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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.


SEM imagesof (A) untreated and (B) GNF-coated nanopipettes. The untreated nanopipettespossess an average pore diameter of 25 nm. Scale bars in panels Aand B are 100 nm. TEM images of (C) GNF coated and (D) untreated nanopipettesedges. The GNF-coated pipettes have a 3–4 nm coating of materialon the surface. The dashed line on image C indicates the line of theunderlying quartz of the pipet. Scale bars in panels C and D are 10nm. The coated pipettes in the images are treated with 1.5 mg mL–1 of GNF solutions before being annealed.
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fig2: SEM imagesof (A) untreated and (B) GNF-coated nanopipettes. The untreated nanopipettespossess an average pore diameter of 25 nm. Scale bars in panels Aand B are 100 nm. TEM images of (C) GNF coated and (D) untreated nanopipettesedges. The GNF-coated pipettes have a 3–4 nm coating of materialon the surface. The dashed line on image C indicates the line of theunderlying quartz of the pipet. Scale bars in panels C and D are 10nm. The coated pipettes in the images are treated with 1.5 mg mL–1 of GNF solutions before being annealed.

Mentions: The deposition of GNFs onto nanopipettes could not be achievedthrough a simple modification of a previously used GNF depositiontechnique (spin-coating or drop-casting). Dip-coating of the pipettetips (Figure 1) offered an adaptable coatingmethod, which could be readily achieved. The spin coating experiments,carried out on flat substrates, were used to estimate the concentrationrequired for a conformal coating. Various concentrations of GNF solutionswere used to explore a variety coating conditions. Subsequent to dip-coating,the pipettes were left to air-dry for 10 min with their tips pointingdownward, which demonstrated the most consistent nanopore coverage.Further orientations for pipettes drying were carried out (includingpointing vertically upward and horizontally). However, this did notprovide consistent nanopore coverage on the electrical measurement(i.e., the I–V curve). Whenexamined optically, the pipettes showed no coatings of GNF solutionswith concentrations of 1.5 mg mL–1 or less; howeverthere was a slight darkening of pipettes coated using 3 mg mL–1. The annealed nanopipettes showed no change in overallappearance and shape (i.e., taper length, color, and angle of tip).The coatings on the pipettes were imaged using both SEM and TEM (Figure 2). SEM images of nanopipettes before and after thecoating process show successful closing of the nanopore. TEM imagesof the pipette shaft show film thicknesses (∼3–4 nm)for the deposited material. A full experimental description is givenin the Supporting Information.


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)

SEM imagesof (A) untreated and (B) GNF-coated nanopipettes. The untreated nanopipettespossess an average pore diameter of 25 nm. Scale bars in panels Aand B are 100 nm. TEM images of (C) GNF coated and (D) untreated nanopipettesedges. The GNF-coated pipettes have a 3–4 nm coating of materialon the surface. The dashed line on image C indicates the line of theunderlying quartz of the pipet. Scale bars in panels C and D are 10nm. The coated pipettes in the images are treated with 1.5 mg mL–1 of GNF solutions before being annealed.
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fig2: SEM imagesof (A) untreated and (B) GNF-coated nanopipettes. The untreated nanopipettespossess an average pore diameter of 25 nm. Scale bars in panels Aand B are 100 nm. TEM images of (C) GNF coated and (D) untreated nanopipettesedges. The GNF-coated pipettes have a 3–4 nm coating of materialon the surface. The dashed line on image C indicates the line of theunderlying quartz of the pipet. Scale bars in panels C and D are 10nm. The coated pipettes in the images are treated with 1.5 mg mL–1 of GNF solutions before being annealed.
Mentions: The deposition of GNFs onto nanopipettes could not be achievedthrough a simple modification of a previously used GNF depositiontechnique (spin-coating or drop-casting). Dip-coating of the pipettetips (Figure 1) offered an adaptable coatingmethod, which could be readily achieved. The spin coating experiments,carried out on flat substrates, were used to estimate the concentrationrequired for a conformal coating. Various concentrations of GNF solutionswere used to explore a variety coating conditions. Subsequent to dip-coating,the pipettes were left to air-dry for 10 min with their tips pointingdownward, which demonstrated the most consistent nanopore coverage.Further orientations for pipettes drying were carried out (includingpointing vertically upward and horizontally). However, this did notprovide consistent nanopore coverage on the electrical measurement(i.e., the I–V curve). Whenexamined optically, the pipettes showed no coatings of GNF solutionswith concentrations of 1.5 mg mL–1 or less; howeverthere was a slight darkening of pipettes coated using 3 mg mL–1. The annealed nanopipettes showed no change in overallappearance and shape (i.e., taper length, color, and angle of tip).The coatings on the pipettes were imaged using both SEM and TEM (Figure 2). SEM images of nanopipettes before and after thecoating process show successful closing of the nanopore. TEM imagesof the pipette shaft show film thicknesses (∼3–4 nm)for the deposited material. A full experimental description is givenin the Supporting Information.

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.