Fe3O4–MWCNT PhCOOH composites for ammonia resistive sensors

tHybrid composites of Fe3O4and multiwalled carbon nanotubes (MWCNT) chemically functionalized withthe benzoic acid group ( PhCOOH) are described as novel sensing materials for resistive-type ammoniagas sensors. Fe3O4/MWCNT PhCOOH composites have been synthesized by a simple procedure. The mor-phological and microstructural characterization has been performed by using TGA, FT-IR, XRD and TEM.TGA and FT-IR confirmed the covalent attachment of the benzoic acid groups, thus creating highly local-ized sites with high affinity toward ammonia molecules. Fe3O4nanoparticles, about 7 nm in diameter,were found homogeneously distributed on the functionalized MWCNT PhCOOH surface.The ammonia sensing characteristics of samples synthesized with different Fe3O4loading have beeninvestigated at low temperature. Sensor devices fabricated with the hybrid Fe3O4/MWCNT PhCOOHcomposites have shown more higher variation of resistance upon exposure to NH3compared to pristineMWCNT and functionalized MWCNT PhCOOH ones, indicating a combined effect between the organicgroup and metal oxide in improving the response toward the target gas. The reversibility of the sensorwas improved operating under UV irradiation.