Significantly modify the processes of intraband and interband Particle size is reduced to a few nanometers. Semiconductors, this observation normally occurs when the This effect is accompanied by an exaltation of theĬoulomb interaction between the charge carriers. Panied by the quantization of the energy levels to discrete Their small size results in an observable quantum-Ĭonfinement effect, defined by an increasing bandgap accom. Surrounded by an organic outer layer of surfactant molecules Made up of between a few hundred and a few thousand atoms, ‘‘quantum dots’’ (QDs), are composed of an inorganic core,
IntroductionĬolloidal semiconductor nanocrystals (NCs), also termed Focusing on recent advances, this Review discusses the fundamental properties and synthesis methods of core/shell and core/multiple shell structures of II–VI, IV–VI, and III–V semiconductors. This effect is a fundamental prerequisite for the use of nanocrystals in applications such as biological labeling and light-emitting devices, which rely on their emission properties. The shell further provides an efficient passivation of the surface trap states, giving rise to a strongly enhanced fluorescence quantum yield. In such core/shell nanocrystals, the shell provides a physical barrier between the optically active core and the surrounding medium, thus making the nanocrystals less sensitive to environmental changes, surface chemistry, and photo-oxidation. The possibility to tune the basic optical properties of the core nanocrystals, for example, their fluorescence wavelength, quantum yield, and lifetime, by growing an epitaxial-type shell of another semiconductor has fueled significant progress on the chemical synthesis of these systems. 163Ĭolloidal core/shell nanocrystals contain at least two semiconductor materials in an onionlike structure. Core/shell materials Core/Shell Semiconductor Nanocrystals Peter Reiss,*Myriam Protie`re, and Liang Li From the ContentsĬlassification of Core/Shell Systems.