Journal of Thin Films, Coating Science Technology & Application Original Research
Effect of 4 wt% Manganese Doping on the Structural and Room-Temperature Gas-Sensing Properties of Sri Lankan Natural Graphite Thin Films for Ammonia and Ethanol Detection
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Abstract
The development of low-cost, room temperature gas sensors is of considerable interest for environmental monitoring and industrial safety applications. In this study, a 4 wt% manganese (Mn)-doped natural graphite thin film gas sensor was fabricated using high-purity Sri Lankan vein graphite (BCD20, 99.1% carbon content) deposited on patterned indium tin oxide (ITO) substrates by the Doctor Blade technique. The structural, morphological, and gas sensing properties of the fabricated sensor were systematically investigated. X-ray diffraction (XRD) analysis confirmed the successful incorporation of Mn into the graphite matrix through a shift of the characteristic (002) diffraction peak from 25.97° to 26.58°, together with the appearance of Mn related diffraction peaks. Scanning electron microscopy (SEM) revealed a compact microstructure with a porosity of approximately 12.33%, while particle size analysis shoed that most graphite particles were distributed within the 10-20 µm range. Gas sensing performance was evaluated toward 1000 ppm ammonia (NH3) and ethanol (C2H5OH) at room temperature. The 4 wt% Mn-doped sensor exhibited sensitivity of 10.96% for NH3 and 13.16% for C2H5OH, representing improvements of approximately 72% and 84%, respectively, compared with the undoped natural graphite sensor. Furthermore, the response and recovery times were significantly reduced, demonstrating enhanced sensing kinetics following Mn incorporation. These findings demonstrate that Mn doping effectively enhances the structural and sensing characteristics of Sri Lankan natural graphite, highlighting its potential as a low-cost room temperature sensing material for NH3 and C2H5OH detection.
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