Temperature-controlled assembly and morphology conversion of CoMoO₄·3/4H₂O nano-superstructured grating materials

The regular and homogeneous single-crystal CoMoO₄·3/4H₂O nanorods, with the diameters ca. 100–300 nm and lengths ca. 8–15 μm, have been successfully prepared by a simple and facile precipitation method. Their morphology conversion from broom-like to cage-like structure has been firstly reported through controlling the reaction temperature. The broom-like microbunches were obtained at 50 °C while at 80 °C, dispersive nanorods can be prepared. As the temperature reached 90 °C, the morphology of the products converted to cage-like microspheres. SEM results show that the reaction temperature has a critical role in both the formation of the products and their morphologies. The UV–visible diffuse reflectance absorbance spectra of the products display two intense, broad absorbance bands cover almost the whole ultraviolet and visible region except for a narrow region around 450 nm, which is in the region for purple light. Based on the experimental results, a possible formation mechanism was also proposed. The synthesis strategy is simple, facile, mild, and has a good reproducibility. The as-prepared products may have potential applications in optics, catalysis, and grating materials.