Chemical surface treatment with toluene to enhance sensitivity of NO2 gas sensors based on CuPcTs/Alq3 thin films

A nitrogen dioxide (NO2) gas sensor based on the blend of copper phthalocyanine-tetrasulfonic acid tetrasodium/tris-(8-hydroxyquinoline)aluminum (CuPcTs/Alq3) thin films was fabricated. The effect of chemical surface treatment with toluene on the structural, surface morphology and device sensitivity has been examined. The X-ray diffraction (XRD) patterns of as-deposited and toluene-treated films exhibit a broad hump peak at 2θ = 24°. The atomic force microscopy (AFM) measurements show that the average particle diameter decreases with immersing time. The needle like shapes can be seen from scanning electron microscopy (SEM) images for films treated with toluene for an immersing time of 60 min. Gas sensor characterizations demonstrate that all samples have superior NO2 gas sensitivity at a operating temperature of 373 K. The increase of the sensor sensitivity with increasing chemical treatment time up to 60 min was observed. All films show the stable and repeatable response patterns.