Quantum dots are nanocrystalline semiconductor particles between 1-10 nm in size that display quantized energy levels. Their spectral properties depend on their size - smaller quantum dots emit higher energy light while larger ones emit lower energy. This allows using quantum dots of different sizes to produce a range of colors. Potential applications of quantum dots include use in TV and display technologies due to their pure colors and long lifetimes. Quantum dots are also being explored for biological and chemical applications such as cancer treatment where they can target organs more precisely than conventional drugs.

1. A Biodiction
(A Unit of Dr. Divya Sharma)
Quantum Dots and Its Applications
Dr. Divya Sharma
Assistant Professor

2. QUANTUM DOTS
Semiconductor
Nanocrystalline
material

3. QUANTUM DOTS
 Quantum dots are small particles of a semiconductor, a
nanocrystalline material
 Typical dimensions range from 1-10 nm
 In an atom, the energy levels are quantized due to the
confinement of electrons
 QDs are produce distinctive colors determined by the
size of particles

4.  Quantum dots have unique spectral properties :
 Broad absorption
 Narrow emission
 Wavelength depends on size

5. QUANTUM CONFINED
SYSTEM
Depends on
their Energy
level

6. HOW DOES QUANTUM
DOTS WORK
How atom make
light

7. How atoms make light. After
absorbing energy:
a. An electron inside an atom is
promoted to a higher energy
level further from the nucleus
b. When it returns, the energy is
given out as a photon of light
c. The color of the light
depends on the energy levels
and varies from one atom to
another.
Quantum dots produce light in a similar way because
the electrons and holes constrained inside then give
then similarly discrete, quantized energy levels.
However, the energy levels are governed by the size
of the dot rather than the substance from which it’s
made

8. QUANTUM SIZE
EFFECTS
Distinctive color
depends on
their
wavelength of
size

9.  In quantum dots, the energy levels become discrete and
the energy gap becomes larger, compared to a bulk
made of the same material
 Band gap is very critical parameter in many electronic
and optical application
 According to Quantum mechanics, energy of photons
relates to the wavelength (color) of photons, this means
When light behaves like conductor, some electrons are
jump from valence band to conduction band
Returning electrons from conduction band to valence band
release photons with amount of energy equal to band gap

10.  Various size of QDs results in quantum confinement
and hence, different band gap.
 Different band gap of QDs results in different color emit
 QDs are artificially prepared nanostructured, which have
many varied properties depend on their size
Increasing Size
Varied Colors
Different size
2nm 3nm 4nm 5nm 7nm
Color controlled by QDs particle size

11. QUANTUM SIZE
EFFECT
Emission color
ranging from
violet to red
As the
nanomaterial
become
larger, the
energy gap
become
smaller, and
the QDs
change his
color

12. TYPES OF QUANTUM
DOTS
Distinguish
types of QDs

13. TYPES OF QUANTUM DOTS
Quantum dots are made largely from the elements:
o II and VI group of the period system - Cadmium
chalcogenides (CdS, CdSe, CdTe), zinc (ZnS, ZnSe,
ZnTe), and
o III and V groups - Phosphides and Indium
arsenides

14. APPLICATION OF
QUANTUM DOTS
Varied
applications
depend on their
size

15. APPLICATIONS
1. Quantum Dots TVs and Display
Due to their unique physical properties of QDs, they
will be at the core of next-generation displays
Compared to organic luminescent material used in
organic light emitting diodes [OLEDs], QD based
materials have purer colors, longer lifetime, lower
manufacturing cost and lower power consumption.

16. 2. Biological and Chemical applications
 QDs are findings important medical applications,
including potential cancer treatment.
Advantage: Targeted at single organs, such as liver
much more precisely than conventional drugs.
 QDs are being used in place of organic dyes in
biological research.
Eg.: They can be used like nanoscopic light bulbs to
light up and color specific tells that needs to be
studied under a microscope.

17. ADVANTAGES
OF QUANTUM
DOTS
 QDs can substitute bulk,
expensive, and inefficient
materials
 QDs adsorb photons of light
and then re-emit longer
wavelength photons for a
period of time
 The high control over the
wavelength of the reemitted
photon
 QDs require only a small
amount of energy to be
excited
 QDs can be used in various
forms. Eg.: as small crystal in
liquid solutions, as quantum
dust and in bead form. All
these existing forms make

18. THANK-YOU
A Biodiction
(A Unit of Dr. Divya Sharma)