Selective Sensing Characteristics of Ca Doped BeO Nano-sized Tube toward H₂O and NH₃

By means of density functional calculations, the structural and electronic properties of chem-ical modification of pristine and Ca-doped BeO nanotubes were investigated with NH₃ and H₂O molecules. It was found that the NH₃ and H₂O molecules can be adsorbed on the Be atom of the tube sidewall with the adsorption energies of about 36.1 and 39.0 kcal/mol, respectively. Density of states analysis shows that the electronic properties of the BeONT are slightly changed after the adsorption processes. Substitution of a Be atom in the tube surface with a Ca atom increases the adsorption energies by about 7.4 and 14.7 kcal/mol for NH₃ and H₂O, respectively. Unlike the pristine tube, the electronic properties of Ca-doped BeONT are sensitive to NH₃ and H₂O molecules. Also, the Ca-doped tube is much more sensitive to H₂O molecule than NH₃ one.