In this study, samples of gas sensors based on graphite-paper were made using easy and low cost HB pencil graphite drawing method on the commercial paper and immersion in 0.02 g/l palladium chloride solution during different time periods. Structural, chemical and sensing characteristic of samples were studied using X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and standard sensing measurements. XRD characterization before pencil graphite drawing on the paper, showed the cellulose fibers and calcium carbonate existence in the paper structure of the sensor. Also XRD characterization of pencil graphite drawn sample represented a new peak related to pencil graphite in the pattern of XRD. The FE-SEM images illustrated that the layered structure of graphite on the substrate paper which was immersed in palladium chloride solution, causes an improvement in response of the sensor which is exposed to the vapor of organic compounds. The EDS analysis demonstrated that the atomic and weight percentage of carbon atoms in the graphite structure after soaking in palladium chloride solution for one hour, have an increase that is appeared probably due to the percolation of palladium influence in the graphite structure. The presence of clay in the pencil graphite structure was confirmed. Result of XPS analysis showed chemical bonds related to carbon and oxygen atoms and also the presence of hydroxyl functional group. Gas sensing measurements under controlled conditions in the chamber were performed at room temperature. Resistance of graphite-paper samples before and after immersion in palladium chloride solution exposed to vapor of organic compounds and oxygen gas in different time durations, was measured by four probe method, and it was found that the immersion in palladium chloride solution, has a significant increase considering the response of the sensor which provides an appropriate example of graphite-paper sensor. The results of the sensing experiments showed that these sensors have an acceptable selectivity exposed to organic compound vapor and also alcohol vapor.
