BENZOPHENONE PHOSPHORESCENCE IN SUSPENSIONS OF DERIVATIZED SILICA NANOPARTICLES

VALERIA B. ARCE; HEBE SARAVÍ CISNEROS; DANILA RUIZ; PAULA CAREGNATO; MERCEDES SCHIAVONI; VERONICA C. MORA; MÓNICA C. GONZALEZ; PATRICIA ALLEGRETTI; DANIEL O. MÁRTIRE

Cordoba

Congreso; 9ª Conferencia Latinoamericana de Fisicoquimica Organica.; 2007

Derivatized silica nanoparticles were prepared by esterification of the silanol groups of fumed silica nanoparticles with alcohols using a modification of the procedures cited in references 1 and 2. These particles were characterized by Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller analysis (BET), transmission electron microscopy (TEM), and total organic carbon (TOC).   Butoxylated silica nanoparticles (BSN) suspensions in water: acetonitrile mixtures were used as quenchers of benzophenone (BP) phosphorescence in time-resolved experiments at the excitation wavelengths of 266 and 337 nm. The bare silica nanoparticles are unreactive toward benzophenone triplet state (BP*). Thus, the phosphorescence quenching by butoxylated silica nanoparticles should be due to H- abstraction from the butoxy groups to yield the diphenylketyl radical. [1] Gabriel C. Ossenkamp, Tim Kemmitt, and Jim H. Johnston, Langmuir. 2002, 18, 5749-5754. [2] Gabriel C. Ossenkamp, Tim Kemmitt, and Jim H. Johnston, Chem. Mater. 2001, 13, 3975-3980. [3] Koichi Okamoto, Noboru Hirota and Masahide Terazima, J. Chem. Soc., Faraday Trans., 1998, 94, 185-194. [4] Scaiano, J. C. J. Photochem.1973, 2, 81. [5] Wagner, P. J Chemistry of excited triplet organic carbony compounds. Topics Curr.1976, Chem. 66, 1–52. [6] Wagner, P. J. and B.-S. Park.. Org. Photochem.1991, 11, 227–366. [7] Yousry M. A. Naguib, Colin Steel, Saul G. Cohen, and Michael A. Young, J . Phys. Chem. 1987, 91, 3033-3036. [8] Shield, S.R.; Harris, J.M. J. Phys. Chem. B  2000, 104, 8527-8535.