Defect and Substitution-Induced Silicene Sensor to Probe Toxic Gases

Abstract

Structural, electronic, and gas-sensing properties of pure, defected, and substituted silicene monolayer have been studied using first-principles calculations based on density functional theory. The spin-polarized calculations with van der Waals effect taken into consideration have revealed that the pristine silicene sheet rarely adsorbs the CO 2 , H 2 S, and SO 2 gas molecules, which restricts the gas-sensing application of this 2D material. However, inducing vacancy defect in silicene drastically changes the electronic properties, and as a consequence it also improves the binding of exposed gas molecules significantly. Our Bader charge analysis reveals that a considerable amount of charge is being transferred from the defected silicene to the gases, resulting in binding energy improvement between silicene and the gas molecules. The change in binding energies has further been explained by plotting density of states. In addition to the vacancy defects, we have also considered the substitution of Al, B, N, and S in silicene. We found that the sensing propensity of silicene is more sensitive to the vacancy defect, as compared with the impurities.

Adsorption of gas molecules on a graphitic GaN sheet and its implications for molecule sensors

“…We found that the change of band gaps for the most stable structures of NH 3 and SO 2 molecules adsorbed on the PL-GaN sheet was 0.097 and 0.049 eV with respect to the corresponding pure sheet. Therefore, the NH 3 and SO 2 molecules can be detected by calculating the conductivity change in the PL-GaN sheet before and aer the adsorption process.…”

“…Furthermore, comparing with the DOS of the pure PL-GaN sheet, the total DOSs of the molecule-sheet compositions and LDOS of the corresponding molecules show that the considered molecular gases modulate the electronic properties of the PL-GaN sheet in different ways: (i) the chemical adsorption of SO 2 and NH 3 molecules introduces unoccupied local states in the conduction band, suggesting that the conductance of these systems can be enhanced notably. Also, LDOS analysis showed that adsorption of NH 3 and SO 2 molecules produced fully occupied states in the valence band, and these states were nonlocalized, indicating that the interaction between these molecules and the sheet was strong. This was consistent with the calculated adsorption energy.…”

“…Based on analyzing adsorption energies, forms of adsorption (chemically or physically), charge transfer, and the change of band structures, the PL-GaN sheet exhibits strong sensitivity and selectivity for SO 2 and NH 3 , while it appears inefficient to sense HCN, H 2 S, CO, O 2 , H 2 , CO 2 , and H 2 O. In combination with the fact that the recovery time, the PL-GaN sheet should be a promising reusable sensor for highly sensitive and selective NH 3 detection with short recovery time, and a disposable sensor for SO 2 detection.…”

“…It is expected that the electrical resistivity of the PL-GaN sheet will also be inuenced by the gas molecule adsorption in a similar way. In the present work, we employ rst-principles calculations to accurately describe the adsorption behavior and electronic properties of the SO 2 , NO 2 , HCN, NH 3 , H 2 S, CO, NO, O 2 , H 2 , CO 2 , and H 2 O molecules on the PL-GaN sheet, in order to explore the feasibility of using the PL-GaN sheet as reusable gas sensors. It is well known that pollutional components, such as SO 2 , NO 2 , HCN, NH 3 , H 2 S, CO, and NO are the byproduct of various chemical and biological processes and considered to be hazardous, more importantly, they are the most common pollutional gases in industrial and agricultural production, and our daily life.…”

“…Other molecules were prone to physically adsorbing on the PL-GaN sheet. Apparently, the band structures were modied aer adsorption of NH 3 and SO 2 molecules, indicating that the adsorption of the two molecules changed the electronic properties of the PL-GaN sheet. Considering the recovery time, the PL-GaN sheet should be a promising gas sensor for NH 3 detection.…”