Copper indium sulfide/ zinc sulfide (CuInS<sub>2</sub>/ZnS) core/shell quantum dots (QDs) are an important class of nanomaterials for optoelectronic, photovoltaic and photoluminescence applications. They consist of lower toxicity materials (than the prototypical Cd-based QDs) and show long fluorescence lifetimes, which opens up great potential in biological imaging applications. It is particularly important to develop reproducible synthetic methods for this new class of nanomaterials in order to maintain small sizes with high quantum yields.  CuInS<sub>2</sub> core QDs have been shelled with ZnS  at various temperatures from  90-210°C for reaction times ranging from a few minutes to a couple of hours to examine the role of both thermodynamics and kinetics on the shell growth. Temperature was found to have a larger effect on the photoluminescence intensity and lifetime than the reaction time indicating more thermodynamic than kinetic control. Using High Resolution TEM and ICP-MS, it was observed that shelling initially results from cation exchange, leading to negligible size increase upon shelling but a significant increase in fluorescence. Only after a second round of injection does a ZnS shell grow onto the particles, increasing the particle size. By analyzing the radiative and non-radiative contributions to the decay processes in the QDs, we related the changes in structural properties during shelling to their optical properties.

Influence of shelling temperature and time on the optical and structural properties of CuInS2/ZnS quantum dots

249th National Meeting (2015)

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