Synthesis of cadmium-free colloidal semiconductor nanocrystals for display and biological applications

Abstract

Quantum dots (QDs) are the semiconductor nanocrystals (NCs) in quantum confinement regime, i.e., the size regime within the characteristic exciton Bohr radius. This enables the control of band gap through varying the size of particles, and attempts have been made to apply the NCs in display and biological applications. Many studies focused on cadmium (Cd)-based QDs, which show superior optical and physicochemical properties such as optical anisotropy that are necessitated for future displays. Nevertheless, as heavy metals are strictly regulated in Europe and North America and Cd shows high cytotoxicity, it is unpromising to utilize Cd-based NCs in practical applications. In this dissertation, I realize the superior properties of Cd-based NCs in Cd-free NCs and imply the possibility for commercialization and biocompatibility. The shape control of Cd-free NCs is realized by synthesizing InP nanoplates with various morphologies using cation exchange reaction from Cu3-xP nanoplates. Further, ZnSe, InP and InAs QDs were utilized as seeds to synthesize branched NCs, of which asymmetric shape relates to the optical anisotropy. Lastly, incorporation of Cd-free NCs to nitrogen-fixing bacteria realized the photoinduced ammonia production at ambient temperature and pressure.