Fluorescence properties of pyrene derivative aggregates formed in polymer matrix depending on concentration

Ito, Fuyuki; Kakiuchi, Toshifumi; Sakano, Takeshi; Nagamura, Toshihiko

doi:10.1039/c003023f

Cited by 36 publications

(35 citation statements)

References 28 publications

(41 reference statements)

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“…[5][6][7][8][9][10] Along this line, we studied fluorescence properties of 30 aggregates in poly(vinyl alcohol) (PVA) matrix. 11,12 The segregation of solute molecules in PVA films prepares aggregates with a size of nm to µm and the high viscosity in the polymer film decelerates the temporal evolution of size and morphology of aggregates. 13,14 By applying this method of polymer matrix 35 isolation, we found that the unique fluorescence in longer wavelength range appeared in the segregation processes of pyrene ammonium (PyAm) 11 and perylene ammonium (PeryAm) 12 derivatives and, interestingly, this new emission continuously redshifted with increasing concentration of the solute.…”

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Properties and evolution of emission in molecular aggregates of a perylene ammonium derivative in polymer matrices

Ito

Sato

Ugachi

et al. 2015

Photochem Photobiol Sci

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5Size-dependent fluorescent properties of aggregates of a perylene ammonium derivative (PeryAm) were studied by steady-state and time-resolved spectroscopic methods. Quantitative analyses of aggregated states in aqueous solution indicated that the aggregation proceeded through dimer units of PeryAm. Fluorescence of the aggregate in the PVA film prepared from the aqueous solution continuously redshifted with an increase in the concentration of PeryAm in the mother liquor, while keeping the 10 absorption spectra almost the same band shapes. Fluorescence anisotropy values of aggregates in the PVA film were dependent on the monitoring wavelength and time profiles of the fluorescence in longer wavelength showed fast rise just after the pulsed excitation. These results indicated the efficient energy transfer to the stable sites in aggregates. Fluorescence microscope images showed aggregates were segregated in the PVA film and the color of the emission was dependent on the size of the aggregate. 15Under the steady-state irradiation, the emission color of the aggregates was changed from green to yellow, which was attributable to the association of a small cluster of PeryAm with the green emission resulting in the formation of yellow-colored aggregates. On the basis of these results, we discussed the mechanisms and the dynamics of the aggregation and size-dependent emission in aggregates.

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confidence: 99%

Properties and evolution of emission in molecular aggregates of a perylene ammonium derivative in polymer matrices

Ito

Sato

Ugachi

et al. 2015

Photochem Photobiol Sci

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“…4,17 Initially, the concentration in solution was relatively low, thus an equilibrium state was established between the monomer and J-aggregates. The Jaggregates begin from the smallest cluster of two monomers 10 formed via intermolecular interactions. This small cluster is unstable because of unfavorable surface free energy and dissociates before crystal formation.…”

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“…[7][8][9] In principle, fluorescence 25 spectroscopy can be used to probe the progress of molecular assembly on the scale of just a few molecules or that of a bulk process. Previously, we proposed that concentration-dependent changes in fluorescence spectra for pyrene 10 from Aldrich and used as received. CN-MBE-doped PMMA thin films with a PMMA concentration fixed at 2 wt% were prepared by drop-casting DCE solutions onto glass cover slips.…”

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Fluorescence visualization of the molecular assembly processes during solvent evaporation via aggregation-induced emission in a cyanostilbene derivative

Ito

Fujimori

2014

CrystEngComm

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Initial stage of organic crystal formation during solvent evaporation was observed by using aggregation-induced enhanced emission, indicating fluorescence from J-aggregates was established prior to the increase in total intensity at 10 assembly process, which suggested that the kinetics of the transformation of J-aggregates into embryonic nuclei, and subsequently to crystal can be visualized by the fluorescence.Organic molecular materials have wide applications in electroluminescence, solar cells, and pharmaceutical products. 1, 2 15Intermolecular interactions are significant factors for the development of higher functionality in these applications. To optimize the interactions, it is necessary to understand molecular packing or polymorphism during crystal growth, including nuclei formation.3-5 To clarify crystal growth, there has been widely 20 studied by X-ray crystallography, infrared spectroscopy, nuclear magnetic resonance, and transmission electron microscopy 6 . 4Many organic molecules exhibit characteristic spectral changes that depend on their electronic states, how they assemble, their size, and their ambient environment. [7][8][9] In principle, fluorescence 25 spectroscopy can be used to probe the progress of molecular assembly on the scale of just a few molecules or that of a bulk process. Previously, we proposed that concentration-dependent changes in fluorescence spectra for pyrene 10 from Aldrich and used as received. CN-MBE-doped PMMA thin films with a PMMA concentration fixed at 2 wt% were prepared by drop-casting DCE solutions onto glass cover slips. Fluorescence spectra were recorded with a Shimadzu RF-5300PC fluorescence spectrophotometer. Droplet with 10 µL fluorescence 60 color and intensity, as well as the morphology of the crystals, were captured with an inverted fluorescence microscope (Olympus IX71), equipped with a UPlanFl 4×/0.13 PhL (Olympus) objective lens, a CCD camera (Sigma Koki SK-TC202USB-AT), and a USB 4000 (Ocean Optics) spectrometer, 65 which was not corrected for the wavelength dependence of the detectors. All experiments were performed at room temperature. spectra from 330-nm excitation of these films cast from DCE solutions. At concentrations <0.1 mol%, peak emission was observed at 440 nm, with a shoulder at 420−430 nm. At increased concentrations, the fluorescence peak shifts to 470 nm and narrows. Aggregate species were observed with the fluorescence 80 microscope at concentrations >1.0 mol% (Fig. ESI 1). Thus the spectral shift and narrowing of the fluorescence originated from CN-MBE J-aggregates. 15 To identify the emissive species at lower concentrations, excitation spectra of the CN-MBE/PMMA films were acquired (Fig. ESI 2), indicating the broad excitation 85 spectra at 355 nm for concentrations <0.1 mol% is most likely a

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“…We have investigated the fluorescence properties of pyrene ammonium derivative (PyAm, Figure 1) in poly(vinylalcohol) (PVA) thin films [8]. The fluorescence spectra of PyAm in the PVA film at a lower concentration showed only a monomer emission.…”

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confidence: 99%

“…They proposed lattice softening of the nanoparticles as a cause of the size-dependent optical properties. Yao et al reported the size dependence of the emission spectra for pyrazoline nanoparticles, which originated from the formation of charge transfer excitons due to the flexibility and various inter-and intramolecular overlapping structures in the nanoparticles [5].We have investigated the fluorescence properties of pyrene ammonium derivative (PyAm, Figure 1) in poly(vinylalcohol) (PVA) thin films [8]. The fluorescence spectra of PyAm in the PVA film at a lower concentration showed only a monomer emission.…”

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Fluorescence properties of nanoaggregates of pyrene ammonium derivative and its photoinduced dissolution and reaction in tetrahydrofuran/aqueous solutions

2014

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We studied the fluorescence properties of nanoaggregates of pyrene ammonium derivative (PyAm) and their photoinduced dissolution and reaction in tetrahydrofuran (THF)/aqueous solution. The final concentration (dye concentration after reprecipitation) dependence of the fluorescence peak was measured. The fluorescence peak of PyAm that originated from the excimer is shifted to the long wavelength side increasing with the final concentration, which is ascribable to the characteristic fluorescence spectral changes depending on their size. The size-dependent fluorescence change in the nanoaggregates is related to some molecular conformation, packing, and elastic properties of the nanoparticles at the surface. To understand the fluorescence properties of the intermediates from aggregates to crystals is important for the studies of organic nanocrystals/aggregates prepared by the reprecipitation methods. We also determined the fluorescence spectra of the PyAm nanoaggregates in a THF/aqueous solution by photoinduced dissolution and reaction. It originated from the photochemical reaction between PyAm and THF. Changes in the perpendicular light scattering intensity by photoirradiation supports the photoinduced dissolution of PyAm in the THF/aqueous solution. These findings are important in the research field of photochemical reactions in organic nanocrystals. KeywordsOrganic nanocrystal; fluorescence properties; size dependence; photochemical reaction; photoinduced dissolution 2 IntroductionOrganic nano-materials are widely investigated in terms of their unique optical properties [1]. Kasai and Nakanishi et al. first reported that the fluorescence spectra of perylene nanocrystals, which were prepared by the reprecipitation method, depended on their size, and the fluorescence spectra of the nanoparticles differ from that of the bulk crystals [2,3]. There are many reports about organic nanoparticles in the past decade [4][5][6][7]. They proposed lattice softening of the nanoparticles as a cause of the size-dependent optical properties. Yao et al. reported the size dependence of the emission spectra for pyrazoline nanoparticles, which originated from the formation of charge transfer excitons due to the flexibility and various inter-and intramolecular overlapping structures in the nanoparticles [5].We have investigated the fluorescence properties of pyrene ammonium derivative (PyAm, Figure 1) in poly(vinylalcohol) (PVA) thin films [8]. The fluorescence spectra of PyAm in the PVA film at a lower concentration showed only a monomer emission. The fluorescence peak shifted to the long wavelength side with the increasing dye concentration, which was assigned to a dimer or excimer-like emission. The concentration-dependent fluorescence changes originated from the PyAm aggregates formed in the PVA matrix by phase separation. The size of the PyAm aggregates in the PVA thin films increased with the increasing dye concentration. The peaks of the dimer and/or excimer-like fluorescence originated from the aggregates that ...

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Fluorescence properties of pyrene derivative aggregates formed in polymer matrix depending on concentration

Cited by 36 publications

References 28 publications

Properties and evolution of emission in molecular aggregates of a perylene ammonium derivative in polymer matrices

Properties and evolution of emission in molecular aggregates of a perylene ammonium derivative in polymer matrices

Fluorescence visualization of the molecular assembly processes during solvent evaporation via aggregation-induced emission in a cyanostilbene derivative

Fluorescence properties of nanoaggregates of pyrene ammonium derivative and its photoinduced dissolution and reaction in tetrahydrofuran/aqueous solutions

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