Unraveling the effect of Ti doping on the sensing properties of AlN nanotubes toward acrylonitrile gas

The adsorption of acrylonitrile (AC) is explored onto a pure and a Ti-doped AlN nanotube (AlNNT) through density functional theory computations. An adsorption energy of (E_ad) −6.8 kcal/mol is predicted when AC comes nearer the pure AlNNT, which shows that the adsorption is weak. Also, there is no considerable change in the electronic properties of the pure AlNNT. Doping the AlNNT with titanium (Ti) improves its performance, making it more reactive and sensitive to AC. Our calculations of standard Gibbs free energy of formation indicate that replacing an Al atom in the structure of the AlNNT with a Ti atom is more favorable than an N atom. Doping a Ti atom into the surface of the AlNNT changes E_ad of AC from −6.8 to −22.2 kcal/mol. The sensing response significantly rises to 94.7 after Ti-doping, which shows that there is an increase in the electrical conductivity of the AlNNT. Finally, we show that the Ti-doped AlNNT can selectively detect AC in the presence of HCN, formaldehyde, ethanol, toluene, and acetone. The recovery time for the desorption of AC from the surface of the Ti-doped AlNNT is computed to be 15.0 s, which has a short recovery time.