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DNA-decorated graphene chemical
sensors
Brett Goldsmith, Ye Lu, Nicholas Kybert, A.T. Charlie JohnsonUniversity of PennsylvaniaDepartment of Physics and Astronomy
Graphene Transistors
Vb
Silicon Gate
SiO2
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Vg
initial
Graphene Transistors
Vb
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Vg
Vb
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Vg
400 C anneal
Ishigami et al. Nano Letters (2007)
Yaping Dan, A.T.C. Johnson et al, Nano Letters, 2009
initialclean
Effect of Cleaning on Sensing
Cleaning causes:- Reduction in carrier density here from 3.3×1012/cm2 to 6.2×1011/cm2
- Increase in mobility here from 1000 cm2/V-s to 2600 cm2/V-s
- Decrease in chemical sensitivity
Yaping Dan, A.T.C. Johnson et al, Nano Letters, 2009
Why ssDNA?• Chemical sensing is moving beyond “single
type” sensors – focus on useful diversity and “electronic nose” approaches
• Diverse chemistry (e.g., 420 ~ 1012
sequences for 20-mer)• Existing literature on ssDNA functionalized
sensors.
White J, et. al., PLoS Biol 2008
Zuniga C, et. al., APL. 2009 Staii C, A.T.C. Johnson et. al., Nano Lett., 2005
mechanical
optical
electronic
DNA Deposition
Sequence 1: 5’ GAG TCT GTG GAG GAG GTA GTC 3’Sequence 2: 5’ CTT CTG TCT TGA TGT TTG TCA AAC 3’
- 200 mg/mL single stranded DNA solution
- non-covalent functionalization
- graphene is exposed to DNA for 45 minutes
- DNA code is used to alter the chemical properties of the applied bio-polymer
1mm
DNA-graphene interaction
initialclean ssDNA
ssDNA deposition leads to
- expected gate shift
- lowered mobility
Vb
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Vg
DNA-graphene interaction
modeling would predict around 1.5×1014 bases/cm2 at 100% coverage
we measure an increase in doping of around 6.2×1011 /cm2 carriers
direction is consistent with negatively charged adsorbates
ssDNA deposition leads to
- expected gate shift
- lowered mobility
graphene
CNT
Johnson, R. R.; Johnson, A. T. C., et. al., Nanoletters 2008
Sensing Results - DMMP
DMMP
- no response with clean graphene
- response with ssDNA is concentration dependent
- response changes depending on sequence of applied ssDNA
Sequence 1: 5’ GAG TCT GTG GAG GAG GTA GTC 3’Sequence 2: 5’ CTT CTG TCT TGA TGT TTG TCA AAC 3’
2% 4% 6% 8% 10% 12%
Chemically Gating in Two Directions
DMMPPropionic Acid
Chemical gating response, probably mediated by water – direction and magnitude is similar to ssDNA-CNT responses
2% 4% 6% 8% 10% 12%
4% 6% 8% 10%
Similar Molecule Sensingsequence 2
sequence 1
2% 6% 9% 12% 15%
2% 6% 9% 12% 15%
- Changes in sequence show a dramatic ability to change chemical sensitivity- demonstrates differentiation between very similar chemicals
Summary- Clean graphene makes a poor chemical sensor
- Graphene can be easily functionalized with ssDNA, with a predictable gate shift
- ssDNA-graphene devices show vastly improved chemical sensing over pristine graphene
- Changing ssDNA sequence does alter chemical sensitivity of graphene
Thank YouJohnson Group UPenn
Prof. A.T. Charlie Johnson
Matthew Berck
Dan Singer
Nicholas Kybert
Thomas Ly
Jen Daily
Dr. Zhengtang Luo
Dr. Brett Goldsmith
Luke Somers
Ye Lu
Mitch Lerner
*Supported by the Intelligence Community Postdoctoral Fellowship Program, JSTO DTRA,The Nano/Bio Interface Center