Emission properties of quantum dots assembled in the polyelectrolyte multilayer

Mercaptosuccinic acid capped CdTe quantum dots (QDs) were assembled on glass substrates modified with polyelectrolyte multilayers (PEMs) consisting of poly(ethylenimine) (PEI), poly(diallyldimethylammonium chloride) (PDDA) and poly(sodium 4-styrenesulfonate) (PSS). PEMs were built up via Layer-by-Layer (LbL) technique to form the structure of PEI-(PSS/PDDA)n. The adsorption of QDs on different number of PSS/PDDA bilayer was analyzed using Surface Plasmon resonance (SPR), from which it was found that more QDs were adsorbed on two bilayers of PSS/PDDA compared with that on one. It was further confirmed by the increased photoluminescence (PL) intensity as the number of PSS/PDDA bilayer increases. I also found a great enhancement of PL intensity accompanied by a slight blue-shift of PL spectrum when putting the films/QDs system in water environment, and the PL intensity was found to be related with the ionic strength (NaCl) in aqueous solution. Further assembling of PDDA monolayer or PDDA/PSS bilayer will gradually quench the PL emission of QDs.Bachelor of Engineering (Chemical and Biomolecular Engineering