We synthesized carbon nano-onions (CNOs) using a low-voltage spark discharge in a liquid and studied the effects of liquid type and pulse duration. By the pulsed electric discharge between two graphite rods of 120 mm length and 6 mm diameter submerged into a 200 ml toluene or ethanol, hollow CNOs with diameters ranging from 10 to 30 nm were produced. CNOs produced using toluene grew more carbon shells than does the sample produced using ethanol. The sample that was synthesized using pulsed plasma with pulse duration of 5 mu s showed more carbon shells (10-30) than the sample prepared by 12 mu s (2 to 10). High performance liquid chromatography (HPLC) and high resolution transmission electron microscopy analyses confirmed that the sample produced at 12 mu s pulsed plasma contains fullerene C-60, while the sample prepared at 5 mu s does not.