Anionic surfactant-assisted hydrothermal synthesis of high-aspect-ratio ZnO nanowires and their photoluminescence property

ZnO nanowires with high-aspect-ratio of up to ca. 600 were synthesized in a quaternary reverse microemulsion containing sodium dodecyl sulfate (SDS) / water / heptane / n-hexane via a hydrothermal method. SDS, as an anionic surfactant, plays an important role in the formation of morphologies. Subsequently, we studied lots of key influencing factors including the molar ratio (w) value of NaOH to Zn(OAc)₂, the reaction temperature, and the instance without the quaternary reverse microemulsion. The selected-area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM) reveal the single-crystal nature of the ZnO nanowires. The morphologies and crystalline structure of the as-obtained products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and powder X-ray diffraction (XRD), respectively. Through this route, we can obtain a mass of products and the method is both convenient and reproducible. Finally, we measured the photoluminescence (PL) spectra and found that the ZnO nanowires exhibited green-orange emission at 525 nm and short ultraviolet emission at 380 nm and the ZnO nanomaterials with different aspect ratio (length to diameter) (L / D) showed PL intensity disciplinary change. Aiming at this phenomenon, we propose a reasonable mechanism to explain the PL spectra of the ZnO nanomaterials in detail.