Gold nanoparticles of variable sizes have been exploited to study their influence on the emission behavior of methylamino derivative of pyrene. The probe molecules adsorbed onto the metallic surfaces suffer strong quenching of their fluorescence and the rate of quenching efficiency with particle size is different for two different size regimes. The size regime dependence of the particles on the fluorescence quenching process have been rationalized in view of the dependence of surface area on the size of the particles. The mechanism of fluorescence quenching on the gold surfaces has been treated in the light of electron and energy-transfer processes. (C) 2004 Elsevier B.V. All rights reserved.