DFT studies of acrolein molecule adsorption on pristine and Al-doped graphenes.

The ability of pristine graphene (PG) and Al-doped graphene (AlG) to detect toxic acrolein (C3H4O) was investigated by using density functional calculations. It was found that C3H4O molecule can be adsorbed on the PG and AlG with adsorption energies about -50.43 and - v30.92 kcal mol(-1) corresponding to the most stable configurations, respectively. Despite the fact that interaction of C3H4O has no obvious effects on the of electronic properties of PG, the interaction between C3H4O and AlG can induce significant changes in the HOMO/LUMO energy gap of the sheet, altering its electrical conductivity which is beneficial to sensor designing. Thus, the AlG may be sensitive in the presence of C3H4O molecule and might be used in its sensor devices. Also, applying an external electric filed in an appropriate orientation (almost stronger than 0.01 a.u.) can energetically facilitate the adsorption of C3H4O molecule on the AlG.

NH3 on a BC3 nanotube: effect of doping and decoration of aluminum.

The adsorption of the NH3 molecule was investigated on pristine, Al-doped and Al-decorated BC3 nanotubes (BC3NT) using density functional theory calculations. It was found that NH3 prefers to be adsorbed on a B atom of the tube wall, releasing energy of 1.02 eV. Al-doping increases the acidity of the tube surface and, therefore, its reactivity toward NH3 so that the released energy in this case is about 1.62 eV, while decorating the BC3NT with Al atom decreases the acidity and reactivity. Although Al-doping has no significant effect on the electronic properties of the BC3NT, Al-decoration significantly reduces its HOMO/LUMO energy gap from 2.37 to 1.16 eV so that the tube becomes an n-type semiconductor. However, we believe that the acidity of the BC3NTs may be controlled by doping or decoration of Al atoms.

A large gap opening of graphene induced by the adsorption of CO on the Al-doped site.

We investigated CO adsorption on the pristine, Stone-Wales (SW) defected, Al- and Si- doped graphenes by using density functional calculations in terms of geometric, energetic and electronic properties. It was found that CO molecule is weakly adsorbed on the pristine and SW defected graphenes and their electronic properties were slightly changed. The Al- and Si- doped graphenes show high reactivity toward CO, so calculated adoption energies are about -11.40 and -13.75 kcal mol(-1) in the most favorable states. It was found that, among all the structures, the electronic properties of Al-doped graphene are strongly sensitive to the presence of CO molecule. We demonstrate the existence of a large Eg opening of 0.87 eV in graphene which is induced by Al-doping and CO adsorption.

Exohedral and endohedral adsorption of alkaline earth cations in BN nanocluster.

Adsorption of three alkaline earth cations inside and outside of a B(12)N(12) nano-cage in aqueous medium was investigated using density functional theory. The results obtained are discussed in terms of thermodynamic, geometric, and electronic properties. Based on the calculation of enthalpy changes at 298 K and 1 atm, the adsorption of the considered cations was found to be exothermic outside the cluster while it is endothermic inside. It was also found that the exohedral adsorption favorability of the cluster increases in the series: Ca(2+) < Mg(2+) << Be(2+) with Gibbs free energy changes in the range of -0.08 to -1.53 eV at B3LYP/6-31G (d) level of theory. Overall, interaction of the cations with the cluster influences the electronic properties of the cluster through stabilizing the HOMO and LUMO as well as reducing the energy gap between them. However, the electronic properties changed much more in the case of endohedral adsorption in comparison with the exohedral adsorption.