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ABSTRACT: New BODIPY dyes with two 4-formylphenyl, 4-(2,2-dimethoxycarbonylvinyl)phenyl and 4-(2,2-dicyanovinyl)phenyl groups at the 3- and 5-positions have been successfully designed and synthesized via palladium-catalyzed coupling reaction or Knoevenagel-type condensations. Structural modification of the BODIPY core via conjugation-extending residues significantly affects the spectroscopy and photophysical properties of the BODIPY fluorophore. These substituents cause the largest bathochromic shift in both absorption and emission spectra, which are shifted toward the red compared to its 4-phenylsubstituted analogue. Additionally, the fluorescence quantum yields and the Stokes shifts are also significantly higher than the corresponding phenyl-substituted dye. New BODIPY dyes have a high laser photostability, superior to that of commercial dyes with laser emission in the same spectral region, such as Perylene Red and Rhodamine 640. The substitution introduced in these derivatives allows to obtain tunable laser emission with a bandwidth of 0.15 cm(-1) and a tuning range of up to 50 nm. So with these three dyes it is possible to cover the spectral range 590-680 nm in a continuous way and with stable laser emission and small linewidth.
Physical Chemistry Chemical Physics 07/2010; 12(28):7804-11. · 3.57 Impact Factor
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ABSTRACT: Absorption and fluorescence spectroscopies with linearly polarized light are applied to study the anisotropic behavior of
a fluorescence dye (rhodamine 6G, R6G) adsorbed in ordered clay (laponite, Lap) particles. Films elaborated by the spin-coating
technique provide a parallel stacking of clay layers in the supported substrates. The posterior intercalation of the R6G molecules
into the interlayer space of Lap films with a preferential orientation with respect to the normal to the clay layers gives
rise to a macroscopic orientation of dye molecules into the 2D surfaces. Such an organization induces an anisotropic behavior
with a photoresponse of dye/clay films to the plane of the polarized light. A mathematic procedure, based on the evolution
of the fluorescence anisotropy with the twisting angle of the films with respect to the excitation light, is used to evaluate
the preferential orientation of R6G molecules in Lap films. The fluorescence method can be extended to study the preferential
orientation of fluorescent molecules adsorbed in any organized rigid 2D system.
KeywordsFluorescence Anisotropy-Fluorescence Dyes-Organized 2D Systems-Rhodamine 6G-Clay Films-Absorption with Polarized Light
01/2010: pages 1-35;
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ABSTRACT: New tailormade BODIPY dyes have been synthesized by a simple protocol to reach wavelength finely tunable laser action from 540 to 625 nm while maintaining highly efficient and photostable laser emission. The new dyes are analogues of the commercial dye PM597 with the eight position free (PTH8) or substituted by the groups acetoxymethyl (PTAlk) or p-acetoxymethylphenyl (PTAr). The photophysical properties strongly depend on the geometrical distortion from planarity of the indacene core generated by the presence of the bulky 2,6-di-tert-butyl groups and the eight substituent. In both liquid and polymeric solid solutions, lasing efficiencies of up to 63 and 48%, respectively, were observed under transversal pumping at 532 nm with high photostabilities. In the case of PTAlk incorporated into silicon-containing solid organic matrices, the laser emission remained at 92% of its initial intensity value after 100,000 pumping pulses in the same position of the sample at 30 Hz repetition rate. The laser action of the new dyes enhances that of the parent dye PM597 and outperforms the lasing behavior of dyes considered to be benchmarks over the green-yellow to red spectral region.
The Journal of Physical Chemistry A 07/2009; 113(28):8118-24. · 2.95 Impact Factor
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ABSTRACT: The photophysical properties of multichromophoric dyes with borondipyrromethene (BODIPY) and poly- p-phenylene (di- p-phenylene and tri- p-phenylene) groups in the same molecule are studied in detail. The excitation of the polyphenylene moiety in the UV region leads to a strong visible fluorescent emission of the BODIPY chromophore, via intramolecular excitation energy transfer between both groups. Consequently, these multichromophoric dyes are characterized by a large "virtual" Stokes shift, with a high fluorescence capacity and an efficient laser emission. On the other hand, the photophysical properties of a related dichromophoric dye with a hydroxy end group at the di- p-phenylene moiety show an important decrease in the fluorescent emission due to a photoinduced electron transfer process in basic media. Therefore, its photophysical properties are sensitive to the environmental acidity/basicity and could be applied as a proton sensor.
The Journal of Physical Chemistry A 11/2008; 112(43):10816-22. · 2.95 Impact Factor
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ABSTRACT: In our search for efficient and photostable laser dyes, four new dyes with the basic structure of the commercial BODIPY laser dye PM567, with either an 8-diphenylene or an 8-p-triphenylene group, both substituted at the terminal polyphenylene position with an acetoxymethyl (dyes P2Ar1Ac and P3Ar1Ac, respectively) or a methacryloyloxymethyl group (dyes P2Ar1MA and P3Ar1MA, respectively), have been synthesized. The photophysical and lasing properties of the dyes have been studied both dissolved in liquid solvents (acetoxymethyl dyes) and incorporated into solid polymeric matrices, in the latter case as solutions (acetoxymethyl dyes) or as copolymers with methyl methacrylate (methacryloyloxymethyl dyes). In liquid solution, the photophysics of P2Ar1Ac and P3Ar1Ac is scarcely affected by the number (two or three) of p-phenylene units. Quantum mechanical calculations reveal that the p-phenylene units in these dyes are twisted ca. 37 degrees each other, an that the first 8-p-phenylene group stands nearly perpendicular to the aromatic BODIPY plane, resulting in electronic decoupling of the two chromophores. P2Ar1Ac exhibits a somewhat lower photodegradation quantum yield under UV and visible irradiation, if compared with P3Ar1Ac or with PM567, likely because of its also lower rate constant for the reaction with in situ-generated singlet molecular oxygen. Both acetoxymethyl dyes emit laser radiation in solution in all the solvents tried, under transversal pumping at 532 nm. In ethyl acetate, with a dye concentration of 0.80 x 10(-3) M, laser efficiencies as high as 80% have been observed. When the 8-polyphenylene dyes were incorporated into solid poly(methyl methacrylate) (PMMA) matrices, as solutions or as copolymers, the fluorescence emission increased with respect to that of the parent PM567 dye dissolved in the same matrix, and lasing efficiencies in the range 18-31% were obtained, with good photostability. The dye P2Ar1Ac dissolved in PMMA was found to exhibit the best overall laser behavior, with a good balance between efficiency and photostability.
Photochemical and Photobiological Sciences 08/2008; 7(7):802-13. · 2.58 Impact Factor
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ABSTRACT: The absorption and fluorescence properties of rhodamine 6G (R6G) in organophilic laponite (Lap) clay films are studied. For this purpose, organo-Lap clays are synthesized by the incorporation of dodecyltrimethylammonium (C12TMA) as surfactant into the interlayer space of Lap clays. Two organo-Lap clays are prepared: one with moderate surfactant content (around 70% of the total cation-exchange capacity (CEC) of the clay) and a second with a high surfactant loading (about 130% CEC). Supported films are elaborated by the spin-coating technique and characterized by several techniques such as atomic force microscopy, elemental CHN analysis, X-ray diffraction, and thermogravimetry. IR spectroscopy reveals that the intercalation of R6G into organo-Lap films takes place at the detriment of the adsorbed C12TMA molecules. The photophysical properties of R6G monomers in the interlayer space of Lap films are improved by the presence of surfactant molecules. Moreover, organophilic environments can reduce the dye aggregation and favor the formation of fluorescent J-type aggregates, enhancing the fluorescence ability of dye/clay films with high dye contents. This improvement depends on the surfactant content.
Journal of Colloid and Interface Science 06/2008; 321(1):212-9. · 3.07 Impact Factor
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ABSTRACT: The structural, electronic and photophysical properties of three new asymmetric, highly fluorescent difluoroborondipyrromethene (BODIPY) dyes, bearing an amino or an acetamido group at position 3 of the chromophoric core, have been studied in different apolar, polar and polar/protic solvents. The presence of the 3-amido group extents the delocalization of the pi-system, leading to bathochromic shifts in the absorption and fluorescence bands, as predicted by quantum mechanic calculations. The 3-amino dye shows photophysical properties highly dependent on the solvent polarity and acidity, and is characterized by a hypsochromic shift of its absorption band, with regard to the corresponding acetylated dye, as well as a low fluorescence quantum yield in acid media with proton concentration lower than 4 x 10(-4) M. In media with higher proton concentration, the BF(2) bridge group of the 3-amino dye is removed, yielding the corresponding non-fluorescent dipyrromethene precursor. These results suggest that the 3-amino dye could be used as a fluorescence probe for the study of the acidity of different environments.
Journal of Fluorescence 04/2008; 18(5):899-907. · 2.11 Impact Factor
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ABSTRACT: We report on the synthesis and photophysical and lasing properties of new linear and cross-linked fluorinated polymeric materials doped with two BODIPY chromophores such as PM567 and PM597. The total fluorine content of the matrixes was varied adding to methyl methacrylate (MMA) different volumetric proportions of monomers with increased number of fluorine atoms: 2,2,2-trifluoromethyl methacrylate, 2,2,3,3,3,-pentafluoropropyl methacrylate (PFMA), and 2,2,3,3,4,4,4-heptafluorobutyl methacrylate. The rigidity of the materials was modified adding to PFMA di-, tri-, and tetra-functionalized comonomers such as ethyleneglycol dimethacrylate, pentaerythritol triacrylate, and pentaerythritol tetraacrylate. When the fluorine-modified organic matrixes were transversally pumped at 532 nm, highly stable laser operation with high, not-optimized efficiencies up to 42% was obtained. The highest photostability was recorded for PM597 doped MMA/PFMA 70/30 linear matrix, with no sign of degradation in the laser output after 500 000 pump pulses at 30 Hz, corresponding to an accumulated pump energy of 12 300 GJ/mol. The laser action depended more on the composition of the fluorinated comonomer than on the actual fluorine content with respect to the total weight of the matrix. Narrow line width operation with tuning ranges of up to 37 nm was obtained with both pyrromethene dyes when some of the samples were incorporated into a grazing incidence grating oscillator. Good correlations between the photophysical properties and the lasing behavior have been observed. The remarkable improvement in photostability exhibited by the fluorine-modified organic hold promise in the development of industrial oriented laser applications of organic solid-state materials.
12/2006;
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ABSTRACT: X-ray diffraction and Vis-absorption spectroscopy with linearly polarized light are used to determine the orientation of rhodamine 6G (R6G) dye in the interlayer space of supported films of Laponite B (Lap) clay with different dye loadings. XRD profiles suggest that the d001 interlayer space increases with the relative amount of dye in the clay surface, probably due to a more perpendicular disposition of the adsorbed molecules with respect to the clay layers in high dye content films. This orientation reduces the covering area per adsorbed molecule, providing a more compact and packed arrangement of the dye molecules. This is confirmed by linearly polarized absorption spectra, from which the orientation angle of the adsorbed molecules with respect to the clay layer can be evaluated. Indeed, R6G/Lap supported films present an anisotropy effect and, depending on the dye loadings, different evolutions of the dichroic ratio with the twisted δ angle between the normal to the film and the incident beam are observed. For very diluted R6G/Lap films, the R6G monomers adopt an inclined disposition of around 62° with respect to the film normal. Increasing the loadings, dimer, and higher-order aggregates of R6G can be disposed in two preferential orientations: an inclined angle of around 60°, common in all loading samples, favors long-displaced coplanar aggregates, characterized by an absorption J-band, and a second more perpendicular disposition of the monomer units as the dye content is increased leading to short-displaced coplanar aggregates, identified by an absorption H-band.
07/2005;
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ABSTRACT: The photoluminescence response of Rhodamine 6G (R6G) laser dye intercalated into solid thin films of Laponite (Lap) clay is studied as a function of dye loading. Fluorescence spectroscopy (steady-state and time-resolved techniques) was used to characterize the R6G species adsorbed into the solid films. For very diluted R6G loadings (</=0.1% CEC, i.e., the percentage of the total cation exchange capacity of Lap) the fluorescence properties of R6G monomer were characterized, which presents an emission band centered at 548 nm, an average lifetime of 4.2 ns, and a fluorescence efficiency higher than that of the R6G monomer in liquid solution. By increasing the loading, dye molecules tend to self-aggregate, and different dimers are formed in moderate dye concentrations (in the 1-25% CEC range): oblique head-to tail J-type dimers, with weak emission bands at around 575 nm; and sandwich H-type dimers, as efficient quenchers of the fluorescent emission. Higher-order aggregates of R6G in Lap films are formed in high loading samples (>40% CEC), with a reminiscent fluorescence band at around 600 nm.
The Journal of Physical Chemistry B 04/2005; 109(15):7443-50. · 3.70 Impact Factor
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International Reviews in Physical Chemistry 04/2005; 24(2):339-374. · 5.97 Impact Factor
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ABSTRACT: Absorption and fluorescence (steady-state and time-correlated) techniques are used to study the photophysical characteristics of the pyrromethene 650 (PM650) dye. The presence of the cyano group at the 8 position considerably shifts the absorption and fluorescence bands to lower energies with respect to other related pyrromethene dyes; this is attributed to the strong electron-acceptor character of the cyano group, as is theoretically confirmed by quantum mechanical methods. The fluorescence properties of PM650 are intensively solvent-dependent. The fluorescence band is shifted to lower energies in polar/protic solutions, and the evolution of the corresponding wavelength with the solvent is analysed by a multicomponent linear regression. The fluorescence quantum yield and the lifetime strongly decrease in polar/protic solvents, which can be ascribed to an extra nonradiative deactivation, via an intramolecular charge-transfer state (ICT state), favoured in polar media.
ChemPhysChem 12/2004; 5(11):1762-71. · 3.41 Impact Factor
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ABSTRACT: The morphology of thin films of Laponite (Lap) clay elaborated by the evaporation method and spin-coating technique was analyzed by atomic force microscopy and scanning electron microscopy, indicating a better quality film for the latter procedure. Rhodamine 6G (R6G) laser dye was intercalated into these films by ion exchange mechanism, performed by immersing the clay film into adequate dye solutions in which the effect of the dye concentration, immersion time, and nature of the solvent on the adsorption process were checked. The adsorption of R6G at the interlayer space of Lap was analyzed by the X-ray diffraction technique, and the presence of several R6G species (monomers and aggregates) was characterized by absorption and fluorescence spectroscopies. Less viscous solvents lead to higher dye loadings, suggesting a diffusional process for the intercalation of the dye in the interlayer spaces of Lap, and polar solvents favor the swellability of the interlayer space giving rise to a more homogeneous distribution of R6G molecules through the film and decreasing the dye aggregation. With the aging of the samples, the dye molecules can migrate through the interlayer spaces, leading to a more expanded distribution of R6G molecules and to the dye deaggregation.
Langmuir 08/2004; 20(14):5709-17. · 4.19 Impact Factor
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ABSTRACT: UV−vis absorption spectroscopy and fluorescence (steady-state and time-resolved) techniques were used to study the photophysical properties of the pyrromethene 597 (PM597) dye in several solvents, which include a wide range of apolar, polar, and protic media. This dye presents a lower fluorescence quantum yield than the well-known PM567 dye because of an increase in the nonradiative deactivation rate constant. This is attributed to a loss of planarity in the excited state provided by the steric hindrance of the tert-butyl groups at positions 2 and 6 of the chromophore core. Such a geometrical change in the excited state leads to an important Stokes shift, reducing the reabsorption and reemission effects in the detected emission in highly concentrated dye solutions. The highest fluorescence quantum yield of PM597 is observed in polar media.
06/2004;
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ABSTRACT: The photophysical, lasing and thermostability properties of newly synthesized analogs of the commercial dye pyrromethene 567 (PM567) have been measured in polymeric matrices of poly(methyl methacrylate) both when used as a dopant and when covalently bounded to the polymeric chain. These analogs have an acetoxy or a polymerizable methacryloyloxy group at the end of a polymethylene chain at Position 8 of the PM567 chromophore core. Clear correlations between photophysical and lasing characteristics are observed. Linking chain lengths with three or more methylene units give the highest fluorescence quantum yields (as high as 0.89) and lasing efficiencies (as high as 41%). The covalent linkage of the chromophore to the polymeric chain via the methacryloyloxy group improves the photostability of the PM567 chromophore.
Photochemistry and Photobiology 08/2003; 78(1):30-6. · 2.41 Impact Factor
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ABSTRACT: The adsorption of Rhodamine 3B (R3B) molecules in Wyoming Montmorillonite (Mont) particles suspended in water was studied by electronic absorption spectroscopy. Several adsorbed R3B species in the Mont tactoids were characterized from the observed changes in the absorption spectra by increasing the relative dye/clay concentration and the stirring time of the samples. R3B molecules can be adsorbed as monomeric units both in the water/clay interface and in the interlayer space, and head-to-tail R3B dimers and trimers were present in the external surface of Mont. The formation of internally adsorbed R3B monomers by the migration of the externally adsorbed species to the interlayer space leads to the deaggregation of the dye molecules in the external surface.
Journal of Colloid and Interface Science 03/2002; 246(2):281-7. · 3.07 Impact Factor
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ABSTRACT: The effect of increasing the rigidity of the host matrix by controlled crosslinking of the polymeric chains on the lasing
and photophysical properties of pyrromethene 567 (PM567) was evaluated. To this end, the dye was dissolved in 2,2,2-trifluoromethyl
methacrylate (TFMA) together with different amounts of the crosslinking monomer ethylene glycol dimethacrylate (EGDMA). Increasing
the concentration of this crosslinker monomer resulted in significant increases in both lasing efficiency and photostability.
Good correlation between fluorescence and lasing properties has been observed, indicating the existence of an optimum degree
of crosslinking for which lasing efficiency and photostabilty reach their highest values. These new solid materials show lasing
efficiencies up to 18% when transversely pumped at 534nm and good photostabilities, with a decrease in the initial laser
output of 45% after 10000 pump pulses.
Applied Physics B 06/2001; 73(1):19-24. · 2.19 Impact Factor
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ABSTRACT: The adsorption of the cationic dye rhodamine 3B in the clay hectorite is studied using electronic absorption and fluorescence emission spectroscopy. The results show the presence of various dye monomers, dimers, and higher aggregates and their interconversion subject to variations in loadings and stirring times. The growth of metachromasy related to generation of dye aggregates is interpreted with the help of exciton theory. Dimers are found to be J-type aggregates whose geometrical parameters are deduced. In some conditions the increase of stirring time leads to a loss of metachromasy that is related to the dye deaggregation. All the observations are interpreted in terms of stacking of clay platelets containing bound monomeric dye to form tactoids followed by dye migration within the large internal framework of the tactoids.
11/1999;
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ABSTRACT: Electronic absorption and fluorescence spectroscopies are applied to study the adsorption of rhodamine 3B dye on Laponite particles in aqueous suspensions. The adsorption on the clay favors the aggregation of the dye. The monomer and aggregates of rhodamine 3B can be adsorbed on both the external and the internal surfaces of Laponite, and their presence depends on the loading of the dye on the clay and the aging of the samples. The aggregation in the interlamellar space leads to the dimer and the trimer (or higher aggregates) of rhodamine 3B with a head-to-tail geometry. The comparison of the present results with those previously reported for the rhodamine 6G/Laponite system demonstrates the effect of the hydrophobicity on the adsorption of dyes in Laponite which affect not only the tendency of the dye to self-associate but also the geometric structure of the aggregates.
07/1998;
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ABSTRACT: laser) pulses. In these solid media the rhodamine chromophore showsaphotophysical behaviour similar to that inaliquid
solution, and its photostability clearly increases when the chromophore is bound to the polymeric chain. These new solid materials
show laser efficiencies that depend on the HEMA/MMA ratio, in some cases with values close to 20%.
Applied Physics B 05/1997; 64(6):651-657. · 2.19 Impact Factor
