Hydrophobicity of Highly Ordered Nanorod Polycrystalline Nickel and Silver Surfaces

Jan Macko,Jaroslav Vojtuš,Zuzana Kostecká,Natália Podrojková,Radim Hrdý,Jaromír Hubálek,Renáta Oriňaková,Roger M Smith,Andrej Oriňak

doi:10.4236/jmmce.2019.75020

Abstract

Highly ordered nickel and silver nanorods arrays prepared by alumina template assisted electrodeposition were investigated to determine the effect of the array geometry on metal surface hydrophobicity and adhesion forces. The nanorod geometry, clustering and pinning were used to characterize surface hydrophobicity and its modulation. A contribution of metal crystallographic orientation to the surface energy was calculated. To characterize nanorod array surface properties and elucidate the source of the particle adhesion effects has been calculated. The dispersive components of surface tension γSD and surface polarizability ks, as surface features that markedly characterize hydrophobicity and adhesion, were calculated. The highest hydrophobicity was found for Ag nanorods with aspect ratio of 10 then Ni nanorods with aspect ratio 10. The same geometry of nanorods particles resulted in different surface hydrophobicity and it was ascribed to the orientation of Ag and Ni crystals formed on the top of nanorods. Due to high hydrophobicity nanorod array surfaces could be used as an antifouling surface in medicine to select areas on implant surface not to be colonized by cells and tissues.

Highlights

Surface properties such as morphology are stable features of the surface, compared to chemical modifications which degrade over time [1]
Minerals and Materials Characterization and Engineering surfaces there are two basic approaches that can be considered to increase surface hydrophobicity: a) decreasing the surface energy by modifying the surface chemistry and b) decreasing the surface energy by increasing the surface roughness to increase the effective surface area, which can be expressed by the apparent contact angle θrough (1) [2]: cosθrough = r cosθ flat where r is the roughness factor defined as ratio of the actual surface area to its horizontal projection for Wenzel model
Silver and nickel coated nanorods were prepared by electrodeposition on alumina oxide (AAO) templates which were dissolved

Summary

Introduction

Surface properties such as morphology are stable features of the surface, compared to chemical modifications which degrade over time [1]. Minerals and Materials Characterization and Engineering surfaces there are two basic approaches that can be considered to increase surface hydrophobicity: a) decreasing the surface energy by modifying the surface chemistry and b) decreasing the surface energy by increasing the surface roughness to increase the effective surface area, which can be expressed by the apparent contact angle θrough (1) [2]: cosθrough = r cosθ flat (1) [2]. Where r is the roughness factor defined as ratio of the actual surface area to its horizontal projection for Wenzel model. For the alternative Cassie-Baxter model the apparent contact angle is described by (2) [2]. One method of increasing hydrophobicity of a surface by increasing the effective area is to coat it with a layer of nanorods.

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