A quantum dot (fluorescent semiconductor nanocrystal) is a semiconductor whose excitations are confined in all three spatial dimensions. As a result, the quantum dots have properties that are between those of bulk semiconductors and those of discrete molecules. Simplistically, quantum dots detectors are semiconductors whose conducting characteristics are closely related to the size and shape of the individual crystal. Generally, the smaller the size of the crystal, the larger the band gap, the greater the difference in energy between the highest valence band and the lowest conduction band becomes, therefore more energy is needed to excite the dot, and concurrently, more energy is released when the crystal returns to its resting state. One of main advantages in using quantum dots is that because of the high level of control possible over the size of the crystals produced, it is possible to have very precise control over the conductive properties of the material and fine tune the peak sensitivity to the frequency being detected.