The present invention relates to the employment of molecular crystals as bactericidal, viricidal and algicidal devices, but more particularly to the molecular semiconductor crystal tetrasilver tetroxide Ag4 O4 which has two trivalent and two monovalent silver atoms per molecule, and which through this structural configuration enables electronic activity on a molecular scale capable of killing algae and bacteria via the same mechanism as macroscale electron generators. The concept of molecular scale semiconductor devices for the storage of information has been the subject of much activity in recent years so that the concept of a molecular scale device performing such functions as storing information or acting as resistors, capacitors or photovoltaic devices is well accepted. The molecular device of this invention is a multivalent silver diamagnetic semiconductor. Now the bactericidal activity of soluble divalent silver (Ag II) complex bactericides is the subject of U.S. Pat. No. 5,017,285 of the present inventor. The inventor has also been granted U.S. Pat. Nos. 5,078,902, 5,073,382, 5,089,275, and 5,098,582, which all deal with Ag II bactericides but more particularly with (respectively) halides, alkaline pH, stabilized complexes and the divalent oxide. It is the last patent, i.e., U.S. Pat. No. 5,098,582, and its perfection that has led to my original concept of the molecular device of the present invention. Now said patent designated AgO as divalent silver oxide, the popular name of the compound. Indeed, the Merck Index (11th Edition) designates the oxide as silver(II) oxide (AGO) (entry 8469). However, it also states that it is actually a silver(I)-silver(III) oxide with a molecular weight of 123.88. Said oxide is actually on a molecular level Ag4 O4 where one pair of silver ions in the molecule is trivalent and another pair is monovalent.