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Selectively Sized Graphene-Based Nanopores for in Situ Single Molecule Sensing.

Crick CR, Sze JY, Rosillo-Lopez M, Salzmann CG, Edel JB - ACS Appl Mater Interfaces (2015)

Bottom Line: The precise tailoring of nanopore size is a significant step toward achieving this, as it would allow for a nanopore to be tuned to a corresponding analyte.The translocation of DNA is studied as the pore size is varied, allowing for subfeatures of DNA to be detected with slower DNA translocations at smaller pore sizes, and the ability to observe trends as the pore is opened.This approach opens the door to creating a device that can be target to detect specific analytes.

View Article: PubMed Central - PubMed

Affiliation: †Department of Chemistry, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom.

ABSTRACT
The use of nanopore biosensors is set to be extremely important in developing precise single molecule detectors and providing highly sensitive advanced analysis of biological molecules. The precise tailoring of nanopore size is a significant step toward achieving this, as it would allow for a nanopore to be tuned to a corresponding analyte. The work presented here details a methodology for selectively opening nanopores in real-time. The tunable nanopores on a quartz nanopipette platform are fabricated using the electroetching of a graphene-based membrane constructed from individual graphene nanoflakes (ø ∼30 nm). The device design allows for in situ opening of the graphene membrane, from fully closed to fully opened (ø ∼25 nm), a feature that has yet to be reported in the literature. The translocation of DNA is studied as the pore size is varied, allowing for subfeatures of DNA to be detected with slower DNA translocations at smaller pore sizes, and the ability to observe trends as the pore is opened. This approach opens the door to creating a device that can be target to detect specific analytes.

No MeSH data available.


(A)Plot of the repeating square wave potential applied to the multilayeredgraphene membranes. A corresponding current trace from a nanoporecoated using 1.5 mg mL–1 of GNF solution is shown.(B) Shows the current increase/time trace for the first 20 s of eachpore opening sequences for the same pipette, generated by using the average positivecurrent flow (shown in 3A, from ∼0–10 ms in the squarewave cycle). The trend shows a general increase in current after eachopening sequence. (C) Nanopipette I–V plots after subsequent nanopore opening sequences. Thepore opens from completely closed to a final estimate size of 8.7nm after 9 sequences. (D) Plot of the pore current at positive andnegative potentials as the pore is opened. The corresponding estimatedpore size is also shown.
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fig3: (A)Plot of the repeating square wave potential applied to the multilayeredgraphene membranes. A corresponding current trace from a nanoporecoated using 1.5 mg mL–1 of GNF solution is shown.(B) Shows the current increase/time trace for the first 20 s of eachpore opening sequences for the same pipette, generated by using the average positivecurrent flow (shown in 3A, from ∼0–10 ms in the squarewave cycle). The trend shows a general increase in current after eachopening sequence. (C) Nanopipette I–V plots after subsequent nanopore opening sequences. Thepore opens from completely closed to a final estimate size of 8.7nm after 9 sequences. (D) Plot of the pore current at positive andnegative potentials as the pore is opened. The corresponding estimatedpore size is also shown.

Mentions: The nanopore size was also estimated through conductivitymeasurements. The uncoated pipettes showed a conductance of 4.3 nS(±0.3 nS) at 0.1 M KCl. This is estimated to be a pore size of25 nm (±2 nm) according to the model described by Steinbock etal.51 The estimated pore diameters werealso comparable to literature recently reported.5 This value did not change upon undergoing the annealingprocess. Graphene deposition provided pore blockages for the majorityof the treated pipettes at all concentrations, with the relative amountsof blockages increasing with concentration; 50% for 1 mg mL–1, 84% for 1.5 mg mL–1, and 93.5% for 3 mg mL–1. The graphene-coated pipettes showed average conductancevalue (7 ± 0.8 pS) when electrically tested, indicating thatthe nanopore is closed. The pore opening process was aimed at steadilyopening the membrane covering the nanopore. The protocol designedfor opening uses a rapidly alternating current (±1.0 V at a frequencyof 100 Hz), the pore opening was monitored by measuring current flowand subsequent I–V measurements(Figure 3). This opening technique was selectedbecause graphene materials have been shown to exhibit delaminationand redox chemistry under an applied potential, while rapid reversalof applied potentials ensures a steady opening process.52,53


Selectively Sized Graphene-Based Nanopores for in Situ Single Molecule Sensing.

Crick CR, Sze JY, Rosillo-Lopez M, Salzmann CG, Edel JB - ACS Appl Mater Interfaces (2015)

(A)Plot of the repeating square wave potential applied to the multilayeredgraphene membranes. A corresponding current trace from a nanoporecoated using 1.5 mg mL–1 of GNF solution is shown.(B) Shows the current increase/time trace for the first 20 s of eachpore opening sequences for the same pipette, generated by using the average positivecurrent flow (shown in 3A, from ∼0–10 ms in the squarewave cycle). The trend shows a general increase in current after eachopening sequence. (C) Nanopipette I–V plots after subsequent nanopore opening sequences. Thepore opens from completely closed to a final estimate size of 8.7nm after 9 sequences. (D) Plot of the pore current at positive andnegative potentials as the pore is opened. The corresponding estimatedpore size is also shown.
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Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4543996&req=5

fig3: (A)Plot of the repeating square wave potential applied to the multilayeredgraphene membranes. A corresponding current trace from a nanoporecoated using 1.5 mg mL–1 of GNF solution is shown.(B) Shows the current increase/time trace for the first 20 s of eachpore opening sequences for the same pipette, generated by using the average positivecurrent flow (shown in 3A, from ∼0–10 ms in the squarewave cycle). The trend shows a general increase in current after eachopening sequence. (C) Nanopipette I–V plots after subsequent nanopore opening sequences. Thepore opens from completely closed to a final estimate size of 8.7nm after 9 sequences. (D) Plot of the pore current at positive andnegative potentials as the pore is opened. The corresponding estimatedpore size is also shown.
Mentions: The nanopore size was also estimated through conductivitymeasurements. The uncoated pipettes showed a conductance of 4.3 nS(±0.3 nS) at 0.1 M KCl. This is estimated to be a pore size of25 nm (±2 nm) according to the model described by Steinbock etal.51 The estimated pore diameters werealso comparable to literature recently reported.5 This value did not change upon undergoing the annealingprocess. Graphene deposition provided pore blockages for the majorityof the treated pipettes at all concentrations, with the relative amountsof blockages increasing with concentration; 50% for 1 mg mL–1, 84% for 1.5 mg mL–1, and 93.5% for 3 mg mL–1. The graphene-coated pipettes showed average conductancevalue (7 ± 0.8 pS) when electrically tested, indicating thatthe nanopore is closed. The pore opening process was aimed at steadilyopening the membrane covering the nanopore. The protocol designedfor opening uses a rapidly alternating current (±1.0 V at a frequencyof 100 Hz), the pore opening was monitored by measuring current flowand subsequent I–V measurements(Figure 3). This opening technique was selectedbecause graphene materials have been shown to exhibit delaminationand redox chemistry under an applied potential, while rapid reversalof applied potentials ensures a steady opening process.52,53

Bottom Line: The precise tailoring of nanopore size is a significant step toward achieving this, as it would allow for a nanopore to be tuned to a corresponding analyte.The translocation of DNA is studied as the pore size is varied, allowing for subfeatures of DNA to be detected with slower DNA translocations at smaller pore sizes, and the ability to observe trends as the pore is opened.This approach opens the door to creating a device that can be target to detect specific analytes.

View Article: PubMed Central - PubMed

Affiliation: †Department of Chemistry, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom.

ABSTRACT
The use of nanopore biosensors is set to be extremely important in developing precise single molecule detectors and providing highly sensitive advanced analysis of biological molecules. The precise tailoring of nanopore size is a significant step toward achieving this, as it would allow for a nanopore to be tuned to a corresponding analyte. The work presented here details a methodology for selectively opening nanopores in real-time. The tunable nanopores on a quartz nanopipette platform are fabricated using the electroetching of a graphene-based membrane constructed from individual graphene nanoflakes (ø ∼30 nm). The device design allows for in situ opening of the graphene membrane, from fully closed to fully opened (ø ∼25 nm), a feature that has yet to be reported in the literature. The translocation of DNA is studied as the pore size is varied, allowing for subfeatures of DNA to be detected with slower DNA translocations at smaller pore sizes, and the ability to observe trends as the pore is opened. This approach opens the door to creating a device that can be target to detect specific analytes.

No MeSH data available.