MWCNT/Polyaniline Nanocomposites Used for pH Nanosensors of Marine Waters

Abstract

Polymer nanocomposites of conductive polymer, polyaniline (PANI) with multi-walled carbon nanotubes (MWCNTs), have gained a great interest for their application in environmental and water quality monitoring (where pH value becomes one of the reliable data). Compared to the inorganic counterparts, conducting polymers have advantage in achieving high sensitivity and selectivity by virtue of their chemical and structural diversity. In the framework of FP7 project COMMON SENSE (OCEAN 2013.2-614155), screen-printed electrodes as a pH nanosensors based on nanocomposites of conductive polymer matrix-PANI and MWCNT were prepared by electrochemical polymerization. Characterization was performed by several spectroscopic techniques and electrical measurements. Electrochemical synthesis of the PANI-based composites was performed at 0.75 V vs. saturated calomel electrode (SCE) for 40 and 60 minutes. The working conditions were determined using electrochemical steady-state polarization measurements. Morphology of the produced composites was observed using scanning electron microscope (SEM), structural characteristics were studied using Raman spectroscopy, while thermal stability was determined using thermal gravimetric analysis (TGA/DTA). The results point out on fibrous and porous structure of PANI-based composites, with strong interaction between quinoidal structure of PANI with carbon nanostructures via p–p stacking according to Raman spectroscopy measurements. TGA coupled with DTA showed the increased thermal stability of the studied composites. The obtained nanocomposites exhibited a high value of conductivity which attributed to the synergy effect of the conductive polymer matrix and carbon nanostructure. Resistivity (i.e., conductivity) changes were measured at different pHs (4 to 10) as well as in different marine regions.