Figure 2.

Schematic summarizing the approaches of NC-centered modifications that have been implemented toward improving TTA-UC. Top left: emphasis on development of nontoxic NCs. Top middle: the energy of a NC band gap is size dependent. Top right: passivation of the NC surface is often achieved by ligand addition or coating the surface with another material. Bottom left: the number of dimensions in which NCs are confined can be altered. Bottom middle: the Bohr exciton diameter, and therefore the possible extent of quantum confinement, varies between NC compositions. Bottom right: at the surface of the NCs, vacancies can be filled by the binding group of the ligand or by the shell material.