Solvothermal Synthesis of Hierarchical Colloidal Nanocrystal Assemblies of ZnFe(2)O(4) and Their Application in Water Treatment

Hierarchical colloidal nanocrystal assemblies (CNAs) of ZnFe(2)O(4) have been synthesized controllably by a solvothermal method. Hollow ZnFe(2)O(4) spheres can be formed with the volume ratios of ethylene glycol to ethanol of 1:4 in the starting systems, while solid ZnFe(2)O(4) CNAs are obtained by adjusting the volume proportion of ethylene glycol to ethanol from 1:2 to 2:1. Magnetometric measurement data showed that the ZnFe(2)O(4) CNAs obtained with the volume ratios of 1:2 and 1:1 exhibited weak ferromagnetic behavior with high saturation magnetization values of 60.4 and 60.3 emu·g(−1), respectively. However, hollow spheres showed a saturation magnetization value of 52.0 emu·g(−1), but the highest coercivity among all the samples. It was found that hollow spheres displayed the best ability to adsorb Congo red dye among all the CNAs. The formation mechanisms of ZnFe(2)O(4) CNAs, as well as the relationship between their structure, crystallite size, and properties were discussed based on the experimental results.