Facile Synthesis of the Composites of Polyaniline and TiO₂ Nanoparticles Using Self-Assembly Method and Their Application in Gas Sensing

The composites of polyaniline and TiO₂ nanoparticles with different contents were prepared in the aqueous solution of phosphoric acid, in which the phosphoric acid was selected as the protonic acid to improve the conductivity of polyaniline. In the composites, the TiO₂ nanoparticles with the size of about 20 nm were coated by a layer of polyaniline film with a thickness of about 5 nm. Then, the gas sensors were constructed by a liquid–gas interfacial self-assembly method. The gas-sensing properties of the composites-based gas sensors obviously improved after doping with TiO₂ nanoparticles, and the sensor response of the composites increased several times to NH₃ from 10 ppm to 50 ppm than that of pure polyaniline. Especially when the mass ratio of TiO₂ to aniline monomer was 2, it exhibited the best gas response (about 11.2–50 ppm NH₃), repeatability and good selectivity to NH₃ at room temperature. The p–n junction structure consisting of the polyaniline and TiO₂ nanoparticles played an important role in improving gas-sensing properties. This paper will provide a method to improve the gas-sensing properties of polyaniline and optimum doping proportion of TiO₂ nanoparticles.