Reaction between zinc cupferron and alkali at the organic–aqueous interface has been investigated in detail. In the presence of an organic amine, this reaction yields ZnO nanorods, the morphology depending on the concentration of reactants. In the absence of the amine, ultrathin films of ZnO are produced. Amazingly, both the nanorods and thin films are single crystalline in nature, even though the synthesis is carried out at room-temperature. Single-crystalline, substrate-free ultrathin films of ZnO, is indeed an extraordinary feature of synthesis at the liquid–liquid interface. Photoluminescence spectra show defect-related bands besides that due to band edge emission. The nanostructures exhibit ferromagnetism due to surface defects.