DFT study of NH₃ adsorption on pristine, Ni- and Si-doped graphynes

The electronic sensitivity of pristine, Ni- and Si-doped graphynes to ammonia (NH₃) molecule was investigated using density functional theory, including dispersion correction. It was found that NH₃ is weakly adsorbed on the sheet, releasing energy of 2.9–4.4 kcal/mol, and the electronic properties of the sheet are not significantly changed. Although both Ni-doping and Si-doping make the sheet more reactive and sensitive to NH₃, Si-doping seems to be a better strategy to manufacture NH₃ chemical sensors because of higher sensitivity. Our calculations show that the HOMO/LUMO gap of the Si-doped sheet is significantly decreased from 2.13 to 1.46 eV after the adsorption of NH₃, which may increase the electrical conductance of the sheet. Therefore, the doped sheet might convert the presence of NH₃ molecules to electrical signals. Moreover, the shorter recovery time of the Si-doped sheet is because of the middle adsorption energy of 39.3 kcal/mol in comparison with 55.1 kcal/mol for the Ni-doped sheet. - Highlights: • Sensitivity of the pristine, Ni- and Si-doped graphynes to NH₃ was investigated. • NH₃ is weakly adsorbed on the sheet, releasing energy of 2.9–4.4 kcal/mol. • Si-doping of the sheet is introduced as a strategy to manufacture NH₃ sensors