Colloidal platinum-ruthenium bimetallic nanoparticles with 2.3 nm were synthesized in solution and then immobilized on tin dioxide powder to make a supported nanocatalyst (Pt-Ru/SnO2). The immobilized bimetallic nanoparticles had the same size and size distribution as the solution dispersed ones. Selective hydrogenation of o-chloronitrobenzene to o-chloroaniline was performed over the as-prepared Pt-Ru/SnO2 nanocatalyst without using any solvent; 99.5% selectivity to o-chloroaniline at 100% conversion was achieved. (C) 2013 Elsevier B.V. All rights reserved.