tz9b00200_si_004.csv (45.47 kB)

Quantification of a PbClx Shell on the Surface of PbS Nanocrystals

Download (45.47 kB)
posted on 25.06.2019 by Samuel W. Winslow, Yun Liu, James W. Swan, William A. Tisdale
Differences between the properties of PbS nanocrystals prepared using a large excess of PbCl2 and those prepared using other Pb sources have led to speculation that a thin PbClx shell may be present on the surface of PbCl2-derived PbS nanocrystals. However, characterization of this chloride layer has proven to be challenging because of the poor contrast provided by electron and X-ray scattering probes. Here, we show that small-angle neutron scattering (SANS) provides the compositional sensitivity needed to unambiguously quantify the PbClx shell that is present on the surface of PbCl2-derived PbS nanocrystals. Using a charge-balanced structural model, the scattering contribution of a ∼0.3 nm thick surface PbClx layer is parsed separately from ligand carboxylate head groups and PbS in the core. Global fitting of the SANS data across a solvent deuteration series enables unique determination of the spatial distribution of each material. These results are corroborated by quantitative nuclear magnetic resonance (NMR) and energy-dispersive X-ray spectroscopy (EDS). This work resolves a discrepancy in reported sizing curves for PbS nanocrystals prepared by different syntheses and further demonstrates the power of SANS in resolving molecular structure in soft and hybrid nanomaterials.