Absorption behaviour of methanolic rhodamine 6G solutions at high concentration

Lu, Yutian; Penzkofer, Alfons

doi:10.1016/0301-0104(86)85002-9

Cited by 114 publications

(61 citation statements)

References 36 publications

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“…Dimerization leads to a red shift of the fluorescence emission, and thus it is possible to°follow°the°dimer°formation°as°a°function°of°concen-tration°in°solution°(Figure°4). The°inset°of°Figure°4°shows°the°maximum°emission wavelength of RBS solutions in acetonitrile at different concentrations up to 1 mM, which is close to the maximum solubility for this type of molecule in organic solvents° [33].°The°maximum°emission°wavelength°shifts from 570 nm at 100 M to almost 598 nm at 1 mM and above. Fluorescence measurements at such high concentrations°in°solution°required°the°use°of°a°special low-volume capillary cuvette to avoid inner filter effects that would otherwise lead to reabsorption of fluorescence°photons° [34].°Plotting°the°maximum°emis-sion wavelength versus the concentration in a logarithmic plot yields a sigmoidic curve.…”

Section: Resultsmentioning

confidence: 63%

Shrinking droplets in electrospray ionization and their influence on chemical equilibria

Wortmann

Kistler-Momotova

Zenobi

et al. 2007

J. Am. Soc. Mass Spectrom.

113

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We investigated how chemical equilibria are affected by the electrospray process, using simultaneous in situ measurements by laser-induced fluorescence (LIF) and phase Doppler anemometry (PDA). The motivation for this study was the increasing number of publications in which electrospray ionization mass spectrometry is used for binding constant determination. The PDA was used to monitor droplet size and velocity, whereas LIF was used to monitor fluorescent analytes within the electrospray droplets. Using acetonitrile as solvent, we found an average initial droplet diameter of 10 m in the electrospray. The PDA allowed us to follow the evolution of these droplets down to a size of 1 m. Rhodamine B-sulfonylchloride was used as a fluorescent analyte within the electrospray. By spatially resolved LIF it was possible to probe the dimerization equilibrium of this dye. Measurements at different spray positions showed no influence of the decreasing droplet size on the monomer-dimer equilibrium. However, with the fluorescent dye pair DCM and oxazine 1 it was shown that a concentration increase does occur within electrosprayed droplets, using fluorescence resonance energy transfer as a probe for the average pair distance. ( An important aspect of the highly dynamic electrospray process concerns the shrinking droplets. After the droplet creation, solvent evaporation and Coulomb explosions lead to a decrease of droplet size until all solvent has evaporated and the final desolvated and ionized analytes are produced. A decrease of droplet size resulting from solvent evaporation will lead to a concentration increase of nonvolatile analytes within the droplets. For dissolved species that participate in a chemical equilibrium, such as free and bound states of partners that can form a noncovalent complex, the question arises whether the increasing concentrations affect the equilibrium position. Given that binding constant determination with ESI-MS usually relies on measuring the relative amounts of free and bound species, a perturbation of the equilibrium introduced by the shrinking droplets would influence the results of such an experiment. Recent studies show that the time between droplet creation and production of desolvated ions in ESI is within milliseconds [5]. In other words, if the association and dissociation reactions are fast, an equilibrium should be able to track a concentration increase within the droplets.The shrinking droplet volume also leads to Coulomb explosions/droplet fission, when the mutual repulsion of charges is high enough to overcome the surface tension of the droplet. The parent droplet ejects several smaller offspring droplets, which together carry 10 -25% of the charge, but only about 5% of the mass of the original droplet [9]. These offspring droplets then segregate within the electrospray, as shown theoretically by Wilhelm et al. [10]. Analytes will not generally be evenly distributed between the parent and offspring droplets. Partitioning processes, which have been investigated by several research g...

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Section: Resultsmentioning

confidence: 63%

Shrinking droplets in electrospray ionization and their influence on chemical equilibria

Wortmann

Kistler-Momotova

Zenobi

et al. 2007

J. Am. Soc. Mass Spectrom.

113

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“…The formation af aggregates as dimers [12], closely spaced pairs [13] and higher oligomers [12,14,15] is mainly studied by analyzing absorption changes.…”

Section: Introductionmentioning

confidence: 99%

“…For rhodamine 6G in methanol and water the absorption behaviour of highly concentrated solutions was studied in [13,16]. Rhodamine 6G in water forms stable ground-state dimers [16].…”

Section: Introductionmentioning

confidence: 99%

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Fluorescence behaviour of highly concentrated rhodamine 6G solutions

Penzkofer

Leupacher

1987

Journal of Luminescence

Self Cite

242

126

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“…The ratio of the absorption cross sections of the vibronic shoulder to the absorption peak is increased in the closely spaced pairs [a A?D (510 nm)/a AD (542 nm) = 0.48; a AM (508 nm)/a AJVI (540 nm) = 0.28]. The enlarged absorption of the vibronic shoulder compared to the absorption peak indicates a slightly larger Franck-Condon shift (difference in equilibrium position between S x state and S 0 state) of the closely spaced pairs compared to the monomers [7,10,[25][26][27].…”

Section: E(\mentioning

confidence: 99%