Identifying Single-Stranded DNA by Tuning the Graphene Nanogap Size: An Ionic Current Approach

Graphene Nanopore Fabrication and Applications

Graphene is a revolutionary material with excellent optical, electrical and mechanical properties and has garnered significant attention in the realm of nanopore technology. Devices incorporating graphene nanopores leverage the material's atomic thickness to enhance detection precision in solid-state nanopores. These nanopores exhibit high spatial resolution and ion selectivity, making them promising sensors for biomolecular detection. Additionally, their unique characteristics suggest their considerable potential for applications in material separation and osmotic power generation. In recent years, several literature reviews on graphene nanopores have been published; however, some have not fully addressed certain important aspects, such as the depth of theoretical analysis, the extent of coverage on technological advancements, and the exploration of potential applications. This paper reviews current fabrication methods, including "top-down" etching and "bottom-up" synthesis, highlighting their advantages and limitations. We also summarize diverse applications of graphene nanopores, such as in biomolecule detection and water desalination. Our findings emphasize the need for a deeper exploration of these aspects, advancing the field by showcasing the broader potential of graphene nanopores in addressing various technological challenges.

Nanopore-based sensors for DNA sequencing: a review

Nanopore sensors, owing to their distinctive structural properties, can be used to detect biomolecular translocation events. These sensors operate by monitoring variations in electric current amplitude and duration, thereby enabling the calibration and distinction of various biomolecules. As a result, nanopores emerge as a potentially powerful tool in the field of deoxyribonucleic acid (DNA) sequencing. However, the interplay between testing bandwidth and noise often leads to the loss of part of the critical translocation signals, presenting a substantial challenge for the precise measurement of biomolecules. In this context, innovative detection mechanisms have been developed, including optical detection, tunneling current detection, and nanopore field-effect transistor (FET) detection. These novel detection methods are based on but beyond traditional nanopore techniques and each of them has unique advantages. Notably, nanopore FET sensors stand out for their high signal-to-noise ratio (SNR) and high bandwidth measurement capabilities, overcoming the limitations typically associated with traditional solid-state nanopore (SSN) technologies and thus paving the way for new avenues to biomolecule detection. This review begins by elucidating the fundamental detection principles, development history, applications, and fabrication methods for traditional SSNs. It then introduces three novel detection mechanisms, with a particular emphasis on nanopore FET detection. Finally, a comprehensive analysis of the advantages and challenges associated with both SSNs and nanopore FET sensors is performed, and then insights into the future development trajectories for nanopore FET sensors in DNA sequencing are provided. This review has two main purposes: firstly, to provide researchers with a preliminary understanding of advancements in the nanopore field, and secondly, to offer a comprehensive analysis of the fabrication techniques, transverse current detection principles, challenges, and future development trends in the field of nanopore FET sensors. This comprehensive analysis aims to help give researchers in-depth insights into cutting-edge advancements in the field of nanopore FET sensors.

Advancement of Next-Generation DNA Sequencing through Ionic Blockade and Transverse Tunneling Current Methods

DNA sequencing is transforming the field of medical diagnostics and personalized medicine development by providing a pool of genetic information. Recent advancements have propelled solid-state material-based sequencing into the forefront as a promising next-generation sequencing (NGS) technology, offering amplification-free, cost-effective, and high-throughput DNA analysis. Consequently, a comprehensive framework for diverse sequencing methodologies and a cross-sectional understanding with meticulous documentation of the latest advancements is of timely need. This review explores a broad spectrum of progress and accomplishments in the field of DNA sequencing, focusing mainly on electrical detection methods. The review delves deep into both the theoretical and experimental demonstrations of the ionic blockade and transverse tunneling current methods across a broad range of device architectures, nanopore, nanogap, nanochannel, and hybrid/heterostructures. Additionally, various aspects of each architecture are explored along with their strengths and weaknesses, scrutinizing their potential applications for ultrafast DNA sequencing. Finally, an overview of existing challenges and future directions is provided to expedite the emergence of high-precision and ultrafast DNA sequencing with ionic and transverse current approaches.

Conductance and tunnelling current characteristics for individual identification of synthetic nucleic acids with a graphene device

Based on combined density functional theory and non-equilibrium Green's function quantum transport studies, in the present work we have demonstrated the quantum interference (QI) effect on the transverse conductance of Hachimoji (synthetic) nucleic acids when placed between the oxygen-terminated zigzag graphene nanoribbon (O-ZGNR) nanoelectrodes. We theorize that the QI effect could be well preserved in π-π coupling between a target nucleobase molecule and the carbon-based nanoelectrodes. Our study indicates that the QI effect, such as anti-resonance or Fano-resonance, affects the variation of transverse conductance depending on the nucleobase conformation. Furthermore, a variation of up to 2-5 orders of magnitude is observed in the conductance upon rotation for all the nucleobases. The current-voltage (I-V) characteristics results suggest a distinct variation in the electronic tunnelling current across the proposed nanogap device for all five nucleobases with the applied bias voltage ranges from 0.1-1.0 V. The different rotation angles keep the distinct feature of the nucleobases in both transverse conductance and tunnelling current features. Both features could be utilized in an accurate synthetic DNA sequencing device.