Gold nanoparticles (Au-NPs) of 8 nm average diameter were obtained by thermal reduction under nitrogen from KAuCl4 in the presence of n-butylimidazol dispersed in the ionic liquid (IL) 1-n-butyl-3-methylimidazolium tetrafluoroborate (BMIm(+)BF(4)(-)). Characterization of the Au-NP was done by transmission electron microscopy (TEM) and dynamic light scattering (DLS). Catalytic activities of the Au-NP/IL dispersion were evaluated in the oxidation of 1-phenylethanol at 100 and 160 degrees C under 4 bar pressure of dioxygen in a base-free system. Au-NP in combination with the radical initiator N-hydroxyphthalimide (NHPI) showed good conversion and selectivity for the oxidation of 1-phenylethanol to acetophenone through formation of an alpha-hydroxy carbon radical. The concomitant side products di(1-phenylethyl)ether and di(1-phenylethyl)peroxide were rationalized by an equilibrium due to the IL matrix of the alpha-hydroxy carbon radical with the 1-phenylethoxy radical. Maximum turnover number was similar to 5200 based on the total number of moles of gold but a factor of about six larger, TON approximate to 31 300, when only considering the Au-NP surface atoms. The fraction (N-S/N-T) of exposed surface atoms (N-S approximate to 2560) for an average 8 nm Au-NP (having N-T approximate to 15 800 atoms in a similar to 17-shell icosahedral or cuboctahedral particle) was estimated here as 0.16. (C) 2013 Elsevier B.V. All rights reserved.