Showing papers on "Excimer published in 1996"
TL;DR: A novel series of polyether dendrimer segments end-capped with pyrenyl, naphthyl, or methyl groups has been prepared by a convergent growth method, and steady-state fluorescence measurements indicate the absence of intramolecular naphthalene excimer in the naphTHyl-capping dendrons.
Abstract: A novel series of polyether dendrimer segments (dendrons) end-capped with pyrenyl, naphthyl, or methyl groups has been prepared by a convergent growth method. Steady-state fluorescence measurements indicate the absence of intramolecular naphthalene excimer in the naphthyl-capped dendrons. However, in the pyrenyl-capped dendrons, excimer emission predominates. Fluorescence from both the naphthyl monomer and pyrenyl excimer are quenched when a suitable electron donor (e.g., a 3-[dimethylamino]phenoxy group) is covalently attached at the dendron focal point. No sensitized emission from the dendron backbone is observed in the chromophore-labeled dendrons, although the control methyl-capped dendron fluoresces weakly at 310 nm when excited at 284 nm. Absorption and fluorescence spectra, fluorescence quantum yields, and fluorescence lifetimes for the chromophore-labeled dendrons are reported.
277 citations
TL;DR: In this paper, the authors investigated the UV-photoablation behavior of glasses and oxide ceramics and found that nanosecond laser pulses lead to plasma mediated ablation in the high fluence regime, whereas the femtosecond ablation process is induced by two photon absorption.
128 citations
TL;DR: In this paper, a dielectric barrier discharge was used to generate excimer radiation in mixtures of the raregases Kr or Xe together with chlorine gas and the characteristics of the emission spectra of the excimers formed, centered around 222 and 308 nm, were obtained for different gas mixtures and total gas pressures using an ultraviolet (UV) monochromator.
Abstract: The generation of excimer radiation in mixtures of the rare‐gases Kr or Xe together with chlorine gas has been investigated by a dielectric barrier discharge. The characteristics of the emission spectra of the excimers formed, centered around 222 and 308 nm, were obtained for different gas mixtures and total gas pressures using an ultraviolet (UV) monochromator. The influence of the gas mixture, chlorine gas concentration, total gas pressure, and buffer gas dependence of the UV intensity has been investigated using chemical actinometry. Conversion efficiencies (from input electrical to output optical energy) as high as 15% can be achieved under optimal conditions. This low‐cost and high‐power excimer lamp system can provide an interesting alternative to conventional UV lamps for industrial large‐scale UV processes.
105 citations
TL;DR: The findings suggest hydrophobic mismatch as the cause of microdomain formation of lipids in fluid, liquid crystalline bilayers, while simultaneously allowing for a high rates of lateral diffusion.
89 citations
TL;DR: After excimer wounds, MMPs are expressed in corneal epithelium and stroma during wound closure and may play an important role in wound healing after excimer laser keratectomy.
Abstract: To determine the expression of matrix metalloproteinases (MMPs) in cornea following excimer laser keratectomy, two sets of experiments were performed In the first experiment, disciform excimer keratectomy was performed on rat corneas The central regenerating epithelium was harvested at 3–96 h post
88 citations
TL;DR: In this article, the authors describe studies carried out related to grating formation for optoelectronics applications using 248 nm and 193 nm excimer lasers, and show that the use of excimer laser illuminated phase masks in a contact printing mode or Talbot reimaging arrangement provide a particularly effective approach to forming submicron period gratings.
69 citations
TL;DR: In this article, van der Waals dimers between benzofuran, dibenzofuran and fluorene were studied in a supersonic jet, and they showed red-shifted excimer/exciplex emission following excitation to their locally excited states.
Abstract: Van der Waals dimers between benzofuran, dibenzofuran, and fluorene were studied in a supersonic jet. These show red-shifted excimer/exciplex emission following excitation to their locally excited states. The dibenzofuran dimer forms an excimer from its zero-point level, while the dibenzofuran−benzofuran and fluorene−benzofuran dimers require a moderate amount of excess vibrational energy for excimer formation. Exciplex formation in dibenzofuran−fluorene was inferred from spectral broadening. Excimer/exciplex formation was attributed to strong mixing of a charge transfer state with the exciton state. The charge transfer state has a low enough energy at its equilibrium geometry to mix, but this requires a large change in geometry from the equilibrium geometry of the locally excited state. There is a barrier in the adiabatic potential surface between the minima of the locally excited state and the excimer/exciplex state. This barrier is larger for greater differences in equilibrium geometry.
60 citations
TL;DR: In this article, pyrene was used as a probe to study the gelation of sodium deoxycholate at pH values close to neutrality, and the results suggest the formation of pyrene excimer as a result of the aggregation process: when two clusters carrying probes form a larger one, pyrene molecules can interact in both ground and excited states.
Abstract: Steady-state and time-resolved fluorescence have been used to study the gelation of sodium deoxycholate at pH values close to neutrality. Pyrene was used as a probe. The results suggest the formation of pyrene excimer as a result of the aggregation process: when two clusters carrying probes form a larger one, pyrene molecules can interact in both the ground and excited states. Fluorescence lifetimes for monomer and excimer pyrene are given and favorably compared to similar systems. A structure for the aggregates is also suggested.
47 citations
TL;DR: In this paper, a self-sensitizable photocrosslinking maleimide-type polymers were synthesized by using (N-cinnamoyloxymethyl)maleimide (1) as a maleimides having a photodimerizable group, nitrophenyl acrylate as a sensitizer monomer, and styrene or methyl acrylated.
Abstract: Self-sensitizable photocrosslinking maleimide-type polymers were synthesized by using (N-cinnamoyloxymethyl)maleimide (1) as a maleimide having a photodimerizable group, nitrophenyl acrylate as a sensitizer monomer, and styrene or methyl acrylate. The fluorescence spectra of these polymers exhibit an excimer band around 455 nm. The excimer intensity of the polymers decreased mainly during the early irradiation time. This decreasing tendency was similar to the increasing tendency of the insoluble fractions of the polymers with irradiation time. These results suggest that the photocrosslinking reaction of the polymers occurs via an excimer formation of the cinnamoyl groups and can be traced by fluorescence spectroscopy.
45 citations
TL;DR: A theoretical analysis of the volume of vaporized water is correlated with measured bubble volumes formed in hemoglobin solution and induces mechanical damage in adjacent tissue during Xenon‐Chloride excimer laser ablation of tissue.
Abstract: BACKGROUND AND OBJECTIVE: Previous studies have demonstrated that during Xenon-Chloride excimer laser ablation of tissue, rapidly expanding and imploding bubbles (diameter <3 mm), predominantly containing water vapor, are formed. These short lived bubbles (life time <300 microseconds) induce mechanical damage in adjacent tissue. In the present study, a theoretical analysis of the volume of vaporized water is correlated with measured bubble volumes formed in hemoglobin solution. STUDY DESIGN/MATERIALS AND METHODS: The dimensions of the rapidly expanding and imploding vapor bubble induced by the XeCl excimer laser pulses (308 nm, 115 ns), delivered via a 300, 550, or 950 microns diameter monofiber in 16% w/v hemoglobin solution (at 37 degrees C), were measured. RESULTS: Theoretical analysis and the experimental data correlated well (correlation coefficient r = 0.97). The diameter of excimer laser induced bubbles increased with increasing pulse energy. For a given radiant exposure, the bubble size was decreased by either decreasing the fiber tip area or by decreasing the absorption coefficient of the hemoglobin solution. CONCLUSION: We conclude that, for a wide range of conditions, theory agrees well with experimental data. Thus, during delivery of excimer laser pulses in blood, bubble dimensions can be reduced by flushing with saline or by reduction of the area radiated with each laser pulse, for example, by pulse multiplexing or using a smaller multifiber catheter
41 citations
TL;DR: In this article, the authors used Kr2* and Xe2* excimer lamps at wavelength of 146 and 172 nm, respectively, to irradiate polytetrafluoroethylene films with vacuum UV light in an ammonia gas atmosphere.
Abstract: Irradiation of polytetrafluoroethylene films with vacuum UV light in an ammonia gas atmosphere resulted in a hydrophilic surface, where abstraction of fluorine atoms, and introduction of nitrogen, oxygen, and hydrogen atoms occurred. We used Kr2* and Xe2* excimer lamps at wavelength of 146 and 172 nm, respectively. The reaction mechanism for chemical surface modification is discussed on the basis of x‐ray photoelectron spectroscopy, secondary ion mass spectroscopy, and attenuated total reflection Fourier transform infrared spectroscopy analyses.
TL;DR: In this article, 2-Methylnaphthalene (MN) exhibits MN excimer fluorescence in both β-cyclodextrin (β-CD) neutral aqueous solutions.
Abstract: 2-Methylnaphthalene (MN) exhibits MN excimer fluorescence in both β-cyclodextrin (β-CD) and γ-cyclodextrin (γ-CD) neutral aqueous solutions. β-CD forms a 1 : 1 inclusion complex with MN, which self...
TL;DR: In this paper, the roughness of polyethylene terephthalate (PET) was measured with a stylus profilometer and the morphology of the irradiated PET films was investigated by scanning electron microscopy after different exposure times.
Abstract: Photochemical dry etching and surface modification of polyethylene terephthalate (PET) was investigated with an incoherent excimer UV source, employing a dielectric barrier discharge in krypton chloride to provide intense narrow-band radiation at λ= 222 nm (KrCl*). The roughness of the exposed PET was measured with a stylus profilometer. The morphology of the irradiated PET films was investigated by scanning electron microscopy (SEM) after different exposure times and the roughness of PET can be controlled by UV intensity and exposure times. Etching rate is 40 times higher than that for photochemical etching of PET with a conventional mercury lamp The chemical changes in the UV-exposed PET surface layer were determined using x-ray photoelectron spectroscopy (XPS) by measurement of the intensity of the C-C, C-O and O-C=O bonds after irradiation with the KrCl* excimer lamp.
TL;DR: In this article, the photophysical processes taking place in the excited state of a donor−bridge−acceptor compound (1) in alkane solvents were studied with time-resolved laser-induced optoacoustic spectroscopy.
Abstract: The photophysical processes taking place in the excited state of a donor−bridge−acceptor compound (1) in alkane solvents were studied with time-resolved laser-induced optoacoustic spectroscopy. 1 contains an aniline/cyanonaphthalene D/A pair, separated by a semiflexible saturated hydrocarbon bridge. Excitation at 308 nm leads to efficient long-range charge separation, followed by rapid Coulomb-induced intramolecular exciplex formation. By monitoring the pressure waves generated by the decay of the excited species, three consecutive heat release processes could be discerned. In order to separate the contributions to the observed acoustic signals of structural volume changes (ΔVstr) and enthalpy changes, experiments were carried out in a series of normal alkanes, differing in their photothermal properties. A value of ΔVstr = −40 ± 5 mL/mol was obtained for the difference in reaction volume between the ground state and the exciplex state of 1. This large contraction should be attributed in part to electrostr...
Journal Article•
TL;DR: Both the thermal increase in the cornea during the photoablation and the decreased aqueous SOD activities suggest that free radicals are formed in theCorneal surface during excimer laser keratectomy, and that they may be responsible for some of the complications of excimer Laser corneal surgery.
TL;DR: In this paper, β-cyclodextrin (β-CD) has been found to form inclusion complexes with 1-methylnaphthalene, 1-ethylnaphthylene, 1-(chloromethyl)naphthyne, and 2-ethyl naphthylene, and the excimer fluorescence is concluded to be due to a 2 : 2 β-CD-alkylnaphorthene inclusion complex.
Abstract: In aqueous solutions, β-cyclodextrin (β-CD) has been found to form inclusion complexes with 1-methylnaphthalene, 1-ethylnaphthalene, 1-(chloromethyl)naphthalene, and 2-ethylnaphthalene. Addition of β-CD to aqueous solutions of 1-methylnaphthalene and 2-ethylnaphthalene has resulted in the observation of the excimer fluorescence of each compound. From simulations of the observed excimer fluorescence intensities of 1-methylnaphthalene and 2-ethylnaphthalene, the excimer fluorescence is concluded to be due to a 2 : 2 β-CD–alkylnaphthalene inclusion complex. In the cases of 1-ethylnaphthalene and 1-(chloromethyl)naphthalene, the excimer formation within the β-CD cavities seems to be prohibited due to the steric hindrance caused by a substituent, although the 2 : 2 β-CD–alkylnaphthalene inclusion complex is likely to be formed. Equilibrium constants for the formation of these 1 : 1 and 2 : 2 inclusion complexes have been evaluated from the monomer and excimer fluorescence intensity changes with β-CD concentration.
TL;DR: In this paper, a crystal growth method for growing UV grade CaF 2 crystals from fluorspar has been developed using purified Bulgarian Fluorspar mixed with 2% PbF 2.
TL;DR: In this paper, the resonance two-photon ionization (R2PI) spectra of the jet-cooled aniline dimers (An-d0)2, (And5)2 and (an-d7)2) have been recorded; the first 225 cm-1 region above the origin was also reproduced by fluorescence excitation spectroscopy.
Abstract: The resonance two-photon ionization (R2PI) spectra of the jet-cooled aniline dimers (An-d0)2, (An-d5)2, and (An-d7)2 have been recorded; the first 225 cm-1 region above the (An-d0)2 origin was also reproduced by fluorescence excitation spectroscopy. Relatively sharp structure near the origin of the local excited state is attributed to intermolecular modes, perhaps of multiple conformers. Broader features at higher energies are assigned to symmetric ring modes coupled to an underlying excimer state. The dispersed fluorescence spectrum excited at the dimer electronic origin suggests that excimer formation occurs soon after the local excited state is pumped. Molecular dynamics simulations support the inference from the spectroscopic observations that hydrogen bonding governs the structure of the aniline dimer.
TL;DR: In this paper, an excimer laser fragmentation-fluorescence spectroscopy (ELFFS) was applied to lead, manganese, nickel and chromium species in the postflame gases of a laboratory burner.
Abstract: Photofragmentation of molecules using an excimer laser with subsequent detection of fluorescence from metal atoms formed in excited states is a viable detection strategy for many metal species. Excimer laser fragmentation-fluorescence spectroscopy (ELFFS) can provide continuous, real-lime monitoring information for metals which evolve from a variety of high-temperature processes, including combustion, Here we apply ELFFS to lead, manganese, nickel and chromium species in the postflame gases of a laboratory burner. Using a 193-nm argon fluoride laser we obtain quantitative relationships between signal strength and concentration in hot combustion products for metals injected into a flame; representative spectra are shown. The effects of quenching environment and laser power on the signal are discussed. The ELFFS technique is sensitive, providing ppb detection limits for these metals in a one-second measurement time.
TL;DR: In this article, the absorption and fluorescence spectra of Bis(4-aminophenyl)ether (DADPE) have been studied in different solvents and at various acid concentrations.
Abstract: Absorption and fluorescence spectra of Bis(4-aminophenyl)ether (DADPE) have been studied in different solvents and at various acid concentrations. The results are compared with the spectral data of 4-Aminodiphenyl ether (ADPE). The fluorescence spectra of DADPE are blue shifted relative to that of ADPE in polar and hydrogen-bonding solvents. A small, but unusual, red shift is observed in the fluorescence spectrum of the monocation relative to that of DADPE in water. These observations reveal that the effect of two amino groups in polar solvents is less than that of one amino group in the excited singlet state. The abnormally red-shifted fluorescence with a peak at around 422 nm at pH 3.5 is due to a dication-solvent exciplex. The formation of the dication-solvent exciplex leads to an excited state equilibria quite different from that in the ground state.
TL;DR: In this paper, the authors measured the fluorescence behavior of poly(ethylene terephthalate) (PET) films prepared by using a spin-casting method and found that the wavelength of the peak was dependent on the casting temperature, T cast.
TL;DR: In this paper, the authors present experimental evidence that in multilamellar liposomes of 1-palmitoyl 2-oleoyl-sn-glycero-3-phosphocholine, in the fluid phase at temperatures above phase transition, TL, and for a probe/phospholipid ratio of 1:75, or lower, the fluorescence decay of the excimer of pyrene follows a kinetic law specific for two-dimensional diffusion-controlled reactions.
Abstract: Diffusion-controlled bimolecular reactions in two-dimensional or quasi two-dimensional space are important in both surface and membrane reaction kinetics. A model reaction that has been extensively used to study the dynamics and structure of phospholipid membranes is the formation of the excimer of pyrene. We present experimental evidence that in multilamellar liposomes of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, in the fluid phase at temperatures above phase transition, TL, and for a probe/phospholipid ratio of 1:75, or lower, the fluorescence decay of 1-palmitoyl-2-(1-pyrenodecanoyl)-sn-glycero-3-phosphocholine and the time-resolved emission of the excimer follow a kinetic law specific for two-dimensional diffusion-controlled reactions. The parameters obtained from the application of this law to the experimental results, either from steady-state or from time-dependent fluorescence, give diffusion coefficients, e.g., D(25 °C) = 3.1 × 10-8 cm2 s-1 and an activation energy for diffusion, Ea = 35 k...
TL;DR: In this paper, the effects of fluorenone concentration in various solvents in the range 10 −6 −10 −3 M on the spectral properties are discussed, and the mechanism of excimer formation has been explained.
Abstract: The electronic absorption and steady state fluorescence spectra of fluorenone in the regions 280–340 and 320–420 nm respectively have been obtained at room temperature for various concentrations in a series of non-polar and polar solvents. The effects of fluorenone concentration in various solvents in the range 10 −6 −10 −3 M on the spectral properties are discussed. In addition to the monomer fluorescence, we have also observed another fluorescence band at longer wavelength in the region 420–600 nm which has been ascribed to excimer formation. The monomer and excimer fluorescence lifetimes of fluorenone in typical solvents such as benzene and acetonitrile have been determined experimentally. By combining our results of steady state fluorescence and measurements of fluorescence lifetimes with previously reported studies of laser-induced fluorescence, the mechanism of excimer formation has been explained. The absence of excimer formation in hexane, cyclohexane and alcohols is discussed.
TL;DR: An excimer laser calibration system capable of characterizing a laser ablation profile can precisely detect laser-beam ablation profiles and may be useful for precise calibration of excimer lasers before human photorefractive and therapeutic surgery.
Abstract: BACKGROUND Excimer laser photoablation for refractive and therapeutic keratectomies has been demonstrated to be feasible and practicable. However, corneal laser ablations are not without problems, including the delivery and maintenance of a homogeneous beam. We have developed an excimer laser calibration system capable of characterizing a laser ablation profile. METHODS Beam homogeneity is determined by the analysis of a polymethylmethacrylate (PMMA)-based thin-film using video capture and image processing. The ablation profile is presented as a color-coded map. Interpolation of excimer calibration system analysis provides a three-dimensional representation of elevation profiles that correlates with two-dimensional scanning profilometry. Excimer calibration analysis was performed before treating a monkey undergoing phototherapeutic keratectomy and two human subjects undergoing myopic spherocylindrical photorefractive keratectomy. Excimer calibration analysis was performed before and after laser refurbishing. RESULTS Laser ablation profiles in PMMA are resolved by the excimer calibration system to .006 microns/pulse. Correlations with ablative patterns in a monkey cornea were demonstrated with preoperative and postoperative keratometry using corneal topography, and two human subjects using video-keratography. Excimer calibration analysis predicted a central-steep-island ablative pattern with the VISX Twenty/Twenty laser, which was confirmed by corneal topography immediately postoperatively and at 1 week after reepithelialization in the monkey. Predicted central steep islands in the two human subjects were confirmed by video-keratography at 1 week and at 1 month. Subsequent technical refurbishing of the laser resulted in a beam with an overall increased ablation rate measured as microns/pulse with a donut ablation profile. A patient treated after repair of the laser electrodes demonstrated no central island. CONCLUSIONS This excimer laser calibration system can precisely detect laser-beam ablation profiles. The calibration system correctly predicted central islands after excimer photoablation in a treated monkey cornea and in two treated human subjects. Detection of excimer-laser-beam ablation profiles may be useful for precise calibration of excimer lasers before human photorefractive and therapeutic surgery.
TL;DR: In this article, a comparison with low-energy photoexcitation shows that singlet and triplet excited states of aromatic polymers produced by high-energy irradiation are mainly derived from geminate recombination between the polymer radical cations and the excess electrons.
Abstract: Radiation-induced processes in polymer films have been studied by pulse radiolysis using transient spectroscopic methods. A comparison with low-energy photoexcitation shows that singlet and triplet excited states of aromatic polymers produced by high-energy irradiation are mainly derived from geminate recombination between the polymer radical cations and the excess electrons. A simultaneous production of singlet and triplet excited states, radical cations, and radical anions of aromatic solutes doped in polystyrene was observed on static quenching of the polystyrene excimer. By use of pyrene as the spectroscopic probe, the absolute yields of the pyrene transient species in the polymer right after the pulse were measured as G(1Py*) ≈ 0.8, G(3Py*) ≈ 1.1, G(Py•+) ≈ 1.5, and G(Py•-) ≈ 1.5 at [Py] = 100 mM. The large ion yields indicate an efficient charge generation in the nonpolar polymer matrix. Charge-scavenging experiments further reveal the ionic origin of the solute excited states. In the case of comple...
TL;DR: In this article, a triazeno chromophore was applied to two different excimer laser sources, KrF at 248 nm and XeCl at 308 nm, to study the surface properties of the polymer after laser treatment.
Abstract: Standard spectroscopic and surface analysis techniques were used to study a triazeno polymer after laser treatment. Two different excimer lasers, KrF at 248 nm and XeCl at 308 nm, were applied as irradiation sources. For both excimer lasers fluences below and above the threshold of ablation were used. In the case of fluences below the threshold of ablation the irradiation led to a decrease of the absorption of the triazeno chromophore. From XPS spectrum and contact angle measurements a surface oxidation of the polymer is identified. After irradiation with fluences above the threshold of ablation for both irradiation wavelengths a different behavior is observed. Irradiation with the XeCl laser led to a less pronounced surface roughening as compared to KrF laser treatment. With the XPS and contact angle measurements, only slight changes could be detected. A totally different behavior was found for irradiation with the KrF excimer laser. The surface of the polymer turned black after the irradiation, and the ...
01 Jan 1996
TL;DR: In this paper, the absolute concentrations of total gas-phase sodium and potassium compounds were determined in the flue gas of a fluidized bed coal combustor at 10 bar using excimer laser-induced fragmentation fluorescence (ELIF).
Abstract: Absolute concentrations of total gas-phase sodium and potassium compounds were determined in the flue gas of a fluidized bed coal combustor at 10 bar using excimer laser-induced fragmentation fluorescence (ELIF). In this in situ and on-line technique, the alkali compound molecules are photodissociated by ArF-excimer laser light at 193 nm, whereby excited Na(3 2 P ) and K(4 2 P ) atoms are formed. Fluorescence from these atoms is simultaneously detected in two separate channels at 589 nm and 768 nm, respectively. The calibration system and data evaluation procedure to convert measured signals to absolute concentrations is described. Studies on lignite and hard coal under several different combustion conditions are reported. The measured concentrations span a dynamic range of more than three orders of magnitude, with a detection limit of
TL;DR: It is shown that the aggregation of molecules can be controlled by variation of the surface roughness, and with increasing layer thickness, the luminescence is dominated by excimer transitions.
Abstract: We investigate high-quality evaporated dye layers of N, N′-dimethylperylene-3,4:9,10-bis-discarboximide of varying thicknesses, using temperature-dependent luminescence. Layers with a nominal thickness much less than a monolayer show monomer emission similar to that of dilute solutions. With increasing layer thickness, the luminescence is dominated by excimer transitions. The excimer linewidth decreases markedly with decreasing temperature. We show that the aggregation of molecules can be controlled by variation of the surface roughness.
TL;DR: In this paper, an investigation was conducted to determine the kinetic processes which produce XeI(B) in a low pressure (0.5-5 Torr) inductive radio frequency discharge sustained in Xe and I2.
Abstract: Low pressure excimer discharges (<1–5 Torr) are of interest for use as ultraviolet sources for lighting applications. XeI(B) is an attractive candidate for excimer lamps due to the low corrosive properties of iodine. The excimer is thought to be formed by either harpoon or ion‐ion recombination reactions, the latter of which requires a third body. The formation of the excimer at low pressures is therefore problematic. To address this issue, an investigation was conducted to determine the kinetic processes which produce XeI(B) in a low pressure (0.5–5 Torr) inductive radio frequency discharge sustained in Xe and I2. The diagnostics applied in this study include laser‐induced fluorescence, optical absorption spectroscopy, and optical emission spectroscopy. Our results indicate that for the experimental conditions, Xe+I2**→XeI(B)+I is a major reaction producing the excimer. This result differs from studies performed at higher pressures which concluded that the harpoon reaction between Xe* and I2 or ionic recombination between Xe+2 and I− are the major sources of XeI(B).
TL;DR: In this article, tetrasodium 1,3,6,8-pyrenetetetrasulfonate (PyTS) and trisodium 8-hydroxy-1, 3, 6, 6 pyrenetrisulfonates (pyranine) were solubilized in separate reversed micellar cores in AOT/n-heptane system.
Abstract: Water-soluble anionic fluorescent molecules tetrasodium 1,3,6,8-pyrenetetrasulfonate (PyTS) and trisodium 8-hydroxy-1,3,6-pyrenetrisulfonate (pyranine) were solubilized in separate reversed micellar cores in AOT/n-heptane system. The reversed micelle system showed an extent of nonradiative energy transfer from PyTS to pyranine higher than for the aqueous solution system in comparison at a critical probe concentration, [P]C. The values of [P]C, where each micelle is occupied by statistically one probe molecule, were determined as a probe concentration where the solubilized disodium 2,6-naphthalenedisulfonate (NpDS) begins to show the intramicellar excimer fluorescence. The results reveal that at surfactant concentrations higher than 0.1 M the AOT reversed micelles are not randomly dispersed in isolated state in n-heptane but form clusters through intermicellar flocculation.