دراسة تأثير الغازات السامة على الخصائص التركيبية، الالكترونيه والطيفية للفسفورين أحادي الطبقة المطعَّم بـ (B, Al) باستخدام نظرية الدالة الوظيفية للكثافة

Study of the Effect of Toxic Gases on Structural, Electronic and Spectral Properties of Phosphorene Monolayer Doped by (B, Al) Using Density Functional Theory

Abstract
This theoretical study included the possibility of designing a gas sensor based on phosphorene to enhance the sensing properties of the toxic gases (CO, H2S, and NO) adsorbed on the surface of pure and doped phosphorene, employing density functional theory DFT for the ground states and time-dependent density functional theory TD-DFT for the excited states. Additionally, this study was conducted using the hybrid functional B3LYP and basis set 6-31G. Also used B and Al atoms as impurities through-replaced by a single phosphorus atom in the monolayer phosphorene nanostructure to study the effect of these toxic gases.
In this work, the structural and electronic and spectral properties were studied by performing geometry optimization of pure and doped monolayer phosphorene using DFT method to calculate the structural properties that included bond lengths, bond angles and dihedral angles; while the electronic properties included calculation of electron affinity, ionization potential, energy gap, adsorption energy and sensitivity. But TD-DFT method used to calculate the spectral properties included the calculations of the UV-Vis spectrum.
When performing geometry optimization on phosphorene nanostructures, Al-doped phosphorene (AlP₁₅) was the most stable, as compared with pure phosphorene (P₁₅) and B-doped phosphorene (BP₁₅), which showed a marked difference from their original structure. Furthermore, the geometry optimization procedure on the (CO/AlP₁₅) nanosensor did not show clear differences from its original structure before optimization, whereas the geometry optimization on other nanosensors showed a clear effect when the toxic gas molecules were adsorbed on their surface.
The energy gap for the B-doped phosphorene (BP₁₅) and Al-doped phosphorene (AlP₁₅) structure was decreased from 1.73 eV for pure phosphorene (P₁₅) to 0.92 eV, and 1.66 eV respectively. On the other hand, when NO gas is adsorbed on the surface of (P₁₅, BP₁₅ and AlP₁₅) nanostructures, the highest analyzed contribution of HOMO-LUMO energy levels was in the case of the NO/BP₁₅ sensor at an energy gap of 2.41eV, while the smallest contribution was in the case of the NO/AlP₁₅ sensor at 1eV; whereas when CO gas is adsorbed on the surface of these nanostructures, the highest contribution of energy levels was in the case of the CO/AlP₁₅ sensor at an energy gap of 1.57eV, while the smallest contribution was in the case of the CO/BP₁₅ sensor at 1.19eV; also when H₂S gas is adsorbed on a its surface, the highest contribution of energy levels in the case of the H₂S/AlP₁₅ was at an energy gap of 1.733eV, while the smallest contribution in the case of H₂S/P₁₅ at 1.25eV.
Thus, the calculated energy gap of a pure and doped phosphorene indicates that the NO/BP₁₅, H2S/BP₁₅ and NO/AlP₁₅ as potential nanosensors. This, in turn, strongly supports the choice of (BP₁₅) as a superior sensitive nanosensor for NO molecules, with a sensitivity reaching 162% and it is a highly sensitive nanosensor for H₂S molecules, with a sensitivity reaching 79%, while the choice of (AlP₁₅) is an acceptable nanosensor for NO gas molecules with a sensitivity reaching 40%. Depending on the gas molecules studied, UV-Vis spectrum calculations of the gas sensors based on phosphorene show a shift toward the IR spectrum (N-IR, and M-IR) with a wavelength range between 2,174nm (NO/BP₁₅) to 9400nm (CO/P₁₅).