This study focuses on the synthesis of non-toxic quantum dots (QDs) for biological applications such as cell labeling, medical imaging, and pathogen and toxin detection. QDs are semiconducting nanoparticles whose fluorescent properties can be tuned via particle size and band gap energy. Following the process of Ostwald ripening, QDs will aggregate after initial synthesis, increasing in size disproportionately with band gap energy, resulting in less stable particles with red-shifted emission wavelengths. In pursuit of stable blue-shifted QDs, favorable conditions were achieved through successful surface modification. Such modifications include varying the solvents, capping agents, and reagent concentrations used. The QDs in this study were synthesized with zinc acetate and lithium hydroxide (LiOH) in two different solvents: ethanol (EtOH) and dimethyl sulfoxide (DMSO). Various capping agents (polyethyleneimine (PEI), glutathione (GSH), dopamine hydrochloride (DA-HCl) were added and the growth kinetics of the samples were measured over a 30-day period using an ultraviolet-visible spectrophotometer and integrating sphere spectrofluorometer. It was determined that 20 μM PEI successfully inhibited the growth kinetics of LiOH-synthesized QDs in EtOH compared to 2 μM PEI. Emission peak maxima were shifted towards shorter wavelengths, corresponding to lower energy and more stable, blue-shifted QDs. Compared to the emission data of PEI-surface modified QDs, dopamine QDs in EtOH showed a marginal increase in emission wavelength for the 30-day trial and glutathione QDs in DMSO showed no trend in emission wavelengths. Analysis of PEI QDs in DMSO showed higher emission wavelengths over 30 days, compared to equivalent QDs in EtOH. In conclusion, the most efficient conditions for biologically stable quantum dots was determined to be 20 μM PEI for both solvents.

Variability study of the synthesis and growth kinetics of surface modified ZnO quantum dots using LiOH

2019 Spring National Meeting

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