Superhydrophobic palmitic acid modified ZnO nanoparticles

A superhydrophobic coating material (PA-ZnO) with a static water contact angle (WCA)>160° has been synthesized by modifying zinc oxide (ZnO) nanoparticles with room temperature stable palmitic acid (PA). ZnO nanoparticles (size ~ 24 nm) with hexagonal wurtzite structure are prepared by hydrothermal method. FTIR study and TEM images confirms the grafting of palmitic acid on ZnO surface. This superhydrophobic nature of PA-ZnO has been attributed to the grafting of palmitic acid on ZnO surface which is confirmed by conducting the WCA measurement of PA-ZnO samples after heating at different temperatures. Surface morphology and roughness were observed as a function of temperature and it was observed that films morphology is changing to smoother films with low air entrapment for higher temperatures. On the same time the root mean square roughness (Rrms) is also reducing. It is observed that the superhydrophobic nature of PA-ZnO nanoparticles reduces with heating at higher temperatures and surface became like hydrophilic for heating temperature of ~ 230 °C. The decrease in the WCA is attributed to the thermal decomposition of palmitic acid from ZnO surface and the same has been confirmed by thermal analysis of PA and PA-ZnO samples.