Hydrothermal syntheses of CuO, CuO/Cu2O, Cu2O, Cu2O/Cu and Cu microcrystals using ionic liquids

In this paper, CuO, CuO/Cu2O, Cu2O, Cu2O/Cu and Cu microcrystals were synthesized via a hydrothermal method by mixing Cu(NO3)2·3H2O and NaOH together in the presence of an ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate([BMIM]BF4) or 1-butyl-3-methylimidazolium chloride([BMIM]Cl). The structures and the morphologies of the obtained products were characterized by means of X-ray diffractometer( XRD), field-emission scanning electron microscopy/energy-dispersive spectroscopy(FESEM/EDS), transmission electron microscopy/selected area electron diffraction(TEM/SAED) and Raman spectroscopy. The result of XRD indicates that Cu2O and Cu microcrystals are cubic phase and the Raman spectra confirm the presence of carbon. The results of FESEM and TEM images show Cu2O microcrystals as rule cubes of 2 μm in length and Cu particles of 5 μm in diameter. According to the difference between crystal structures, bi-component and single component products were synthesized by adjusting the reaction conditions. A possible formation mechanism of Cu2O and Cu was proposed in [BMIM]BF4.