Carbon Nanotube-Polymethine Dye Complexes with Strong Photoluminescence

William Abbot

Nuffield Foundation

• “Improve social well-being through education, research and innovation”

• Nuffield Research Placements – funding to experience a research project environment

www.nuffieldfoundation.org/nuffield-research-placements

Carbon Nanotubes

• Essentially a rolled-up graphene sheet• Single-wall and multi-wall varieties• Different properties based on how they are rolled up:

metallic or semiconducting

http://www.physik.uni-regensburg.de/aktuell/KollSS05/Thomsen-Vortrag.htm

Uses of Carbon Nanotubes• Materials, composites• Electronics• Novel methods of drug delivery

Aim of the Project

• Carbon nanotubes have a huge range of uses• Problem with potential toxicity• A fast, reliable but portable sensor will be

required

Photoluminescence (Fluorescence) in Single-Wall Nanotubes

Left: From Photoluminescence on Carbon NanotubesRight: www.photon.t.u-tokyo.ac.jp

Energy band gap of SWNTs depends on nanotube diameter: the larger the diameter, the smaller the band gap

The Photoluminescence Spectrum

www.originlab.com

• Each peak (bright spot) a carbon nanotube with different wrap angle/diameter

 

S

NN

S

C2H5C2H5X

_

+ ( )n

n = 1, 2, 3, 4, 5

Polymethine Dyes

Absorption depends on the length of the chain (the size of n)

Weighing the material

Graphite flake

SDBS - surfactant

Ultrasonication, 20 kHz, 1.25 hours

Centrifugation,30kRPM, 2 hours

Mixingwith DOB-719

(dye)

H2O

Carbon nanotube powder

Method

Spectroscopic analysis

Results

900 1000 1100 1200 1300300

400

500

600

700

800

Emission Wavelength (nm)

Exc

itatio

n W

ave

len

gth

(n

m)

Initial CNT sample

3000

4000

5000

6000

7000

8000

9000

10000

11000

Inte

nsity

900 1000 1100 1200 1300300

400

500

600

700

800

Emission Wavelength (nm)

Exc

itatio

n W

ave

len

gth

(n

m)

CNT+DOB-719 (0.0001mg/ml)

3000

4438

5875

7313

8750

10188

11625

13063

14500

Inte

nsity

Several new peaks at an excitation wavelength of ~735nm appear for CNT+DOB-719

Carbon Nanotube-Dye Interaction

More efficient, so increases intensity of emitted light

Carbon Nanotube-Dye Interaction

900 1000 1100 1200 1300300

400

500

600

700

800

Emission Wavelength (nm)

Exc

itatio

n W

ave

len

gth

(n

m)

CNT+DOB-719 (0.0001mg/ml)

3000

4438

5875

7313

8750

10188

11625

13063

14500

Inte

nsity

Conclusion

• Carbon nanotubes: very promising but potentially harmful

• Fluorescence enhancing probes for carbon nanotubes are being developed

• Will soon lead to sensor systems

Thanks for Listening

www.nuffieldfoundation.org/nuffield-research-placements