DFT study on VOC detection by Helicobacter pylori using encapsulated and mono-doped gold and silver anchored fullerene C₆₀

Detecting Helicobacter pylori (H. pylori), a bacterium linked to severe gastric conditions, is crucial for effectively treating related diseases. During the infection process, this organism releases various volatile organic compounds (VOCs) such as isoamyl alcohol (3M1B), dimethyl disulfide (DMDS), hydrogen sulfide (H₂S), etcetera, which are used as biomarkers in evaluating the presence of the organism in a system or tissue. This study examines the adsorption behavior of 3M1B, DMDS, and H₂S on a Cu-doped, Au-encapsulated C₆₀ fullerene surface using Density Functional Theory (DFT). The B3LYP functional with the LANL2DZ basis set was utilized for computational analysis. The frontier molecular orbital result revealed the energy gaps to be 0.83 eV for 3M1B-Cu-Au@C60, 0.85 eV for DMDS-Cu-Au@C60, and 0.10 eV for H₂S-Cu-Au@C₆₀ suggesting that 3M1B-Cu-Au@C₆₀ complex has the smallest energy gap and thus, the highest reactivity. 3M1B, DMDS, and H₂S adsorption energies on Cu-Au@C₆₀ were found to be −3.16 eV, −0.74 eV, and −0.57 eV, respectively. This indicates that the VOCs underwent a chemisorption mechanism on the Cu-Au@C₆₀ surface, as 3M1B showed a solid binding compared with others. Additionally, dipole moment calculations indicated values of 10.02 Debye for 3M1B-Cu-Au@C₆₀, 6.32 Debye for DMDS-Cu-Au@C₆₀, and 7.30 Debye for H₂S-Cu-Au@C₆₀, providing further evidence of significant electronic polarization in the adsorbed systems. These findings suggest that the engineering of fullerene C₆₀ by encapsulating Au and Cu doping could be a promising candidate for biosensing and environmental applications.