Quantum dots are nanoscale semiconductors that exhibit size- and composition-dependent optical properties. Their small size ranges from 2-10 nanometers in diameter. Quantum dots can be engineered to emit light at specific wavelengths by controlling their size and composition. They are being used for applications such as biomedical imaging, optoelectronics, quantum computing, and solid-state lighting due to properties like bright and resistant fluorescence. Quantum dots can be conjugated to biological molecules like proteins and antibodies for applications as biomarkers.

1. Quantum Dots

2. Quantum Dots
Quantum dots, also known as
nanocrystals, are a special class of
materials known as semiconductors, which
are crystals composed of periodic groups
of II-VI, III-V, or IV-VI materials.
Quantum dots are unique class of
semiconductor because they are so small,
ranging from 2-10 nanometers (10-50
atoms) in diameter.

3. Quantum Dots
 The usefulness of
quantum dots comes
from their peak emission
frequency's extreme
sensitivity to both the
dot's size and
composition, which can
be controlled using
Evident Technologies'
proprietary engineering
techniques.

4. History of Quantum Dots
 In the 1970s, the
first low dimensional
structures QW
(Quantum Wells)
were developed.
1D (quantum
wires) and 0D
(quantum dots) were
subsequently
developed.

5. Assembly of Quantum Dots

6. Formation of Quantum Dots
 Quantum dots form when very thin
semiconductor films buckle due to the stress
of having lattice structures slightly different in
size from those of the material upon which
the films are grown
These huge pressures, as new layers are
deposited, force the initially flat film to
separate into dots and then pop up into the
third dimension to relieve stress, rather than
continue to grow against resistance in two
dimensions. Continued…

7. Formation of Quantum Dots
 In terms of actual formation,
the process characteristically
went like this: ten atomic layers
of film would form smoothly. As
more layers were deposited,
the film broke up into tiny
pyramid-shaped islands.
 With more layers, the
pyramids self-organized and
coarsened, and then became
dome-shaped islands.

8. Characterization of
Quantum Dots
Quantum Dots can be characterized by two techniques:
 Optical Characterization
 Electrochemical Characterization
 Optical Characterization:
Electron microscopes and atomic force microscopes (AFM) are
widely used for the optical characterization of the size of the qdots.
For the cross-sectional investigation of qdots structures,
transmission electron microscopy (TEM) is the most used.
 Electrochemical Characterization:
Qdots can be detected directly (without the need to be dissolved)
or indirectly by oxidatively dissolving the metal ion into aqueous
metal ions and then electrochemically sensing the ions by using
stripping voltammetry or potentiometry or electrochemical
impedance spectroscopy (EIS).

9. Fluorescent Quantum Dots
 In comparison with organic
dyes and fluorescent proteins,
quantum dots have unique
optical and electronic proper
ties such as:
size tunable light emission
improved signal brightness
resistance against
photobleaching
simultaneous excitation of
multiple fluorescence colors.

10. Quantum Dots For Biomarkers
Quantum dots linked to biological molecules,
such as antibodies, have shown promise as a
new tool for detecting and quantifying a wide
variety of cancer-associated molecules.

11. Conjugation of Quantum Dots
to Biological Molecules
Quatum Dots can conjugate with biological
molecules such as:
 proteins
 peptides
 nucleic acids
 small organic-molecules

12. Applications of Quantum Dots
Optical and optoelectronic devices, quantum
computing, and information storage.
Semiconductors with QDs as Material for
Cascade Lasers
Semiconductors with QDs as Material for IR
Photodetectors
 Injection Lasers with QDs
Color Coded Quantum Dots For Fast DNA Testing
3-D Imaging Inside Living Organism, Using
Quantum Dots
Continued…

13. Applications of Quantum Dots
In a different approach
to creating white light
several researchers at the
Department of Energy's
(DOE) Sandia National
Laboratories have
developed the first
solidstate white light
emitting device using
quantum dots