On the role of Pb⁰ atoms on the nucleation and growth of PbSe and PbTe nanoparticles

In this contribution, a nucleation and growth mechanism of PbSe and PbTe nanoparticles are proposed. The formation and growth of PbSe and PbTe nanoparticles during their reaction synthesis were studied and followed using transmission electron microscopy, and their related techniques. In the synthesis method, trioctylphosphine-selenide and telluride were used as the chalcogen precursors, while lead oleate was employed as the lead precursor. Different synthesis conditions were tested to assess the effect of varying the reaction time, lead to chalcogen ratio, reaction temperature, and lead oleate concentration. The synthesized nanoparticles were characterized by means of electron diffraction, energy dispersive X-ray spectroscopy, scanning transmission electron microscopy, and electron energy loss spectroscopy, to obtain information related to their morphology, crystal structure, and composition. The experimental results suggest that the growth of the lead chalcogenide nanoparticles greatly relies on the reduction of Pb²⁺ ions to Pb⁰ atoms at early reaction times; this reduction of the lead precursor is evidenced by the formation of Pb nanoparticles with sizes between 1 and 3 nm under certain synthesis conditions. These Pb nanoparticles gradually disappear as the reaction progresses, suggesting that the reduced Pb⁰ atoms are able to contribute to the growth of the PbSe and PbTe nanoparticles, reaching sizes between 8 and 18 nm. The current results contribute to a better understanding of the nucleation and growth mechanisms of lead chalcogenide nanoparticles, which will enable the definition of more efficient synthesis routes of these types of nanostructures.