Carbon Nanotubes as BiosensorsCarbon Nanotubes as Biosensors

ME 695Yang Yang

11/30/2004

OutlinesOutlines

IntroductionAmperometric biosensorsCarbon nanotube-modified

amperometric biosensorsConclusionReferences

IntroductionIntroduction

Materials for Biosensors 1. inert metals( Pt. Gold)

2. carbonaceous materials( graphite, carbon fibers, glassy carbon and carbon nanotubes)

IntroductionIntroduction

Carbon Nanotubes Fabrication- catalytic chemical vapor

deposition (CVD) method

IntroductionIntroduction

Types of Carbon Nanotubes1. Armchair (n, n)- all metallic2. 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 nmMulti-walled: dia. 4.0 nm-50.0 nm

Amperometric biosensorsAmperometric biosensors

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

Amperometric biosensorsAmperometric biosensors

a: biocatalystb: transducer—calorimetric, potentiometric, amperometric, pizeo-electricc: amplifierd: integrated circuite: display

Amperometric biosensorAmperometric biosensor

Carbon nanotube-modified Carbon nanotube-modified amperometric biosensorsamperometric 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 Carbon nanotube-modified amperometric biosensorsamperometric 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

*K

Carbon nanotube-modified Carbon nanotube-modified amperometric biosensorsamperometric 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 VMuch better than Pt/Graphite

Comparing curve 3 in (b) and curve 1 in (a), Pt nanoparticles greatly improves the

electrocatalytic activity.

Carbon nanotube-modified Carbon nanotube-modified amperometric biosensorsamperometric 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 Carbon nanotube-modified amperometric biosensorsamperometric 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 biosensorsCarbon nanotube-modified amperometric biosensors

Current responseTo successive Addition of 0.5 mMGlucose.Curve A: bare bppg/biocompositeCurve B: bppg/CNT/biocomposite

Inset: slope 200nA/mMDetection limit: 50 miuMLinear range: 0.2-20mM(human 4.4-6.6 mM

ConclusionsConclusions 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.