The electrochemical deposition of ZnO hierarchical nanostructures directly from PHEMA hydrogel coated electrodes has been successfully demonstrated. A variety of hierarchical ZnO nanostructures, including porous nanoflakes, nanosheets and nanopillar arrays were fabricated directly from the PHEMA hydrogel coated electrodes. Hybrid ZnO-hydrogel composite films were formed with low zinc concentration and short electrodeposition time. A dual-layer structure consisting of a ZnO/polymer and pure ZnO layer was obtained with zinc concentration above 0.01 M. SEM observations and XPS depth profiling were used to investigate ZnO nanostructure formation in the early electrodeposition process. A growth mechanism to understand the formation of ZnO/hydrogel hybrid hierarchical nanostructures was developed. The I-V characteristics of the ZnO-hydrogel composite films in dark and under ultraviolet (UV) illumination demonstrate potential applications in UV photodetection.
Three-dimensional hierarchical ZnO films with lotus-leaf-like micro/nano structures were successfully fabricated via a biomimetic route combining sol-gel technique, soft lithography and hydrothermal treatments. PDMS mold replicated from a fresh lotus leaf was used to imprint microscale pillar structures directly into a ZnO sol film. Hierarchical ZnO micro/nano structures were subsequently fabricated by a low-temperature hydrothermal growth of secondary ZnO nanorod arrays on the micro-structured ZnO film. The morphology and size of ZnO hierarchical micro/nano structures can be easily controlled by adjusting the hydrothermal reaction time. Wettability of hierarchical ZnO thin films was found to convert from superhydrophilicity to hydrophobicity after a low-surface-energy fluoroalkylsilane modification. Improved wetting properties from hydrophobic to superhydrophobic can be tuned by increasing the growth of ZnO nanorods structures.
Highly crystalline TiO2 nanostructures were prepared through a facile inorganic acid-assisted hydrothermal treatment of hexagonal-structured assemblies of nanocrystalline titiania templated by cetyltrimethylammonium bromide (Hex-ncTiO2/CTAB Nanoskeleton) as starting materials. All samples were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The influence of hydrochloric acid concentration on the morphology, crystalline and the formation of the nanostructures were investigated. We found that the morphology and crystalline phase strongly depended on the hydrochloric acid concentrations. More importantly, crystalline phase was closely related to the morphology of TiO2 nanostructure. Nanoparticles were polycrystalline anatase phase, and aligned nanorods were single crystalline rutile phase. Possible formation mechanisms of TiO2 nanostructures with various crystalline phases and morphologies were proposed.
S. Dai, X. Zhang, Z. Du, Y. Huang, and H. Dang. (2010)cite arxiv:1009.1588 Colloids and Surfaces B: Biointerfaces Volume 42, Issue 1, 25 April 2005, Pages 21–28.