Polytetrafluoroethylene bindered hematite (α-Fe2O3) nanostructure for ammonia gas detection at room temperature

In this work, polytetrafluoroethylene (PTFE) conducting polymer bindered hematite nanostructure was prepared by using drop cast method. Ferric oxide (Fe2O3) powder mixed with PTFE was used in the initial solution. The gas sensing performance was studied towards NH3 gas for the prepared samples. Synthesized films were characterized using SEM, XRD, FTIR and UV-vis techniques. According to XRD patterns, single phase of alpha-Fe2O3 could be crystallized after annealing the sample at 300 degrees C for one hour in air. SEM images revealed the presence of alpha-Fe2O3 nano sized grains (80 nm) with a high porous nanostructure. This porous nanostructure develops a wide electron-depleted surface by adsorbing atmospheric oxygen which will make the surface to detect more analytic gas molecules. FTIR confirms the formation of PTFE bindered alpha-Fe2O3 composite. The UV-vis curve exhibits an absorbance onset around 600 nm by confirming the formation of alpha-Fe2O3 in thick film form. The gas sensitivities of samples were measured in 1000 ppm of NH3, methanol vapor and acetone vapor. The gas sensor exhibited a remarkable NH3 sensing performance at room temperature (RT). However, the gas sensitivity of PTFE bindered alpha-Fe2O3 films decreases as the operating temperature is increased above RT contrary to normal metal oxide gas sensors. The highest gas sensitivity of PTFE bindered alpha-Fe2O3 thick films in 1000 ppm of NH3 gas was 23.87% at RT. The response and recovery times in 1000 ppm of NH3 at RT were found to be 45 and 66 s, respectively. Furthermore, the sensing mechanism which provides highly sensitive RT operation with PTFE polymer binder was also discussed.