Wetting Behavior of Metal-Catalyzed Chemical Vapor Deposition-Grown One-Dimensional Cubic-SiC Nanostructures.

Abstract

Superhydrophobic surfaces can be fabricated by using the self-assembled nanoarchitecture of 3C-SiC one-dimensional (1D) nanostructures as they are capable of forming a dense network of micro-nano air pockets without any help from external sources. Herein, the metal-catalyzed growth of 3C-SiC nanowires/nanorods on Si substrates via vapor-liquid-solid mechanism using five different catalysts, that is, chemically synthesized Au nanoparticles and direct current-sputtered thin films of Au, Cu, Ni, and Ti, is reported. Relatively new or unexplored catalysts such as thin films of Cu and Ti, as well as drop-cast Au nanoparticles, were used. An optimized and separate growth was carried out for each catalyst in an inductively heated horizontal cold-wall atmospheric pressure chemical vapor deposition reactor. An insight into the catalytic growth mechanism of 3C-SiC 1D nanostructures has been presented. All of the bare samples exhibited superhydrophilic behavior, whereas hierarchical Au/Pd nanostructure-coated 3C-SiC nanorod samples grown using Au and Ni thin-film catalysts exhibited hydrophobic and superhydrophobic behavior, respectively. As the better results were obtained for Ni thin-film catalysts in terms of growth density and high water contact angle (WCA ≈ 160°), therefore, the growth temperature, as well as the growth time-dependent wetting behavior, was also studied. It was found that the WCA increased as the growth time and temperature increased because of the increase in the growth density, and it finally reached to an optimum value at the growth temperature of 1200 °C and the growth time of 1 h. Furthermore, their wetting behavior was studied by using a variety of high surface tension (water, milk, tea, and glycerin) and low surface tension (organic liquids such as n-hexane, ethanol, etc.) liquids. High surface tension liquids exhibited superhydrophobic behavior, whereas low surface tension liquids exhibited superhydrophilic behavior. Hence, these fabricated nanostructured surfaces can be exploited for oil-water separation, electrowetting, water harvesting, self-cleaning, lab on a chip, and micro-/nanofluidic device applications.