Much like NMR for organic chemists, conventional high resolution transmission electron microscopy (HRTEM) has been one of the primary tools for determining the structure of colloidal quantum dots. Analogous to synthetic impurities, even the best colloidal nanocrystal syntheses yield a distribution of structures which collectively produce the observed ensemble properties. Only by iterative approaches are the nanostructures ultimately optimized. In order to accelerate the development of emergent nanocrystal systems, a correlation method is needed that quickly identifies the particular structural motifs that yield the desired photophysical properties. Time correlated single photon counting spectroscopy coupled with fluorescence microscopy is a powerful tool that reveals the complex photophysics of colloidal quantum dots. Although allowing one to individually interrogate nanocrystals, their single particle fluorescence behavior is often linked to an ideal structure derived from separately obtained HRTEM. Dark particles will go completely undetected, dim particles may be overlooked while small aggregates can appear spectroscopically as a single particle. To address these concerns, we’ve developed an intuitive and reproducible method to correlate the atomic and chemical structure of individual colloidal nanocrystals with the same particle’s fluorescence dynamics. With this correlation technique it is possible to identify sub-populations of structures that exhibit the desired photophysics and then use that knowledge to direct chemistry to produce quantum dots with specifically chosen optical behavior. HRSTEM, advanced STEM-EDS and initial correlation results will be presented for thick shelled InP/ZnSe colloidal quantum dots that exhibit suppressed blinking. Interesting defects were observed in the HRSTEM images while the STEM-EDS maps confirm a substantial inclusion of indium in the shell.

Informing nanocrystal synthesis <i>via </i>correlated atomic structure and single nanocrystal photophysics

256th National Meeting (2018)

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Informing nanocrystal synthesis via correlated atomic structure and single nanocrystal photophysics