- Why quantum dots are only semiconducting ? OR
- only II-IV or III-V groups form quantum dots ?
- can other nanoparticles form zero dimensional also ? OR
Why can't nanopaticles be quantum dots ? Why nanoparticles can be metallic, polymeric etc only. But when we talk about semiconducting nanoparticles, they are quantum dots ?
I am little bit confused that is it necessasry the quantum dots only formed semiconducting. Is it the definition of Q dots ?
Dear Sir,
as per the quantum confinement, metal particles of 1-10 nm and semiconductors up to 100 nm can behave like QDs. Confined dimensions are more often the size of a few wavelengths of electrons and QDs typically contain 1000s to millions of atoms. Applications necessitating quantum confinement employ semiconductors as the dimensions can be more easily achieved.
Quantum dots (0-D): Only confined states and no freely moving particles means Quantum dots exhibit "total confinement", whereas the quantum wells (2-D) and nanowires (1-D) have at least one dimension for the electrons to move freely (i.e. partial confinement). In Zero DOS, no state can be occupied at that energy level.
- QDs: when all the three dimensions are minimized. Dot can be a particle located inside a larger structure or on its surface. It can be part of a colloid or entirely isolated. It can also be a place where electrons have been trapped using electric fields.
Uniqueness of QDs: Density-to-state (i.e. number of available or allowed electrons states per volume at a given energy) function ceases to be continuous.
Importance of Quantum structures:
- Unusual little piece of matter
- have discrete charge states and quantized energy
- we have the capability to improve the size and shape of these electronic oddities.
- we better understand the atoms and thereby inventing real and new devices.
Smaller dimensions of quantum structures make them ideal candidates for high-density data storage (device application), optics, telecommunication and computing.
Hope, it will help you.
Thanks and regards.
Dear Prashant,
In quantum dots is fundamental to have excite electrons depending of the light. The form to do it is having a semiconductor with a band gap passing an electron from valence band to the conduction band. When its size have bound states therefore we have excitons whose confinement depend of such size of the quantum dot. In any case it is fundamental to have a semiconductor as you ask.
Quantum dots are semiconductor nanoparticles that glow a particular color after being illuminated by light. The color they glow depends on the size of the nanoparticle.
When the quantum dots are illuminated by UV light, some of the electrons receive enough energy to break free from the atoms. This capability allows them to move around the nanoparticle, creating a conduction band in which electrons are free to move through a material and conduct electricity. When these electrons drop back into the outer orbit around the atom (the valence band), they emit light. The color of that light depends on the energy difference between the conduction band and the valence band.
The smaller the nanoparticle, the higher the energy difference between the valence band and conduction band, which results in a deeper blue color. For a larger nanoparticle, the energy difference between the valence band and the conduction band is lower, which shifts the glow toward red.
Many semiconductor substances can be used as quantum dots. Nanoparticles of any other semiconductor substance have the properties of a quantum dot. The gap between the valence band and the conduction band, which is present for all semiconductor materials, causes quantum dots to fluoresce.
Read the attached articles for detailed information about QD and their mathmatical analysis.
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