Nanostructure Control in Zinc Oxide Films and Microfibers through Bioinspired Synthesis of Liquid-Crystalline Zinc Hydroxide Carbonate; Formation of Free-Standing Materials in Centimeter-Level Lengths

Free-standing zinc oxide in the forms of films and fibrous materials are expected to be used as functional devices such as piezoelectric devices and catalyst filters without being limited by the growth substrate. Herein, a synthetic morphology-control method for 2D and 1D free-standing ZnO materials with ordered and nanoporous structures by conversion of liquid-crystalline (LC) zinc hydroxide carbonate (ZHC) nanoplates is reported. As a new colloidal liquid crystal, the LC ZHC nanoplate precursors are obtained by a biomineralization-inspired method. The approach is to control the morphology and crystallographic orientation of ZHC crystals by using acidic macromolecules. Their nano-scale and oriented structures are examined. The LC oriented ZHC nanoplates have led to the synthesis of free-standing films and microfibers of ZHC in centimeter-level lengths, with the successful thermal conversion into free-standing films and microfibers of ZnO. The resultant ZnO films and ZnO microfibers have nanoporous structures and preferential crystallographic orientations that preserve the alignment of ZHC nanoplates before conversion. Free-standing films and microfibers of zinc oxide with oriented and nanoporous structures are prepared using a liquid-crystalline (LC) colloidal precursor method. LC zinc hydroxide carbonate (ZHC) nanoplates are obtained through biomineralization-inspired crystallization. Alignment control and subsequent thermal conversion of LC ZHC lead to the synthesis of free-standing ZnO films and ZnO microfibers.image