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Abstract

Commercial glass fibers have been subjected to different activation treatments under neutral and acidic conditions to achieve different coating degrees when silanized with -y-aminopropyltriethoxisi-lane (APES). A fluorescent sulfonamide (PSA) was formed between the amine residue and a fluorescent probe, pyrenesulfonyl chloride (PSC). Reflectance UVVis spectra of the pyrene-doped fibres show that pyrene is present in the form of preassociated dimers when the coating degree is low. Emission and excitation fluorescence spectra revea! the existence of a charge transfer ground-state complex with exciplex emission at 460-515 nm and absorption red-shifted with respect to the S0 � SI transition. Lifetime measurements yield three lifetimes, which are assigned to dimer, exciplex, and monomer emission. From the photophysical data it is concluded that the fibers with the highest silane content have an open structure with the highest fraction of isolated fluorescent moieties.

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“…The sulfonamide group in position 1 does "excimer-like" emission, in which exciplex is the main not alter the symmetry of the molecule very much, and contribution [11]. Figure 1 clearly shows how the spectherefore, solvent effects in pyrene should also operate trum profile changes depending on the nature of the solin the sulfonamide derivative, although the extent of varivent.…”

“…To have some idea about the ane coating is not exactly known [1][2][3][4][5], although there adhesion mechanism between the silane coupling agents and the polymeric matrices, as proposed by Plueddeman [8], it is necessary to know how the polymer matrix One method used in the determination of local propthe figures, is presented in Table I. erties in polymer systems is the measurement of some portion of the optical response of a molecule that is sensiLabeling Procedure tive to a particular property of the local medium [9][10][11]. Pyrene and its derivatives are excellent probes or labels Well-dried silanized glass fibers were put in contact because they usually have long fluorescence lifetimes, for 10 min, at room temperature, with a PSC solution form emissive excimers or exciplexes, and have a fluores-(10 Ϫ4 M ) in acetonitrile (AcN).…”

“…Pyrene and its derivatives are excellent probes or labels Well-dried silanized glass fibers were put in contact because they usually have long fluorescence lifetimes, for 10 min, at room temperature, with a PSC solution form emissive excimers or exciplexes, and have a fluores-(10 Ϫ4 M ) in acetonitrile (AcN). Then the fibers were cence spectrum sensitive to the polarity of the environsubjected to Soxhlet extraction with dried toluene for 16 ment [10][11][12]. 1-Pyrenesulfonyl chloride (PSC) is a h and vacuum-dried for at least 8 h. suitable chromophore that reacts easily with amine groups, yielding sulfonamide derivatives (PSA), which has a very high quantum yield, and it can form excimers Fluorescence Measurements [13] or exciplexes [11], depending on its concentration…”

“…In a previous immersed in 13 solvents for 12 min. After that period, work [11] it was concluded that the pyrene sulfonyl moisteady-state fluorescence spectra were recorded on a Perety attached to the amine-coated glass surfaces present kin Elmer LS-50B fluorimeter, using the standard frontan "excimer-like" band that arises mainly from exciplex face excitation accessory. The excitation wavelength was emission.…”

“…Solvent effects and accessibility of small molecules are studied as a function of exciplex-to-monomer emission (I E /I M ) and I/V ratios. The previously [11]. ␥-Aminopropyltriethoxisilane (APES) 12 Dimethyl sulfoxide and 1-pyrenesulfonyl chloride (PSC) were purchased 13 Water from ABCR and Molecular Probes, respectively, and used…”