QUANTUM NANO DOTS IN MATERIALS FOR APPLICATIONS IN TUMOR IMAGING AND TREATMENT IN CANCER

The quantum dot (QD) is defined as an artificially structured system with the capacity to load electrons (Hanson et al., 2007). Its special physicochemical properties differentiate it from other naturally occurring biogenic and anthropogenic nanoparticles (Hardman, 2006). QDs are one type of nanoparticles (NPs) with three characteristic properties: semiconductors, zero-dimension, and strong fluorescence.Although colloidal semiconductor QDs are single crystals with diameters of a few nanometres, their sizes and shapes can be precisely controlled by the duration, temperature, and ligand molecules during the synthetic processes. The well controlled synthetic process yields QDs with composition- and size-dependent absorption and emission. Generally, as the sizes of QDs are reduced, the electronic excitations shift to higher energies (i.e., shorter wavelengths) , such as CdSe QDs (shown in Figure 1) . Besides, physical properties of QDs influence their fluorescence emissions. The fluorescence emission of colloidal QDs on the surface of a two-dimensional slab of photonic crystals will be enhanced due to a combination of high-intensity near fields with strong coherent scattering, which is related to leaky eigenmodes of the photonic crystal (In QDs' periodically modulated structures, an anomalous resonant phenomenon arises from periodic index modulation of the refractive index, which allows phasematching of externally incident radiation into modes that can be re-radiated into free space). Owing to the fact that these modes possess finite lifetimes within such structures, they are called “leaky eigenmodes