Morphology Control of Green InP/ZnSe/ZnS Quantum Dots and Application in X-ray Imaging

Indium phosphide (InP)-based quantum dots (QDs) have emerged as a promising alternative to cadmium-containing QDs for photonic applications. Nonetheless, the evolution of the synthesis chemistry for InP-based QDs poses a significant challenge, particularly with regard to morphological control. This study demonstrates efficient morphological control of square and spherical green-emissive InP/ZnSe/ZnS QDs. The formation of square-shaped QDs is attributed to the fluoride-induced suppression of {111} facet growth, which promotes shell growth along the {100} facets. Conversely, spherical QDs emerge owing to weak suppression of {111} facet growth. The fluoride is derived from the reaction between ZnF2 powder and oleic acid. It has been demonstrated that coordination between TOP and oleic acid effectively impedes this reaction. Beyond photoluminescence, the QDs exhibit strong and narrow radioluminescence (RL) at 565 nm with a full width at half maximum (FWHM) of 42 nm under X-ray excitation with a light yield of 4.2 × 103 photons/MeV. A QD X-ray imaging film was demonstrated to successfully visualize the internal components of opaque objects. This work demonstrates a ligand-mediated strategy for the morphological control of InP-based QDs and highlights their potential for X-ray imaging.