An easy, novel route to prepare Janus nanoparticles and nano-bowls with tunable shapes has been developed. This approach uses a new kind of monodisperse vinyl-silica nanoparticles as templates to obtain large amounts of uniform Janus particles and nano-bowls (several grams). The efficient method adopts water-based hydrolysis-condensation and seed-emulsion polymerization. The uniform Janus nanopartides and nano-bowls will display wide potential applications in many fields, such as: chemical sensors, construction of complex superstructures and nano-bioreactors. (C) 2011 Elsevier Inc. All rights reserved.