Adsorption of nucleobases on 2D transition-metal dichalcogenides and graphene sheet: a first principles density functional theory study

Adsorption characteristics of DNA/RNA nucleobases on monolayers of transition-metal dichalcogenide (TMD) such as molybdenum disulfide (MoS2) and tungsten disulfide (WS2) have been studied using first principles density functional theory (DFT) with vdW-DF method. The same calculations have been performed with PBE and DFT-D-2 method for comparison. In addition, a comparative study has been done for adsorption with graphene (GRA) also to compare with MoS2 and WS2. We have found that all nucleobases are physisorbed on MoS2 and WS2 due to van der Waals interaction, which is similar to that of nucleobases on GRA. The order of binding energy of the nucleobases with MoS2 and WS2 is G > A > T > C > U using vdW-DF and DFT-D-2 method, which is also similar to that of GRA-nucleobases. Without the inclusion of vdW interaction (PBE only), the order of the binding energies is calculated to be G > C > A > T > U for MoS2 and WS2-nucleobase complexes and G > C > A=T > U for GRA. We have analyzed changes in the electronic structures due to adsorption and the consequences in the calculated optical absorption spectra. Moreover, we have found that the calculated work functions of MoS2, WS2 and GRA decrease after the adsorption of nucleobases. Our results demonstrate that apart from graphene, transition metal dichalcogenides may also be used to detect biomolecules for medical science and biotechnology.