**2. What are quantum dots?**

Quantum dots are colloidal fluorescent semiconductor nanoscale crystals that were firstly produced in the early 1980s [2]. These artificial semiconductor nanoparticles typically have unique optical, electronic, and photophysical properties that make them appealing in promising applications in fluorescent biological labeling, imaging, solar cells, composites and detection and as efficient fluorescence resonance energy transfer donors [3]. Sufficiently miniaturized semiconductor particles show quantum confinement effects, which limit the energies at which electron hole pairs are present in the particles. Based on the relationship between the energy and wavelength of light (or color), the optical properties

#### **Figure 1.**

*Conversion of the light spectrum into different colors depends on the quantum dot size (image: RNGS Reuters/ Nanosys).*

of the particle can be delicately varied depending on its size. Therefore, only by controlling the size of quantum dots, various particles with different colors can be produced to emit or absorb specific wavelengths of light [4]. As shown in **Figure 1**, different sized quantum dots emit different color light due to quantum confinement.

The physics of quantum dots counterpart with a lot of the behaviors that naturally occurring in atomic and nuclear physics of the quantum system.
