Dispersing agents for electrophoretic deposition of TiO2 and TiO2–carbon nanotube composites

Organic anionic molecules such as 2,3-dihydroxybenzoic acid (DBA23), 2,6-dihydroxybenzoic acid (DBA26), 5-sulfosalicylic acid (SSA) and pyrocatecholsulfonphthalein (PCS) were investigated for electrophoretic deposition (EPD) of TiO2 and TiO2–multiwalled carbon nanotube (MWCNT) films from suspensions in ethanol. The adsorption of the molecules on TiO2 surfaces was based on catecholate or salicylate binding, involving adjacent OH groups or adjacent OH and COOH groups, respectively. The adsorption of the anionic molecules allowed efficient dispersion, charging and EPD of TiO2. The deposition yield was studied as a function of DBA23, DBA26, SSA and PCS concentration in TiO2 suspensions and deposition time. An important finding was the possibility of efficient dispersion, charging and EPD of MWCNT using PCS. It was shown that PCS can be used as a universal dispersing agent for co-deposition of TiO2 and MWCNT and fabrication of composite TiO2–MWCNT films. The advantages of the new strategies, compared to other methods described in literature, were discussed. The deposits were studied by Fourier transform infrared spectroscopy, thermogravimetric analysis, differential thermal analysis and electron microscopy. The proposed approach paves the way for EPD of other oxide materials and composites.