Self-Assembly of Peptide-Polyoxometalate Hybrid Sub-Micrometer Spheres for Photocatalytic Degradation of Methylene Blue.

The spontaneous formation of hybrid submicrometer spheres that were composed by a Weakley-type polyoxometalate Na9[EuW10O36]·32H2O (denoted as EuW10) and cationic peptide (K8) through a simple ionic self-assembly method was investigated. The approach presented in this study is an extended research which combined a biomolecule and a functional inorganic polyoxoanion for the fabrication of a multifunctional material. The K8/EuW10 hybrid submicrometer spheres were fully characterized by transmission electron microscopy, field-emission scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, confocal laser scanning microscopy, and fluorescence spectra. The results indicated that the electrostatic interaction, hydrogen-bonding interaction, and combined hydrophobic interaction between EuW10 and K8 favored the formation of the smooth submicrometer sphere structure. Once the EuW10/K8 submicrometer spheres were forming, the fluorescence of EuW10 was reduced due to the hydrogen bonding between the ammonium group of K8 and the oxygen atom of EuW10 that blocked the hopping of the d1 electron in EuW10. Interestingly, our submicrometer spheres showed excellent decomposition efficiency toward organic pollutants such as the dye of methylene blue (MB), suggesting their promising applications in the treatment of wastewater.