Synthesis and surface hydrophobic functionalization of ZnO nanocrystals via a facile one-step solution method

One-dimensional hydrophobic ZnO nanocrystals were successfully prepared via a one-step process through a direct precipitation reaction in aqueous solutions of ZnSO4 and NaOH with self-prepared octadecyl dihydrogen phosphate (C18H37OPO3H2, ODP) as a surface functionalizing reagent. Scanning electron microscope (SEM) and X-ray diffraction (XRD) results showed that the obtained ZnO particles were one-dimensional (1D) with hexagonal crystal structure. Measurements of relative contact angle and active ratio indicated that the obtained 1D ZnO nanocrystals were hydrophobic. The results of Fourier transform infrared spectroscopy (FT-IR) spectrum and X-ray photoelectron spectroscopy (XPS) clearly showed the formation of interfacial chemical bonds between ZnO and ODP. Furthermore, from the results of TGA test, it was confirmed that a certain amount of organic components existed in the 1D ZnO nanocrystals. These results suggested that the formed organics were bonded onto the surface of 1D ZnO nanocrystals during the reaction process, besides, the organics resulted in the perfect compatibility of obtained ODP functionalized ZnO particles with common organic reagents like ethanol, cyclohexane, and acetone. The influences of ODP on the size of the obtained ZnO particles and the mechanism of surface hydrophobic functionalization by ODP were presented.