The invention relates to an accumulator, particularly a prismatic lead accumulator, comprising a housing and at least one stack of plates, which has a plurality of spaced-apart pole plates that are entirely suspended by a fixing element in at least one circumferential direction. Separate valves are provided on the single shaft actuator for each of two valve body slots, each body slot being closed or opened according to the position of the single shaft. The metal nanoparticles of a controlled size may be formed by a thermal decomposition reaction of a metal salt in a passivating solvent.