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 118degreesC. Increasing precursor concentration, accompanied by an additional heating, up to 150degreesC, 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 mum. 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 Omega(-1) cm(-1).