Fluorescence Probes of Pyrene and Pyrene-3-carboxaldehyde for the Sol–Gel Process

Matsui, Kazunori; Nakazawa, Takumi

doi:10.1246/bcsj.63.11

Cited by 33 publications

(10 citation statements)

References 29 publications

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“…Further, it can be noticed that the ratio of the protonated form to the deprotonated form of pyranine is constant ( Table 1), indicating that the interaction of pyranine with the SiO2-system is the same. This corresponds with the results of Matsui and Nakazawa [12] who noticed no change in polarity for matrices made with a different acidity. The variation in the matrix composition changes the fluorescence of pyranine dramatically.…”

Section: Resultssupporting

confidence: 92%

Fluorescence of pyranine in sol-gel based silica and hybrid thin films

Wittouck

Schryver

Snijkers-Hendrickx

1997

J Sol-Gel Sci Technol

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Abstract. The sensitivity of the pyranine fluorescence to protonation/deprotonation is used to follow modifications in cured sol-gel thin films. The acid concentration in the sol-gel solution is varied for TEOS-based coatings and a series of organically modified silanes Si(OR)3R' are added to the TEOS solution. The concentration of the organically modified silane is varied as well as the chain length of the alkylgroup (R').The stationary fluorescence measurements show that the equilibrium between the protonated and the deprotonated form of pyranine changes depending on the type of silica matrix. The deprotonated form is dominant in the cured SiO2 films and the protonation/deprotonation ratio of pyranine is constant for the different acid concentrations used. The protonated form becomes dominant as the concentration of Si(OR)3R' is increased and as the alkyl chain length (W) of the organically modified silanes is augmented.Emission anisotropy measurements of pyranine in the same coatings show that the rotational freedom of the molecule changes due to modifications in the cages for the TEOS-based coatings. These modifications are produced by the acid concentration used to prepare the coatings. An increase in the rotational freedom of pyranine is observed in the TEOS-Si(OR)3R' systems.

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Section: Resultssupporting

confidence: 92%

Fluorescence of pyranine in sol-gel based silica and hybrid thin films

Wittouck

Schryver

Snijkers-Hendrickx

1997

J Sol-Gel Sci Technol

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“…Pyrene has been used as a photoprobe for a number of studies. − The sensitivity of the vibronic structure of its luminescence spectrum to polarity is most relevant to this review and is discussed below. The ability of pyrene to form excimers has been used to study the sol−gel−xerogel transformation in a variety of systems.…”

Section: Spectroscopic Probes Of the Sol−gel Processmentioning

confidence: 99%

“…As a polarity probe, the relative intensities of pyrene vibronic peaks, I 1 and I 5 or I 1 and I 3 , have been correlated with local solvent polarity. − Initial studies ascribed the polarity changes in TMOS and TEOS systems to pyrene aggregation . Later studies showed that polarity in TEOS systems changed relatively little during gelation but did exhibit increasing polarity upon drying. ,, The changes in the I 1 and I 5 ratios between the sol and the xerogel are shown in Figure . These changes were attributed to evaporation of ethanol, effectively increasing the polarity of the silica cage.…”

Section: Spectroscopic Probes Of the Sol−gel Processmentioning

confidence: 99%

Probes of Pore Environment and Molecule−Matrix Interactions in Sol−Gel Materials

1997

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The use of molecular probes to study the nature of the local environment around dopants in silicate sol−gel materials is reviewed. The review selectively focuses on probes of pore solvent composition and molecule−matrix interactions using electronic spectroscopy. The sol−gel environment is complex; to systematize the discussion, four regions are defined. The most commonly probed region is the free liquid region where the surroundings of a dopant molecule are similar to those of an equivalent solution. The molecular composition of the mixed solvent, its polarity, and its pH are discussed. The three regions that are most important in affecting the dopant via molecule−matrix interactions are the interfacial region within a few molecular diameters of the pore wall, the pore wall itself, and the constraining regions where the distances between opposite sides of the pores are about the same as the size of the probe molecule. The aspects of molecular mobility that are reviewed are probe molecule rotation, solvent molecule motion, intramolecular motion (conformational changes), and local intermolecular mobility. Finally, a probe of matrix pore shaping is discussed. In all of the examples that are reviewed, the subject is presented from the operational and experimental measurement point of view, i.e., in terms of specific measured properties. The measured quantities are interpreted on the basis of the location of the probe molecule in the various regions of the sol−gel material and as a function of the stage of processing of the material.

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“…To illustrate the procedure pyrene, a common hydrophobic organic dye molecule, was used. Pyrene's bright, polarity sensitive emission [5] is a convenient marker of encapsulation and molecular behavior [6][7][8][9] and was used to characterize the encapsulating microenvironment within the SiO 2 nanoparticle. This study provides a synthetic and characterization approach that can be used as a guide for the encapsulation of many other optically active organic molecules in SiO 2 .…”

Section: Introductionmentioning

confidence: 99%