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

Outlines

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Introduction

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Amperometric biosensors

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Carbon nanotube-modified amperometric biosensors

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Conclusion

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References

Introduction

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

Introduction

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

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

Amperometric biosensors

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

Amperometric biosensors

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

Amperometric biosensor

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;

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

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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.

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

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.

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

Conclusions

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Materials for biosensors manufacturing

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Concepts of biosensor and amperometric biosensor

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Comparison of current response between conventional biosensors and CNTs-modified shows CNT biosensors respond rapidly and actively

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CNTs are promising materials for fabrication of novel biosensors.