Reduced graphene oxide (rGO) and 5, 10, 15, 20-tetra-p-tolyl-21H, 23H-porphine (TPTP) composite: highly reproducible and repeatable chemiresistive SO₂ sensor

In the current study, a chemiresistive SO₂ sensor based on a composite of reduced graphene oxide (rGO) and 5, 10, 15, 20-tetra-p-tolyl-21H, 23H-porphine (TPTP) was developed and extensively studied. Improved Hummers methods were used to synthesize graphene oxide (GO), and a thermally heating bottom-up approach was used to reduce GO to rGO. Gold electrodes were thermally coated on the transparent sheet using a thermal evaporator. The composite of rGO/TPTP was synthesized using a simple chemical method. Structural, morphological, spectroscopic, electrical, and optical studies were carried out using X-ray diffraction, atomic force microscopy, field emission scanning electron microscopy, Fourier-transfer infrared spectroscopy, Raman spectroscopy, current–voltage, and UV–vis spectroscopy, respectively. The sensing response of rGO/TPTP for various concentrations of sulfur dioxide (SO₂) was investigated in chemiresistive modality. The rGO/TPTP composite chemiresistive sensor displayed exceptional performance, with a consistent response spanning 1 ppm to 10 ppm. It exhibited outstanding repeatability, linearity, stability, and boasted an impressive limit of detection (LOD) of 1 ppm. This LOD is significantly lower than the recommended permissible exposure limit (PEL) of 5 ppm set by OSHA (Occupational Safety and Health Administration), USA. The sensor based on the rGO/TPTP composite exhibited a very fast response and recovery time of 33 s. and 27 s. respectively.