluorescein dipotassium salt by factors of 2.2, 2.8, 1.7, 26.7, and 8.6, respectively.

Intersystem crossing rates and saturation parameters in the triplet state for rhodamine, fluorescein, and acridine dyes

The saturation of the population in the triplet state T1 using a laser excitation ESR technique was observed directly at 77 K. The saturation parameters Isat and the singlet-to-triplet intersystem crossing rate kST were determined for acridine red (AO), rhodamine S (RS), rhodamine B (RB), rhodamine 6G (R6G), fluorescein disodium salt (FDS), 2′,7′-dichlorofluorescein (DF), eosin Y (EY), eosin B (EB), acridine orange (AR), and acridine yellow (AY) in rigid ethanolic solutions. On the basis of the results, the intersystem crossing mechanisims of rhodamine (type R), fluorescein (type F), and acridine (type A) types of the ten dyes are discussed.