The structural, electronic and optical properties of transition metal doped porphyrin (TM@P; TM = Mn, Co, Fe, Cu, Ni, Zn) as well as the effect of CO adsorption on TM@P properties have been investigated using the density functional theory (DFT). The presented results include adsorption energies, bond lengths, electronic configurations, magnetic moments, density of states, frontier molecular orbitals, and UV-Vis. spectra. Our calculation results show that, the CO molecule favors to be adsorbed on TM-doped Porphyrin with its carbon head. The most energetically stable adsorption of CO is reported for Fe doped Porphyrin. The interaction between CO molecules with TM@P is attributed to donation-back donation as well as charge transfer mechanisms. Mn, Co and Fe-doped porphyrins have visible active nature which may be affected by CO adsorption, whereas, Ni, Cu and Zn-doped porphyrins have UV active nature which not affected by CO adsorption. These results may be meaningful for CO removal and detection.

Theoretical calculations based on the Density Functional Theory (DFT) have been performed to investigate the interaction of H₂S as well SO₂ gaseous molecules at the surfaces of Be₁₂O₁₂ and Mg₁₂O₁₂ nano-cages. The results show that a Mg₁₂O₁₂ nano-cage is a better sorbent than a Be₁₂O₁₂ nano-cage for the considered gases. Moreover, the ability of SO₂ gas to be adsorbed is higher than that of H₂S gas. The HOMO–LUMO gap (E_g) of Be₁₂O₁₂ nano-cage is more sensitive to SO₂ than H₂S adsorption, while the E_g value of Mg₁₂O₁₂ nano-cage reveals higher sensitivity to H₂S than SO₂ adsorption. The molecular dynamic calculations show that the H₂S molecule cannot be retained at the surface of a Be₁₂O₁₂ nano-cage within 300–700 K and cannot be retained on a Mg₁₂O₁₂ nano-cage at 700 K, while the SO₂ molecule can be retained at the surfaces of Be₁₂O₁₂ and Mg₁₂O₁₂ nano-cages up to 700 K. Moreover, the thermodynamic calculations indicate that the reactions between H₂S as well SO₂ with Be₁₂O₁₂ and Mg₁₂O₁₂ nano-cages are exothermic. Our results suggest that we can use Be₁₂O₁₂ and Mg₁₂O₁₂ nano-cages as sorbents as well as sensors for H₂S and SO₂ gases.

This study employs density functional theory (DFT) calculations at the B3LYP/6-311+g(d,p) level to investigate the interaction of XH₃ gases (X = N, P, As) with the Mn-phthalocyanine molecule (MnPc). Grimme’s D3 dispersion correction is applied to consider long-range interactions. The adsorption behavior is explored under the influence of an external static electric field (EF) ranging from −0.514 to 0.514 V/Å. Chemical adsorption of XH₃ molecules onto the MnPc molecule is confirmed. The adsorption results in a significant decrease in the energy gap (E_g) of MnPc, indicating the potential alteration of its optical properties. Quantum theory of atoms in molecules (QTAIM) analysis reveals partially covalent bonds between XH₃ and MnPc, and the charge density differenc (Δρ) calculations suggest a charge donation-back donation mechanism. The UV-vis spectrum of MnPc experiences a blue shift upon XH₃ adsorption, highlighting MnPc’s potential as a naked-eye sensor for XH₃ molecules. Thermodynamic calculations indicate exothermic interactions, with NH₃/MnPc being the most stable complex. The stability of NH₃/MnPc decreases with increasing temperature. The direction and magnitude of the applied electric field (EF) play a crucial role in determining the adsorption energy (E_ads) for XH₃/MnPc complexes. The E_g values decrease with an increasing negative EF, which suggests that the electrical conductivity (σ) and the electrical sensitivity (ΔE_g) of the XH₃/MnPc complexes are influenced by the magnitude and direction of the applied EF. Overall, this study provides valuable insights into the suggested promising prospects for the utilization of MnPc in sensing applications of XH₃ gases.

We investigated the detection of chloroform (CHCl₃) using ZnO nanoclusters via density functional theory calculations. The effects of various concentrations of CHCl₃, as well as the deposition of O atoms, on the adsorption over ZnO nanoclusters were analyzed via geometric optimizations. The calculated difference between the highest occupied molecular orbital and the lowest unoccupied molecular orbital for ZnO was 4.02 eV. The most stable adsorption characteristics were investigated with respect to the adsorption energy, frontier orbitals, elemental positions, and charge transfer. The results revealed that ZnO nanoclusters with a specific geometry and composition are promising candidates for chloroform-sensing applications.

DFT calculations at the B3LYP/LanL2DZ level of theory were utilized to investigate the adsorption of H₂S and SO₂ gases on the electronic properties of CuO-ZnO heterojunction structures. The results were demonstrated from the standpoint of adsorption energies (E_ads), the density of states (DOS), and NBO atomic charges. The obtained values of the adsorption energies indicated the chemisorption of the investigated gases on CuO-ZnO heterojunction. The adsorption of H₂S and SO₂ gases reduced the HOMO-LUMO gap in the Cu₂Zn₁₀O₁₂ cluster by 4.98% and 43.02%, respectively. This reveals that the Cu₂Zn₁₀O₁₂ cluster is more sensitive to the H₂S gas than the SO₂ gas. The E_ads values for SO₂ and H₂S were −2.64 and −1.58 eV, respectively. Therefore, the Cu₂Zn₁₀O₁₂ cluster exhibits a higher and faster response-recovery time to H₂S than SO₂. Accordingly, our results revealed that CuO-ZnO heterojunction structures are promising candidates for H₂S- and SO₂-sensing applications.