The potential application of the intrinsic and extrinsic (8,0) zigzag single-walled C3N nansheets as chemical sensor for CO molecules has been investigated using density functional theory calculations. The calculation shows that the pristine sheet is a semiconductor with a HOMO-LUMO gap (Eg) of about 2.19 eV. The pristine and B-doped sheets can weakly adsorb a CO molecule with the adsorption energies of -4.8 and -4.6 kcal mol(-1), and their electronic properties are not sensitive to this molecule. By replacing a C atom with an Al atom, localized impurity states are induced under the conduction level of the sheet. The binding interaction between the CO molecule and the Al-doped sheet becomes much stronger (Ead = -17.8 kcal mol(-1)). After the adsorption of CO on the Al-dope sheet, the Eg of the sheet is significantly decreased from 1.07 to 0.73 eV. This leads to a sizable increase in the resistance of the tube. Thus, the Al-doped sheet can show the presence of CO molecules by an electronic signal because of the change in its resistance and conductivity.

In this work, we present a semi-analytical expression for the temperature dependence of a spinresolved dynamical density-density response function of massless Dirac fermions within the Random Phase Approximation. This result is crucial in order to describe thermodynamic properties of the interacting systems. In particular, we use it to make quantitative predictions for the paramagnetic spin susceptibility of doped graphene sheets. We find that, at low temperatures, the spin susceptibility behaves like T −2 which is completely different from the temperature dependence of the magnetic susceptibility in undoped graphene sheets.

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