Star-shaped colloidal PbS nanocrystals: structural evolution and growth mechanism

Branched nanostructures have attracted considerable interest due to their large surface-to-volume ratio with benefits in photocatalysis and photovoltaic applications. Here we discuss the tailoring of branched structures with a shape of a star based on PbS semiconductor. It exposes the reaction mechanism and the controlling factors that template their morphology. For this purpose, we varied the primary lead precursors, types of surfactant, lead-to-surfactant molar ratio, temperature and duration of the reaction. Furthermore, intermediate products in a growth reaction were thoroughly examined using X-ray diffraction, transmission electron microscopy, Raman scattering, optical absorbance and Fourier transform infrared spectroscopy. The results designated a primary formation of truncated octahedral seeds with terminating {100} and {111} facets, followed by the selective fast growth of pods along the 100 directions toward the development of a star-like shape. The examined intermediates possess a cubic rock salt structure. The observations indicated that small surfactant molecules (e.g. acetate) evolve the branching process, while long-chain surfactants (e.g. oleate) stabilize the long pods as well as mitigate the aggregation process. This study conveys fundamental knowledge for the design of other branched structures, that are attractive for practical use in catalysis, electrochemistry and light-harvesting.

Automated summary

This study focuses on the preparation of star-shaped branched structures based on PbS semiconductors, examining the reaction mechanism and factors controlling their morphology. Various lead precursors, surfactants, ratios, temperature, and duration of the reaction were adjusted, revealing a primary formation of truncated octahedral seeds with {100} and {111} facets followed by fast growth of pods along the 100 directions. Small surfactant molecules were found to promote the branching process, while long-chain surfactants stabilized the pods and reduced aggregation. The findings provide fundamental insights for designing branched structures useful in catalysis, electrochemistry, and light-harvesting applications.