Synthesis, characterization and hydrophobic activity of nanoparticle ZnO functionalized by APTS

Full text: Hydrophobic surfaces (HS) have attracted much attention due to its unique properties such as self-cleaning, non-stickiness and anti-contamination of surfaces. Nevertheless, the study was only started after the detailed study of binary microstructure of the leaf of the lotus flower. The hydrophobicity of solid surfaces is influenced by both the presence of geometric structures 0D and 1D in nanometer or micrometer scales and its chemical composition. Therefore, the HS surfaces may be prepared through either superficial modifications of roughness of materials that have low superficial energy, or reducing their surface energy. On this research, nanoparticles of ZnO were synthesized by the polyol method by reflux at 200°C for 3 hours. The resulting particles had their surfaces modified by the addition of silane (3-Aminopropyl)triethoxysilane (APTS) in different concentrations (0.5 ml, 1.0 ml, and 1.5 ml). After functionalization, the samples were characterized by means of X ray diffraction (XRD), scanning electron microscope (MEV-FEG), infrared spectroscopy, degradation of methylene blue, and measurement of contact angle. XRD patterns revealed that all diffraction peaks of ZnO particles could be indexed to the hexagonal structure without the presence of secondary phases in agreement with the respective Joint Committee on Powder Diffraction Standards (JCPDS) card no. 89-1397. The band located at 3419 cm^-1, which is attributed to -NH₂ groups and 1016 cm^-1,can be assigned to the Si-O stretch, confirms the functionalization of ZnO with APTS. In microscopy it is possible to observe that the mean particle size was 52 nanometers. The particles were embedded in a matrix of PDMS and, later, were applied on glass plates through a traditional airbrushing in order to observe the contact angle. Due to the surface modification of particles, it is possible to increase the saturation contact angle from θ_s 70 to θs 120. (author)