Investigating the Phosphine Chemistry of Se Precursors for the Synthesis of PbSe Nanorods

We studied the role of different Se precursors for PbSe nanorod (NR) synthesis, focusing on phosphine chemistry to understand precursor decomposition. After characterizing the morphology of PbSe nanocrystals (NCs) and NRs with absorption spectra and TEM analyses, we used 31P NMR to correlate morphology with precursor decomposition during synthesis. While spherical PbSe NCs can be produced with a trioctylphosphine selenide (TOPSe)-based synthesis even at low temperatures (50-60 degrees C) or without free phosphine, PbSe NRs are more sensitive to their reaction conditions. At lower temperatures, tris(diethylamino)phosphine selenide (TDPSe) does not show any evidence of Se precursor decomposition, and the presence of amine-based free phosphine in the Se precursor affects the morphology of PbSe NRs dramatically. Further TGA-MS analysis implies that TDP accelerates precursor decomposition and morphology evolution by releasing amine species. A control experiment that added amine into both TOPSe and TDPSe with no free phosphine-based reactions shows amine species enhance the attachment process and morphology change.