*4.1.4. Quantum dots as fluorescence labels-*

The "Quantum dots" (QDs) are nano-crystals, formed by a core of semiconductor and fluorescent material coated with another semiconductor, which have very stable optical properties and a large gap between the wavelengths of emission and excitation of the complement. These nanometric particles could work like labels joining with peptides or antibodies for the recognition of cellular components. They have a high fluorescence, greater photo-stability, multicolored excitation, an adjustable and narrow emission spectrum, and their higher quantum yield, compared with organic fluorochromes. They also have several disadvantages like its high susceptibility to oxidation and photolysis as well as some risks for human health and the environment. They are used to localize tumor biomarkers.
