Colloidal synthesis of Ag(I)-doped CdSe nanoplatelets with partial cation exchange method

Abstract

Colloidal nanoplatelets (NPLs) exhibit strong one-dimensional quantum confinement in the vertical direction. This makes them a highly attractive host system for studying variable doping techniques and effects without variation in the quantum confinement effect. Earlier, core-only CdSe NPLs were converted into Cu2Se and HgSe NPLs, and also CdSe/CdS core/shell NPLs were transformed into Cu2Se/Cu2S, ZnSe/ZnS, and PbSe/PbS NPLs by using full cation exchange (CE) methods. Recently, core-only CdSe NPLs have been doped with Cu(I) ions using high-temperature nucleation doping and post-synthesis partial CE approaches. On the other hand, unlike Cu(I), such monovalent doping with Ag(I) ions has previously not been possible in NPLs as a host system, although silver doping had been widely studied in other host systems. Therefore, there has been no previous report on the doping of Ag(I) into CdSe NPLs to date. To address this gap, in this thesis, Ag(I) doping in CdSe NPLs by using a postsynthesis partial CE technique was developed. A systematic study was carried out to investigate the effects of dopant precursor reactivities, reaction timing, and temperature on the evolution of dopant-related emission as compared to the excitonic emission. In controlled experiments, the excitonic emission peak was eliminated and only dopant-related emission peak was successfully obtained. Finally, temperaturedependent emission kinetics of the as-synthesized Ag(I)-doped CdSe NPLs at varied temperatures ranging from 25 to 298 K were investigated. It was observed that both excitonic and dopant-related emission peaks were blue-shifted and their intensities were considerably increased with the decreasing temperature. As a new dopant-host system, these Ag(I)-doped CdSe NPLs hold a great promise for further systematic spectroscopic studies and possibly various optoelectronic applications.