Transfer of electronic excitation energy from naphthalene to fluorophore indicator on the surface of silica microspheres with covalently or physically bound cyclodextrins

摘要

In order to use electronic excitation energy transfer (TE) for the detection of aromatic hydrocarbons (AHs) in a gas phase, TE from naphthalene (N) to a fluorophore indicator on the surface of silica microspheres (SMs) modified by covalently or physically adsorbed cyclodextrins (CDs) has been studied. It is found that dansylglycine (DG) is an appropriate acceptor of energy, because its absorption spectrum is shifted to the red region of the spectrum and overlaps well with the fluorescent spectra of AHs, while upon excitation at 290 nm its fluorescence is low. It has been demonstrated that, upon the introduction of SMs into the vapors of N and the excitation of N at 290 nm, the fluorescence of DG grows 500 nm more intensively than that of N. A method of quantitative variation of the N vapors pressure and, correspondingly, of the concentration of adsorbed N, based on the measurement of weight loss of the N solution in a nonvolatile solvent (DOS), has been developed. Using this method, the dependencies of intensity of fluorescence was determined for N and DG, as well as the efficiency of TE on the concentration of the adsorbed N. Under the assumption of the Forster mechanism of TE, the Forster radius (23.4 ?) and the average distances between N and DG were estimated. It has been demonstrated that, upon excitation at the absorption band of N, the intensity of DG fluorescence linearly increases with the DG concentration, which makes it possible to use TE for the detection of low concentrations of N. The kinetics of fluorescence at the rapid introduction of the N vapors was studied: first the sorption of N on the surface and fast growth of monomeric F occurs; further, in ～200 s, excimer fluorescence and TE arise. For SMs with adsorbed polymeric CDs, the efficiency of TE from N to DG is several times lower than for SMs with covalently bound CDs.