A quantum dot is a tiny semiconductor particle. They are just nanometers when it comes to size and they are so small that the electronic and optical properties are much different from a larger particle. When it comes to nanotechnology, they are considered to be a central theme and there are many of these that will emit light at certain frequencies if light or electricity happens to be applied to them and these frequencies can be turned in order to change the size of the dots, and even the material and shape which gives it a boost to use in many types of applications.
When it comes to the language of materials science, a nanoscale semiconductor material will be able to tightly confine electron holes or electrons. The quantum dots are also sometimes called an artificial atom. It is this term that emphasizes that they are a single object that has a bound yet discrete electronic state which is similar to a naturally occurring molecule or atom.
These are able to exhibit certain properties that will be an intermediate between things that are considered to be discrete molecules and things that are considered to be bulk semiconductors. These dots have optoelectronic properties that will change as a function of shape and size. The larger ones that have a radius of 5 to 6 nanometers will often emit a longer wavelength which results in the emission of colors like red or orange. The smaller ones that have a radius of 2 to 3 nanometers will often emit a shorter wavelength which results in the emission of colors like green and blue, however the specific sizes and colors will vary based on the exact composition of these quantum dots.
It is because of the highly tunable properties that they are considered to be a wide interest. The potential applications actually include medical imaging, quantum computing, second harmonic generation, diode lasers, LEDs, solar cells and transistors. In addition to all that, the small size of these allow there to be some that can be suspended into a solution which often leads to there being possible uses for spin coating and inkjet printing. Another type of technique where these may have been used is Langmuir Blodgett. It is these processing techniques that result in less time consuming as well as less expensive methods for the fabrication of semiconductors.
These are often described theoretically as being a point like or a 0 D which is also called zero dimensional entities. Many of the properties for these will be based on their dimension, materials, as well as shape. Normally, these are found in differentiating thermodynamic properties that come from bulk material that make them. A type of effect that you may see is melting point depression. The optical type properties of these types of metallic spheres will often be described using the theory of Mie scattering.
There are multiple frameworks for theories that are used to state the structural, electronical and optical properties. They could be divided based on being quantum mechanical, classical, and semiclassical.