PbSe Nanocrystal Assemblies:  Synthesis and Structural, Optical, and Electrical Characterization

Individual PbSe nanocrystals (NCs) were prepared by a chemical reaction between lead-cyclohexanebutirate and tri-butyl-phosphine/selenium precursors in a tri-octyl-phosphine oxide/tri-butyl-phosphine surfactant, at 118 °C. Increasing precursor concentration, accompanied by an additional heating, up to 150 °C, enabled the formation of NCs assemblies: a reaction time duration of 10−60 min led to the formation of monodispersed spherical polycrystalline assemblies whose average diameters ranged between 50−500 nm. A reaction time duration of >60 min enabled the formation of an ordered wire-like assembly, with a typical width of 60−150 nm and a length of 1−5 μm. The assemblies are presumably stabilized by the NCs−NCs dipole−dipole interactions, with an estimated interaction energy of −28 kJ/mol. The electrical measurement of a single wire-like assembly revealed a conductivity of 7.0 Ω-1cm-1.