Anomalous dispersion of bioinspired flower-like microparticles for oil/water separation

Hydrophobic particles have been suffering from aggregation in aqueous media, which limits their applications in oil/water separation. Surfactants have been used to increase the dispersity of the hydrophobic particles in water, but this approach compromises particles' hydrophobicity and oil absorption capabilities. Recently, hierarchical microparticles decorated with nanospikes were found to exhibit long-term anomalous dispersion in liquid medium without adding any surfactants. However, whether this anomalous dispersion phenomenon was applicable to 2D nano-petals decorated microparticles still remains unknown. Here, we developed a ZnO-based flower-like microparticles (FLMPs) whose surfaces were attached with 2D nano-petals, and we examined their anomalous dispersity. Our results showed that both hydrophilic and hydrophobic FLMPs could achieve anomalous dispersity either in water or organic solvents, likely due to reduced interparticle collision by the 2D nano-petals. In addition, the functional hydrophobic FLMPs also possessed a large surface area and superhydrophobic surfaces to efficiently absorb oil spills on water and oil emulsion suspended in water. In contrast, the hydrophobic microbeads (MBs) without nano-petals structure seriously aggregated in water and exhibited reduced oil absorption abilities. Our work demonstrated the new finding of 2D nano-pedal structure-mediated anomalous dispersity, and provided a new method for effective oil/water separation using superhydrophobic particles without surfactants.