A pin-to-plate type spark discharge generator has been studied and compared with a conventional rod-to-rod type spark discharge generator. The pin-to-plate type generator has asymmetric electrodes composed of a pin with a sharp tip as a positive electrode and a grounded plate having a narrow exit hole at the center. In comparison to the conventional rod-to-rod type generator, the pin-to-plate type generator produces much smaller unagglomerated charged nanoparticles with a narrower size distribution and nearly equal charge distribution at higher concentration. In-Sn alloy, silver and copper nanoparticles were tested via these two different configurations, and the size, morphology and charge state of those particles were analyzed with respect to spark parameters and flow pattern in each configuration. The generation of much smaller unagglomerated nanoparticles with a narrow size distribution via the pin-to-plate type generator would be mainly attributed to much faster transport of as-produced particles in comparison to the case of the rod-to-rod type generator. (C) 2012 Elsevier Ltd. All rights reserved.