Effect of TiO2 Nanoparticles on Polyaniline Films Electropolymerized at Different pH

In this work hybrids of titanium nanoparticles and polyaniline are obtained by pulsed electrodeposition at different pH (1.5, 3.9 and 5.9) and characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, cyclic voltammetry, ultraviolet–visible, and Raman spectroscopies. We found that films deposited at pH 5.9 with nanoparticles incorporation are composed of emeraldine meanwhile films without nanoparticles are composed of pernigraniline. As a result, films deposited with nanoparticles incorporation present conductivity 6 times higher than that of films deposited without nanoparticles. Films deposited at pH 3.9 with or without nanoparticles incorporation are both made of pernigraniline. Even though films with nanoparticles incorporation still present higher conductivity. To explain such a result, we performed first-principles calculations on polyaniline/TiO 2 interface. The calculations predict a metallic polyaniline/TiO 2 interface in spite of polyaniline and TiO 2 being semiconductors. At pH 1.5, the presence of nanoparticles has negligible effect on films characteristics. We believe that at low pH (pH 1.5) H atoms tend to bind TiO 2 surface resulting in positively charged nanoparticles, which are further screened by SO 4 –2 anions. Such a screening layer prevents the physical contact between nanoparticles and polyaniline monomers diminishing the effects of nanoparticle presence.