We present a plasma-based technique to synthesize iridium nanoparticles (Ir NPs) for enzyme-free detection of hydrogen peroxide (H2O2). Solutions of Ir salt precursor are electrochemically reduced by a gaseous, atmospheric-pressure microplasma electrode. As compared to Ir NPs synthesized by chemical reduction, Ir NPs synthesized by plasma electrochemical reduction (PER) are free of metallic impurities such as Na. The resulting electrocatalytic properties of the Ir NPs synthesized by PER are found to be superior, including higher sensitivity and selectivity. Finally, we show that this approach can be extended to the fabrication of flexible Ir NP-based biosensors in a single step. (C) 2013 Elsevier B.V. All rights reserved.