Green hydrothermal synthesis and optical absorption properties of ZnO₂ nanocrystals and ZnO nanorods

A green hydrothermal method was proposed for the controllable synthesis of ZnO₂ nanocrystals and ZnO nanorods, using the common and cost-effective 2ZnCO₃·3Zn(OH)₂ powder and 30mass% H₂O₂ aqueous solution as the raw materials. The characterization results from X-ray diffraction, high resolution transmission electron microscopy, transmission electron microscopy and energy dispersive X-ray spectroscopy indicated that the products synthesized at 100–120°C for 6h or at 170°C for 0h were cubic phase ZnO₂ nanocrystals; while those synthesized at 170°C for 3–6h were hexagonal phase ZnO nanorods. The UV–vis absorption spectra showed that the as-synthesized ZnO₂ nanocrystals and ZnO nanorods had optical band gaps of about 4.1 and 3.3eV, respectively.