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QUANTUM DOTS

QUANTUM DOTS
« on: 26 August , 2019, 19:10:15 pm »
Hello everone, my name is Adrián and I am from Spain. Some people have mentioned quantum dots in previous messages and, from my point of view, they are very interesting and important, so I decided to open a new topic just for them.

Quantum dots are monocrystals that have the propertie of being photostable (solar quality not to degrade with heat and sun), monochromatic (single color) and brighter than any fluorochrome (component of a molecule that makes it fluorescent). Quantum dots can be formed from different elements, but when they are reduced to reach a sufficiently small size, their physical properties change, something very useful in a wide range of functions. For example, they are very efficient to absorb light and then emit it. Based on this property, fields such as solar panels, bio images and, of course, screens are being investigated. Some big corporations such as Samsung and LG, have already include quantum dots on some of their products.

In the following video you will find some more information:      https://www.youtube.com/watch?v=z7aqJpKfPC0


What do you think about them?




Adrián :D


Re: QUANTUM DOTS
« Reply #1 on: 28 August , 2019, 11:05:54 am »
Hi Adrián,

I would firstly like to thank you to introduce us such an interesting and essetial topic within nanotechnology: Quantum Dots (QDs). These nanocrystals have an incredibly wide range of applications in differents sectors, from TVs to Solar Panels, therefore is a topic you must investigate on. In order to guide your research, I would propose some questions related with QDs:

  • In other post your fellow Laia said that QDs are zero-dimensional structures. However, it seems paradoxical that an object doesn't have any dimesion. Why is it said that QDs are zero-dimensional? Could you find also one-dimensional or two-dimensional nanostructures?
  • As you could see in the video, QDs can absorb light and emit it afterwards. They also explained in the video that depending in the QDs' size, a defined colour would be emitted. However, the color doesn't depends in the material of the QD! How does a Quantum Dot works? How can we explain this size dependency on the colour emitted?
  • Once you know how QDs work, can you think on how these crystals can be a revolution in the production of more effective solar panels. Have you managed to find or think of other applications of QDs within the field of Energy and Enviroment?

I would really like to hear your answers!
Javier Herrero, Veteran.

Re: QUANTUM DOTS
« Reply #2 on: 02 September , 2019, 13:35:40 pm »
Hello everyone!
I know it seems quite impossible to say that an object has no dimension. It's said that the QDs are zero-dimensional because they are basically a point.

Mathematically, the topological dimension is an entire number, which can be defined for any topological space. For a space formed by a point the topological dimension is 0, for a line it's 1, for the euclidean plane it's 2, etc.

An object has a dimension 'm' when any coating of that object has at least a dimension of 'm + 1'. So the point has a dimension m = 0
It seems very strange and difficult to understand, so I leave a photo.
[img] 0D.jpg [ /img]

In a one-dimensional material, electrons are confined in two directions (x, y / y, z / x, z). They can only be moved in one direction. A couple of examples of one-dimensional nanostructures are nanowires and nanotubes.
In contrast, in one of two dimensions the electrons are confined in only one direction (x / y / z). They can move in two directions. E.g. thin films.


In reference to the size dependency:
When a QD is illuminated by UV light, the electrons inside receive enough energy to break free from the atoms. This ability allows them to move around, in this process they create a conduction band where electrons are free to move through the material and conduct electricity.

When these electrons drop into the outsider orbit around the atom (the valence band), they emit light. Its color depends on the difference of the energy between both bands, the conduction and the valence one.

The smaller the nanoparticle is, the higher the energy difference between the two bands, which results in a dark blue color.
For a larger nanoparticle, the energy difference between the bands is lower, which results in red.


Kind regards,
Laia  :)

Re: QUANTUM DOTS
« Reply #3 on: 02 September , 2019, 13:42:01 pm »
Hello again!
I don't know why the image it's not visible, so I'll let the link to it.
https://t3.ftcdn.net/jpg/01/30/07/62/500_F_130076243_oroIr2WqTlc86VAikZoKKyzjRtzpf3sK.jpg

And also an image that explains the size dependency.
https://www.dummies.com/wp-content/uploads/287759.image0.jpg

Laia   ;)

Hello everyone!
I know it seems quite impossible to say that an object has no dimension. It's said that the QDs are zero-dimensional because they are basically a point.

Mathematically, the topological dimension is an entire number, which can be defined for any topological space. For a space formed by a point the topological dimension is 0, for a line it's 1, for the euclidean plane it's 2, etc.

An object has a dimension 'm' when any coating of that object has at least a dimension of 'm + 1'. So the point has a dimension m = 0
It seems very strange and difficult to understand, so I leave a photo.
[img] 0D.jpg [ /img]

In a one-dimensional material, electrons are confined in two directions (x, y / y, z / x, z). They can only be moved in one direction. A couple of examples of one-dimensional nanostructures are nanowires and nanotubes.
In contrast, in one of two dimensions the electrons are confined in only one direction (x / y / z). They can move in two directions. E.g. thin films.


In reference to the size dependency:
When a QD is illuminated by UV light, the electrons inside receive enough energy to break free from the atoms. This ability allows them to move around, in this process they create a conduction band where electrons are free to move through the material and conduct electricity.

When these electrons drop into the outsider orbit around the atom (the valence band), they emit light. Its color depends on the difference of the energy between both bands, the conduction and the valence one.

The smaller the nanoparticle is, the higher the energy difference between the two bands, which results in a dark blue color.
For a larger nanoparticle, the energy difference between the bands is lower, which results in red.


Kind regards,
Laia  :)

Re: QUANTUM DOTS
« Reply #4 on: 04 September , 2019, 18:02:45 pm »
Hello everyone!

I have founded some info about QDs in solar cells:

The solar photovoltaic market is one of the fastest developing energy markets in the world. In order for solar energy to succeed, a new technology is required that can provide superior efficiencies and lower the costs below standard silicon PV panels. Quantum dot solar cells just might be that technology.

A quantum dot solar cell (QDSC) is a solar cell that uses quantum dots as the captivating photovoltaic material. It is used to replace bulky materials such as silicon, or copper indium gallium selenide. Quantum dots have bandgaps that are adjustable through a wide array of energy levels by changing the size of the dots. If scientists continue investigating about this, QDSC might become the most effective option for solar panels.

You can find some more information in the following website, I hope you find it usefull: https://www.researchgate.net/publication/228523138_Quantum_dot_solar_cell