Current work in the field of luminescent, semiconductor nanoparticles often combines luminescent nanomaterials with different band gap energies to form core-shell structures (e.g. CdSe/CdS, CdTe/CdSe). This prevents leakage of excited electrons to non-emitting surface defects and results in an emission quantum yield comparable to the brightest molecular fluorophores like fluorescein. These luminescent core-shell nanomaterials exhibit broad absorbance spectra, narrow emission peaks, high photostability, and size-dependent emission wavelength tunabilty, which make them attractive alternatives to molecular fluorophores in fluorescence imaging applications. Interestingly, the combinations of CdSe and CdS or CdTe and CdSe in core-shell nanostructures result in a single emission peak, even though these materials emit light at different wavelengths when crystalized separately. Electronic interactions between the core and shell materials is one possible explanation for this phenomenon; however, these interactions are not fully understood. Understanding and controlling these interactions will open possibilities for new composite nanomaterials with unique and useful properties. In this study we aim to form composite core-shell structures with two emitting nanomaterials, CdSe and CdS. The CdSe and CdS luminescent layers are separated by a higher band gap energy material to prevent leakage of electrons from the CdSe core to CdS shell. The study compares the emission properties of CdSe/CdS/ZnS and CdSe/ZnS/CdS/ZnS composite nanostructures. Our experiments aim to optimize the synthesis conditions necessary to separate the emission peaks of CdSe and CdS and to control the ratio between the distinct emission peaks to enable optical coding. The presentation will describe the synthesis of the composite nanomaterials, characterization of their size, morphology and stability using high-resolution transmission electron microscopy (TEM), and light-scattering measurements and their luminescence properties using steady-state luminescence and fluorescent lifetime imaging spectroscopy. These nanocomposites are prime candidates for multiplexed, live cell imaging and labeling assays.

Synthesis of composite nanoparticles for optical nanocoding applications

248th National Meeting (2014)

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