*2.5.3 Dielectric confinement effect*

The effects of dielectric confinement can be analyzed by adjusting the restricted semiconductor region's dielectric constant and the confining potential barrier that surrounds it. Since the potential barriers created by compositional changes in a quantum well do not create a large difference in the dielectric constant, this effect is always dispersed. Depending on the processing and fabrication process, a quantum rod, quantum dot, or quantum well may be inserted in another semiconductor or dielectric, such as glass or polymer, and these quantum designs may be characterized by organic ligands, dispersed in a liquid, or merely encompassed by air. When the surrounding medium's dielectric constant is ultimately smaller than that of the confined semiconductor system, such media will exhibit a greater shift in the dielectric constant and significant changes of optical properties due to dielectric confinement [12, 13].

### **2.6 Nanoscopic interaction dynamics**

Controlling the dynamics of local interactions inside nanostructure media that enhance complex radiative transitions is a model accomplished using a nanocrystal host environment with low-frequency phonons to reduce multi-phonon relaxation of excitation energy in order to increase emission efficiency of rare-earth ion's. Since rare-earth ion's electronic transitions are highly susceptible to nanoscale interactions, manipulating the existence of electronic interactions requires only a nanocrystalline media, allowing for the use of a glass or plastic medium in a wide range of device technologies. As discussed further below, nanoscale electrical contacts between two electronic centers result in novel optical transitions and improved optical communications [6]. This sub-section will provide a glimpse of interaction dynamics occurred at nanoscale range.

#### *2.6.1 New cooperative transitions*

Two adjacent species may interact through a series of ions, atoms, or molecules to generate optical absorption bands or to allow novel multiphoton absorption

*Nanophotonics: Fundamentals, Challenges, Future Prospects and Applied Applications DOI: http://dx.doi.org/10.5772/intechopen.98601*

## **Table 4.**

*Manifestations observed under the effect of quantum confinement.*

processes. The production of biexcitons in a quantum-confined system or a semiconductor yields new optical absorption and emission of lower energy than two individual excitons, and the energy difference correlates to the excitons binding energy. The joining of many excitons to form a multiexciton or exciton string has also been suggested as an expansion of the biexciton principle. In the context of a molecular structure, an example will be the creation of multiple aggregates, known as a J-aggregate of dyes, which is a head-to-head alignment of various dye dipoles [14]. The other kind of nanoscale electronic interaction takes place whenever an electron-donating group or molecule comes into close proximity to an

electron-withdrawing group or molecule in nanoscopic space, new optical transitions occur. An organometallic structure is an example of association of an inorganic ion to a wide number of organic groups. Novel optical transformations engaging charge transfer from metal to ligand (MLCT) or, in some situations, light absorption causes a reverse charge transfers, provided by these types of organometallic structures [7]. An intermolecular organic donor (D)–acceptor (A) complex, is another example, which produces charge transfer species D + A in the excited state despite the fact that the constituents D and A are colorless and have no visible absorption. These charge-transfer complexes have clear visible color resulting from recent charge transfer transitions in the visible spectrum [6].
