Nanocrystals in the lower-nanometer-size range are attracting growing interest due to their unique properties. A simple and versatile atmospheric direct current mini-arc plasma source has been developed to produce nanoparticles as small as a few nanometers. The nanoparticles are formed by direct vaporization of solid precursors followed by a rapid quenching. Both semiconductor tin oxide and metallic silver nanoparticles have been produced at rates of 1–10 mg/h using the mini-arc source. Transmission electron microscopy and X-ray diffraction analyses indicate that most nanoparticles as produced are nonagglomerated and crystalline. Size distributions of nanoparticles measured with an online scanning electrical mobility spectrometer are broader than the self-preserving distribution, suggesting that the nanoparticle growth is coagulation-dominated, and that the particles experience a range of residence times. The electrical charges carried by as-produced aerosol nanoparticles facilitate the manipulation of nanoparticles. The new mini-arc plasma source hence shows promise to accelerate the exploration of nanostructured materials.