Selective sensing of DNA/RNA nucleobases by metal-functionalized silicon nanowires: A DFT approach

Ultrasensitive chemical sensors based on silicon nanowires (SiNW) are optimal for detection of biological species, since they are fast and non-invasive, their fabrication is compatible with current semiconductor technology, and silicon is a biocompatible material. SiNW-based DNA sensors are well known, but there are few studies regarding the interaction of SiNWs with the single DNA/RNA nucleobases: Guanine (G), Cytosine (C), Adenine (A), Thymine (T), and Uracil (U). This work uses Density Functional Theory to study the interaction between the single nucleobases and SiNWs decorated with Cu, Ag and Au atoms, to determine their potential use as nucleobase detectors or carriers, or even to use nucleobase-functionalized SiNWs as sensing platform for other chemical species. Numerical results show remarkable changes of the nanowire's band gap upon adsorption of nucleobases. Likewise, the adsorption energies of the nucleobases on the functionalized SiNW follow the trend C > G > A > T > U. Cu-functionalized nanowires are suitable for the electrical detection of cytosine, while Au-functionalized nanowires may detect thymine and uracil. On the other hand, large variations of the nanowire work function were found when guanine and adenine are adsorbed on Cu-functionalized nanowires.