He, Self-assembly of single-crystal ZnO nanorod arrays on flexible activated carbon fibers substrates and the superior photocatalytic degradation activity, Applied Surface Science (2020), doi: https://doi. ABSTRACT: The synthesis of one-dimensional nanocrystals on flexible substrates has attracted a great attention in the last decade. We here report an integrated approach using a sequential solgel and hydrothermal synthesis method to successfully assemble well-aligned single-crystalline

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... ZnO nanorod arrays (ZnO NRAs) on activated carbon fibers (ACFs). The ZnO NRAs, with high rod surface area (up to 20 m 2 g -1 ), high aspect ratio (rod length/rod diameter, ca. 20:1) and high defect level (indicated by an extremely sharp blue emission, strong green and yellow emissions), were shown to grow nearly perpendicularly on the ACFs surface. The pre-coating of ZnO seed layers on ACFs surface during sol-gel synthesis is vital for the growth of the ordered ZnO nanorod arrays. The structural and optical properties of ZnO NRAs/ACFs can be adjusted by tuning the synthesis parameters for sol-gel and hydrothermal steps. As compared to the ZnO NRAs grown on the stiff substrates (e.g., silicon wafer, fluorine-doped tin oxide glass, GaN and metal sheets), ZnO NRAs grown on ACFs have very high surface area and intensive blue, green and yellow emissions. The novel ZnO NRAs/ACFs show excellent photocatalytic degradation of methylene blue and robust recyclability as compared to the individual ZnO nano particles (powder, NRs and NRAs). KEYWORDS: ZnO, nanorod array, flexible substrate, defect, aspect ratio, photocatalysis Introduction One-dimensional (1D) materials, such as nanosheets, nanowires and nanorods, with wellordered alignments and unique structures, have attracted extensive research attention in nanoscience and nanotechnology. Various technological applications have been identified for such materials, for example in sensors, solar cells, transducers and photocatalysis [1, 2] . Zinc oxide (ZnO), a wide band-gap (3.37 eV) semiconductor with a high exciton binding energy of 60 meV at room temperature [3] , is regarded as a promising photocatalytic material. In several reports[4], ZnO shows better performance than the well-known TiO 2 , e.g., for photocatalytic degradation of