title: Hierarchical Nanoflowers on Nanograss Structure for a Non-wettable Surface and a SERS Substrate.
abstract: Hierarchical nanostructures of CuO nanoflowers on nanograss were investigated for self-cleaning and surface plasmonic applications. We achieved the hierarchical nanostructures using one-step oxidation process by controlling the formation of flower-like nanoscale residues (nanoflowers) on CuO nanograss. While the nanograss structure of CuO has a sufficient roughness for superhydrophobic characteristics, the additional hierarchy of nanoflowers on nanograss leads to a semi-reentrant structure with a high repellency even for a very small droplet (10 nL) of low surface tension liquid such as 25 % ethanol (~35 mN/m), thus providing non-wettable and self-cleaning properties. Furthermore, the CuO hierarchical nanostructure serves as a substrate for surface-enhanced Raman spectroscopy (SERS). Both of the CuO nanograss and nanoflower provide many nanoscale gaps that act as hot-spots for surface-enhanced Raman signal of 4-mercaptopyridine (4-Mpy), thus enabling a non-destructive detection in a short analysis time with relatively simple preparation of sample. Especially, the CuO nanoflower has larger number of hot-spots at the nanogaps from floral leaf-like structures, thus leading to three times higher Raman intensity than the CuO nanograss. These multifunctional results potentially provide a path toward cost-effective fabrication of a non-wettable surface for self-maintenance applications and a SERS substrate for sensing applications.
authors.affiliation: School of Integrated Technology, Yonsei University, Incheon, Republic of Korea.|Yonsei Institute of Convergence Technology, Yonsei University, Incheon, Republic of Korea.
authors.forename: Jun-Young
authors.initials: JY
authors.lastname: Lee
authors.affiliation: School of Integrated Technology, Yonsei University, Incheon, Republic of Korea.|Yonsei Institute of Convergence Technology, Yonsei University, Incheon, Republic of Korea.
authors.forename: Jaehyun
authors.initials: J
authors.lastname: Han
authors.affiliation: School of Integrated Technology, Yonsei University, Incheon, Republic of Korea.|Yonsei Institute of Convergence Technology, Yonsei University, Incheon, Republic of Korea.
authors.forename: Jihye
authors.initials: J
authors.lastname: Lee
authors.affiliation: Yonsei Institute of Convergence Technology, Yonsei University, Incheon, Republic of Korea.
authors.forename: Seungmuk
authors.initials: S
authors.lastname: Ji
authors.affiliation: School of Integrated Technology, Yonsei University, Incheon, Republic of Korea. jongsoukyeo@yonsei.ac.kr.|Yonsei Institute of Convergence Technology, Yonsei University, Incheon, Republic of Korea. jongsoukyeo@yonsei.ac.kr.
authors.forename: Jong-Souk
authors.initials: JS
authors.lastname: Yeo
keywords: CuO nanostructure; Hierarchical structure; Non-wetting; Oleophobic; Superhydrophobic; Surface-enhanced Raman spectroscopy