Controlled Synthesis of Different Shapes of Cu2O via γ-Irradiation

Herein, we report a facile synthesis of submicrometer-to-micrometer-sized single-crystalline Cu2O particles with cetyltrimethylammonium bromide (CTAB) as a capping material or template by gamma-irradiation under ambient conditions. The morphologies of Cu2O single-crystalline particles, such as eight-pod cubic, six-armed star-like, octahedral, and spindle-like structures, were obtained in high yield by controlling the ratio of the concentration of CTAB to that of copper ions, in which CTAB serves as a nucleation and growth controller. Moreover, we demonstrated that the dose rate and radical scavengers (e.g., small molecular alcohols) can also influence the morphologies of Cu2O through adjusting the reduction rate of Cu2+ ions, making the gamma-irradiation method more versatile to control the shapes of inorganic crystals. The band gap of six-armed star-like Cu2O calculated from the UV-vis spectrum corresponds to 2.85 eV, which is larger than the direct band gap (2.17 eV) of the bulk Cu2O. Another value of 1.97 eV hints excitonic discrete energy level in forbidden band arising from the crystal defects of as-prepared Cu2O single crystal.