Linking experimental findings and theoretical insights on the mechanochemical synthesis of PbTe quantum dots: The effect of ethylene glycol

Abstract

It is provided a new pathway for obtaining the formation of small dimensional PbTe nanostructures during milling, including quantum dots (QDs). It is possible via the addition of ethylene glycol (EG) which is the key factor to decide the final morphology and size of small dimensional PbTe nanostructures. Therefore, in this work, the effects of EG, as a process control agent (PCA), on the growth mechanisms of PbTe QDs are experimental and theoretically investigated. To achieve this goal, the behavior between EG and inorganic PbTe interface interactions is explored via density functional theory (DFT). The occurrence of PbTe is detected by using X-ray diffraction technique and the mechanical kneading suppression is verified through electron microscopy results. The formation of rounded and quasi faceted PbTe QDs are ruled by structural-defect and imperfect oriented attachment mechanisms respectively, which are strongly evidenced by high-resolution transmission electron microscopy. Interactions between EG and low-index surfaces are modeled by dispersion-corrected DFT calculations. Through the electrostatic potential mapped on the van der Waals isosurfaces, adsorption modes of the selected PCA on the PbTe surface are proposed, allowing rationalizing the facets exposed by the PbTe QDs after the surface treatment. Changes induced by the EG molecule, as PCA, are rationalized in terms of surface energy. Interactions with the PbTe surfaces stabilize the (100) facet, while destabilize the (111) facet. Wulff constructions support the formation of particles, in the nanometric scale, with cubic or cubic with rounded edges.