Investigation of graphene dopant concentration on europium oxide thick film using screen-printed method for carbon dioxide gas sensing

• Main Author: Sanmugavelan, Kuberahventhan
• Format: Thesis
• Language: English; English
• Published: 2025
• Subjects: T Technology; TA Engineering (General). Civil engineering (General)
• Online Access: http://eprints.utem.edu.my/id/eprint/29317/

The development of gas sensing devices that operate effectively at room temperature is crucial for improving environmental monitoring systems, particularly the sensitive detection of carbon dioxide (CO2). Europium oxide (Eu2O3) has potential as a sensing material but lacks sensitivity, stability, and response time at room temperature, making it unsuitable for real-world application. The objective of this research is to improve CO2 detection capabilities under ambient conditions by systematically incorporating graphene dopants into Eu2O3 thick films. In addition to an undoped Eu2O3 gas sensor, thick film sensors with different graphene concentrations of 0.1%, 0.5%, 1%, 2%, and 5% by weight were fabricated using the screen-printing method on Kapton substrates. The gas sensors were characterised using Field Emission Scanning Electron Microscopy (FESEM) for morphological assessment, Energy Dispersive X-ray (EDX) for compositional analysis, Raman spectroscopy for structural evaluation, and X-ray Diffraction (XRD) for crystallographic analysis. Their performance was evaluated in a controlled laboratory environment, with CO2 detection carried out at concentrations of 30, 50, and 70 sccm at room temperature. The aim of this study was to determine the optimum graphene concentration that maximises sensor response time, recovery characteristics, detection sensitivity, repeatability, hysteresis, and stability. Based on the experimental results, the 2% Eu2O3/Gr gas sensor exhibited the best performance, with a low resistance of 0.0874 GΩ and enhanced sensitivity towards CO2 at concentrations of 30, 50, and 70 sccm, with values of 2.40, 2.37, and 2.34, respectively. The 2% Eu2O3/Gr sensor demonstrated a 2.1-fold gain in sensitivity (26.50 pA/sccm), a 4.5-fold improvement in resolution, and a 2.2-fold decrease in standard deviation, along with a linearity of 98.04% compared to the undoped Eu2O3 sensors. Graphene’s large surface area and high conductivity facilitate CO2 adsorption and charge transfer between Eu2O3 and CO₂ molecules, resulting in enhanced production of carbonate species through redox reactions with Eu3+ ions. The ideal graphene doping level was found to be 2%, which maintained the structural integrity of the Eu2O3 gas sensors while increasing conductivity. In summary, this research demonstrates that graphene-doped Eu2O3 thick films offer a viable approach for room-temperature CO2 gas detection, with enhanced stability, sensitivity, and response times. Further research into graphene concentration and fabrication methods may provide deeper insight into the relationship between dopant concentration and sensing performance, supporting the development of effective CO2 sensors for industrial and environmental applications.