Abstract
The influence of the acid catalyst concentration on the structural evolution of a sol-gel system was studied by doping TEOS based starting solutions with two fluorescent probes: a polystyrene chain (M n =1700) and a much shorter alkane chain (M=172), both of them labeled at both ends with 1-pyrenyl. For this purpose, each probe was incorporated in two TEOS∶H2O∶C2H5OH mixtures (molar ratios 1∶4∶1), one at pH 1.2 and the other at pH 2.5 (respectively below and above the isoelectric point of silica). Very low concentrations of the probes were used (≤10−6 M), so the pyrene dimmers and excimers were formed only intramolecularly. The ratios of excimer to monomer fluorescence intensities at excitation wavelength of 360 nm (where mainly the ground state pyrene dimmers are excited) were studied as a function of time. Different evolutions of these ratios were observed, which allowed us to predict that the silica structure developsvia the formation of primary particles, even at pH values below the isoelectric point of silica, where it is not possible to directly detect their formation.
Similar content being viewed by others
References
D.W., Schaefer, J.E. Martin, P. Wiltzius, and D.S. Cannell, Phys. Rev. Letters,52, 2371 (1984).
J.K. Kjems, T. Freltoft, D. Richter, and S.K., Sinha, Physica,136, B 285 (1986).
E.J.A. Pope and J.D., Mackenzie, J. Non-Cryst. Solids,101, 198 (1988).
J.K. Bailey, T. Nagase, S.M. Broberg, and M.L. Mecartney, J. Non-Cryst. Solids109, 198 (1989).
J.K. Bailey, C.W. Macosko, and M.L. Mecartney, J. Non-Cryst. Solids125, 208 (1990).
B. Valeur, inMolecular Luminescence Spectroscopy: Methods and Applications, Part 3, edited by S.G. Schulman, (Wiley-Interscience, New York, 1991).
J. Samuel, Y. Polevaya, M. Ottolenghi, and D. Avnir, Chem. Mater.6, 1457 (1994).
V.R. Kaufman and D. Avnir, Langmuir2, 717 (1986).
N. Negishi, T. Fujii, and M. Anpo, Heterogeneous Chem. Rev.1, 231 (1994).
L.M. Ilharco, A.M. Santos, M.J. Silva, and J.M.G. Martinho, Langmuir11, 2419 (1995).
J. Brandrup and E.H. Immergut (Eds.),Polymer Handbook, 3rd ed. (John Wiley & Sons, New York, 1989).
M.A. Winnik, A.E.C. Redpath, K. Paton, and J. Danhelka, Polymer25, 91 (1984).
J.M.G. Martinho, M.H. Martinho, M.A. Winnik, and G. Beinert, Makromol. Chem.190, 1333 (1989).
M.M.E. Severin-Vantilt and E.W.J.L. Oomen, J. Non-Cryst. Solids159, 38 (1993).
B. Himmel, Th. Gerber, and H. Bürger, J. Non-Cryst. Solids91, 122 (1987).
C.J. Brinker and G.W. Scherer, J. Non-Cryst. Solids70, 301 (1985).
S. Sakka and H. Kozuka, J. Non-Crystalline Solids100, 142 (1988).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Ilharco, L.M., Santos, A.M., Silva, M.J. et al. Comparison of the structural information on sol-gel systems provided by pyrene labeled fluorescent probes. J Sol-Gel Sci Technol 8, 877–882 (1997). https://doi.org/10.1007/BF02436954
Issue Date:
DOI: https://doi.org/10.1007/BF02436954