Identifying the effect of tributyl phosphate on the growth of PbTe quantum dots: Linking experimental and theoretical approaches

Abstract

The effects of tributyl phosphate (TBP), as a process control agent (PCA), on morphology, size and dispersion of PbTe quantum dots (QDs), at 5 h of milling time, are investigated. By using X-ray diffraction, the occurrence of PbTe is detected, while the PbTe formation and morphology, during milling, are studied via transmission electron microscopy (TEM). According to TEM results, the occurrence of nearly spherical and faceted PbTe QDs are ruled by highly structural-defect and oriented attachment mechanisms, respectively. What is more, mechanical kneading is effectively inhibited when 3 wt% TBP is added during milling. Dispersion-corrected density functional theory (DFT) calculations are carried out to understand the factors that affect growth and morphology of PbTe QDs. DFT results demonstrated that both the intrinsic characteristics of PbTe and the adsorption of certain reaction species are responsible for the shape control of PbTe QDs, which is useful to propose adsorption modes of TBF on PbTe surface and to rationalize the facets exposed by PbTe after the surface treatment. In agreement with experimental results, Wulff constructions proposed are cube-like quantum dots with sharp edges, but rounded edges are possible as well.