This talk will describe how the anion composition of ternary silver bromoiodide nanocrystals determines their shape through the introduction of twin defects as the nanocrystals are made more iodide-rich. Ternary silver bromoiodide nanocrystals grow as single-phase, solid solutions with the rock salt crystal structure for anions compositions ranging from 0 ≤ x &lt; 0.38. With increasing iodide content the morphology of the nanocrystals evolves from cubic to truncated cubic to hexagonal prismatic. Structural characterization indicates the cubic nanocrystals are bound by {100} facets whereas the hexagonal platelet nanocrystals possess {111} facets as their top and bottom surface. Calculations based on first-principles density functional theory show that iodide substitution in AgBr stabilizes {111} surfaces and that twin defects parallel to these surfaces possess a low formation energy. These experimental observations and calculations are consistent with a growth model in which the presence of multiple twin defects parallel to a {111} surface enhances lateral growth of the side facets and changes the nanocrystal shape. The extension of this method to control the shape of other metal halide nanocrystals based on anion composition will also be discussed. <br/>

Compositionally-induced twin defects control the shape of ternary silver halide nanocrystals

254th National Meeting (2017)

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