Monodisperse PVP-stabilized Pt nanoparticles (PtNPs) with an average diameter of 1.4 +/- 0.3 nm were efficiently produced via the complete reduction of Pt4+ ions by BH4- in a micromixer. Because of microfluidic mixing, hydrolytic decomposition of BH4- by the PtNPs formed in the initial stage of the reaction was suppressed, and hence, the PtNP yield was higher than that in the conventional batch mixing. The results of various spectroscopic analyses including EXAFS, FTIR of CO and XPS revealed that the microfluidically synthesized PtNPs were negatively charged and had a high population of edges and vertices on their surface. (C) 2011 Elsevier B. V. All rights reserved.