Adsorption of gas molecules on Gd@Aun (n = 14, 15) clusters and their implication for molecule sensors

Abstract

First-principles calculations are performed to study the adsorption of CO, NO, NO₂, O₂, CO₂, N₂, and H₂O molecules on Gd@Au_n (n = 14, 15) clusters. The adsorption geometries, adsorption energies, charge transfer, and electronic properties are obtained. We find that the toxic molecules (CO, NO, and NO₂) are chemically adsorbed on the Gd@Au_n (n = 14, 15) clusters with strong binding, and this can lead to finite charge transfer, while other common molecules (O₂, CO₂, N₂, and H₂O) are physisorbed on the Gd@Au_n (n = 14, 15) clusters, expect for O₂ molecules on the Gd@Au₁₄ cluster. The electronic properties of the Gd@Au_n (n = 14, 15) clusters are significantly influenced by NO and NO₂ adsorption, especially their electric conductivity. Furthermore, for the Gd@Au₁₅ cluster, it is found that the adsorption energy (E_ads) of −0.498 eV for NO and −0.725 eV for NO₂ corresponds to recovery times of about 7 × 10⁻¹² and 11.8 s, respectively, indicating that the Gd@Au₁₅ cluster should be a good NO and NO₂ sensor with quick response and short recovery time. However, the very strong adsorption of NO and NO₂ on the Gd@Au₁₄ cluster (E_ads ≥ 1.00 eV) makes desorption difficult. Therefore, the Gd@Au₁₅ cluster can be expected to be an excellent gas sensor for NO and NO₂ detection.