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Abstract
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The gas response of metal oxide-based sensors depends strongly on its adsorption properties. To
explore the potential sensing capability of pristine and nitrogen modi ̄ed TiO 2 /graphene oxide (GO)
heterostructures, the adsorption of NO 2 molecule on the N-doped nanocomposites was investigated
using density functional theory (DFT) calculations. Six possible con ̄gurations were simulated
based on the estimated adsorption energies. The binding sites were located over the oxygen, doped
nitrogen and ̄ve-fold coordinated titanium atoms of TiO 2 . The electronic properties including
atomic Mulliken population, projected density of states and molecular orbitals were investigated in
detail. The N–O bonds of the NO 2 molecule were signi ̄cantly increased after the adsorption process.
The adsorption of NO 2 molecule on the N-doped nanocomposite is more energetically favorable than
the adsorption on the undoped one. The results suggest that NO 2 chemisorbs on the considered
nanocomposites. Mulliken population analysis reveals a noticeable charge transfer from the nano-
composite to the molecule, which indicate that NO 2 acts as a charge acceptor. Molecular orbital
calculations show that the highest occupied molecular orbitals (HOMOs) of the studied systems were
mainly localized on the adsorbed NO 2 molecule. The signi ̄cant overlaps in the projected density of
states (PDOS) spectra of the interacting atoms con ̄rm the formation of chemical bonds between them.
There is a direct relationship between the results of charge transfer and sensing responses. N-doped
nanocomposites have better sensing response than the undoped ones. The results highlight the pos-
sibility to develop innovative highly e±cient NO 2 sensors based on novel TiO 2 /GO nanocomposites.
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