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 Energy band gap of SWNTs depends on nanotube diameter: the larger the diameter, the smaller the band gap Left: From Photoluminescence on Carbon Nanotubes

Right: www.photon.t.u-tokyo.ac.jp

The Photoluminescence Spectrum

• Diameter ∝ 1 Size of Band Gap • Energy ∝ 1 Wavelength • Each peak (bright spot) a carbon nanotube with different wrap angle/diameter

www.originlab.com

Polymethine Dyes

S + N C 2 H 5 ( ) n X

_

S N C 2 H 5

n

= 1 , 2 , 3 , 4 , 5 Absorption depends on the length of the chain (the size of

n

)

Method

Carbon nanotube powder Graphite flake H 2 O Weighing the material Spectroscopic analysis SDBS - surfactant Mixing with DOB-719 (dye) Ultrasonication, 20 kHz, 1.25 hours Centrifugation, 30kRPM, 2 hours

Results

800 700 600 500 400 Initial CNT sample 11000 10000 9000 8000 7000 6000 5000 4000 3000 800 700 600 500 400 CNT+DOB-719 (0.0001mg/ml) 300 300 900 1000 1100 1200 Emission Wavelength (nm) 1300 900 1000 1100 1200 Emission Wavelength (nm) 1300 Several new peaks at an excitation wavelength of ~735nm appear for CNT+DOB-719 14500 13063 11625 10188 8750 7313 5875 4438 3000

Carbon Nanotube-Dye Interaction

Carbon Nanotube-Dye Interaction

800 700 600 500 400 300 CNT+DOB-719 (0.0001mg/ml) 14500 13063 11625 10188 8750 7313 5875 4438 3000 900 1000 1100 1200 Emission Wavelength (nm) 1300 More efficient, so increases intensity of emitted light

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