Engineering Optical Properties of Doped Quantum Dots by Chemical Reactions

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Understanding the origin of emitting species and the contribution of the surface ions in quantum dots (Qdots) towards the overall photoluminescence are important and much remains to be explored. The current thesis primarily deals with the decisive role of the surface ions in doped Qdots and their potential to react with external chemical species, thereby tuning their optical properties. This was approached with three different binary quantum dots (Qdots); having the same host but different dopants. Experimental results reveal that systematic removal (via chemical means) of the surface ions as well as ions present in the immediate vicinity, resulted in reproducible changes in emission quantum yield as well as emission energy, which ascertained their contribution towards the overall emission. Furthermore, significance of electronic state of the dopant ions in the emission of the Qdots has been successfully demonstrated. When they react with redox reagents such as sodium borohydride and potassium peroxodisulfate, anticipated change in their oxidation state is reflected through significant changes in their emission spectra. This thus implies that the Qdots could be used as potential redox probes for local oxidation/redox milieu in mammalian cells.
Supervisor: Arun Chattopadhyay