Research on Al12C12 as a gas sensor for detecting of CH4, CO, H2, NO and NH3 based on density functional theory

Abstract

This study evaluated the CH₄, CO, H₂, NH₃, and NO–sensing abilities of Al₁₂C₁₂ nanocages by using density functional theory. The geometry optimisation, cohesive energy, adsorption energy, and other electronic properties of Al₁₂C₁₂ nanocages and complexes after gas adsorption were calculated. The Al₁₂C₁₂ nanocage is highly symmetric and consists of eight hexagonal and six tetragonal rings. The Al₁₂C₁₂ nanocage had a cohesive energy of 4.6 eV and an energy gap of 1.593 eV, indicating that Al₁₂C₁₂ nanocages are stable and have semiconductor-like properties. The gas that the Al₁₂C₁₂ nanocage most effectively adsorbed was NH₃. The NH₃ complex not only had largest adsorption energy and shortest adsorption distance but also transferred the most charges and had the largest dipole moment. Mulliken charge transfer theory and molecular electrostatic potential analyses were used to evaluate charge transfer and distribution. The charge distribution of the Al₁₂C₁₂ nanocage differed depending on the type of gas, with NH₃ resulting in the greatest number of charges being transferred. Density of states analysis was performed, and the results indicate that the complex was primarily composed of 3p orbitals of C and Al. The highest occupied molecular orbital and lowest unoccupied molecular orbital were analysed. Interactions with various gases significantly reduced the energy gap values of pure nanocages, and those of the NH₃ and NO complexes were significantly reduced because of changes in the 3p orbitals of the C and Al atoms. This study demonstrates that pure Al₁₂C₁₂ nanocages have potential as materials for the detection of NH₃ and NO gas.