Integrated X-ray photoelectron spectroscopy and DFT investigations of DNA adsorption on nanostructured SiOx surface

The adsorption of DNA on SiOx and nanostructured-SiOx substrates has been investigated here in order to understand their binding behaviour. The XPS results indicate that DNA binding on nanostructured-SiOx introduces chemical states like Si...O...N and Si...N. On the other hand, on SiOx surface only Si...O...N state is observed. Formation of Si...O...N and Si...N states emphasize the dominant participation of nitrogenous DNA bases during the adsorption as well as transport of charge carriers. We complement the experimental findings with first principles DFT investigations on the linkage of DNA base, adenine, with SiOx and nanostructured-SiOx, respectively. DFT results show that linkage appears to occur via electrostatic interaction and charge transfer from the substrate to the nitrogen bases of DNA. The molecular electrostatic potential maps, highest occupied molecular orbitals and lowest unoccupied molecular orbitals support the experimental findings. These results will be important for biosensing applications.