Shape evolution, photoluminescence and degradation properties of novel Cu ₂O micro/nanostructures

Three kinds of novel cuprous oxide (Cu ₂O) micro/nanostructures are synthesized via a facile template-free hydrothermal method. Two factors are critical for the growth process of typical samples: the concentration of copper ions (Cu(II)) and the addition of Polyvinylpyrrolidone (PVP) as surfactant. It is found that the application of ethanol as solvent speeds up the reduction rate of Cu(II), and it promotes the aggregating of Cu ₂O nanocrystals at the preliminary stage to form irregular spherical structures. Photoluminescence (PL) properties of the three kinds of samples and their photocatalytic activities for degradation of Methyl Orange (MO) are also measured. The sample with higher concentration of copper vacancy (V _Cu) defects has better photocatalytic ability, indicating that besides the morphology of Cu ₂O nano/microcrystals, the defects in crystalline structures can also influence their electrical characteristics, and thus change their photocatalytic activity. This provides a potential method to improve the photocatalytic performances of Cu ₂O crystals.