Yttrium- and zirconium-decorated Mg12O12–X (X = Y, Zr) nanoclusters as sensors for diazomethane (CH2N2) gas

Abstract

Diazomethane (CH₂N₂) presents a notable hazard as a respiratory irritant, resulting in various adverse effects upon exposure. Consequently, there has been increasing concern in the field of environmental research to develop a sensor material that exhibits heightened sensitivity and conductivity for the detection and adsorption of this gas. Therefore, this study aims to provide a comprehensive analysis of the geometric structure of three systems: CH₂N₂@MgO (C1), CH₂N₂@YMgO (CY1), and CH₂N₂@ZrMgO (CZ1), in addition to pristine MgO nanocages. The investigation involves a theoretical analysis employing the DFT/ωB97XD method at the GenECP/6-311++G(d,p)/SDD level of theory. Notably, the examination of bond lengths within the MgO cage yielded specific values, including Mg15–O4 (1.896 Å), Mg19–O4 (1.952 Å), and Mg23–O4 (1.952 Å), thereby offering valuable insights into the structural properties and interactions with CH₂N₂ gas. Intriguingly, after the interaction, bond length variations were observed, with CH₂N₂@MgO exhibiting shorter bonds and CH₂N₂@YMgO showcasing longer bonds. Meanwhile, CH₂N₂@ZrMgO displayed shorter bonds, except for a longer bond in Mg19–O4, suggesting increased stability due to shorter bond distances. The study further investigated the electronic properties, revealing changes in the energy gap that influenced electrical conductivity and sensitivity. The energy gap increased for Zr@MgO, CH₂N₂@MgO, CH₂N₂@YMgO, and CH₂N₂@ZrMgO, indicating weak interactions on the MgO surface. Conversely, Y@MgO showed a decrease in energy, suggesting a strong interaction. The pure MgO surface exhibited the ability to donate and accept electrons, resulting in an energy gap of 4.799 eV. Surfaces decorated with yttrium and zirconium exhibited decreased energies of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), as well as decreased energy gap, indicating increased conductivity and sensitivity. Notably, Zr@MgO had the highest energy gap before CH₂N₂ adsorption, but C1 exhibited a significantly higher energy gap after adsorption, implying increased conductivity and sensitivity. The study also examined the density of states, demonstrating significant variations in the electronic properties of MgO and its decorated surfaces due to CH₂N₂ adsorption. Moreover, various analysis techniques were employed, including natural bond orbital (NBO), quantum theory of atoms in molecules (QTAIM), and noncovalent interaction (NCI) analysis, which provided insights into bonding, charge density, and intermolecular interactions. The findings contribute to a deeper understanding of the sensing mechanisms of CH₂N₂ gas on nanocage surfaces, shedding light on adsorption energy, conductivity, and recovery time. These results hold significance for gas-sensing applications and provide a basis for further exploration and development in this field.