Reverse%20Micellar%20Synthesis

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Reverse Micellar Synthesis of Cadnium Selenium
(CdSe) Quantum Dots(QDs)
Alejandro Galvan Mentors Prof. Roger
Dorsinville Alberto Tonizzo IUSL High School
Summer Program Summer 2006
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Understanding What is a Quantum Dot?

• A Quantum Dot (semiconductor nanocrystal)
  contains discrete energy, much like an Atom. They
  are sometimes called artificial atoms.

Quantum Dot
Atom
http//home.arcor.de/cybertaro/kosmologie/atom.jpg
http//oemagazine.com/fromTheMagazine/oct02/images
/quantumdotsill.jpg
A quantum dots energy levels can be controlled
by changing their size and shape and the depth of
their potential. There are anywhere from 100 to
1,000 electrons in a quantum dot and their size
ranges from 2 to 10 nanometers, or 10 to 50
atoms, in diameter.
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Quantum Dot Contd.

• An Atom ranges from0.1 to 0.5 nanometers
  (1  10-10 m to 5  10-10 m).
• A quantum dot ranges from 2 to 10 nanometers.

http//www.nanotech-now.com/images/QDot-nanocrysta
l-size.jpg
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Other Features
The larger the quantum dot, the redder the
fluorescence, and the lower the energy of the
emitted light. The smaller the dot, the bluer the
fluorescence, and the higher the energy.
http//www.evidenttech.com/qdot-definition/images/
08-tun.jpg
http//en.wikipedia.org/wiki/Quantum_dot
Quantum dots have found their way into our homes.
For example, the new Play Station 3 and HD DVD
players both use a blue laser for data reading.
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Understanding Micelles
Head Hydrophilic
H2O (Water)
Oil
Oil
H2O
Tail Hydrophobic
Reverse Micelle
Normal Micelle
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Objective

• We are using QDs (quantum dots) to find a new
  material that can absorb strong laser light
  frequency (optical limiting) making the light of
  the laser weak. This material can protect human
  eyes, devices etc. It is intensity dependent
  (i.e., the stronger the laser light the more the
  material absorbs).

New Material (Filter)
High Intensity Laser Light
Low intensity Light (not harmful)
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The Experiment
1.In order to make this new material we are using
a toluene dispersion of reverse micelles
containing CdSe (Cadmium Selenide) quantum dots.

• Solvent Toluene

• H3C

NH2
(Molecular Formula C10H23N)
2.This solution was put in a polystyrene matrix
and also in a PMMA (polymethyl methacrylate)
matrix to make a transparent film. 3.We are
trying to fabricate (through the spin coating
technique) thin films consisting of this mixture.
In fact solution are not sufficient for device
applications.
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Spin Coating Machine
Solution of reverse Micelles and Toluene
Quartz used to make the thin-film
http//www.eng.uc.edu/dshi/biomat404/lab_tour/Spi
n.jpg
1 drop/min.
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Our Quantum Dot
Micelles are organic substances used to
stabilize the Quantum Dot.
NH2
Cluster or Quantum Dot
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Spectrophotometer
http//www.gmi-inc.com/Categories/cary5000.htm
http//lma.in2p3.fr/Images/perkin2.jpg
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Absorption Spectrum
Main absorption frequency
2.Low absorption Intensity
1.Scattering of Light
From the peak frequency you can calculate the
size of the Quantum Dot
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Absorption Spectrum
Main absorption frequency
1.Very low absorption Intensity
2.Stil some scattering of Light
From the peak frequency you can calculate the
size of the Quantum Dot
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Results
We did see some absorption at 415 nm which
indicated the presence of a stable Cadmium
Selenide quantum dot. However the preparation
methods used (Polystyrene 50mg/ml, PMMA
(polymethyl methacrylate 50mg/ml) did not
result in a transparent film due to scattering of
light. Ideally we would like a transparent film
so that our quantum dot can be more frequency
specific in terms of being used as a filter.
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Further Work

• Preparation of CdSe QDs capped in micelles made
  of different alkyl amines (i.e., octadecylamine
  instead of decylamine).Fabrication of thin films
  out of this dispersion are anticipated to be more
  transparent and present a long range order
  (hexagonal lattice).

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Acknowledgments
Mentors Prof. Roger Dorsinville Alberto
Tonizzo IUSL High School Summer
Program N.A.S.A./C.O.S.I. The Harlem Children
Society