A reactor and method for production of nanostructures produces, for example, metal oxide nanowires or nanoparticles. The reactor includes a metal powder delivery system wherein the metal powder delivery system includes a funnel in communication with a dielectric tube; a plasma-forming gas inlet, whereby a plasma-forming gas is delivered substantially longitudinally into the dielectric tube; a sheath gas inlet, whereby a sheath gas is delivered into the dielectric tube; and a microwave energy generator coupled to the dielectric tube, whereby microwave energy is delivered into a plasma-forming gas. The method for producing nanostructures includes delivering a plasma-forming gas substantially longitudinally into a dielectric tube; delivering a sheath gas into the tube; forming a plasma from the plasma-forming gas by applying microwave energy to the plasma-forming gas; delivering a metal powder into the dielectric tube; and reacting the metal powder within the plasma to form metal oxide nanostructures.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
 The invention was supported, in whole or in part, by a grant, No. W9113M-04-C-0024, from Nanowire Technology for Missile Defense of the U.S. Army Space Missile Defense Command; a grant, No. DE-FG36-05G085013A, from the U.S. Department of Energy/Kentucky Rural Energy Consortium; and a grant, No. DE-FG02-05ER64071, from the U.S. Department of Energy which supports the Institute for Advanced Materials and Renewable Energy at the University of Louisville. The Government has certain rights in the invention.