DNA-decorated graphene chemical

sensors

Brett Goldsmith, Ye Lu, Nicholas Kybert, A.T. Charlie JohnsonUniversity of PennsylvaniaDepartment of Physics and Astronomy

Graphene Transistors

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Silicon Gate

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Graphene Transistors

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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

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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