Synthesis of Wurtzite In and Ga Phosphide Quantum Dots Through Cation Exchange Reactions

Precise control over the crystal structure of colloidal quantum dots (QDs) is of importance for not only tailoring the optical/electronic properties of QDs but also synthesizing heteronanostructures with complex shapes through seeded growth strategy. For environmentally benign InP-based QDs, while substantial progress has been made in size-monodispersity and fluorescence intensity, synthesis of wurtzite InP QDs remains highly challenging. Herein, we synthesize metastable wurtzite monodisperse InP QDs through cation exchange reaction from Cu3P nanocrystals. The moderate exchange conditions and the subtle variation of the anion sublattice enable the preservation of the hexagonal crystal structure of the templating Cu3P nanocrystals. Changing the size of Cu3P nanocrystals results in wurtzite InP QDs with controllable size that show size-dependent optical properties. Additionally, wurtzite GaP and ternary InGaP alloy QDs can be obtained by adopting proper Ga and In precursors, highlighting the versatility of cation exchange reactions to synthesize wurtzite III-V QDs that are not attainable through traditional routes. Finally, we show that a gradient ZnSeS shell growth on wurtzite InP QDs leads to fluorescent QDs with emission peak wavelength between 674 and 754 nm. We anticipate this study will promote the synthesis of anisotropic heterostructures with unique optical properties where wurtzite In(Ga)P QD seeds are required.