Butoxylated silica nanoparticles (BSN) were prepared by esterification of the silanol groups of fumed silica nanoparticles with butanol. These particles were characterized by FTIR, BET, TEM, and TOC. 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 phosphorescence signals obtained in the presence of the nanoparticles were fitted to biexponential decays. Both decays were accelerated in the presence of increasing amounts of BSN. A model including the reversible adsorption of BP on BSN and supported by computer simulations accounts for the observed results.