Surface modification and cathodic electrophoretic deposition of ceramic materials and composites using celestine blue dye†
A new method has been developed for the surface modification of inorganic particles, which allowed their efficient electrostatic dispersion and cathodic electrophoretic deposition (EPD). The approach is based on the use of cationic celestine blue (CB) dye as a charging and dispersing agent. The key advantages of this approach are related to its applicability to different materials and strong adsorption of CB to the inorganic surfaces, which is of critical importance for efficient particle dispersion. Proof-of-concept studies involved the EPD of thin films of various materials, such as TiO2, MnO2, Mn3O4, BaTiO3, halloysite nanotubes, zirconia and yttria. The results of the deposition rate measurements, Fourier transform infrared spectroscopy, UV-vis and quartz crystal microbalance studies provided an insight into the mechanism of CB adsorption, which involved the interactions of the OH groups of the catechol ligand of CB and metal atoms on the particle surface. It was demonstrated that CB can be used as an efficient dispersing agent for the nanoparticle synthesis by chemical precipitation methods. The feasibility of EPD of various oxide materials paved the way to the EPD of various composites using CB as a co-dispersant for the individual components. Thin films of individual oxides and composites were investigated by electron microscopy and X-ray diffraction methods. The benefits of cathodic EPD for nanotechnology were demonstrated by the formation of nanostructured MnO2 films on commercial high surface area current collectors for energy storage in electrochemical supercapacitors. Testing results showed that the method allowed the fabrication of efficient electrodes with high capacitance and excellent capacitance retention at high charge–discharge rates. The new method paves the way for the deposition of other functional materials and composites for advanced applications.