According to the work of Kayani et al. , the band at 624 cm -1 is attributed to copper oxide with oxidation number +1, copper (I) oxide, and Cu2O, commonly known as cuprite. This band was not identified in the spectrum of the nanoparticles synthesized in this work. Instead, the presence of the band in the 520 cm -1 region indicates that the oxide is in the form of CuO, i.e., copper (II) oxide, with oxidation number +2, known as tenorite .