In this project the molecular fingerprints of normal and mutated DNA/RNA nucleobases on various 2DMNR have been determined using the 2D-MES method, as well as determining the influence of the 2DMNR characteristics such as its width and the potential defects on the molecular adsorption and transport properties. The selected NBs are adenine (A), cytosine (C), guanine (G), thymine (T), uracil, 5-methylcytosine (5mC), and 5-hydroxymethylcytosine (5hmC), in which the latter two were selected because of their potential role in cancer cell growth. The DFT codes VASP, SIESTA, and TranSIESTA have been utilized in the 2D-MES to firstly calculate the most stable conformation of the NB-2DMNR systems, and, subsequently calculate its transport characteristics.
To this end, transmission profiles of the introduced NB–2DMNR systems were calculated and it was shown that once a DNA/RNA base is adsorbed onto the 2DMNR's surface, the ballistic electron transfer mode exhibits a new path with dips at certain energies. To investigate the possibility of uniquely assigning the emerged Fano dips as molecular fingerprints to each nucleobase in 2DMNR based sequencing device, we calculate and plot the differential conductance (Δg) spectra of each NB–2DMNR system for a certain range of bias and gate voltages were calculated. Comparing the obtained 2D and three-dimensional (3D) Δg maps indicated that 2DMNR can be employed to unambiguously recognize and distinguish various NBs provided 2DMES is applied. By calculating the conductance sensitivity, it was also shown that 2DMNR is able to recognize various nucleobases with acceptable sensitivity under the application of 2DMES technique.
Motivated by the successful application of 2DMES method on graphene nanoribbon (GNR), the capability of germanene nanoribbons (GeNRs) and graphdiyne nanoribbons (AGDNRs) as a feasible, accurate, and ultra-fast sequencing device under the application of 2DMES was investigated. The calculated 2D and 3D Δg maps (Figure 1) for different studied systems, in contrast with 1D current–voltage profiles, exhibited explicitly distinct features which enable unambiguous recognition of nucleobases. This means that, in practice, providing the Δg spectrum for each NB while the NB is translocating the width of nanoribbon can be utilized for unambiguous molecular recognition. The provided Δg maps for various nucleobases can be stored in a data set for DNA/RNA sequencing purpose. Also, in order to demonstrate the admissible susceptibility of the introduced nano bio-sensors to recognize various bases, the conductance sensitivity of the proposed system was calculated and it was shown that the proposed devices can provide large sensitivities for different nucleobases at different gate voltage values, making it applicable for molecular sensing usages.
In order to extend the proposed method to the field of spintronics and the use of spin instead of charge, the structural, electronic, and spintronic properties of graphitic carbon nitride (g-C3N4) monolayers were investigated. Possessing remarkable structural, electronic, and magnetic characteristics, g-C3N4 can be a promising candidate to develop a spin driven nano-biosensor as well as a building block of futuristic nanoelectronics and spintronic systems. Using first-principles calculations, a comprehensive study on the structural stability as well as electronic and magnetic properties of triazine-based g-C3N4 nanoribbons (gt-CNRs) was performed.
