Synthesis of PbSe nanowires: the impact of alkylphosphonic acid addition

Reaction of Pb oleate with trioctylphosphine (TOP)/Se in 1-octadecene under appropriate conditions yields PbSe nanowires. The parameters found to be critical for the isolation of exclusively one-dimensional material are the Pb : Se ratio and the temperature profile used during synthesis. Addition of strongly coordinating tetradecylphosphonic acid (TDPA) to the system has a profound impact on the surface morphology, with increasing TDPA concentration producing narrower, smoother nanowires when all other parameters are held constant. The wire morphology and structural data are consistent with a combination of oriented attachment on < 111 > surfaces, yielding wires with a [100] axial orientation, and a ligand-mediated competition between growth on < 111 >, < 110 > and < 100 > planes. The products possess 10-20 nm diameters, with lengths generally over one micron, and have been characterized through SEM, TEM, EDS, electron diffraction, and optical spectroscopy.