The self-assembled monolayer (SAM) on inorganic metal
oxides is
highly applicable in making different kinds of surface phenomena such
as superhydrophobicity, functional group-modified surfaces, corrosion
resistance, and so on. The formation of stearic acid SAMs on the TiO2 substrate depends on a few factors, and the cleanability
of the substrate surface can be considered as the critical criterion
for the formation of the SAM layer. The solvent, concentration of
the adsorbate, immersion time, and temperature can be identified as
other factors that are crucial for growing a uniform and highly dense
monolayer. SAM layers always build up spontaneously on a suitable
substrate, but the growth rate and arrangement can be changed by varying
the external factors. These factors highly affect the chemisorption
of stearic acid molecules onto the TiO2 substrate and building
a well-ordered pattern on the surface without defects. This study
mainly focuses on identifying the critical conditions of the external
factors in obtaining a high-performance superhydrophobic surface.
The crystal structure and surface morphologies of the substrate materials
are characterized by powder X-ray diffraction and scanning electron
microscopy, and the surface wettability is characterized by contact
angle measurements. High superhydrophobicity is observed at the optimum
conditions of the factors. Ethanol is used as the solvent; the temperature
is about 40 °C; and 600 ppm of stearic acid is the critical concentration
in obtaining a superhydrophobic surface with 100 min of immersion
time, while the contact angle is 151.38°. Simultaneously, if
the concentration is 1000 ppm and the immersion time is 120 min, the
surface shows high superhydrophobicity with a contact angle of 162.06°.
These critical conditions are found to be adequate for building well-ordered
stearic acid SAMs on the TiO2 substrate.