Electrochemistry of Graphene devices towards ballistic transport and biological sensors

1. Electrochemistry of Graphene devices towards ballistic transport and biological sensors Luis A. Jauregui and Jonathan C. Claussen Proposal Defense 22 April 2009

2. Outline • Introduction • Motivation • Electrochemical Biosensors • Glucose Biosensors • Graphene and Pd in Electrochemical Biosensors • Fabrication • Graphene Defects / Electrical Characterization • Preliminary Results • Future Work

3. Motivation Cancer Parkinson’s Disease Mani el al. ACS Nano, 2009

4. Nanostructured Amperometric Biosensors • Graphene • High electrical conductivity • High surface area • Electrocatalytic defect sites • Biofunctionalization capability • Biocompatible A: Planar graphene sheet B: CNTs rolled graphene sheets Katz et al., ChemPhysChem, 2004, 5, 1084 - 1105 • Pd Nanoparticles • High electrically conductivity • High surface area • Electrocatalytic • Biofunctionalization capability • Biocompatible Pd Nanoparticles AndrasVladar, NIST Laboratories http://www.nist.gov/public_affairs/techbeat/tb2008_0108.htm

5. Electrochemical Biosensors Read-Out Signal Transduction Biological Recognition Molecule Advantages of Electrochemical Biosensors Rapid – steady state electrical signal within seconds Real-time detection – bed side diagnostics Portable – hand held devices Low cost – global impact Types of Electrochemical Biosensors Potentiometric device Amperometric device

6. Amperometric Sensing 3 Electrode set-up • 1) Auxiliary electrode (Pt wire) • 2) Working electrode (Graphene and Pd nanocubes) • 3) Reference electrode (Ag/AgCl) A V Reference Electrode Auxiliary Electrode Working Electrode Working Potential +500 mV Phosphate Buffer Solution (PBS) (pH 7.4)

7. Amperometric Glucose Sensing 50 mM 25 mM 10 mM Current (nA) Glucose 5 mM 2e- 2e- 2e- 2e- H202 H202 H202 H202 Time (s) Glucose Oxidase (GOx) Biochemical Reactions

8. Electrochemcial Glucose Biosensors First Enzymatic Glucose Sensor: (1962) -oxygen electrode that measured the amount of oxygen consumed (L. Clark Jr., C. Lyons, Ann. NY Acad. Sci. 1962, 102, 29) -750 mV First H202-based Glucose Sensor: (1973) -oxidized hydrogen peroxide (G. Guilbault, G. Lubrano, Anal. Chim. Acta 1973, 64, 439) +700 mV Glucose Oxidase (GOx) Enzyme Robust -operates within a large pH range (pH 5.5 – 7.5) -maintains activity for long periods post immobilization Benchmark Enzyme -utilized for 40 years in glucose sensing

9. Outline • Introduction • Fabrication • Exfoliated Graphene on Si/SiO2 • Pd nanocube electrodeposition • Graphene Defects / Electrical Characterization • Preliminary Results • Future Work

10. Fabrication Graphene/Pd Biosensor Electrodeposited Pd Indium Wire/Contact Gold Contact Exfoliated Graphene SiO2 (300 nm) Si

11. Outline Introduction Fabrication Graphene Defects / Electrical Characterization Preliminary Results Future Work

12. Graphene disorders • Intrinsic • Surface ripples • Topological defects: pentagons, heptagons and Stone-Wales defects (possibly can lead to scattering) • Extrinsic • Adatoms • Vacancies • Charges on top of graphene or in the substrate • Extended defects, as cracks and edges K. S. Novoselov, "Electronic properties of graphene," in 21st International Winterschool on Electronic Properties of Novel Materials, Kirchberg, AUSTRIA, 2007, pp. 4106-4111.

13. Edge defects Graphene damage by eBEAM irradiation Zetl’s group, http://www.physics.berkeley.edu/research/zettl/projects/graphenehole/hole.html

14. Graphene biosensor applications - Graphene-based single-bacterium resolution biodevice and DNA transistor: interfacing graphene derivatives with nanoscale and microscalebiocomponents They show that the DNA tethering process on the CMGs was preferential on thicker than on thinner CMGs and on wrinkles than on flat surfaces of CMGs. So far, not much work has been done using graphene as biosensor N. Mohanty and V. Berry, "Graphene-Based Single-Bacterium Resolution Biodevice and DNA Transistor: Interfacing Graphene Derivatives with Nanoscale and MicroscaleBiocomponents," Nano Letters, vol. 8, pp. 4469-4476, Dec 2008.

15. Chemical functionalization of graphene with defects Interestingly, for the case of complete coverage, the binding energy is smaller for the hydrogen on graphene with defects than on the perfect graphene. This means that completely hydrogenated graphene (graphane24,57) is less stable with defects than without them. D. W. Boukhvalov and M. I. Katsnelson, "Chemical Functionalization of Graphene with Defects," Nano Letters, vol. 8, pp. 4373-4379, 2008. D. C. Elias et al, "Control of Graphene's Properties by Reversible Hydrogenation: Evidence for Graphane," Science, vol. 323, pp. 610-613, Jan 2009.

16. Graphene oxide Pd decorated R. S. Sundaram, "Electrochemical modification of graphene," Advanced Materials, vol. 20, pp. 3050-3053, Aug 2008.

17. Outline Introduction Fabrication Graphene Defects / Electrical Characterization Preliminary Results Future Work

18. Pd deposition on graphene Before After Why this area is not covered by Pd?.

19. Pd deposition on graphene

20. Future Work Amperometric sensing of H202 Enzyme immobilization on Graphene/Pd for glucose sensing Vary graphene defects by plasma etching or e-beam irradiation Time variation of Pd deposition Electrical characterization of free Pd decorated graphene regions

21. Questions Thank you!!