Controllable Fabrication of Sub-10 nm Graphene Nanopores via Helium Ion Microscopy and DNA Detection
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Abstract:
Solid-state nanopores have become a prominent tool in the field of single-molecule detection. Conventional solid-state nanopores are thick, which affects the spatial resolution of the detection results. Graphene is the thinnest 2D material and has the highest spatial detection resolution. In this study, a graphene membrane chip was fabricated by combining a MEMS process with a 2D material wet transfer process. Raman spectroscopy was used to assess the quality of graphene after the transfer. The mechanism behind the influence of the processing dose and residence time of the helium ion beam on the processed pore size was investigated. Subsequently, graphene nanopores with diameters less than 10 nm were fabricated via helium ion microscopy. DNA was detected using a 5.8 nm graphene nanopore chip, and the appearance of double-peak signals on the surface of 20 mer DNA was successfully detected. These results serve as a valuable reference for nanopore fabrication using 2D material for DNA analysis.Keywords:
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Field ion microscope
Focused ion-beam milling with a sub-10 nm diameter beam of gallium ions has been used to fabricate field-ion specimens from a multilayer film nanostructure containing 100 repetitions of a bilayer deposited directly onto a planar substrate. Successful field-ion specimen preparation has allowed the observation of these layers on the atomic scale by both field-ion imaging and atom probe compositional analysis.
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Characterization
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Selective detection of attomolar proteins was achieved using gold lined nanopores in a nanopore blockade sensor.
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Protein detection
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Graphene sheets was a fascinating material with its tantalizing applied foreground.A prerequisite for exploiting most proposed applications for graphene was to seek for a method that readily and simply produced graphene sheets in large quantities.By far,graphene sheets can be prepared by three techniques in general.Among them,oxidation and reduction processing graphene sheets was the most suitable for producing graphene sheets in large quantity.XRD,transmission electron microscopy and FT-IR spectra analysis indicated that graphene single sheets were readily synthesized through the chemical processing.Moreover,the crystal structure of the graphene nanosheets was maintained intact after chemical functionalisation.
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We report the effect of depth on fabrication of nanopore on silicon substrate by utilizing one-step focused ion beam (FIB) milling. The conical shaped of nanopores were successfully fabricated by optimizing the milling parameters of FIB system. The milling depth, base diameter and tip diameter of the resulting nanopores were characterized using field emission scanning electron microscope (FESEM). The minimum diameter of the conical shaped nanopore was found to be 66.51 nm. Moreover, when aspect ratio is less than unity, the redeposited material will land on the tip of the nanopores and adhere at the sidewall for high aspect ratio. This result will be beneficial towards the new generation of nanopore-based DNA sequencing.
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To slow the translocation of single-stranded DNA (ssDNA) through a solid-state nanopore, a nanopore was narrowed, and the effect of the narrowing on the DNA translocation speed was investigated. In order to accurately measure the speed, long (5.3 kb) ssDNA (namely, ss-poly(dA)) with uniform length (±0.4 kb) was synthesized. The diameters of nanopores fabricated by a transmission electron microscope were controlled by atomic-layer deposition. Reducing the nanopore diameter from 4.5 to 2.3 nm slowed down the translocation of ssDNA by more than 16 times (to 0.18 μs base(-1)) when 300 mV was applied across the nanopore. It is speculated that the interaction between the nanopore and the ssDNA dominates the translocation speed. Unexpectedly, the translocation speed of ssDNA through the 4.5 nm nanopore is more than two orders of magnitude higher than that of double-stranded DNA (dsDNA) through a nanopore of almost the same size. The cause of such a faster translocation of ssDNA can be explained by the weaker drag force inside the nanopore. Moreover, the measured translocation speeds of ssDNA and dsDNA agree well with those calculated by molecular-dynamics (MD) simulation. The MD simulation predicted that reducing the nanopore diameter to almost the same as that of ssDNA (i.e. 1.4 nm) decreases the translocation speed (to 1.4 μs base(-1)). Narrowing the nanopore is thus an effective approach for accomplishing nanopore DNA sequencing.
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He notes that, since graphene's discovery, scientists working with natural graphite to produce graphene have used what is known as the Hummers method to turn graphene oxide into reduced graphene oxide (or rGO - a term which [Gordon Chiu] says has been incorrectly and interchangeably used with the term'graphene').
Because graphite has the same composition and arrangement as graphene, natural graphite is a popular and cost-effective precursor in the production of many graphene materials, including graphene nanoplatelets, reduced graphene and graphene oxide, Dr Elena Polakova, CEO of Graphene Laboratories told IM.
In order to restore some of graphene's natural properties - because graphene oxide is not conductive like graphene - we reduced the samples to create reduced graphene oxide. We then went a step further and converted the reduced graphene oxide into a paste with applications in conductive inks and coatings.
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Graphene foam
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Graphene 基于 graphene 有唯一的物理性质，和许多 proof-of-concept 设备是 demonstated。因为，为 graphene 的申请的一个前提是它以一种控制方式的生产在这些层的 graphene 层和缺点的数字显著地影响运输性质。在这份报纸，我们简短在 graphene 和基于 graphene 的 composites 的控制合成上考察我们的最近的工作，方法到的发展在干净精力应用并且为定序的快速的 DNA 描绘 graphene 的 graphene 层，和使用。例如，我们使用了钻电子光谱学描绘 graphene 层的数字和结构，在整个 Ni 电影底层上的生产单个层的 graphene，是的综合分散得好的减少的 graphene 氧化物一致地有唯一的金 nanodots 的 grafted，和制作 graphene nanoscrolls。我们也在器官的太阳能电池并且直接探索了 graphene 的应用，定序的 ultrafast DNA。最后，我们探讨挑战那 graphene 在它的合成和干净精力和生物察觉到应用的静止的脸。
Graphene foam
Bilayer graphene
Nanodot
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Using nanopores for single-molecule sequencing of proteins - similar to nanopore-based sequencing of DNA - faces multiple challenges, including unfolding of the complex tertiary structure of the proteins and enforcing their unidirectional translocation through nanopores. Here, we combine molecular dynamics (MD) simulations with single-molecule experiments to investigate the utility of SDS (Sodium Dodecyl Sulfate) to unfold proteins for solid-state nanopore translocation, while simultaneously endowing them with a stronger electrical charge. Our simulations and experiments prove that SDS-treated proteins show a considerable loss of the protein structure during the nanopore translocation. Moreover, SDS-treated proteins translocate through the nanopore in the direction prescribed by the electrophoretic force due to the negative charge impaired by SDS. In summary, our results suggest that SDS causes protein unfolding while facilitating protein translocation in the direction of the electrophoretic force; both characteristics being advantageous for future protein sequencing applications using solid-state nanopores.
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Transport protein
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