Cold crystallization and morphology control of ZnO nanostructures for chemical sensors

Abstract Cold crystallization and morphology control of ZnO nanostructures have been achieved. Various ZnO nanostructures, such as ZnO rod arrays, high c ‐axis‐oriented stand‐alone ZnO self‐assembled films, ZnO particulate films, ZnO nanorod arrays, semicircular ZnO nanowhisker assemblies, bunched rose‐ and core–shell‐like ZnO particles, twin ZnO nanoarray assemblies, ZnO nanotubes, and ZnO nanoflowers, have been developed using the hexagonal crystal structure of ZnO. These structures have advantages, such as high anisotropy, high specific surface area, high crystallinity, and characteristic crystal facets, and can be applied in devices such as photoelectric conversion sensors, chemical sensors, gas sensors, batteries, and catalysts. Additionally, various nanostructures using other oxide materials are expected to be developed by applying the scientific knowledge obtained from the cold crystallization and morphology control of ZnO. Cold crystallization, which is a long‐standing challenge in the field of ceramics, has been realized, which is a historical turning point in the field of ceramics research.