M-Encapsulated Be12O12 Nano-Cage (M = K, Mn, or Cu) for CH2O Sensing Applications: A Theoretical Study

Abstract

DFT and TD-DFT studies of B3LYP/6-31 g(d,p) with the D2 version of Grimme's dispersion are used to examine the adsorption of a CH₂O molecule on Be₁₂O₁₂ and MBe₁₂O₁₂ nano-cages (M = K, Mn, or Cu atom). The energy gap for Be₁₂O₁₂ was 8.210 eV, while the M encapsulation decreased its value to 0.685-1.568 eV, whereas the adsorption of the CH₂O gas decreased the E_g values for Be₁₂O₁₂ and CuBe₁₂O₁₂ to 4.983 and 0.876 eV and increased its values for KBe₁₂O₁₂ and MnBe₁₂O₁₂ to 1.286 and 1.516 eV, respectively. The M encapsulation enhanced the chemical adsorption of CH₂O gas with the surface of Be₁₂O₁₂. The UV-vis spectrum of the Be₁₂O₁₂ nano-cage was dramatically affected by the M encapsulation as well as the adsorption of the CH₂O gas. In addition, the adsorption energies and the electrical sensitivity of the Be₁₂O₁₂ as well as the MBe₁₂O₁₂ nano-cages to CH₂O gas could be manipulated with an external electric field. Our results may be fruitful for utilizing Be₁₂O₁₂ as well as MBe₁₂O₁₂ nano-cages as candidate materials for removing and sensing formaldehyde gas.

Keywords: DFT and TD-DFT; adsorption; alkali and transition metals; beryllium oxide; formaldehyde; sensor.

Figure 1

Optimized structures for (a) Be₁₂O₁₂, (b) KBe₁₂O₁₂, (c) MnBe₁₂O₁₂, and (d) CuBe₁₂O₁₂ nano-cages.

Figure 2

Charge density difference ($\mathsf{\Delta }\rho$) at 0.001 au isovalue for (a) KBe₁₂O₁₂ (b) MnBe₁₂O₁₂ (c) CuBe₁₂O₁₂ nano-cages. Red and blue colors refer to negative and positive $\mathsf{\Delta }\rho$ values; $\mathsf{\Delta }\rho ={\rho }_{{\mathrm{M}\mathrm{B}\mathrm{e}}_{12}{\mathrm{O}}_{12}}-({\rho }_{{\mathrm{B}\mathrm{e}}_{12}{\mathrm{O}}_{12}}+{\rho }_{\mathrm{M}})$.

Figure 3

The molecular electrostatic potential maps (MESP) for (a) Be₁₂O₁₂, (b) KBe₁₂O₁₂, (c) MnBe₁₂O₁₂, and (d) CuBe₁₂O₁₂ nano-cages.

Figure 4

HOMO, PDOS, and LUMO for (a) Be₁₂O₁₂, (b) KBe₁₂O₁₂, (c) MnBe₁₂O₁₂, and (d) CuBe₁₂O₁₂ nano-cages. HOMO and LUMO surfaces are plotted at ± 0.02 isovalue. Brown and green colors refer to positive and negative isovalues, respectively.

Figure 5

UV-vis spectra for Be₁₂O₁₂, KBe₁₂O₁₂, MnBe₁₂O₁₂, and CuBe₁₂O₁₂ nano-cages.

Figure 6

Optimized structures for (a) CH₂O/Be₁₂O_12, (b) CH₂O/KBe₁₂O_12, (c) CH₂O/MnBe₁₂O₁₂, and (d) CH₂O/CuBe₁₂O₁₂.

Figure 7

Charge density difference ($\mathsf{\Delta }\mathsf{\rho }$) at 0.001 au isovalue for (a) CH₂O/Be₁₂O₁₂, (b) CH₂O/KBe₁₂O₁₂, (c) CH₂O/MnBe₁₂O₁₂, and (d) CH₂O/CuBe₁₂O₁₂ complexes. Red and blue colors refer to negative and positive $\mathsf{\Delta }\mathsf{\rho }$ values; $\mathsf{\Delta }\mathsf{\rho }={\mathsf{\rho }}_{\mathrm{C}{\mathrm{H}}_2\mathrm{O}/{\mathrm{M}\mathrm{B}\mathrm{e}}_{12}{\mathrm{O}}_{12}}-({\mathsf{\rho }}_{\mathrm{M}{\mathrm{B}\mathrm{e}}_{12}{\mathrm{O}}_{12}}+{\mathsf{\rho }}_{\mathrm{C}{\mathrm{H}}_2\mathrm{O}})$.

Figure 8

HOMO, PDOS, and LUMO for (a) CH₂O, (b) CH₂O/Be₁₂O₁₂, (c) CH₂O/KBe₁₂O₁₂, (d) CH₂O/MnBe₁₂O₁₂, and (e) CH₂O/CuBe₁₂O₁₂ complexes.

Figure 9

(a) Electric field direction relative to the nano-cage, and the charge density difference ($\mathsf{\Delta }\mathsf{\rho }$) isovalue surfaces at 0.00005 au for EF values of −514 and +514 kV/mm for (b) CH₂O, (c) Be₁₂O₁₂, (d) KBe₁₂O₁₂, (e) MnBe₁₂O₁₂, and (f) KBe₁₂O₁₂. $\mathsf{\Delta }\rho ={\rho }_{ E=\pm 514}-{\rho }_{ E=0}$, X-component of dipole moment (D_x) in Debye. Red and blue colors represent negative and positive $\mathsf{\Delta }\mathsf{\rho }$ values, respectively.

Figure 10

Dipole moment vs. electric field at different mediums for (a) CH₂O, (b) Be₁₂O₁₂ and MBe₁₂O₁₂ substrates, and (c) CH₂O/Be₁₂O₁₂ and CH₂O/MBe₁₂O₁₂ complexes.

Figure 11

Adsorption energies (E_ads) for CH₂O/Be₁₂O₁₂ and CH₂O/MBe₁₂O₁₂ complexes.

Figure 12

NBO charges of CH₂O molecule (${\mathrm{Q}}_{\mathrm{C}{\mathrm{H}}_2\mathrm{O}}$) vs. electric field for CH₂O/Be₁₂O₁₂ and CH₂O/MBe₁₂O₁₂ complexes.

Figure 13

HOMO–LUMO energy gap (E_g) vs. electric field for (a) Be₁₂O₁₂ and CH₂O/Be₁₂O₁₂, (b) KBe₁₂O₁₂ and KCH₂O/Be₁₂O₁₂, (c) MnBe₁₂O₁₂ and CH₂O/MnBe₁₂O₁₂, and (d) CuBe₁₂O₁₂ and CH₂O/CuBe₁₂O₁₂.

Figure 14

The change percentage for HOMO–LUMO energy gap (ΔE_g) vs. electric field.

Figure 15

UV-vis spectra for CH₂O/Be₁₂O₁₂, CH₂O/KBe₁₂O₁₂, CH₂O/MnBe₁₂O₁₂, and CH₂O/CuBe₁₂O₁₂ complexes for EF values of (a) −514 kV/mm, (b) 0 kV/mm, and (c) +514 kV/mm, respectively.

Figure 16

(a) $\overline{\mathrm{E}}$_ads and (b) E_g against the number of adsorbed CH₂O molecules.