School of Chemistry - Theses
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ItemSpectroelectrochemistry of Semiconductor Nanocrystals( 2021)Semiconductor nanocrystals exhibit well-known, size-dependent optical and electronic properties. Control over the charge carriers in semiconductor nanocrystals enables the possibility to tune the optical response. One way to achieve this is through electrochemistry. Carrier modulation through electrochemical methods allows more precise control over electron transfer compared to methods such as photocharging and chemical redox reactions. By combining electrochemistry with spectroscopic techniques, the charged states in semiconductor nanocrystals can be studied in detail. A spectroelectrochemical setup has been developed to study the charging of semiconductor nanocrystals in solution and its influence on absorption and photoluminescence (PL). A negative trion state can be generated in CdSe quantum dots (QDs) and stabilised for hours under an applied cathodic potential. By monitoring both the absorbance and fluorescence changes, one can determine whether charge carriers are free or trapped. The total number of electrons injected into the QDs can be estimated from current and coulometry measurements. Hole injection into CdSe QDs induces corrosion of the lattice, whereas injection into nanocrystals shelled with CdS induces bleaching. Coupling the spectroelectrochemical setup with time-resolved PL measurements reveals the trion lifetime of CdSe/CdS QDs as a function of shell thickness. In the last section of the thesis, the effects of charge injection on CdSe nanoplatelets (NPLs) is explored. In contrast to QDs, hole injection into the NPLs enhances the photoluminescence.