摘要：为了研究基于核壳结构磁珠@TiO₂(MB@TiO₂)微米马达的正趋光性运动行为,利用超声辅助溶胶凝胶法在磁珠表面包覆薄TiO₂层,制备核壳结构的MB@TiO₂微米马达;采用扫描电子显微镜、透射电子显微镜、光学显微镜对MB@TiO₂微米马达的结构、形貌和运动性能进行表征。结果表明:MB@TiO₂微米马达呈核壳结构,其受光面和背光面在紫外光照射下发生的非对称光催化反应,使水介质中的H₂O₂光催化分解产物,在微米马达两侧不均匀分布形成浓度梯度;由于H⁺产物浓度梯度产生指向光源的扩散泳力占主导作用,MB@TiO₂微米马达呈现出朝向光源的正趋光性运动行为;正趋光性运动行为使得MB@TiO₂微米马达可以克服重力轻易翻越障碍,实现在复杂地形环境中航行或在远离基板的体相水中运动;结合TiO₂壳层的光催化活性和MB内核的磁响应性,MB@TiO₂微米马达未来有望作为易磁分离的"游动"光催化剂应用于环境治理。

关键词：微纳米马达；磁珠；趋光性；光催化

Abstract: In order to study the positive phototaxis behavior of core－shell structured magnetic bead@TiO₂ ( MB@TiO₂ ) micromotors，the surface of magnetic beads was coated with a thin TiO₂ layer using ultrasonic-assisted sol-gel method to prepare core－shell structured MB @TiO₂micromotors．The structure，morphology，and motion behaviors of MB@TiO₂micromotors were characterized by scanning electron microscope( SEM) ，transmission electron microscope( TEM) ，and optical microscope．The results show that the MB@TiO₂ micromotors have a core－shell structure．The asymmetric photocatalytic reactions between the light-irradiated surface and the shadowed surface of the MB@TiO₂ micromotors under ultraviolet light is used to make the photocatalytic products of hydrogen peroxide unevenly distribute on both sides of the micromotor to form a concentration gradient．The diffusiophoretic force produced by the H⁺ concentration gradient pointing to the light source predominates，and thus the MB@TiO₂ micromotors exhibit positive phototaxis toward the light source．Due to its positive phototaxis behavior，the MB@TiO₂ micromotors can easily overcome gravity to climb obstacles and swim in complex terrain or bulk water far from the substrate． In addition，combining the photocatalytic activity of the TiO₂shell and the magnetic responseof the MB core，the MB@TiO₂ micromotors are expected to be used as the“swimming”photocatalystsin environmental remediation witheasy magnetic separation in the future． 

Keywords: micro-nanomotor; magnetic bead; phototaxis; photocatalysis