Phosphorene is a single layer of black phosphorous, recently synthesized. Its two-dimentional structure is similar to the carbon-based graphene, however, it is semiconductor compared to graphene with zero gap. So this material has attracted much attention due to its potential usage for electronic or optoelectronic devices. Because of a lone pair of electrons on each phosphorous atom, however, pristine phosphorene may be extremely reactive with air, especially with oxygen, and thus the oxidation of phosphorene would be unavoidable during synthesis and/or fabrication processes unless they were done in a vacuum environment.