Synthesis of novel ZnO/ZnAl₂O₄ multi co-centric nanotubes and their long-term stability in photocatalytic application

Based on the Kirkendall effect, novel double, triple and quadruple co-centric nanotubes of ZnO/ZnAl₂O₄ have been successfully fabricated by combining the two techniques of electrospinning and atomic layer deposition. The as-prepared samples were annealed at 900 °C under air. Their morphological, structural and optical properties were studied by Scanning Electron Microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Energy-Dispersive X-ray spectroscopy (EDX), UV-visible spectrophotometry, Raman spectroscopy, photoluminescence (PL) and reflectance emission. The performances and long-term stability of these multi co-centric nanotubes for photocatalytic applications have been evaluated under the same conditions. As result, in the photodegradation of methyl orange (MO) under UV irradiation, the triple and quadruple co-centric nanotubes of ZnO/ZnAl₂O₄ exhibit a higher photodegradation efficiency (94% and 99%, respectively) in repeated and long-term applications compared to the pure ZnO which has very low long-term photocatalytic stability. Thus, the fact of coupling these two semiconductors ensured a high photocatalytic activity and long term stability.