Adsorption of DNA nucleobases on single-layer Ti3C2 MXene and graphene: vdW-corrected DFT and NEGF studies

We investigated the interaction of DNA nucleobases [adenine (A), guanine (G), thymine (T), and cytosine (C)] with single-layer Ti3C2 MXene using Van der Waals (vdW)-corrected density functional theory and non-equilibrium Green’s function methods. All calculations were benchmarked against graphene. We showed that depending on the initial vertical height of a nucleobase above the Ti3C2 surface, two interaction mechanisms are possible, namely, physisorption and chemisorption. For graphene, DNA nucleobases always physisorbed onto the graphene surface irrespective of the initial vertical height of the nucleobase above the graphene sheet. The PBE+vdW binding energies for graphene are high (0.55–0.74 eV) and follow the order G > A > T > C, with adsorption heights in the range of 3.16–3.22 Å, indicating strong physisorption. For Ti3C2, the PBE+vdW binding energies are relatively weaker (0.16–0.20 eV) and follow the order A > G = T > C, with adsorption heights in the range of 5.51–5.60 Å, indicating weak physisorption. The binding energies for chemisorption follow the order G > A > T > C, which is the same order for physisorption. The binding energy values (5.3–7.5 eV) indicate very strong chemisorption (∼40 times larger than the physisorption binding energies). Furthermore, our band structure and electronic transport analysis showed that for physisorption, there is neither significant variation in the band structure nor modulation in the transmission function and device density of states. The relatively weak physisorption and strong chemisorption show that Ti3C2 might not be capable of identifying DNA nucleobases using the physisorption method.