The advancement in DNA sequencing has massively improved the biological and medicinal research, leading to the development of new medical diagnosis and forensic applications. It puts forward a pool of information that could be harnessed to realize personalized medicine toward various deadly diseases. Recent developments in solid-state nanopore-based sequencing technology have drawn much attention owing to its potential to achieve fast, cost-effective, reliable, and single-shot nucleotide identification. Here, we have proposed atomically thin graphene and χ3 borophene nanopore-based devices for DNA sequencing. The structural and electronic properties of the graphene pore and χ3 borophene pore with and without DNA nucleotides have been studied by employing first-principles density functional theory (DFT) calculations. Using the DFT and non-equilibrium Green’s function formalism (NEGF), we have studied the transverse conductance and current–voltage (I–V) characteristics of all the systems. We have observed that nucleotides are weakly interacting with the χ3 borophene pore compared with the graphene pore, indicating higher translocation speed and shorter residence time inside the χ3 borophene pore. In case of both the nanopores, the operating current across the devices is within the range of microampere (μA), which is several orders higher magnitude than that of the previously reported nanogap/nanopore-based devices. The I–V results show that the graphene nanopore-based device is promising for individual identification of nucleotides compared to the χ3 borophene pore-based device, and the results are promising compared to even the graphene nanogap-based systems reported earlier.

Solid-state material-based protein sequencing techniques have emerged as a paradigm that is capable of decoding the sequence of amino acids in protein by electrical detection. We studied a graphene nanoslit device for ultrafast protein sequencing using electronic transport calculations. The first-principles consistent-exchange van der Waals density functional (vdW-DFcx) calculations have been employed to study the structural and electronic properties of the pristine graphene nanoslit and graphene nanoslit + amino acid systems. Ten amino acid molecules, namely, alanine (Ala), arginine (Arg), aspartic acid (Asp), glutamic acid (Glu), glycine (Gly), histidine (His), lysine (Lys), phenylalanine (Phe), proline (Pro), and tyrosine (Tyr), are considered. The electronic quantum transport properties of pristine graphene nanoslit and graphene nanoslit + amino acid systems are studied using the nonequilibrium Green's function (NEGF) combined with the density functional theory (DFT) approach. Significant changes in the electronic transmission conductance are observed in the graphene nanoslit device in the presence of certain amino acids. The computed conductance sensitivity and current− voltage (I−V) characteristics indicate that selective identification of amino acids is possible through the graphene nanoslit device. This study may be a practical guide toward the development of a graphene nanoslit-based device for ultrafast protein sequencing applications.

Cs3Sb2X9 (X = Cl, Br, and I) perovskites containing less toxic elements, known as two-dimensional (2D) materials, generate enormous research interest due to their inherent photovoltaic properties. Tuning the band gap and understanding the change in the band type in these materials are essential for practical applications in photovoltaics. In this article, we have studied an indirect to direct band gap transition in Cs3Sb2Cl9–x Br x with Br substitution, and a possible explanation is provided from both experimental and theoretical studies. Incorporation of Br in Cs3Sb2Cl9 is confirmed from powder X-ray diffraction, scanning electron microscopy–energy dispersive X-ray spectroscopy, and Raman studies. Rietveld refinement of powder X-ray diffraction data revealed that Br prefers the terminal position over the bridging position with initial substitution and induces a distortion in the Sb­(Cl/Br)6 polyhedra. Further higher substitution of Br results in occupation of both terminal and bridging positions. Optical study shows that trigonal Cs3Sb2Cl9 has an indirect band gap of 2.88 eV, while the Br analogue, Cs3Sb2Br9, has a direct band gap of 2.43 eV. Theoretical study also confirms that Cs3Sb2Cl9 is an indirect band gap material, which undergoes a transition to a direct band gap type with minimal (two moles) substitution of Br in Cs3Sb2Cl9–x Br x . However, in these compounds, it is observed that with Br substitution, the valence band maximum remains unaltered, whereas the conduction band minimum changes from the A-point to the Γ-point. Analysis of the density of states of the halide and Sb revealed that the conduction band is contributed from Sb p, halide p (terminal), and halide s (bridging) states. The splitting of p-states of halides and Sb just above the Fermi level induced by the change in the terminal Cl/Br–Sb–Cl/Br bond angle is observed to be the primary reason for the transition of the band from an indirect to direct type with Br substitution. Understanding of the underlying relationship among the structural distortion, electronic properties, and band gap tuning will help in designing suitable materials with desired optoelectronic properties.

Recently synthesized two-dimensional hydrogen boride (HB) with a hexagonal boron network offers excellent opportunities for nanoscale electronic device applications. Herein, we have proposed a type of field-effect transistor (FET) nanodevice based on a two-dimensional HB sheet for individual identification of amino acids. Using first-principles consistent-exchange van der Waals density-functional (vdW-DF-cx) calculations, we have studied the effects produced by the adsorption of each amino acid on the electronic properties of the HB-based nanodevice for its detection. The adsorption energies, adsorption heights, and the charge transfer of each amino acid can be deliberated as demonstrative of all 10 amino acids: alanine (Ala), arginine (Arg), aspartic (Asp), glutamic acid (Glu), glycine (Gly), histidine (His), lysine (Lys), phenylalanine (Phe), proline (Pro), and tyrosine (Tyr). Furthermore, the electronic transport properties of the HB nanodevice and HB + amino acid setup are studied by the nonequilibrium Green’s function (NEGF) formalism combined with the density functional theory (DFT) approach. Our results show that the adsorption of each amino acid on the HB nanodevice gives Fano resonance in the electronic transmission function. The sensitivity analysis and current–voltage (I–V) characteristic results indicate that selective detection of amino acids is possible. Thus, we believe that the HB-based device may be promising for the prospect of protein sequencing.

Recent advances in cost-effective, ultra-rapid, and efficient DNA sequencing are in the saddle of the advancement of the personalization of medicines for understanding and early-stage detection of several killer diseases. Paying attention to a timely need for the development of solid-state nanodevices for rapid and controlled identification of DNA nucleotides, in this report, we theoretically explored the potential of labeling techniques in the sequencing of DNA nucleotides through solid-state graphene nanogap electrodes using the quantum tunneling current approach. Our study boasts the idea that labeling of DNA nucleotides can solve major hurdles of DNA sequencing, such as improving the signal-to-noise ratio, slowing down translocation velocity, and controlling orientational variations. Employing the first-principle density functional theory study, we identify unique interaction energy values for each labeled nucleotide having remarkable differences in the range of 0.10–0.74 eV. The zero-bias transmission spectra of the proposed setup suggest that the detection of the nucleotides is possible by applying very low gate voltages. Moreover, the labeling of nucleotides amplifies the conductance sensitivity considerably. I–V characteristics suggest that electrical recognition of each labeled nucleotide can be carried out at both lower (0.3 V) and higher (0.8 V) bias voltages with single-molecule resolution, although the maximum current sensitivity is observed at a higher bias voltage. The proposed sequencing device possesses high sensitivity and selectivity characteristics that are crucial for experimental purposes. We find that our results are rich compared to unlabeled nucleotides-based graphene nanopore/nanogap devices. Hence, the study will certainly motivate the experimentalists toward the application of a labeled DNA nucleotide system for ultra-rapid DNA sequencing by using the tunneling current approach.