Investigating the Effect of Hierarchical Carbon Micro/Nano Spheres on the Surface Wettability: Experimental and Theoretical Study

Carbon spheres with controllable structures (i.e., nano and microstructure) were prepared by using a hydrothermal method. By adjusting the concentration of glucose solution at a both constant temperature and constant process time in a sealed autoclave, the total size of carbon spheres (CSs) was changed from nano to microscale. Then micronanobinary carbon spheres structure (MNCS) was successfully obtained by coating colloidal solution of carbon nanospheres (CNSs, average diameter of 186 nm) and microspheres (CMSs, average diameter of 5 μm) on the FTO substrates. It was realized that by annealing of the carbon spheres under vacuum condition, their functional groups were reduced, therefore, this effected on the wetting behavior of carbon spheres. The effect of hierarchical roughness as a beneficial factor on the superhydrophobicity of CSs was analyzed by the investigation of the contact angle (CA). The highest CA was measured for the mixture structures containing both the micro and nanoscale spheres. Based on the new research, CA of the surface with micronanobinary structure is larger than the nanostructure and the nanostructure is larger than the microstructure and above all, theoretical calculations confirmed the experimental measurements.