| AVS 61st International Symposium & Exhibition | |
| Thin Film | Monday Sessions |
| Session TF-MoA |
| Session: | Self-Assembled Monolayers, Layer-by-Layer Assemblies, and Hydrophobic/Amphiphobic Thin Films |
| Presenter: | Kavita Yadav, Indian Institute of Technology Delhi, India |
| Authors: | K. Yadav, Indian Institute of Technology Delhi, India B.R. Mehta, Indian Institute of Technology Delhi, India J.P. Singh, Indian Institute of Technology Delhi, India |
| Correspondent: | Click to Email |
In recent years, production of materials with tunable wetting properties is of immense interest. The extreme water repellent property of superhydrophibic surfaces and complete water spreading on superhydrophilic surface allow them to have considerable technical potential for various applications. The wetting properties of the materials can be explained by their surface chemistry and topographical structures.
In this report, we demonstrate that the growth ambient induced drastic change in wetting properties of indium oxide (IO) nanowires. The IO nanowires were synthesized by using chemical vapor deposition method where Ar gas (200 sccm) was used as carrier gas. The deposition parameters were calibrated in such a way to obtain nanowire morphology. Three different ambient conditions were used for growth of IO nanowires; (a) Ar gas mixed with water vapors, (b) only Ar gas and (c) Ar gas mixed with hydrogen gas (50 sccm) and keeping other deposition parameters constant. The Scanning electron microscope (SEM) images confirm that all the three samples have nanowires like morphology. The diameter and length of nanowires ranges from 50 - 120 nm and 6 - 15 µm. The contact angle measurements were done on all the three samples. It is found that the nanowires prepared in presence of Ar gas mixed with water vapors (oxidising ambient) are superhydrophilic in nature with contact angle of 8 ̊ ± 5 ̊. The IO nanowires synthesized in presence of only Ar gas are hydrophobic in nature with contact angle of 144 ̊ ± 4 ̊ whereas the IO nanowires synthesized in presence of Ar gas mixed with H2 gas (reducing ambient) are superhydrophobic in nature with contact angle of 168 ̊ ± 2 ̊ and water droplet rolling downward with a roll-off angle of 3 ̊ over the superhydrophobic surface. The mechanism behind the drastic change in contact angle on IO nanowires prepared in different growth ambient is examined by using photoluminescence (PL) and electron paramagnetic resonance (EPR) measurements. The mechanism of change in wetting properties of IO nanowires has been proposed and can be attributed as on the reduced surface where oxygen vacancy are more, only molecular water is stable and absorb weekly. This is most likely because of the lack of surface oxygen that could accept hydrogen from dissociated water or decrease water dissociation probability and hence the surface is superhydrophobic. Whereas the sample prepared in oxidizing ambient have more surface oxygen and hence both molecular and dissociative adsorption of water is possible results in superhydrophilic surface. The photoinduced reversible wetting properties of IO nanowires (sample b) are also studied.