Science can be orientated to discover unknown species or explore space, and we all know that the discoveries are extraordinary with great values. But the public tends to think that most of the species on earth are listed and observed, and that space now is a matter of capacity. Capacity to travel, and next the capacity to still be there when the rocket has arrived. But most people are unaware of a crowd of researchers, in their laboratories, working and shaping the future of our civilizations. Some people are desperate about our natural resources are wasted, and they contemplated a very grim future for the planet. It is true that in everyday news we are witnessing the climate change, one of the most dramatic consequence of our way of using technologies. It is difficult for researchers working, for example, at attonuclei to communicate about their discoveries regarding quantum dots. Firstly, because it is highly confidential, and, secondly, because it is a demanding exercise.
What are quantum dots ?
Quantum dots were not discovered in nature, human beings make them. The other name for quantum dots and which is more helpful to understand what they are is artificial atoms. If you have only a vague idea of what an atom is; it is useful then to indicate that an atom was understood at first as an element that cannot be further divided. It is necessary to go back to 440 BC and read the reasoning of Democritus, a Greek philosopher, who forged the name atom. He explained that if you divide a stone till the remain of an element that cannot be further divided, then you have an atom. Then, we have to wait till the 19rth century for the theory to be analysed and researched, and today, we know that atoms are composed of quarks (the smallest particles) which in turn composed :
- nucleus
- protons
- electrons.
In the 21st century, human beings are making, not nature, crystals which function is to become semiconductor material. These new elements forged by man have the characteristics to be very small, we are speaking of nanometres. What are they made of ? It would be possible to find indium arsenide, cadmium sulphide, or cadmium selenide. How can they be identified ? Quantum dots, when illuminated, glow a specific colour. According to the size of the nanoparticle, the colour will change. When the electrons are released from the atoms because they have received UV lights, they will create either a conductance band or a valence band. The difference in energy between these two bands generates a specific colour. If the nanoparticle is very small, then it will be possible to obtain a very strong blue colour. If the nanoparticle is bigger, then the created colour will be a deep red. The confinement of the quantum dot in only a few nanometres leads to the free charge carriers of the quantum dots to endure “quantum confinement“, and most importantly, in all three spatial dimensions. Because it is totally directed by human beings, the researchers have the capacity to control the size distribution of quantum dots at the same time they are making them.