Quantum dots can emit any color of light, by changing the size of dots, It can emit different colors.

1. QUANTUM DOTS
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TARAN PREET SINGH (MS12044)

2. What Really Quantum Dots Are??

3. QUANTUM DOTS (QDs) are nanometer-scale semiconductor crystals composed
of groups II–VI e.g.( CdS, CdSe ) or III–V elements, and are defined as particles
with physical dimensions smaller than the exciton Bohr radius, whose excitons
are confined in all three dimensions of space.
The term “quantum dot” was coined by Mark Reed in 1988; however, they were
first discovered in a glass matrix by Alexey Ekimov in 1981 and in colloidal
solutions by Louis E. Brus in 1985.

4. ENERGIES IN SEMICONDUCTOR

5. Electrons and holes are confined in all three dimensions of space by a
surrounding material with a larger bandgap.
Discrete energy levels (artificial atom).
A quantum dot has a larger bandgap.
Like bulk semiconductor, electrons tend to make transitions near the edges of
the bandgap in quantum dots.

6. The confinement of the electrons results in
the appearance of the energy states
shown in the figure(right)
The energy of the lowest state is given by:
The energy of the other states is
E1 = h2
8mL2
En = n2h2 = E1 n2
8mL2

7. Where Energy of the quantum
dot is dependent on Size of the
quantum dot due to QUANTUM
CONFINEMENT EFFECT.

8. Controlling the size of nanocrystal,
quantum dots can be tuned to emit
any color of light.

9. HOW TO MAKE QUANTUM DOTS
Quantum dots can be made by various methods such as :
LITHEOGRAPHY
COLLIDAL SYNTHESIS
EPITAXY
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10. COLLOIDAL SYNTHESIS
Colloidal semiconductor Nano crystals are synthesized from
precursor compounds dissolved in solutions, much like
traditional chemical processes.
i.e: lead sulfide(PbS), lead selenide(PbSe), cadmium
selenide(CdSe), cadmium sulfide(CdS), indium arsenide(InAs),
and indium phosphide(InP)

11. FABRICATION
CMOS technology can be employed to
fabricate silicon quantum dots. Ultra small
(L=20 nm, W=20 nm) CMOS transistors
behave as single electron quantum dots
when operated at cryogenic temperature.

12. ELECTROCHEMICAL ASSEMBLY
Highly ordered arrays of quantum dots may also
be self-assembled by electrochemical techniques.
A template is created by causing an ionic reaction
at an electrolyte-metal interface which results in
the spontaneous assembly of nanostructures.

13. OPTICAL PROPERTIES OF QUANTUM DOTS
a - EXCITION b - EMISSION

14. Quantum confinement effects give rise to unique optical and electronic properties in QDs, giving them
numerous advantages over current fluorophores, such as organic dyes, fluorescent proteins and
lanthanide chelates.
The narrow emission and broad absorption spectra of QDs makes them well suited to multiplexed
imaging, in which multiple colours and intensities are combined to encode genes, proteins .

15. PHOTOSTABILITY
Photostability is yet another factor in most fluoroscence application, where the quantum dot is having
the advantage, unlike organic dyes(fluorophores) which BLEACH after only few minutes after exposure
of light, QD are photostable can go multiple cycle of excitation and emission for hours with high level of
brightness and photobleaching threshold.
QD is shown more photostable than organic dyes Dihydrolipoic acid (DHLA)-capped cadmium
selenide-zinc sulfide (CdSe-ZnS) QDs showed no loss in intensity after 14 h, and were nearly 100
times as stable as, and also 20 times as bright as, rhodamine 6 G.

16. APPLICATIONS

17. Q-LED
Quantum dots may some day light
your homes, offices, streets,
and entire cities.
Quantum dot LED’s can now
produce any color of light, including
white.
Quantum dot LED’s are extremely
energy efficient. They use only
a few watts, while a regular
incandescent lamp uses 30 or more
watts for the same amount of light

18. QUANTUM COMPUTING
A linear array of quantum dots that can be
defined by metal electrodes on silicon
with voltage applied so that single
electron is trapped at each quantum dot
at low temperature . Place in a external
magnetic field, the Zeeman spin states of
these electrons constitute cubits of the
QUANTUM COMPUER

19. MEDICAL IMAGING
Quantum dots may one day save your life.
Medical imaging has begun to use colloidal
(in liquid solution) quantum dots much like
the ones you’ll look at today. The photo
below
shows human red blood cells, in which
specific membrane proteins are targeted and
labeled with quantum dots. The number of
purple features, which indicate the nuclei of
malaria parasites, increases as malaria
development progresses.

20. Quantum dots last longer in your system
and are brighter than many organic dyes
and fluorescent proteins previously used
to illuminate the interiors of cells. They
also have the advantage of monitoring
changes in cellular processes (they last a
long time) while most high-resolution
techniques like only provide images of
cellular processes frozen at one moment
Quantum dots (red dots above) can be designed
to bind to specific
cell receptors (green things). In this way
researchers can monitor all
kinds of processes in living cells

21. QUANTUM DOTS IN HD TV

22. REFERENCES
T. Jamieson et al. / Biomaterials 28 (2007) 4717–4732
www.researchgate.net/post/What_is_Quantum_confinement_effect
www.wikipedia.com/quantumdot
cs.lbl.gov/news-media/news/2015/what-theblank-makes-quantum-dots-blink