Colloidal photoemissive nanoparticles

Nanoparticles possess distinctive properties compared to those of their bulk counterparts. They can be prepared as colloids using molecules which play a key role in their preparation, colloidal stability, functionality, and/or optical features. These molecules can act as solvents, surfactants, reactants and ligands. Photoactive nanoparticles exhibit unique optical features due to the combined effect of their nanometric scale and the derived quantum confinement effect. The degree and type of response to size is related to their composition. They can form either colourless or colourful colloids, emit light either at longer wavelengths than those of the absorbed light (down-conversion luminescence) or at shorter wavelengths (up-conversion luminescence). In addition, the nanostructures can exhibit enhanced properties compared with their bulk counterparts, (for example, superior chemical sensing) due to their intrinsic large surface/volume ratio and their functionality can be further enhanced by ligand exchange or modification. Moreover, the processability of colloidal nanoparticles is crucial to many of their applications, such as for light-emitting devices and in optoelectronics, among other applications.