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    Quantum Dot PDF

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    ALI ASHRAF
    Quantum dots are nanometer-sized semiconductor particles that emit light at specific wavelengths when energy is applied. [1] Their optical properties can be tuned by changing their size, shape, material composition, and structure. [2] Smaller quantum dots emit shorter wavelengths of light (blue/violet), while larger quantum dots emit longer wavelengths (red/yellow). [3] They have applications in biomedical imaging, solar cells, LEDs, and displays due to their tunable light emission and high photostability.

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    Quantum Dot PDF

    Uploaded by

    ALI ASHRAF
    170 views22 pages
    Quantum dots are nanometer-sized semiconductor particles that emit light at specific wavelengths when energy is applied. [1] Their optical properties can be tuned by changing their size, shape, material composition, and structure. [2] Smaller quantum dots emit shorter wavelengths of light (blue/violet), while larger quantum dots emit longer wavelengths (red/yellow). [3] They have applications in biomedical imaging, solar cells, LEDs, and displays due to their tunable light emission and high photostability.

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    Quantum dots are nanometer-sized semiconductor particles that emit light at specific wavelengths when energy is applied. [1] Their optical properties can be tuned by changing their size, shape, material composition, and structure. [2] Smaller quantum dots emit shorter wavelengths of light (blue/violet), while larger quantum dots emit longer wavelengths (red/yellow). [3] They have applications in biomedical imaging, solar cells, LEDs, and displays due to their tunable light emission and high photostability.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    170 views22 pages

    Quantum Dot PDF

    Uploaded by

    ALI ASHRAF
    Quantum dots are nanometer-sized semiconductor particles that emit light at specific wavelengths when energy is applied. [1] Their optical properties can be tuned by changing their size, shape, material composition, and structure. [2] Smaller quantum dots emit shorter wavelengths of light (blue/violet), while larger quantum dots emit longer wavelengths (red/yellow). [3] They have applications in biomedical imaging, solar cells, LEDs, and displays due to their tunable light emission and high photostability.

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    of 22

    PRESENTATION 1

    Nanomaterial and applications


    Topic:
    Quantum dots: Synthesis, Properties & its
    Applications

    QD core
    QD shell
    Protective
    shell
    What are Quantum Dots?
    A quantum dot is a nanometer-sized semiconductor particle traditionally with a core-
    shell structure. Quantum dots are widely used for their unique optical properties, as
    they emit light of specific wavelengths if energy is applied to them. These wavelengths
    of light can be accurately tuned by changing various properties of the particle,
    including shape, material composition, and size.
    Background

    copper chloride

    1980

    Russian physicist cadmium selenide


    Alexei Ekimov of the State
    Optics Institute Vavilov

    Alexander Efros Louis Brus


    Russian physicist, 1982 American Chemist, 1983
    Explain the behaviour of these small He made the first colloidal Quantum
    crystals by the confinement of their dots of Cadmiuim Sulphide.
    electrons.
    Introduction:

    Definition:
    “If all the three dimensions of a material are reduced to nano range, then the
    nanomaterial or the structure is called the quantum dot.”
    Example: CdSe, PbSe, PbTe, InP. The CdSe quantum dots have 5nm red dots and
    1.5nm violet dots.

    Quantum confinement:

    3-D 2-D or
    Quantum wells

    1-D or 0-D or
    Quantum Wires Quantum Dots
    Fig: Quantum confinement, 3-D, 2-D, 1-d, 0-D.
    Working Principle:

    Excitation can be caused by the


    quantum dot coming into contact with
    a light or electricity source.

    Smaller QDs Bigger QDs


    Shorter WL Longest WL
    Blue light Red light
    Quantum Size Effect:

    Radius 2~3 nm
    Smaller QDs Emit Shorter Wavelength
    Violet, Blue, Green

    Bigger QDs Radius 5~6 nm


    Emit Longer Wavelength
    Yellow, Orange, Red

    Quantum dots are artificially


    prepared nanostructure, which have
    many varied properties depend on
    their size. As the nanomaterial
    becomes larger, the energy gap
    become smaller and QDs change its
    color.
    Basic Structure of Quantum Dots:
    Types of Quantum dots:

    Core type quantum dots: Core shell quantum dots: Alloyed quantum dots:
    Properties of quantum dots: Factors

    • superior photostability
    • Size-dependent optical properties
    o Size

    • High extinction coefficient o Shape


    • Brightness
    o Composition
    • Large Stokes shift
    • Bond gap energy o Structure
    • High quantum yield
    • High photostability
    • High molar extinction coefficients.
    Optical Properties: Spectral properties:

    • Broad absorption
    • Narrow emission
    • Wavelength
    depend on size
    Synthesis of Quantuam Dots:

    Graphene Quantum dot synthesis methods:

     Cut larger blocks of


    C into small pieces
     Abundant C raw
    material
     Straightforward and
    easy method

     Complex reaction
    steps
     Specific organic
    materials making
    difficult to optimize
    the condition
    Top-down approaches:

    i. Hydrothermal method:
    ii. Chemical oxidation method:
    Bottom-up approaches:

    i. Microwave method
    ii. Electron beam irradiation method:
    Silicon Quantum Dots:
    Applications:
    Applications of GQDs:
    Any question

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