How Do Quantum Dots Work?

QDs are semiconductor nanoparticles where the quantum confinement effect is the working principle. This action keeps electrons and holes in a nano-sized box, changing their optical and electronic properties drastically.

Quantum Confinement

Quantum confinement describes the way that electron energy states split up when a material is condensed to the scale analogous to or smaller than the de Broglie wavelength of the electron wavefunction. It occurs because the electron wavefunction is locked up within nanostructures in spatial entanglement so that the electrons can only be at particular energies. Quantum dots are like three-dimensional "boxes" with electrons and holes locked inside a finite space and creating discrete energy levels.

Impact of Quantum Confinement on Optical and Electronic Properties

The quantum confinement effect significantly affects the optical and electronic behaviour of quantum dots:

Tunable Emission Wavelengths: The emission wavelength of quantum dots is proportional to their size. The smaller the quantum dot, the shorter its emission wavelength, and vice versa. That's because quantum dots' spacing at the energy level fluctuates as they get bigger, and their emission wavelengths change.

Size-tunable emission spectra of QDs

Optical Properties: Quantum dots are very efficient photoluminescent dots with a small spectral distribution due to quantum confinement. These properties are extremely desirable for quantum dots in display technology and bioimaging.

The quantum confinement effect doesn't only affect the underlying physical characteristics of quantum dots, it opens up an abyss of possibilities for using them in high-tech domains. You can also control quantum dots' size and shape, so their optical behaviour can be tailored to a specific application need.

How Does Quantum Dot Size Affect Performance?

Relationship Between Size and Emission Color

Quantum dots are the size and emission colour of a rhodium atom. For the most part, small quantum dots glow blue, big quantum dots glow red. It's because quantum dots of different sizes have bandgap energy variations that influence the wavelength of the reflected light. If a quantum dot's size decreases, for example, the bandgap energy increases and the emission wavelength is shifted towards shorter wavelengths – from red to blue.

Importance of Dimension (2D vs. 3D)

Quantum dots have very strong optical effects depending on their size. In 2D quantum dots, for example, the bandgap energy is very sensitive to change with size and gives highly customizable emission colours. But in 3D quantum dots this alteration is much smaller because electrons and holes are more evenly distributed in 3D systems, and thus sizes change the bandgap less. Therefore, 2D quantum dots are usually chosen for applications where a specific emission wavelength is needed, like bioimaging and display technology.

Practical Examples of Size-Dependent Applications

The quantum dot's size dependence is useful in a wide range of areas. In bioimaging, for example, quantum dots of different sizes can mark several biological targets at once, making multiplex imaging possible.

Quantum dots for biomedical applications

As in display technology, you can manipulate the size of quantum dots to constantly adjust the light to go from blue to red, making displays look better in terms of color.

This is also the case in solar cells, where the number of quantum dots can be regulated so as to maximise light absorption and energy conversion.

Not only do quantum dots' sizes influence the hue of their light, but also their effectiveness for other tasks. By finely regulating quantum dots' size, fast, flexible technological answers to problems of any kind can be found.