Phase-manipulable synthesis of Cu-based nanomaterials using ionic liquid 1-butyl-3-methyl-imidazole tetrafluoroborate

Using the ionic liquid (IL), 1-butyl-3-methyl-imidazole tetrafluoroborate, and the precursor Cu7Cl4(OH)(10)center dot H2O, series of phase-manipulable Cu-based nanomaterials were synthesized by hydrothermal and microwave assisted routes, respectively. The structural characters of the as-prepared CuO, CuO/Cu2O composites and pure Cu nanoparticles were investigated by XRD, SEM, TEM and HRTEM, and their surface photovoltaic properties were studied by surface photovoltage spectra. Via hydrothermal route Cu2+ ions were found to be reduced gradually into Cu+ and subsequently Cu-0 with increasing the IL, and various phase ratio of CuO, Cu2O and Cu composite nanosheets and pure Cu nanoparticles were obtained. This implies that the IL could function as both a reductant in the oxygen-starved condition and a template for the nanosheet products. The H-1-NMR result of the IL supports it being a reductant. In microwave assisted route, however, only monoclinic single crystalline CuO nanosheets were obtained, which indicates the IL being a template only in oxygen-rich condition. Therefore, the crystal phase, composition and morphology of the Cu-based products could be controlled by simply adjusting the quantity of the IL and oxygen in solution routes. The molecular structure of the IL after oxidation reactions was investigated by H-1-NMR and a possible reaction mechanism was proposed. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim