Colloidal copper indium sulfide-based (hetero)nanocrystals: Synthesis, optical properties, and use as FRET probes

Abstract

Ternary copper indium sulfide (CuInS2) nanocrystals have drawn much attention because of their low toxicity, large absorption coefficients across a broad spectral range, and large global Stokes shifts. Moreover, they possess unparalleled photoluminescence tunability spanning a spectral window that extends from the visible to the second near-infrared biological window. The combination of these features makes CuInS2 nanocrystals promising materials for a wide range of applications, such as solar cells, light emitting devices, and biomedical applications. However, the synthesis of colloidal CuInS2 nanocrystals has yet to reach the same level of mastery already achieved for binary semiconductor nanocrystals, such as Cd- and Pb-chalcogenides. In this thesis, we develop synthesis strategies to obtain ternary CuInS2 nanocrystals with well-controlled size, shape, and composition, and study their size-dependent optical properties. They are also used as cores or seeds for heteroepitaxial overgrowth of ZnS semiconductors, yielding either isotropic or anisotropic CuInS2/ZnS heteronanocrystals with high photoluminescence quantum yields. The surface of these core/shell nanocrystals can be functionalized by organic molecules or polymers to transfer them into water or to construct Förster resonance energy transfer-based nanoprobes in combination with organic dye molecules. Potential applications of the nanocrystals prepared in this thesis are summarized.