Nanoparticles are continuously synthesized from submerged magnesium, zinc, and silver rods 1-2 mm in diameter by microwave plasma in pure water at 20 kPa. Magnesium-hydroxide nanoplates shaped as triangles, truncated triangles or hexagons with 25-125 nm in size are synthesized with a production rate of 60 g h(-1). Zinc-oxide nanoparticles formed as sharp sticks with diameters of 50 nm and lengths of 150-200 nm are synthesized with a production rate of 14 g h(-1). Silver nanoparticles with a diameter of approximately 6 nm are synthesized with a production rate of 0.8 g h(-1). The excitation temperature is estimated by applying the Boltzmann plot method in assumption of local thermodynamic equilibrium. The excitation temperatures obtained from hydrogen, magnesium, and zinc lines are 3300 100 K, 4000 +/- 500K, and 3200 +/- 500 K, respectively. (C) 2011 Elsevier B.V. All rights reserved.