Hydrothermal synthesis and photocatalytic activity of CdO2 nanocrystals.

CdO(2) nanocrystals with different sizes were synthesized via the hydrothermal reaction of 3CdSO(4).8H(2)O and H(2)O(2) in 1.25-6.25 vol.% ammonia solutions at 100-140 degrees C for 12h. The resultant products were characterized by powder X-ray diffraction, transmission electron microscope, thermal gravimetric and differential scanning calorimetry, and UV-vis absorption spectra. It was concluded that the resultant products were pure cubic phase CdO(2) nanocrystals, and they would decompose at temperatures higher than 180 degrees C. In addition, degradation of methyl orange in aqueous solution (20.0mg/l) was carried out with the CdO(2) nanocrystals as photocatalyst under ultraviolet light irradiation. The experimental results showed that even a little amount (0.2g) of as-prepared CdO(2) nanocrystals could catalyze degradation of 500 ml methyl orange solution above 99% after 5h of illumination, and smaller size made for higher photocatalytic activity of CdO(2) nanocrystals.