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Carbon Nanotube based Electrode and Sensor Fabrication

Carbon Nanotube based Electrode and Sensor Fabrication. M. Meyyappan Director, Center for Nanotechnology NASA Ames Research Center Moffett Field, CA 94035 http://www.ipt.arc.nasa.gov. Acknowledgement. • Jun Li • Cattien Nguyen • Lance Delzeit • Hou Tee Ng • Kris Matthews • Bin Chen

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Carbon Nanotube based Electrode and Sensor Fabrication

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  1. Carbon Nanotube based Electrode and Sensor Fabrication M. Meyyappan Director, Center for Nanotechnology NASA Ames Research Center Moffett Field, CA 94035 http://www.ipt.arc.nasa.gov

  2. Acknowledgement • Jun Li • Cattien Nguyen • Lance Delzeit • Hou Tee Ng • Kris Matthews • Bin Chen • Ramsey Stevens • Jing Li • Martin Cinke • Alan Cassell • Jie Han

  3. Edge Plane: electron transfer rate ~ 0.1 cm/s Basal Plane electron transfer rate < 10-7 cm/s HOGP Glassy Carbon R. L. McCreery, in Electroanalytical Chemistry, Ed. A. J. Bard, 17, 221-374 (1991). Carbon Black Carbon Fiber Commonly Used Carbon Electrodes HOPG

  4. Macro-, Micro-, and Nano- Electrodes I total = Iplanar + Iradial GC 2mm dia. Carbon fiber 7mm dia. Semi-infinite planar linear diffusion Semi-infinite hemispherical diffusion: Current exhibits a steady state Nanoelectrodes ?

  5. Carbon Nanotube ElectrodesPrevious Work MWCNT bundle Dia. ~200 nm, length ~30 mm MWCNT bundle Dia. 600 mm, length ~1.5 mm R. M. Crooks et al, J. Am. Chem. Soc., 121, 3779 (1999). P. M. Ajayan et al, Nano Lett., 1(2), 87(2001).

  6. The Fabrication of CNT Nanoelectrode Array (1) Growth of Vertically Aligned CNT Array (2) Dielectric Encapsulation (3) Planarization (4) Electrical Property Characterization By Current-sensing AFM re ce (5) Electrochemical Characterization Potentiostat we

  7. (a) (b) Growth of CNT Array with Varied Density • Criteria: • Good conductivity in metal underlayer, contact points, and CNTs • Good alignment • Controlled density

  8. Dielectric (SiO2) Encapsulation By TEOS CVD SiO2 CNTs Top View Side View (30º tilt)

  9. Fabrication of CNT Nanoelectrodes J. Li et al, Appl. Phys. Lett., 81(5), 910 (2002) Top view 45 degree perspective view Side view after encapsulation Top view after planarization

  10. nA Characterization of Electrical Properties Topography Current Image Cross-section Profile

  11. Electrical Properties of CNTs +1mA 0 -1mA -5V 0 +5V HP analyzer Current Sensing AFM Four-probe station And HP parameter analyzer

  12. Electrochemical Properties of CNT Nanoelectrode Array As-prepared electrode DEp > 600 mV After pretreatment DEp = ~100 mV CV of 1 mM K4Fe(CN)6 in 1.0 M KCl at 20 mV/s

  13. Nanoelectrode Array at Different Densities CNT coverage: < 5% Average nearest-neighbor distance: > 1000 nm CNT coverage: ~ 20% Average nearest-neighbor distance: ~200-300 nm

  14. Nanoelectrode Array at Different Densities CNT coverage: < 1 % Approaching nanoelectrode High CNT coverage: ~ 20% Similar to a macro- planar electrode CV of 1 mM K4Fe(CN)6 in 1.0 M KCl at 20 mV/s

  15. Chemical Functionalization Highly selective reaction of primary amine with surface –COOH group

  16. Chemically Attached Fc Derivatives • Cyclic voltammetry at 20 mV/s • DEp = ~30 mV • surface adsorbed species • quasi-reversible due to defects in CNTs • AC voltammetry • enhanced sensitivity

  17. Functionalization of DNA Cy3 image Cy5 image

  18. CNT DNA Sensor Using Electrochemical Detection 2+ 2+ 3+ 3+ e • MWNT array electrode functionalized with DNA/PNA probe as an ultrasensitive sensor for detecting the hybridization of target DNA/RNA from the sample. • Signal from redox bases in the excess DNA single strands • The signal can be amplified with metal ion mediator oxidation catalyzed by Guanine.

  19. Electrochemical Detectionof DNA Hybridization 1st – 2nd scan: mainly DNA signal 2nd – 3rd scan: Background 1st, 2nd, and 3rd cycle in cyclic voltammetry

  20. Technical Platform Top View Each individual electrode is electronically addressable with an array of CNTs with d ~ 10 to 100 nm dnn ~ 500 nm to 5000 nm Side View 10 to 200 mm Each Electrode Immobilized with A Specific PNA or DNA Probes

  21. Coupling to Cy3-labeled DNA Nanotubes with spin-on glass film 1. EDC/Sulfo-NHS H2O Washed 2. DNA* 60oC/1 hr. *DNA = H2N(CH2)6-ACACGAGTCAGCGCAGCCATCGC-Cy3

  22. Hybridization Test Nanotubes with Spin-on Glass EDC/Sulfo-NHS H2O Washed PNA* 60oC/1 hr. Washes Hybridization c-DNA-(Cy3-labeled)# *PNA = H2N(CH2)6-GCCGATGCACC #c-DNA = CGGTACGTGG-Cy3

  23. Functionalization Using a Glow Discharge

  24. Atomic H Functionalization: FTIR

  25. Atomic H Functionalization: UV

  26. Conclusions • Vertically aligned CNTs can be used to fabricate nanoelectrode array. • The electrical and electrochemical properties of such nanoelectrode array have been thoroughly characterized. • Chemical functionalization has been demonstrated to be highly selective at CNT ends. • CNT nanoelectrode array has potential applications as highly sensitive DNA sensors

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