1. Carbon Nanotubes as Biosensors ME 695 Yang 11/30/2004

2. Outlines Introduction Amperometric biosensors Carbon nanotube-modified amperometric biosensors Conclusion References

3. Introduction Materials for Biosensors 1. inert metals( Pt. Gold) 2. carbonaceous materials( graphite, carbon fibers, glassy carbon and carbon nanotubes)

4. Introduction Carbon Nanotubes Fabrication- catalytic chemical vapor deposition (CVD) method

5. Introduction Types of Carbon Nanotubes 1.Armchair (n, n)- all metallic 2.Zig-zag(n, 0)-1/3 metallic(n=3k); 2/3 semi-conducting (remainder) 3.Chiral(n, m)-1/3 metallic(n-m=3k); 2/3 semi-conducting (remainder) Single-walled: dia. 0.4 nm-2.0 nm Multi-walled: dia. 4.0 nm-50.0 nm

6. Amperometric biosensors Biosensors: 1. converts a biological response into an electrical signal; 2. for determine the concentration of substances and other biological parameters.

7. Amperometric biosensors a: biocatalyst b: transducer—calorimetric, potentiometric, amperometric, pizeo-electric c: amplifier d: integrated circuit e: display

8. Amperometric biosensor

9. Carbon nanotube-modified amperometric biosensors Preparation of carbon-nanotube electrode with Pt nanoparticles 1.Grow CNT directly from graphite substrate to form CNT electrode; 2.Purify CNT electrode; 3.Pt nanoparticles are dispersed on CNT electrode by potential step deposition to obtain Pt/CNT electrode; 4. Immobilize GOD onto Pt/CNT electrode to obtain GOD/Pt/CNT electrode by bathing Pt/CNT in enzymatic solution for 12 hr; 5. GOD/Pt/CNT electrode immersed in Nafion solution to prevent falling off;

10. Carbon nanotube-modified amperometric biosensors Current response to successive injection of 0.1 mM hydrogen peroxide 1-5: CNT electrodes; 6: Graphite electrodes CNT electrodes more electrocatalytic active than Graphite electrodes

11. Carbon nanotube-modified amperometric biosensors Current response to successive injection of 0.1 mM hydrogen peroxide 2(0.2V)-3(0.6): Pt/CNT electrodes; 1(0.6V): Pt/Graphite electrodes Response behavior of Pt/CNT at 0.6 V Much better than Pt/Graphite Comparing curve 3 in (b) and curve 1 in (a), Pt nanoparticles greatly improves the electrocatalytic activity.

12. Carbon nanotube-modified amperometric biosensors Current response to successive injection of 0.1 mMglucose Curve 1: Nafion/GOD/CNT Curve 2: Nafion/GOD/Pt/CNT Potential 0.6 V Pt/CNT composite better for immobilization of GOD than CNT/Graphite

13. Carbon nanotube-modified amperometric biosensors Another method of preparing CNT- based Glucose electrode 1. Wash MWCNT, polish the surface of basal plane pyrolytic graphite(bppg) electrode; 2. Rubbing electrode with filter paper containing 2 mg MWCNT for 1 min. 3. Mixing 50 miuL sol-gel composite solution with 50 miuL glucose oxidase solution then dope 20 miuL on modified MWCNT bppg electrode 4. Dry in air flow.

14. Carbon nanotube-modified amperometric biosensors Current response To successive Addition of 0.5 mM Glucose. Curve A: bare bppg/biocomposite Curve B: bppg/CNT/biocomposite Inset: slope 200nA/mM Detection limit: 50 miuM Linear range: 0.2-20mM(human 4.4-6.6 mM

15. Conclusions Materials for biosensors manufacturing Concepts of biosensor and amperometric biosensor Comparison of current response between conventional biosensors and CNTs-modified shows CNT biosensors respond rapidly and actively CNTs are promising materials for fabrication of novel biosensors.