Nano Cu2O should be sealed in vacuum and stored in cool and dry room and it should not be exposure to air. In addition, the product should be avoided under stress.
Cuprous oxide (Cu2O) is very unstable, during application or exposure to air, very small percentage of the material might be oxidized to Copper Oxide (CuO), or restore to Copper (Cu) – we use high purity metal copper for making Cu2O nanopowder。
Therefore, containing little impurity phase (CuO or Cu) is quite normal and very difficult to remove it. However it generally does not affect any performance.