MATERIAIS PARA SENSORES ÓPTICOS DE pH BASEADOS EM FILMES FINOS DE POLIANILINA E SEUS NANOCOMPÓSITOS COM NANOTUBOS DE CARBONO

MATERIALS FOR OPTICAL pH SENSORS BASED ON THIN FILMS OF POLYANILINE AND POLYANILINE/CARBON NANOTUBES NANOCOMPOSITES. In this work we demonstrate the high potentiality of polyaniline or polyaniline/carbon nanotubes thin films as selective and reliable optical pH sensors. The films were prepared based on the liquid/liquid interfacial route, deposited over glass or quartz planar substrates, and characterized by UV-Vis, Raman and Fourier transform infrared spectroscopy (FTIR), as well as scanning electron microscopy. The polyaniline was obtained in its green and conductive structure, salt emeraldine, which is converted to the blue emeraldine base in alkaline condition. The color sensitivity of the film is easily followed by UV-Vis spectroscopy, allowing the elaboration of different analytical curves in a broad pH range (2 to 12). Sensor performance tests demonstrated high sensitivity (0.08394 A/pH) and excellent performance at higher pHs, with detectable pH variations in very narrow ranges, as well as excellent repeatability and reproducibility, essential for continuous industrial applications.